In 1 RCT, catheter ablation was superior to anti- arrhythmic medications at suppressing frequent PVCs arising from the RVOT.S8.1-4 Observational studies have shown that radiofrequency cath- eter ablation is effective in the treatment of idio- pathic VA arising from the RVOT and LV outflow Thesiteofablationmaybebelow or above the pulmonic valve in the RVOT.S8.1-9,S8.1-13 Although most RVOT VA can be ablated within the RV, 10% may require ablation within the pulmonic Serious complications are infre- quent. For LV outflow tract VA, the site of ablation below the aortic valve,S8.1-2,S8.1-6 at the aorto-mitral or on the epicardial surface of the LV summit.S8.1-3,S8.1-17,S8.1-18 The mitral and tricus- pid annulae are less common sites of idiopathic VA, but these VA can also be effectively treated with Approximately 10% of idiopathic VA may arise from the summit of the LV. Some can be ablated from the great cardiac vein or the epicardial surface, but others arise from an inaccessible region in close proximity to the left coronary artery precluding effective ablation.S8.1-14 Intramural sites of origin are infrequent but may require ablation on both the endocardial and epi- cardial surfaces of the LV ostium.S8.1-3 Complications from ablation of outflow tract VA are infrequent, but bleeding complications related to arterial and venous access, pericardial tamponade, and dam- age to the coronary arteries can occur. 2. In a prospective randomized comparison of anti- arrhythmic medications versus catheter ablation, metoprolol or propafenone was shown to have modest effectiveness when used to suppress RVOT PVCs, though with a far higher rate of recurrence than catheter ablation.S8.1-4 Non-dihydropyradine calcium channel blockers suppress arrhythmia in 8.2. Papillary Muscle VA Recommendation for Papillary Muscle VA (PVCs and VT) References that support the recommendation are summarized in Online Data Supplement 47. COR LOE Recommendation I B-NR In patients with symptomatic VA arising from the papillary muscles for whom antiarrhythmic medications are ineffective, not tolerated, or not the patient s preference, catheter ablation is useful.S8.2-1 S8.2-5 Recommendation-Specific Supportive Text 1. The papillary muscles of the LV or RV can be the site of origin of VA in the presence or absence of struc- tural heart disease.S8.2-1 S8.2-5 Idiopathic left and right ventricular papillary muscle VA are most commonly PVCs and NSVT, and are usually exercise-related and may be induced by intravenous epinephrine or These arrhythmias have a focal, nonreentrant mechanism. Any of the 3 RV papillary muscles may be the site of origin and catheter ablation is usually effective.S8.2-2 In 1 study, successful ablation was achieved in all 8 patients with a reduction in PVC burden from 17 20% to In the left ventricle, the site of origin may be either the posteromedial or the anterolat- eral papillary muscles.S8.2-1,S8.2-4,S8.2-5 Multiple VA QRS morphologies were observed in 47% of patients, and ablation on both sides of the papillary muscle is required in some patients.S8.2-4 Achieving adequate catheter stability can be challenging. Acute abla- tion success is high, but recurrences are more fre- quent than for idiopathic outflow tract VA. Serious complications, including valve injury, appear to be infrequent. The risks of catheter ablation include bleeding related to arterial and venous access and a low risk of pericardial tamponade. 8.3. Interfascicular Reentrant VT (Belhassen Tachycardia) Recommendations for Interfascicular Reentrant VT (Belhassen Tachycardia) References that support the recommendations are summarized in Online Data Supplement 48. COR LOE Recommendations I B-NR In patients with verapamil-sensitive, idiopathic LVT related to interfascicular reentry for whom antiarrhythmic medications are ineffective, not tolerated, or not the patient s preference, catheter ablation is I B-NR In patients with sustained hemodynamically tolerated verapamil-sensitive, idiopathic LVT related to interfascicular reentry, intravenous verapamil is recommended for IIa C-LD In patients with recurrent verapamil-sensitive idiopathic LVT, chronic therapy with oral verapamil can be useful.S8.3-7 S8.3-10 Recommendation-Specific Supportive Text 1. Idiopathic LVT is due to reentry involving a portion of the LV Purkinje system, usually the left posterior fascicle as the retrograde limb of the circuit and an incompletely defined segment of LV tissue as the anterograde limb, a portion of which is verapamil CLINICAL STATEMENTS AND GUIDELINES These VTs are typically sustained with a QRS that has a right bundle-branch block configuration with a superior axis. Less frequently an inferior axis VT or a relatively narrow QRS VT occurs as a result of alternate reentry paths, also involving a part of the Purkinje system. Beta block- ers or verapamil typically terminate these arrhyth- mias, but they fail to prevent recurrences in some The target of catheter ablation for the most common form is usually the distal insertion of the anterograde limb of the Purkinje system along the inferior portion of the LV septum near its junc- tion with the left posterior fascicle. Catheter abla- tion is acutely successful in >90% of patients with a risk of recurrence of approximately 10%. This VT may resemble fascicular VA that are due to a focal mechanism in the left anterior or left posterior fas- cicles of the LV His-Purkinje system. These fascicular arrhythmias usually have a focal mechanism with the target of catheter ablation being the site of earliest electrical activation recorded with a presystolic fas- cicular potential. Catheter ablation is highly effective for intrafascicular and fascicular VA. Serious compli- cations are infrequent and include bleeding at the site of arterial or venous access and a small risk of bundle branch block or atrioventricular block. 2. Idiopathic LVT is based on reentrant mechanism involving tissue with slow conduction properties along the LV septum as the anterograde limb and the normal left posterior fascicle of the His- Purkinje system as the retrograde limb. The slow conduction zone is verapamil-sensitive.S8.3-3 S8.3-6 These arrhythmias typically have a right bundle- branch block morphology with superior axis, though reversal of the circuit may produce a rela- tively narrow QRS during VT. Verapamil typically terminates these arrhythmias in the anterograde slow conduction zone.S8.3-3 S8.3-6 3. Although no RCTs have been published, the chronic use of oral verapamil for verapamil-sen- sitive idiopathic LVT has been reported to control this tachycardia in many patients, including both adults and children.S8.3-5,S8.3-8 S8.3-10 8.4. Idiopathic Polymorphic VT/VF Recommendations for Idiopathic Polymorphic VT/VF References that support the recommendations are summarized in Online Data Supplement 49. COR LOE Recommendations I B-NR In young patients (<40 years of age) with unexplained SCA, unexplained near drowning, or recurrent exertional syncope, who do not have ischemic or other structural heart disease, further evaluation for genetic arrhythmia syndromes is I B-NR In patients resuscitated from SCA due to idiopathic polymorphic VT or VF, an ICD is recommended if meaningful survival greater than 1 year is expected.S8.4-9 S8.4-13 I B-NR For patients with recurrent episodes of idiopathic VF initiated by PVCs with a consistent QRS morphology, catheter ablation is useful.S8.4-11,S8.4-14 Recommendation-Specific Supportive Text 1. When combined with clinical evaluation, genetic testing can provide a diagnosis in up to 13% to 60% of younger (<40 years of age) survivors with the most common genotypes identified associated with long QT syndrome, catecholaminergic polymorphic ventricular tachy- cardia, and Brugada syndrome.S8.4-8 Drowning/ near drowning events are particularly associated with LQT1 and catecholaminergic polymorphic ventricular tachycardia; genetic mutations in long QT syndrome and catecholaminergic polymorphic ventricular tachycardia have been identified in 23% of patients with unexplained near-drown- exertion-related cardiac arrest, particularly in children, may be related to long QT syndrome, catecholaminer- gic polymorphic ventricular tachycardia, or to calmodulin/triadin-mediated long QT syndrome/ catecholaminergic polymorphic ventricular tachy- cardia mutations, which may require additional specialized genetic testing.S8.4-1,S8.4-2,S8.4-4,S8.4-16 S8.4-18 Single-driver auto crashes should prompt the consideration of arrhythmic causes. The yield of genetic testing is higher if a family history of SCD at a young age is present. Referral to specialized genetic testing centers is important if local exper- tise is unavailable. 2. VF in the absence of identifiable structural heart disease or known genetic arrhythmia syndromes such as catecholaminergic polymorphic ventricu- lar tachycardia, long QT syndrome, short QT syn- drome, Brugada syndrome, or J wave syndromes is usually the result of short coupled PVCs arising from the Purkinje system in either the right or left ventricles or, less commonly, from the ventricular The recurrence risk after resuscitation of idiopathic VF is very high.S8.4-12 Among 38 consecutive patients from 6 different centers who underwent ablation of primary idio- pathic VF initiated by short coupled PVC, 87% had experienced 2 VF episodes in the preceding Because idiopathic VF is associated with Recommendations for Idiopathic Polymorphic VT/VF (Continued) COR LOE Recommendations CLINICAL STATEMENTS AND GUIDELINES a very high risk of recurrent VF, an ICD is indi- cated to prevent SCD. Catheter ablation of the triggering focus has proved to be highly effective in eliminating the repetitive PVCs which induce VF in these patients.S8.4-11 During a median post- procedural follow-up of 63 months, 7 (18%) of 38 patients undergoing catheter ablation of idio- pathic VF induced by short coupled PVCs experi- enced VF recurrence at a median follow-up of 4 months. Five of these 7 patients underwent repeat ablation without VF recurrence. Thus, although catheter ablation is very effective in idiopathic VF, the recurrence risk remains substantial after an apparently successful procedure and the patient should be protected with an ICD. The subcuta- neous ICD may not be a good therapy for these patients due to the higher risk of T-wave over- sensing seenin this population; however, data are 3. Idiopathic VF may be initiated by PVCs that arise from the outflow tracts or the His-Purkinje system within either the right ventricle or left Some patients have clusters of VF episodes (electrical storm) that typi- cally present as PVCs initiating polymorphic VT/VF. The PVCs usually have a consistent QRS morphol- ogy and a short coupling interval and can be tar- geted for ablation to control the arrhythmia.S8.4-11 For PVCs from the Purkinje system, the ablation target is a high-frequency Purkinje potential pre- ceding the PVCs. When episodes are induced by short-coupled PVCs arising from the outflow tracts, the ablation target is the site of earliest ventricular activation. Patients with idiopathic VF often have periods of frequent VT/VF interspersed with peri- ods of relative quiescence.S8.4-11,S8.4-14 To maximize the probability of successful ablation, the proce- dure is best performed during periods of frequent PVCs. Less-frequent episodes of VF may be ame- nable to ablation if frequent PVCs with a consis- tent QRS morphology are present. When the PVCs can be identified, ablation is highly successful, but late recurrences are observed in approximately 10% of patients such that implantation of an ICD is prudent even if ablation is acutely successful. The risks of catheter ablation include bleeding at the site of arterial or venous access and a small risk of pericardial tamponade. Therapy with quinidine acutely and chronically can suppress recurrent VF episodes in some patients.S8.4-22 9. PVC-INDUCED CARDIOMYOPATHY Recommendations for PVC-Induced Cardiomyopathy References that support the recommendations are summarized in Online Data Supplement 50. COR LOE Recommendations I B-NR For patients who require arrhythmia suppression for symptoms or declining ventricular function suspected to be due to frequent PVCs (generally >15% of beats and predominately of 1 morphology) and for whom antiarrhythmic medications are ineffective, not tolerated, or not the patient s preference, catheter ablation is useful.S9-1,S9-2 IIa B-NR In patients with PVC-induced cardiomyopathy, pharmacological treatment (eg, beta blocker, amiodarone) is reasonable to reduce recurrent arrhythmias and improve symptoms and LV function.S9-3,S9-4 Recommendation-Specific Supportive Text 1. Frequent PVCs (usually >15% of the total num- ber of beats) may produce a reversible form of However, it is sometimes difficult to ascertain whether the PVCs caused LV dysfunction or whether progressive LV dysfunc- tion caused frequent PVCs. LV dysfunction has been associated with greater PVC burden (>10% and usually >20%), NSVT, a retrograde P-wave after the PVCs, and interpolated PVCs.S9-6,S9-15 In a prospective study of catheter ablation for PVC-induced cardiomyopathy, ablation was com- pletely successful in 80% of patients.S9-19 LV func- tion normalized within 6 months in 82% of the 22 patients who had depressed ventricular dys- function at baseline. Thus, frequent PVCs may be a reversible cause of LV dysfunction that can be effectively treated with catheter ablation. It is often difficult to determine if apparent LV dys- function reflects impaired LV function or inability to accurately assess LV function due to the fre- quent ectopic activity. In patients who have a high density of PVCs with normal ventricular function, optimal treatment and surveillance for prevention and detection of decline in ventricular function have not been established. 2. In a double-blind parallel study of 30 patients with or without ischemic heart disease with >30 PVCs per hour comparing sotalol to propranolol, proarrhythmic effects were present in 1 patient on sotalol. There was no significant difference in suppression of PVCs (sotalol 65%, proprano- lol 44%), with reduction in ventricular couplets being 99% for sotalol and 49% for propranolol. There was a significant increase in QTc in patients In a double-blind, randomized, CLINICAL STATEMENTS AND GUIDELINES placebo-controlled study of 674 patients with HF and LVEF <0.40 attributed to ischemic or NICM and 10 PVCs per hour, amiodarone significantly reduced VA, slowed heart rate, and was associ- ated with an increase in LVEF by 42% at 2 years with a nonsignificant trend toward reduction in Whether the VA was contributing to ventricular dysfunction in these patients is unknown. 10. VA AND SCD RELATED TO SPECIFIC POPULATIONS In athletes, VAs range from isolated PVCs, cou- plets, and NSVT, to sustained VT and SCA leading to Infrequent PVCs and short runs of repetitive NSVT, especially in the absence of structural heart dis- ease, are more common in nonathletes, but they are generally benign, requiring only a limited workup and rarely lead to disqualification for sports.S10.1-2,S10.1-3 In contrast, longer runs of NSVT, especially when exer- cise-induced, and sustained VT and SCA/SCD are in- frequent, but they have a higher incidence in athletes than that reported for the general population in the corresponding age groups. Reported estimates of SCD range from 1 per 53703 athlete-years in the National Collegiate Athletic Association databaseS10.1-4 per 200000 in Minnesota high school students.S10.1-5 Among those studies judged to have better epidemio- logical protocols, estimates were in the range of 1 per These figures compare with a general population risk of 1.0 to 1.9/100000 in adolescents and young adults.S10.1-7,S10.1-8 Moreover, there appears to be both sport and sex differences in the magnitude of risk, with males being at higher risk than females in most sports,S10.1-7,S10.1-9 blacks at higher risk than whites, and male basketball players being the single highest risk group in the United States, 1 A study that included both competitive and rec- reational athletes showed that both groups are at a higher risk for SCD than the general population, with recreational athletes having greater cumulative SCD occurring at an older age, and a different distribution of diseases. Postmortem data on SCD in athletes reveal that 25% to 40% are autopsy- negative, suggesting a role for genetic molecular dis- orders in these victims S10.1-4,S10.1-10,S10.1-11 and for family Another limitation of SCD data analysis in ath- letes centers on noncardiac causes, some of which mimic cardiac events. Noncardiac causes include acute neurological disorders, drug abuse, heat stroke, rhabdomyolysis, sickle cell disorders, suicides, and Nonetheless, arrhythmias in ath- letes remain the most common medical cause of death and many occur as the first cardiac event. The most common structural cause of SCAs and SCDs in athletes in the United States is HCM, fol- lowed by anomalous origins of coronary arteries, with myocarditis contributing a smaller but significant Beyond these, the other inherited disorders contribute to the distribution of causes of a SCD in athletes, many of which can be suspected or identified by a careful family history and preparticipa- tion ECGs. In general, management of arrhythmias in athletes follows that in nonathletes. In regard to interventions, it is now generally recommended that AEDs be available at training and facilities for competitive athletes,S10.1-16 with less specific statements for AED availability at ven- ues (eg, tennis courts) or circumstances (eg, jogging or small group runs) in which recreational athletics are oc- curring. Many athletes who have had corrective procedures (repair of congenital or developmental defects such as anomalous origins of coronary arteries)S10.1-17,S10.1-18 are on therapy for inherited disordersS10.1-19 or have ICD im- and are able to participate in athletics de- pending on the nature and severity of the disease and with appropriate precautions and counseling regarding potential residual risks.S10.1-19,S10.1-20 For example, ath- letes with acquired disorders such as myocarditis are advised against exercise for at least 3 to 6 months after disease resolution. Recommendations for Pregnancy References that support the recommendations are summarized in Online Data Supplement 51. COR LOE Recommendations I B-NR In mothers with long QT syndrome, a beta blocker should be continued during pregnancy and throughout the postpartum period including in women who are I C-EO In the pregnant patient with sustained VA, electrical cardioversion is safe and effective and should be used with standard electrode IIa B-NR In pregnant patients needing an ICD or VT ablation, it is reasonable to undergo these procedures during pregnancy, preferably after the first trimester.S10.2-4,S10.2-5 Recommendation-Specific Supportive Text 1. Women with long QT syndrome should be coun- seled about maternal and fetal risks prior to CLINICAL STATEMENTS AND GUIDELINES pregnancy to ensure ongoing beta-blocker ther- apy. The risk of SCA or SCD is significantly higher during the 9 months after delivery, most notably among women with LQT2.S10.2-1,S10.2-6,S10.2-7 A large retrospective analysis from the long QT syndrome registry demonstrated an odds ratio of 40.8 for syncope, SCA, or SCD among women with long QT syndrome in the 9 months postpartum; treatment with beta blockers during pregnancy was independently associated with decreased Overall arrhythmic events during preg- nancy are not increased among women receiving In a case- control study, women with LQT1 who did not receive beta blockers during pregnancy, particu- larly those with prior syncope, were at significantly increased risk of SCA or syncope.S10.2-8 Frequency of events returned to prepregnancy levels after Maternal use of beta blockers during pregnancy is associated with decreased newborn birth weight and hypoglycemia,S10.2-9 but it is not associated with increased risk of Fetal bradycardia is asso- ciated with fetal long QT syndrome and should not independently provoke discontinuation of ; these infants are at increased risk of death and require care- ful neonatal monitoring and treatment.S10.2-13 As 50% of offspring may be affected with long QT syndrome, with highest risk of adverse events in infancy and childhood, screening of the newborn at birth and during infancy for long QT syndrome 2. Available data on electrical fields associated with properly applied AED patches suggest that the fetus is safe; no observational data are available to the contrary. Anterolateral defibrillator pad placement is preferred with the lateral pad/pad- dle placed under the breast tissue, which is an important consideration in the pregnant patient. 3. The ICD in pregnant women is safe and For the rare circumstance of preg- nant women with an immediate indication for an ICD, or less common indications for VT ablation during pregnancy, the radiation risk to the fetus is The procedure is usually per- formed after the first trimester unless there are circumstances that demand an earlier procedure. Wearable cardioverter-defibrillators have been used in peripartum cardiomyopathy while await- ing repeat assessment of recovery of ventricular The subcutaneous implantable cardioverter-defibrillator is a potential alternative to conventional ICDs, although data are unavail- able to support a recommendation. 10.3. Older Patients With Comorbidities Recommendation for Older Patients With Comorbidities See Systematic Review Report.S10.3-1 COR LOE Recommendation IIa B-NRSR For older patients and those with significant comorbidities, who meet indications for a primary prevention ICD, an ICD is reasonable if meaningful survival of greater than 1 year SR indicates systematic review. Synopsis Refer to the Systematic Review for the 2017 ACC/ AHA/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death for the complete systematic evidence review for additional data and analyses.S10.3-1 The re- sults from the question What is the impact of ICD im- plantation for primary prevention in older patients and patients with significant comorbidities? (Part 2) and the writing committee s review of the totality of the lit- erature were used to frame our decision-making. Rec- ommendations are based on a body of evidence that includes the systematic review conducted by the ERC and are denoted by the superscript SR (eg, LOE: B-RSR ). Comorbidities included various combinations of renal disease, chronic obstructive pulmonary disease, atrial fibrillation, and heart disease, among others. Recommendation-Specific Supportive Text 1. Older age is defined as 75 years. The ERC s analyses are helpful in clearly demonstrat- ing that neither age nor comorbidities alone should be exclusions for an ICD. However, the data included in the analysis are limited. Firstly, most data are from non- randomized studies and both selection and uniden- tified confounding biases can never be fully adjusted for. It is likely that the more frail patients are already appropriately not offered ICDs and are thus not includ- ed. Secondly, because most of the studies are nonran- domized, these findings signify only an association and not causality. Also, older adults are prone to higher complication rates, shorter life expectancies (and thus, fewer years during which they could derive benefit from an ICD), and varying preferences.S10.3-2 For these reasons, it is important to take a particularly nuanced and patient- centered approach to treating these patients. 10.4. Chronic Kidney Disease Patients with chronic kidney disease (CKD) are at an in- creased risk of SCD compared with the general popula- CLINICAL STATEMENTS AND GUIDELINES tion, yet the risk versus benefit of primary prevention ICDs has been unclear; data from observational stud- ies have been conflicting, and patients with moderate or severe CKD, especially patients with end-stage renal disease (ESRD) on dialysis were not included in the piv- otal RCTs of ICDs.S10.4-1 S10.4-5 Furthermore, prior data had significant limitations given that patients who received ICDs have been compared inconsistently with a control group with CKD that did not receive primary prevention ICDs and the degree of renal insufficiency likely influ- ences survival benefit.S10.4-6 Patients with CKD, especially ESRD on dialysis, appear to be at increased risk of ICD- related complications. A significant number of sudden deaths are unassociated with VA in this population.S10.4-7 Therefore, the ERC was asked to address the impact of ICDs on mortality in patients with CKD. The ERC conducted a specific analysis of 5 studies that explored renal dysfunction. A meta-analysis of these studies suggested that an association exists be- tween ICD implantation and improved survival.S10.4-8 An important limitation is that only 2 studies specifi- cally studied patients with ESRD and most data ana- lyzed were from observational studies.S10.4-8,S10.4-9 In view of these limitations, the writing committee concluded there was not enough data to inform a recommenda- tion on ICD implantation in patients with ESRD on di- alysis. Decisions regarding ICDs in patients with CKD, especially those with ESRD, should be individualized and take into consideration the patient s functional sta- tus, number of comorbidities, and preferences, among other factors. 10.5. Valvular Heart Disease Patients with valvular heart disease should be evaluated and treated according to GDMT for valvular heart dis- ease and, when LVEF is depressed, GDMT that applies to NICM to reduce the risk of SCD.S10.6-23 VA in patients with valvular heart disease can be caused by any of the mechanisms responsible for VA in other cardiac disease including ischemic heart disease, MI, severe LV hyper- trophy, adrenergic-dependent rhythm disturbances, or an inherited molecular abnormality. Patients with valvular heart disease and VA are generally evaluated and treated using current recommendations for each The presence of a VA alone does not con- stitute an indication for valve repair or replacement. In general, there is more knowledge on the risk for SCD in patients with aortic stenosis than other valvular lesions with a risk of 1% to 1.5% per year.S10.6-2 Most patients who die suddenly have been symptomatic from their Although recurrent NSVT may place a patient with severe aortic stenosis at risk for syncope, the management of such a patient is guided by the severity of the valvular lesion. Mitral valve prolapse has been implicated as a cause of SCD, although a study of 18786 patients found no increased risk of SCA for patients with bileaflet mitral valve prolapse versus single leaflet mitral valve prolapse or no mitral valve prolapse.S10.6-5 LV fibrosis in the papil- lary muscles has been described in some mitral valve prolapse patients with VA or SCD.S10.6-6 Further, a possi- ble syndrome for SCD has been described that includes bileaflet mitral valve prolapse, female sex, T wave ab- normality, and complex ventricular ectopy.S10.6-7 Guid- ance for treatment of patients with NICM, whether val- vular or otherwise in origin, is provided in the current guideline (see Sections 7.2.1 and 7.2.2 for primary and secondary prevention). 10.6. Sex-Related Differences in the Risk of SCD The information on associations between sex and VA and SCD is largely limited to epidemiological, cohort, and observational studies. Various population studies, primarily focused on SCD due to ischemic heart disease, have demonstrated age gradients in SCD risk among men and women.S10.6-8 S10.6-10 These include a 10-year lag in SCD incidence in women compared with men. How- ever, risk factor burden among women has the same proportional effect as in men, with a 17-fold increase in risk from the lowest to highest deciles.S10.6-9 Impor- tantly, 69% of the SCDs in women were first cardiac A study of lifetime risk of SCD stratified at 45, 55, 65, and 75 years of age identified persistently lower and similar proportions of lifetime risk of SCD among women versus men in each of the strata.S10.6-10 The difference between women and men is somewhat smaller at ages below and above 75 years, largely be- cause of a reduced risk in men. The overall lifetime risk of SCD was 1 in 9 among men and 1 in 30 among In studies of outcomes after out-of-hospital car- diac arrest, women were older, had more SCAs in homes, and fewer shockable rhythms (VT/VF) than This was associated with a somewhat lower probability of survival overall; however, women with VT/VF and those with pulseless electrical activity had better outcomes than men.S10.6-12 A retrospective analy- sis of out-of-hospital cardiac arrest reported that survival improved over a 10-year period, with more favorable outcomes in men as well as younger women.S10.6-13 Two studies demonstrated better outcomes in wom- en with VT/VF, despite adverse risk factor profiles in Another large study demonstrated that despite similar prehospital return of spontaneous cir- culation and survival to discharge, younger women had lower 1-month neurologically intact survival than the 50 A 17-year retrospective analysis CLINICAL STATEMENTS AND GUIDELINES did not demonstrate any difference between men and women, although total outcomes improved.S10.6-17 The proportion of ischemic heart disease-associated SCAs among women surviving out-of-hospital cardiac arrest was significantly lower than in men, but ischemic heart disease remained the most powerful predictor and women were also significantly less likely to have severe LV dysfunction (LVEF 35%) or previously recognized ischemic heart disease.S10.6-19 Women appear to be less likely to benefit from thera- peutic hypothermia postcardiac arrest; however, in the younger age group, neurologic recovery in women was better than in older women.S10.6-20 Women are less likely to have SCA during competitive athletic events. A large study including both recreational and competitive ath- letes across a large age range noted that SCA in women during athletic events was 1 in 20 of that in men.S10.6-21 A large literature review from 1980 to 1992 dem- onstrated that women accounted for 70% of re- corded cases of cardiovascular medication related This is consistent with QT interval dif- ferences among men and women. A retrospective anal- ysis of quinidine discontinuation reported a significant difference in discontinuation between men and women (66% versus 84%) largely due to prolonged QT.S10.6-23 A study of catheter ablation for VT reported that overall outcome was similar between men and women.S10.6-24 The only sex difference was the greater probability of women having RVOT VT and a greater probability of men having LV outflow tract VT. 10.7. Medication-Induced Arrhythmias Recommendations for Medication-Induced Arrhythmias References that support the recommendations are summarized in Online Data Supplements 52 and 53. Digoxin COR LOE Recommendation I B-NR Administration of digoxin antibodies is recommended for patients who present with sustained VA potentially due to digoxin Medication-induced QT prolongation and torsades de pointes COR LOE Recommendations I B-NR In patients with recurrent torsades de pointes associated with acquired QT prolongation and bradycardia that cannot be suppressed with intravenous magnesium administration, increasing the heart rate with atrial or ventricular pacing or isoproterenol are recommended to suppress the I C-LD For patients with QT prolongation due to a medication, hypokalemia, hypomagnesemia, or other acquired factor and recurrent torsades de pointes, administration of intravenous magnesium sulfate is recommended to suppress the arrhythmia.S10.7-4,S10.7-5 I C-LD For patients with torsades de pointes associated with acquired QT prolongation, potassium repletion to 4.0 mmol/L or more and magnesium repletion to normal values (eg, 2.0 mmol/L) are beneficial.S10.7-6,S10.7-7 Sodium channel blocker related toxicity COR LOE Recommendations IIa C-LD In patients taking sodium channel blockers who present with elevated defibrillation or pacing thresholds, discontinuing the presumed responsible medication or reprogramming the device can be useful to restore effective device therapy.S10.7-8,S10.7-9 III: Harm B-NR In patients with congenital or acquired long QT syndrome, QT-prolonging medications are Recommendation-Specific Supportive Text 1. Typical arrhythmias related to digoxin toxicity include enhanced atrial, junctional, or ventricu- lar automaticity (with ectopic beats or tachy- cardia) often combined with atrioventricular VT that is fascicular or bidirectional in origin is suggestive of digoxin toxicity.S10.7-12 Severe digoxin overdose causes hyperkalemia and cardiac standstill. The diagnosis is established by the combination of characteristic rhythm distur- bances, ancillary symptoms (visual disturbances, nausea, changes in mentation), and elevated serum concentrations. Potentiating factors may include hypothyroidism, hypokalemia, or renal Treatment of digoxin toxic- ity is based on the severity. In mild cases, dis- continuing the medication, monitoring rhythm, and maintaining normal serum potassium may Intravenous magnesium is often administered if VAs are present.S10.7-12 Occasionally, temporary pacing may be needed for atrioventricular block or asystole.S10.7-13 For more severe intoxication (serum digoxin con- centrations exceeding 4 ng/mL and with serious arrhythmias such as VT), the treatment of choice is digoxin-specific Fab antibody.S10.7-1 In 1 series of 150 severely intoxicated patients, response was rapid (30 minutes to 4 hour), and 54% of patients presenting with a cardiac arrest sur- Adverse effects include worsening of the underlying disease (increased ventricular rate during AF, exacerbation of HF) and hypokalemia. Doses lower (and less expen- sive) than the full neutralizing dose are sufficient as long as cardiac arrest is not imminent.S10.7-2 Recommendations for Medication-Induced Arrhythmias (Continued) COR LOE Recommendations CLINICAL STATEMENTS AND GUIDELINES Digoxin concentration monitoring is unreliable after antidigoxin antibody administration. 2. Monitoring high-risk patients during initiation of QT-prolonging antiarrhythmic medications and recognition of the syndrome when it occurs are the first steps. Temporary pacing is highly effective in managing torsades de pointes that is recurrent after potassium and magnesium supplementation.S10.7-3 Isoproterenol can also be used to increase heart rate and abolish postectopic pauses.S10.7-3 3. Intravenous magnesium can suppress episodes of torsades de pointes without necessarily shortening Repeated doses may be needed, titrated to suppress ectopy and nonsustained VT episodes while precipi- tating factors are corrected.S10.7-4 Magnesium toxicity (areflexia progressing to respiratory depression) can occur at high serum concentrations, but this risk is very small with the doses usually used to treat tors- ades de pointes, 1 to 2 g intravenously.S10.7-14 Allelic variants in clinical long QT disease genes have been identified in patients with medication- induced torsades de pointes.S10.7-7,S10.7-15 S10.7-18 Further, whole exome sequencing implicates an increased burden of rare potassium channel vari- ants in the risk of medication-induced torsades de These findings do not yet sup- port general genetic screening for prediction of medication-induced torsades de pointes. In long QT syndrome, genetic testing may be performed in the index case who experienced medication- induced torsades de pointes and, if he/she did not survive that event, electrocardiographic screening of first-degree relatives may be performed. 4. Maintaining serum potassium between 4.5 mEq/L and 5 mEq/L shortens QT and may reduce the chance of recurrent torsades de pointes.S10.7-6,S10.7-7 5. In large clinical trials, sodium channel blockers increasedmortalityamongpatientsconvalescingfrom but similar trends were also seen with ear- lier trials of mexiletineS10.7-21 Based on CAST, flecainide is contraindicated in patients with ischemia, prior MI, and is avoided in patients with other structural heart diseases.S10.7-20 Sodium channel blockers increase defibrillation energy requirement and pacing thresholdsS10.7-8,S10.7-9 ; as a consequence, patients may require repro- gramming or revision of pacing or ICD systems or changes in their medication regimens (although modern pacing systems that provide automatic pacing threshold testing and adjustment of pac- ing output have mitigated the risk of loss of cap- ture). Sodium channel blockers can convert AF to slow atrial flutter, which can show 1:1 atrioven- tricular conduction with wide QRS complexes that can be confused with VT.S10.7-23 Sodiumchannelblockers,likeprocainamideand flecainide, can occasionally precipitate the typical Brugada syndrome ECG.S10.7-24,S10.7-25 This has been reported not only with antiarrhythmic medications but also with tricyclic antidepressantsS10.7-26 and Whether this represents unmasking individuals with clinically unapparent Brugada syndrome (see Section 7.9.1.3) or one end of a broad spectrum of responses to sodium channel blockers is unknown. In the setting of sodium-channel blocker tox- icity, limited animal data suggest that adminis- tration of sodium, as sodium chloride or sodium bicarbonate, may improve conduction slowing or suppress frequent or cardioversion-resistant Successful treatment with beta block- and intravenous fat emulsion and/or extracorporeal membrane oxygenation has also 6. QT-prolonging medications (www.crediblemeds. are not used in patients with congenital or acquired long QT syndrome unless there is no suitable alternative or the benefit greatly exceeds the risk. Episodes of torsades de pointes can be precipitated by exposure to a QT-prolonging medi- cation, and underlying prolongation of the QT (from genetic and clinical risk factors) increases Medications implicated in torsades de pointes are found in several medication classes, including antiarrhythmics, antihistamines, antibi- otics, antifungals, antidepressants, antipsychotics, opiates, and anticancer agentsS10.7-10 (Table 10). 10.8. Adult Congenital Heart Disease Recommendations for Adult Congenital Heart Disease References that support the recommendations are summarized in Online Data Supplement 54. COR LOE Recommendations I B-NR Adult patients with repaired complex congenital heart disease presenting with frequent, complex, or sustained VA, or unexplained syncope should undergo evaluation for potential residual anatomic or coronary abnormalities.S10.8-1 S10.8-6 I B-NR In patients with adult congenital heart disease and complex or sustained VA in the presence of important residual hemodynamic lesions, treatment of hemodynamic abnormalities with catheter or surgical intervention as feasible is indicated prior to consideration of ablation or an ICD.S10.8-3,S10.8-7 S10.8-12 I B-NR In patients with adult congenital heart disease and hemodynamically unstable VT, an ICD is recommended after evaluation and appropriate treatment for residual lesions/ ventricular dysfunction if meaningful survival of greater than 1 year is expected.S10.8-13 S10.8-17 CLINICAL STATEMENTS AND GUIDELINES I B-NR In patients with adult congenital heart disease with SCA due to VT or VF in the absence of reversible causes, an ICD is recommended if meaningful survival of greater than 1 year is expected.S10.8-13 S10.8-17 IIa B-NR In adults with repaired tetralogy of Fallot physiology with high-risk characteristics and frequent VA, an electrophysiological study can be useful to evaluate the risk of IIa B-NR In adults with repaired tetralogy of Fallot physiology and inducible VT/VF or spontaneous sustained VT, implantation of an ICD is reasonable if meaningful survival greater than IIa B-NR In patients with adult congenital heart disease with recurrent sustained monomorphic VT or recurrent ICD shocks for VT, catheter ablation can be effective.S10.8-21 S10.8-25 IIa B-NR In adults with repaired severe complexity adult congenital heart disease and frequent or complex VA, a beta blocker can be beneficial to reduce the risk of SCA.S10.8-26 IIa B-NR In patients with repaired moderate or severe complexity adult congenital heart disease with unexplained syncope and at least moderate ventricular dysfunction or marked hypertrophy, either ICD implantation or an electrophysiological study with ICD implantation for inducible sustained VA is reasonable if meaningful survival of greater than 1 year is IIb B-NR In patients with adult congenital heart disease and severe ventricular dysfunction (LVEF <35%) and symptoms of heart failure despite GDMT or additional risk factors, ICD implantation may be considered if meaningful survival of greater than 1 year is III: Harm B-NR In patients with adult congenital heart disease who have asymptomatic VA, prophylactic antiarrhythmic therapy with class Ic medications (ie, flecainide, propafenone) or amiodarone is potentially Synopsis Tetralogy of Fallot (TOF) is defined as, congenital heart disease with RVOT obstruction and ventricular septal defect, often requiring right ventricle to pulmonary artery conduit placement or pulmonary valve replace- ment; includes TOF and double-outlet right ventricle. Moderate complexity congenital heart disease is de- fined as congenital heart disease requiring intracardiac surgical repair, other than isolated atrial and ventricular septal defects; includes TOF, aortic stenosis, coarctation of aorta, and Ebstein anomaly of the tricuspid valve. Severe complexity congenital heart disease is defined as cyanotic congenital heart disease requiring intracar- diac repair in infancy, often with staging procedures; includes transposition of the great arteries, truncus ar- teriosus, and single ventricle anatomy (Figure 16). Recommendation-Specific Supportive Text 1. The association of VT with RV hemodynamic abnormalities was first established in patients with repaired TOF.S10.8-33 Multiple studies since that time have demonstrated the correlation of hemodynamic residue and ventricular dysfunction with risk of VT or SCD in patients with congeni- tal heart disease.S10.8-1,S10.8-3 S10.8-6,S10.8-18,S10.8-34 S10.8-36 Presentation with frequent or complex VA may indicate worsening hemodynamic function, coro- nary artery compromise, or decreased perfusion in the setting of ventricular hypertrophy. Evaluation may also include exercise testing to assess func- Careful evaluation of hemo- dynamic status for optimization of management Potentially treatable residual hemodynamic problems may be identified dur- ing hemodynamic evaluation, such as outflow tract stenosis or significant regurgitation, which may benefit from either catheter or surgical Patients with markedly reduced ventricular function, elevated end-diastolic pressures, or pulmonary hypertension should be treated for underlying hemodynamic problems as part of their arrhyth- mia management. 2. The correlation of residual hemodynamic abnor- malities with VA has been most extensively studied in patients with repaired TOF, where RV hyperten- sion, residual pulmonary outflow tract obstruction or regurgitation, and RV dilation are risk factors In these studies, frequent PVCs correlated with risk of clinical or inducible sustained VT. A com- bined approach of surgery for structural abnor- malities with map-guided arrhythmia surgery has been used with success,S10.8-3,S10.8-8,S10.8-10,S10.8-12 but elimination of VT circuits may be limited by deep endocardial or LV origin of VT and limitations of operative mapping; an empiric approach to VT surgery is generally not recommended as it has limited effectiveness and carries risk of ventricu- Pulmonary valve replace- ment in patients with TOF may result in improved hemodynamics and functional status, but it may not eliminate the risk of VTS10.8-3,S10.8-12 ; postopera- tive reassessment for the need for an ICD is per- formed after the early recovery period. 3. Correction of residual hemodynamic/structural abnormalities contributing to VT may improve ventricular function and reduce symptoms, but Recommendations for Adult Congenital Heart Disease (Continued) COR LOE Recommendations CLINICAL STATEMENTS AND GUIDELINES it may inadequately prevent the risk of subse- quent VT or SCA. The use of ICDs in adult con- genital heart disease patients for secondary prevention accounts for approximately 50% of implantations presently, at a mean age of 36 to Patientswithadultcongenital heart disease experience appropriate shock rates of 3% to 6% per year, with equivalent or slightly increased frequency of appropriate shocks for sec- ondary prevention indications.S10.8-14,S10.8-15,S10.8-17 Table 11. Congenital Heart Disease: Risk Factors for VA/SCD Congenital Heart Disease Incidence of VA Incidence of SCD Higher Risk Characteristics Simple complexity RV dilatation Pulmonary hypertension Moderate complexity Tetralogy of FallotS10.8-1,S10.8-2,S10.8-5,S10.8-6,S10.8 28,S10.8 34,S10.8 36,S10.8 Frequent or complex VA Sustained VT QRS duration 180 ms Inducible sustained VT Atrial tachycardia Decreased LVEF Dilated right ventricle Severe PR Severe PS Aortic stenosis S10.8 27,S10.8 44,S10.8 56 Severe LV hypertrophy Aortic stenosis mean pressure gradient >40 mmHg Ventricular dysfunction Coarctation of aortaS10.8 28,S10.8 29, 2% 2% Aneurysm at repair site Aortic stenosis Systemic hypertension Premature coronary artery disease Atrial fibrillation Wide complex tachycardia Mitral regurgitation Dilated RVOT Severe complexity Transposition of the great arteriesS10.8 27,S10.8 44 S10.8 48,S10.8 Atrial switch Atrial switch 2% 3% 9.5% Mustard repair Arterial switch 2% 1% Prior VSD closure cc-TGA 10% 17% 25% Unexplained syncope Atrial tachycardia Coronary orifice stenosis Systemic ventricular dysfunction Severe tricuspid regurgitation 10% 4% Multiple surgical repairs Coronary anomalies Ventricular dysfunction and/or hypertrophy Fontan repair for univentricular physiology*S10.8 27,S10.8 37, Longer duration of follow-up Ascites Protein-losing enteropathy *Univentricular physiology includes: Tricuspid atresia, Double inlet left ventricle, Mitral atresia, Hypoplastic left heart, Unbalanced AV septal defect. ASD indicates atrial septal defect; cc-TGA, congenitally corrected transposition of the great arteries; LV, left ventricular; LVEF, left ventricular ejection fraction; PR, pulmonary regurgitation; PS, pulmonary stenosis; RV, right ventricular; RVOT, right ventricular outflow tract; SCD, sudden cardiac death; VA, ventricular arrhythmia; VSD, ventricular septal defect; and VT, ventricular tachycardia. CLINICAL STATEMENTS AND GUIDELINES Patients with adult congenital heart disease expe- rience a higher rate of complications and inap- propriate shocks compared with other adult 4. Challenges of ICD implantation in patients with adult congenital heart disease may include ana- tomic complexity, intracardiac shunts, and limited vascular access to the ventricle. Patients with adult congenital heart disease receiving an ICD have an increased rate of complications of 26% to 45%, as well as inappropriate shocks in 15% to 25% of Limited studies on the use of subcutaneous implantable cardioverter- defibrillator implantation, particularly in patients with single ventricle anatomy,S10.8-41 report improved success by using right in addition to left parasternal lead positioning for screening.S10.8-42 Patients with a single ventricle or a systemic right ventricle may not tolerate defibrillation thresh- old testing, resulting in multiorgan system fail- ure. Patients with complex anatomy, such as older patients with univentricular physiology, or patients with significantly reduced ventricular function, marked hypertrophy, or multiple prior surgeries, may benefit from earlier consideration of heart transplantation before renal or liver dys- function progresses. 5. Patients with repaired TOF who are at an increased risk of sustained VT include those with prior pal- liative systemic to pulmonary shunts, unexplained syncope, frequent PVCs, atrial tachycardia, QRS duration 180 ms, decreased LVEF or diastolic dysfunction, dilated right ventricle, severe pulmo- nary regurgitation or stenosis, or elevated levels of BNP. Patients with TOF physiology and subop- timal hemodynamic status are more likely to have inducible sustained VT,S10.8-18,S10.8-19,S10.8-33,S10.8-35 and inducible sustained VT correlated with an increased risk of SCA in a multicenter cohort Evaluation of hemodynamics for residual abnormalities is important, with catheter or surgical treatment of important lesions prior to consideration of ICD implantation. 6. In a multicenter cohort, inducible sustained VT in patients with TOF was an independent risk factor for subsequent clinical VT or SCDS10.8-19 ; patients in that early study had cardiomegaly and prior palliative shunts. Patients with repaired Figure 16. Prevention of SCD in patients with adult congenital heart disease. Colors correspond to Class of Recommendation in Table 1. See Section 10.8 for discussion. *High-risk features: prior palliative systemic to pulmonary shunts, unexplained syncope, frequent PVC, atrial tachycardia, QRS duration 180 ms, decreased LVEF or diastolic dysfunction, dilated right ventricle, severe pulmonary regurgitation or stenosis, or elevated levels of BNP. Frequent VA refers to frequent PVCs and/or nonsustained VT. ACHD indicates adult congenital heart disease; BNP, B-type natriuretic peptide; EP, electrophysiological; ICD, implantable cardioverter-defibrillator; LVEF, left ventricular ejection fraction; PVC, premature ventricu- lar complexes; SCD, sudden cardiac death; TOF, tetralogy of Fallot; VA, ventricular arrhythmia; and VT, ventricular tachycardia. CLINICAL STATEMENTS AND GUIDELINES TOF account for approximately 50% of ICD implantations in adult congenital heart Appropriate ICD shocks occur in up to 7.7% per year of patients with TOF receiving the ICD for primary prevention, compared with 9.8% per year in patients with a secondary pre- In another study including patients with TOF as well as other lesions, inducible sustained VT did not correlate with subsequent appropriate Because of the high incidence of inappropriate shocks in 20% to 30% and compli- cations in at least 30% of patients with adult con- genital heart disease,S10.8-14 S10.8-17,S10.8-39,S10.8-40,S10.8-43 in addition to financial and psychological burdens, shared decision-making regarding primary preven- tion ICDs is essential. 7. In patients with recurrent sustained monomorphic VT, catheter ablation of VT can be effective.S10.8-21 S10.8-25 Hemodynamic repair, at the time that an arrhythmia is being ablated surgically, should be considered. For patients with complex adult congenital heart disease, care should be provided at experienced centers. After successful catheter ablation of VT, implantation of an ICD for those who do not have an ICD is an individu- alized decision based on overall functional and physi- ological status and shared decision making. Careful monitoring during follow-up for recurrent arrhyth- mias is essential. 8. The highest risk of SCD associated with repaired congenital heart disease reported from large con- temporaneous cohorts is in patients with transpo- sition of the great arteries with atrial baffle repair, Ebstein anomaly of the tricuspid valve, aortic ste- nosis, and univentricular physiology.S10.8-44 S10.8-47 Patients with Senning or Mustard atrial baffle repairs are at an increased risk for SCA, particularly The atrial baffle is noncom- pliant restricting ability to augment volume and may be associated with pulmonary vein stenosis and increased end-diastolic pressures. RV ischemia and infarction occur, with perfusion defects identi- fied by myocardial perfusion studies in >40% of patients in this population.S10.8-49,S10.8-50 Risk factors for cardiac arrest in patients with transposition and atrial baffle repairs include prior ventricu- lar septal defect closure, symptoms of HF, atrial arrhythmia, RVEF <30% to 35%, and QRS dura- In the single multicenter study assessing outcomes after implantation of an ICD in patients with prior atrial baffle repair of transposition of the great arteries, the lack of beta blockers was associated with a high risk of appro- priate ICD therapy.S10.8-26 Atrial arrhythmias fre- quently precede VT in transposition patients, and treatments for atrial tachycardia including cath- eter ablation, antitachycardia pacing algorithms, and beta blockers are important to reduce ICD 9. The risk of SCD is increased among patients with adult congenital heart disease compared with the general population, with the median age at death ranging from 30 to 49 years of The risk of SCD is highest among patients with moderate or severe complexity congenital heart disease, and accounts for approximately 25% of cardiac causes Patients with septal defects and a positive fam- ily history of septal defects, cardiomyopathy, or bundle-branch block/conduction defects may have the gene mutation NKX2.5, which portends an increased risk of early SCD; genetic testing and early consideration of ICD implantation if positive Patients with repaired complex forms of congenital heart disease have undergone multiple intracardiac surgeries in the first few decades of life with resultant hypertro- phy and risk for subendocardial ischemia as well as scar formation contributing to VT/VF. Risk fac- tors for SCD include increasing complexity of heart disease, VA, SVT, progressive increase in QRS duration, systemic ventricular dysfunction, and subpulmonary ventricular dysfunction.S10.8-1,S10.8-5, Extrapolation of data regarding specific measures of ventricular function warranting implantation of primary prevention ICDs from adult patients with NICM is unrealistic. The development of unex- plained syncope in patients with moderate or severe complexity adult congenital heart disease may be a harbinger of risk for SCD; electrophysi- ological study with consideration for an ICD as primary prevention can be beneficial. 10. ICDs implanted in patients with adult con- genital heart disease, who are in their 40s and 50s, for primary prevention indications now account for >40% to 67% of implanted devices in patients with adult congenital heart In these patients, appropriate shocks are delivered in 14% to 22% of patients in the first 3 to 5 years of fol- In patients with con- genital heart disease and severely depressed ventricular function, or single ventricle anat- omy, defibrillation threshold testing may pose excessively high risk. In patients without vas- cular access or prior Fontan repairs, the risk of reoperation with sternotomy for epicardial ICD implantation may outweigh the potential ben- efits, and consideration for transplant evaluation may be preferable. Subcutaneous implantable CLINICAL STATEMENTS AND GUIDELINES cardioverter-defibrillator implantation may be an appropriate option for some patients.S10.8-42,S10.8-53 11. Adult patients with complex adult congenital heart disease typically have hypertrophy and ventricular dysfunction of varying degrees, increasing their risk for worsening ventricular function with antiarrhythmic medications. In the only large study of antiarrhythmic medi- cations for congenital heart disease, the use of flecainide was associated with proarrhyth- mia in 5.8% of patients and SCA in 3.9% of The use of amiodarone is gener- ally reserved for refractory symptomatic VA or asymptomatic VA that can aggravate ventricu- lar dysfunction, due to the high risk of adverse effects including thyroid dysfunction, particularly among females and patients with univentricular 11. DEFIBRILLATORS OTHER THAN TRANSVENOUS ICDS 11.1. Subcutaneous Implantable Cardioverter-Defibrillator Recommendations for Subcutaneous Implantable Cardioverter- Defibrillator References that support the recommendations are summarized in Online Data Supplement 55. COR LOE Recommendations I B-NR In patients who meet criteria for an ICD who have inadequate vascular access or are at high risk for infection, and in whom pacing for bradycardia or VT termination or as part of CRT is neither needed nor anticipated, a subcutaneous implantable cardioverter-defibrillator is IIa B-NR In patients who meet indication for an ICD, implantation of a subcutaneous implantable cardioverter-defibrillator is reasonable if pacing for bradycardia or VT termination or as part of CRT is neither needed nor III: Harm B-NR In patients with an indication for bradycardia pacing or CRT, or for whom antitachycardia pacing for VT termination is required, a subcutaneous implantable cardioverter-defibrillator should not be Synopsis In patients being considered for a subcutaneous im- plantable cardioverter-defibrillator, a preimplant ECG to establish QRS-T wave morphology is needed to re- duce the risk of under sensing of VT/VF and the risk of inappropriate shocks.S11.1-9 S11.1-11 The subcutaneous implantable cardioverter-defibrillator is implanted using primarily anatomical landmarks, thereby minimizing the need for fluoroscopy. The subcutaneous implantable cardioverter-defibrillator consists of a pulse generator that is placed at the midaxillary line between the fifth and sixth intercostal spaces and a lead with 2 sensing electrodes and a shocking coil, positioned subcutane- ously adjacent to the sternum. As with the transvenous ICD, the pulse generator housing serves as an electrode for defibrillation but, in addition, it can also serve as an optional electrode for sensing. The subcutaneous implantable cardioverter-defibrillator cannot achieve adequate arrhythmia sensing for all patients, and elec- trocardiographic screening to assess sensing is required prior to implantation.S11.1-10,S11.1-11 Some advocate exer- cise testing after device implantation to ensure proper sensing with exercise. Both transvenous and subcutaneous implantable cardioverter-defibrillators have SVT-VT discriminators that can be programmed to facilitate discrimination of SVT from VT; however, these discriminators do not always work. If sustained VT is confirmed, therapy to terminate the arrhythmia is delivered. All ICDs provide shocks to terminate VT or VF, but shocks in an awake patient are painful and associated with decreased QoL. Transvenous ICDs are capable of bradycardia pacing as well as antitachycardia pacing that can terminate many VTs painlessly. Subcutaneous implantable cardioverter- defibrillators provide limited postshock bradycardia pacing but do not provide either bradycardia or antit- achycardia pacing. The subcutaneous implantable cardioverter-defibril- lator recommendations supplant, but do not nullify, the need for waiting periods and other requirements to be satisfied for ICD/CRT implantation specified in other parts of this document. Recommendation-Specific Supportive Text 1. The subcutaneous implantable cardioverter- defibrillator was designed to avoid the need for venous access and some of the complications of inserting transvenous lead(s)S11.1-1 S11.1-4 that include pneumothorax, hemothorax, and cardiac Difficulties in achieving venous access can prolong the implantation procedure and occasionally result in failed ICD implantation. These difficulties are more likely to be encoun- tered in patients with limited venous access such as patients with ESRD. In a study of 27 patients with ESRD, the subcutaneous implantable car- dioverter-defibrillator was not associated with an increased risk of procedural complications or The risk of infection appears to be lower with subcutaneous implant- able cardioverter-defibrillators than with transve- Therefore, a subcutaneous CLINICAL STATEMENTS AND GUIDELINES implantable cardioverter-defibrillator may be pre- ferred in patients who are at high risk of infec- tion, such as those with a prior device infection, ESRD, diabetes mellitus, or who are chronically immunosuppressed. 2. Nonrandomized studies show that the subcu- taneous implantable cardioverter-defibrillator reliably detects and converts VF during defibril- lation threshold testing and successfully termi- nates spontaneous sustained VT that occurs In 1 study of 314 patients, the 180-day complication-free rate was 99%, and the success of VF termination with first shock was >90%.S11.1-2 All spontaneous epi- sodes of VT/VF recorded in 21 patients (6.7%) were successfully converted, and there were no lead failures, endocarditis or bacteremia, tam- ponade, cardiac perforation, pneumothorax, or hemothorax associated with the subcutaneous patients enrolled in the EFFORTLESS (Evaluation of Factors Impacting Clinical Outcome and Cost Effectiveness of the S-ICD) registry,S11.1-3 the com- plication-free rate was 94%, at 360 days. First shock conversion efficacy was 88% with 100% overall successful clinical conversion after a maxi- mum of 5 shocks. In 882 patients enrolled in investigational device exemption trials and the 111 spontaneous VT/ VF events were treated in 59 patients; 90.1% were terminated with 1 shock, and 98.2% were terminated within the 5 available shocks. The estimated 3-year inappropriate shock rate was 13.1% most due to oversensing of cardiac sig- nals, and mortality was 4.7%. Device-related complications occurred in 11.1% of patients. An ongoing trial will compare the effect of the sub- cutaneous implantable cardioverter-defibrillator with that of the transvenous ICD on the out- comes of inappropriate shocks, complications, shock efficacy, and mortality.S11.1-13 3. The subcutaneous implantable cardioverter- defibrillator is incapable of bradycardia pac- ing, biventricular pacing, or antitachycardia pacing. Therefore, patients who need any of these types of pacing from an ICD should not be offered a subcutaneous implantable cardioverter- Some clinical scenarios may come up in which a transvenous pacemaker for bradycardia pacing in a patient with a subcutane- ous implantable cardioverter-defibrillator which is needed; this can be performed as long as the pacing is not unipolar. Leadless pacing devices for patients who require bradycardia pacing will be evaluated with the subcutaneous implantable cardioverter-defibrillator in the near future. 11.2. Wearable Cardioverter-Defibrillator Recommendations for Wearable Cardioverter-Defibrillator References that support the recommendations are summarized in Online Data Supplement 56. COR LOE Recommendations IIa B-NR In patients with an ICD and a history of SCA or sustained VA in whom removal of the ICD is required (as with infection), the wearable cardioverter-defibrillator is reasonable for the prevention of SCD.S11.2-1 S11.2-4 IIb B-NR In patients at an increased risk of SCD but who are not ineligible for an ICD, such as awaiting cardiac transplant, having an LVEF of 35% or less and are within 40 days from an MI, or have newly diagnosed NICM, revascularization within the past 90 days, myocarditis or secondary cardiomyopathy or a systemic infection, the wearable cardioverter-defibrillator may be Synopsis The wearable cardioverter-defibrillator is a vestlike de- vice worn under the clothing that continuously moni- tors the heart rhythm and automatically delivers an electric shock when VF or VT is detected. This device is intended to be worn continuously, 24 hours per day, except when the wearer is bathing or showering. The wearable cardioverter-defibrillator has been ap- proved in the United States by the US Food and Drug Administration for patients who are at risk for SCA and are not candidates for or refuse an implantable A science advisory from the AHA summarizes the data and recommendations for the use of the wearable cardioverter-defibrillator.S11.2-4 Effective- ness of the wearable cardioverter-defibrillator in recog- nition and defibrillation of VF has been demonstrated in a number of studies, although no RCTs support the use of the wearable cardioverter-defibrillator. Among 3569 patients who received the device for various reasons, for at least 1 day in the US manufacturer registry, there were 80 VT/VF events in 59 patients, with a frequency of 1.7% per patient-year. First shock efficacy was 99%, with postshock survival of 90%. Overall, 2% of the pa- tients received an inappropriate shock.S11.2-1 Recommendation-Specific Supportive Text 1. Removal of an ICD for a period of time, most commonly due to infection, exposes the patient to risk of untreated VT/SCD unless monitoring and access to emergency external defibrillation is maintained. In 1 series of 354 patients who received the wearable cardioverter-defibrillator, the indication was infection in 10%.S11.2-3 For patients with a history of SCA or sustained VA, CLINICAL STATEMENTS AND GUIDELINES the wearable cardioverter-defibrillator may allow the patient to be discharged from the hospital with protection from VT/SCA until the clinical situation allows reimplantation of an ICD. 2. The patients listed in this recommendation are represented in clinical series and registries that demonstrate the safety and effectiveness of the wearable cardioverter-defibrillator. Patients with recent MI, newly diagnosed NICM, recent revascularization, myocarditis, and secondary cardiomyopathy are at increased risk of VT/SCA. However, the wearable cardioverter-defibrillator is of unproven benefit in these settings, in part because the clinical situation may improve with therapy and time. In patients awaiting transplant, even with anticipated survival <1 year without transplant, and depending on clinical factors such as use of intravenous inotropes and ambient VA, a wearable cardioverter-defibrillator may be an alternative to an ICD. 11.3. Automated External Defibrillator External defibrillation can save lives when used with- in minutes of the onset of VF. The AED is an efficient method of delivering defibrillation to persons expe- riencing out-of-hospital cardiac arrest, and its use by first responders is safe and effective.S11.3-1 S11.3-3 Federal efforts have been effective in placing AEDs in airports/ airplanes and federal buildings, while varying efforts at the state and community levels have been effective in placing AEDs in many. but not all, schools, sporting events, high-density residential sites, and airports as well as in police and fire department vehicles.S11.3-4 S11.3-7 Resuscitation protocols with or without AED placement are required in most states for fitness clubs, although alternate indoor exercise facilities may have higher rates of arrest and provide for increased survival over other indoor public sites.S11.3-8 In a study population of 21 million, survival to hospital discharge was nearly twice as high when an AED was applied for out-of-hospital Expanded and coordinated place- ment of AEDs in the community, including in high-risk geographic locations such as schools and organized sports arenas, can substantially increase the proportion of patients with cardiac out-of-hospital cardiac arrest who receive AED therapy.S11.3-10 The US Food and Drug Administration has approved over-the-counter sales of AEDs. Approximately 70% of SCAs occur in the home, and the rate of survival to hospital discharge after AED placement by emergency medical services is significant- ly lower for arrest at home (12%) versus public settings However, in an RCT of AEDS, home AED placement did not improve the survival of patients re- covering from an anterior MI.S11.3-12 Appropriate device location to reduce time delay after onset of SCA is criti- cal. In addition to prevention, critical components of survival from SCA include immediate recognition and activation of the emergency response system, early high-quality CPR, and rapid defibrillation for shockable 12. SPECIAL CONSIDERATIONS FOR CATHETER ABLATION Recommendations for Catheter Ablation References that support the recommendations are summarized in Online Data Supplement 57. COR LOE Recommendations I C-LD In patients with bundle-branch reentrant VT, catheter ablation is useful for reducing the risk of recurrent VT and ICD shocks.S12-1 S12-3 IIa B-NR In patients with structural heart disease who have failed endocardial catheter ablation, epicardial catheter ablation can be useful for reducing the risk of recurrent monomorphic Synopsis Bundle-branch reentrant VT is due to reentry involving the bundle branches. Catheter ablation is the preferred therapy for this VT, which is encountered in <10% of patients with recurrent sustained monomorphic VT and structural heart disease (see Section 7.2.3). Recommendation-Specific Supportive Text 1. Bundle-branch reentrant VT can occur in any form of heart disease associated with slow infra- Hisian conduction. 