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. The most common mecha- nism involves antegrade conduction over the right bundle branch and retrograde conduction over the left bundle branch, thereby produc- ing left bundle-branch block QRS morphology during VT, which is often rapid and poorly tol- erated. Catheter ablation of the right or left bundle branch interrupts the circuit and is usually After ablation, severely impaired atrioventricular conduction can be present, requir- ing permanent pacing, which can have hemody- Many patients have other inducible scar related VTs or meet eligibil- ity for an ICD due to severity of associated heart disease. 2. Endocardial catheter ablation failure can be due to location of the arrhythmia substrate in the midmyocardium or epicardium, and this is more likely in patients with nonischemic rather than ischemic cardiomyopathy, and in arrhythmogenic right ventricular cardiomyopathy.S12-7 S12-9 In the CLINICAL STATEMENTS AND GUIDELINES epicardial ablation was required in 30% of patients with VT related to NICM com- pared with 1.2% of patients with ischemic car- diomyopathy. A wide QRS with marked slurring of the initial portion of the QRS and a QS com- plex in the lateral or inferior leads during VT sug- gests an epicardial circuit in NICM, but the ECG does not reliably predict epicardial VT locations in patients with prior MI. Preprocedural cardiac MRI and intraprocedural electroanatomic mapping are useful tools to guide the localization of epi- cardial scar that may be the source of reentrant Pericardial adhesions prevent percu- taneous access in some patients, notably many with prior cardiac surgery. Percutaneous pericar- dial access for mapping and ablation is associated with a serious complication rate of approximately 5% and tamponade from RV puncture or lac- eration that can require emergent surgery or be fatal, coronary artery injury and phrenic nerve injury can occur.S12-11,S12-12 Reported experience is from tertiary referral centers. 13. POSTMORTEM EVALUATION OF SCD Recommendations for Postmortem Evaluation of SCD References that support the recommendations are summarized in Online Data Supplement 58. COR LOE Recommendations I B-NR In victims of SCD without obvious causes, a standardized cardiac-specific autopsy is I B-NR In first-degree relatives of SCD victims who were 40 years of age or younger, cardiac evaluation is recommended, with genetic counseling and genetic testing performed as indicated by clinical findings.S13-3 IIa B-NR In victims of SCD with an autopsy that implicates a potentially heritable cardiomyopathy or absence of structural disease, suggesting a potential cardiac channelopathy, postmortem genetic testing IIa C-LD In victims of SCD with a previously identified phenotype for a genetic arrhythmia- associated disorder, but without genotyping prior to death, postmortem genetic testing can be useful for the purpose of family risk Recommendation-Specific Supportive Text 1. A comprehensive postmortem protocol has been recommended for the routine evaluation of sub- jects (typically <40 years of age) who die sud- denly without a prior diagnosis of a condition and circumstances of death that could be reasonably implicated in the cause of unexpected SCD.S13-1 One study documented the added value of post- mortem examination at a specialized cardiac with particular value for clarifying an apparent overdiagnosis of cardiomy- opathy by nonspecialized centers. Pathological findings limited to the specialized conduction sys- tem were demonstrated in 22% of cases.S13-9 A misdiagnosis of cardiomyopathy was reported in 37% of referred cases that were ultimately deter- mined to be structurally normal. The etiologic data for specialized cardiac evaluation are not general- izable to the overall population because of skew- ing of age at the time of SCD. In another study of SCD patients at ages ranging from <1 year to >80 years (mean, 38.2 years; median, 38 years), the peak incidence of SCD occurred between the ages of 31 and 60 years, with a 5- to 7-fold excess of males/females in that age range.S13-10 For the overall group, 42% of SCD were due to ischemic heart disease, 12% viral myocarditis, and 5% cardiomyopathy, with 15% being unexplained by autopsy. For the subgroup <35 years of age, 13.5% were attributed to ischemic heart disease and 24.9% were unexplained. In the subgroup >55 years of age, only 0.8% were unexplained. In patients who die suddenly despite an ICD, interrogation of the ICD is important to confirm proper device functioning and can provide infor- mation on the mechanism of death. 2. Comprehensive cardiac screening including 12-lead ECG, possible signal averaged ECG, echocardiogram, and ambulatory rhythm moni- toring or exercise testing of first-degree relatives of decedents with sudden unexpected death may identify a probable heritable cardiac cause of death in up to 30% of cases.S13-11 S13-13 Genetic testing should be targeted based on the results of Genetic testing in selected first-degree relatives may result in identification of inherited conditions including long QT syndrome, catecholaminergic polymorphic ventricular tachy- cardia, Brugada syndrome, arrhythmogenic right ventricular cardiomyopathy, and HCM in 4% to 3. For the purpose of family risk profiling, it is important to use the disease-specific genetic test panel that corresponds to the autopsy findings. Risk profiling of family members of an SCD victim suspected of having an inherited cardiomyopathy at autopsy is important. Although phenotyping of surviving family members is crucial, genotyp- ing of the SCD proband provides a mechanism for efficient follow-up evaluation of those rela- tives with the disease-causing mutation found CLINICAL STATEMENTS AND GUIDELINES in the proband. To be able to harvest quality DNA for such testing, medical examiners, hos- pital pathologists, and private pathologists need standards for harvesting and storing samples for later genetic testing. Family members of SCD probands who died suddenly (first cardiac event, death from natural causes, last seen alive and well within 12 hours), with autopsy findings showing structural abnormalities of uncertain significance (eg, ventricular hypertrophy, myocardial fibrosis, or minor ischemic heart disease [n=41]) had a 51% prevalence of genetic variants associated with sudden arrhythmic deaths, compared with 47% among a comparison group in which pro- band autopsies were completely negative.S13-15 4. Identification of the genotype can facilitate family 14. TERMINAL CARE Recommendations for Terminal Care References that support the recommendations are summarized in Online Data Supplement 59. COR LOE Recommendations I C-EO At the time of ICD implantation or replacement, and during advance care planning, patients should be informed that their ICD shock therapy can be deactivated at any time if it is consistent with their goals and preferences. I C-EO In patients with refractory HF symptoms, refractory sustained VA, or nearing the end of life from other illness, clinicians should discuss ICD shock deactivation and consider the patients goals and preferences. Synopsis A particularly challenging area of medicine is recogniz- ing when life-prolonging therapies may become bur- densome or even harmful. This is particularly true near the end of life for patients with ICDs in whom once life- prolonging shocks may only cause unnecessary morbid- ity and distress to both patients and loved ones. Recommendation-Specific Supportive Text 1. Current evidence suggests that many patients are unaware of the possibility that their ICD can be deactivated without surgery.S14-1 S14-3 During deci- sion-making, clinicians do not routinely inform patients about ICD deactivation.S14-4 Clinicians even disagree on whether discussions of deac- tivation should occur when patients are making a decision about an ICD-related procedure.S14-5 As a result, patients often do not include wishes about deactivation in advance care planning Consequently, surrogates usually make decisions about ICD deactivation without any prior discussions with the patient.S14-6 In hypo- thetical scenarios, patients with ICDs were able to identify scenarios in which they might choose to deactivate their ICD.S14-1,S14-7 This discussion can occur at any time, but it is particularly important to have it at the time of initial ICD implantation, at the time of reimplantation, and during prepa- ration of advance care plans. 2. When ICDs are not deactivated at the end of life, patients and families suffer unnecessarily. Families have had unpleasant experiences of watching their loved one die while getting shocked repeat- edly by an ICD.S14-8 In 1 survey of hospice staff, half of those surveyed noted that a deceased patient had been shocked by an ICD during the year prior to the survey.S14-9 This is unnecessary and easily preventable by having caring, patient-centered discussions with patients and their loved ones. In general, patients want their clinicians to initiate so this recommenda- tion is carefully worded to put the responsibility of initiating the discussion on the clinician. Ethically, patients and surrogates are free to choose to deactivate antitachycardia function.S14-11 S14-13 Most patients only elect deactivation of the anti- tachycardia functions while leaving the pacing function on. Even at the end of life, pacing (either for bradycardia or for resynchronization therapy) may be an important aspect of the patient s QoL and may facilitate more alert and meaningful personal interactions. These differences are easily misunderstood, so they need careful explanation. 15. SHARED DECISION-MAKING Recommendations for Shared Decision-Making References that support the recommendations are summarized in Online Data Supplement 60. COR LOE Recommendations I B-NR In patients with VA or at increased risk for SCD, clinicians should adopt a shared decision-making approach in which treatment decisions are based not only on the best available evidence but also on the patients health goals, preferences, and I B-NR Patients considering implantation of a new ICD or replacement of an existing ICD for a low battery should be informed of their individual risk of SCD and nonsudden death from HF or noncardiac conditions and the effectiveness, safety, and potential complications of the ICD in light of their health goals, preferences, and CLINICAL STATEMENTS AND GUIDELINES Synopsis During most of their lives, people prefer to do everything possible to prevent SCD and prolong life. However, many people may get to a point in their lives where SCD is not the worst outcome. Patients may report a desire to die in their sleep.S15-6 Decisions related to SCD can be quite emotional; according to the patient s wishes, shared de- cision regarding end-of-life therapy making may involve caregivers such as family members or friends. Recommendation-Specific Supportive Text 1. Consideration of patient preferences is impor- tant for VA diagnosis and management deci- sions. Patient preferences for invasive therapies and acceptance of SCD risk vary and may evolve throughout the course of their illness. The writing committee endorses a shared decision-making approach as part of the general care for patients at risk for VA and SCD. A commonly accepted def- inition of the shared decision-makingS15-7 includes 4 components: 1) at least 2 participants, the cli- nician and patient, be involved; 2) both parties share information; 3) both parties take steps to build a consensus about the preferred treatment; and 4) an agreement is reached on the treatment to implement. Sharing a decision does not mean giving a patient a list of risks and benefits and telling them to make a decision a practice some authors have called abandonment. S15-8 Notably, a recommendation based on evidence or guide- lines alone is not shared decision-making. Rather, a recommendation based both on the evidence as well as an understanding of the patients health goals, preferences, and values is essential to achieving true shared decision-making. Also, the possibility of deactivation of an existing ICD should be discussed with patients who have ter- minal illnesses. 2. ICDs prolong lives as highlighted in many places within this guideline. However, a patient with HF or advanced noncardiac illness may elect to forgo replacement of an ICD when faced with the pros- pect of continual decline in health and functional status from either progressive HF or some other competing morbidity. Unfortunately, research suggests that patients are ill-informed when faced with understanding the risks, benefits, and downstream burdens of their ICDs. Patients with an ICD tend to overes- timate the benefit of this therapy and underes- timate its risks.S15-1 S15-3 Likewise, patients who decline an ICD also frequently underestimate their personal risk of VA and SCD.S15-4,S15-5 Stud- ies of clinician decision-making demonstrate that clinicians often overestimate the benefits while downplaying the potential harms.S15-3 In kind, ICD replacement is also an important point in time where patients and clinicians should discuss whether replacing an ICD is still consistent with the patients goals. What made sense at 70 years of age may not make sense at 80 years of age. Patients may have had progressive disease or developed poor QoL. These factors can all change the risk/benefit ratio of the ICD and the patients preferences. 16. COST AND VALUE CONSIDERATIONS The key principles of value assessment as part of clini- cal practice guidelines have been discussed in detail.S16-1 Economic outcomes of clinical management strategies can be documented empirically using the same re- search designs as used in establishing clinical outcomes, including RCTs and observational comparisons. In ad- dition, simulation models are often used to assess the value of management strategies, because the standard for cost-effectiveness studies is to compare life-time outcomes, and clinical studies usually have follow-up of a few years at most. Standards for economic model- ing in health care have been published by an expert Economic assessments of alternative management strategies for VA and prevention of SCD have primarily andobser- In all studies, patients who received ICDs had higher long-term costs. The high initial cost of the ICD device and the implantation procedure leads to higher long- term costs, because there are few, if any, subsequent cost-savings from implanting an ICD. ICDs without resynchronization capability do not reduce hospital re- admissions and may increase late costs due to device monitoring, complications, and replacement. However, the cost of the device and the procedure may change significantly over time. The trial based assessments of the cost-effectiveness of the ICD are based on 3 to 6 years of follow-up, which is considerably shorter than the lifetime perspective that is standard in cost-effectiveness models. Because most of the incremental cost of the ICD is incurred imme- diately, while most of the potential effectiveness (life- years of survival added by the ICD) is accrued over many years, estimates of ICD cost-effectiveness based on lim- ited trial follow-up have a systematic bias toward show- ing lower value. Trial based economic studies that pro- jected long-term ICD outcomes have consistently found more favorable cost-effectiveness ratios than estimates restricted to the duration of trial follow-up.S16-4 S16-7 A CLINICAL STATEMENTS AND GUIDELINES lifetime simulation model applied to each major trial of primary prevention ICDs also reported consistently more favorable estimates of cost-effectiveness than the estimates based on limited trial follow-up.S16-11 Because the framework proposed for assessing value in ACC/ AHA clinical practice guidelines uses benchmarks based on lifetime estimates,S16-1 we have generally relied on the model-based estimates of ICD cost-effectiveness in applying value ratings to recommendations in this guideline. The initial cost of an ICD device is similar regardless of the clinical indication, so variations in ICD cost-ef- fectiveness are driven primarily by potential differences in clinical effectiveness in extending survival in differ- ent patient populations. The effect of the years of life added by an ICD on its incremental cost-effectiveness ratio is illustrated in Figure 17: the cost-effectiveness ratio becomes rapidly unfavorable as the extension in survival time falls below 1 year, particularly below 0.5 year. This inverse relation strongly suggests that the value provided by an ICD will be highest when the risk of arrhythmic death due to VT/VF is relatively high and the risk of nonarrhythmic death (either cardiac or noncardiac) is relatively low, such that a meaning- ful increase in survival can be expected from the ICD. Thus, appropriate patient selection is fundamental to high value care in using the ICD to prevent SCD. It should also be recognized that cost-effectiveness is also influenced by the costs for the ICD and implanta- tion procedure, which are likely to change significantly over time. The empirical evidence suggests that ICDs are not effective for primary prevention of SCD when im- planted early after CABGS16-15 or an acute myocardial An analysis of individual patient lev- el data from 3 secondary prevention trialsS16-18 showed a significant variation (P=0.011) in the clinical effec- tiveness of ICDs between patients with an LVEF 35% (hazard ratio: 0.66) and an LVEF >35% (hazard ratio: 1.2). Some studies and simulation models suggest that ICDs might prolong life expectancy to a greater extent when used in higher-risk patients than in lower- In contrast, there is little evidence of variation in the effectiveness or cost-effectiveness of the ICD based on factors such as age or sex.S16-20 Most studies of ICD effectiveness and value have been per- formed on patients with reduced LV function due to prior MI or NICM. There are few data on the effec- tiveness or value of an ICD for other potential clinical indications, such as cardiac channelopathies or HCM, although studies have suggested that their potential cost effectiveness in such patients will depend on their underlying risk of SCD, with little evidence of value in 17. QUALITY OF LIFE ICD implantation has not had a significant effect on QoL in the overall population of patients enrolled in Several studies have, however, demon- strated that the subset of patients who receive inap- propriate ICD shocks have worse QoL than patients who have an ICD but have not had inappropriate Because an ICD is designed to prevent SCD rather than to reduce symptoms, it would not be ex- pected to improve QoL or functional status directly, but may have indirect, negative effects in some pa- tients due to device complications, or indirect, positive effects in some patients due to reassurance of having a protective device in place. Figure 17. Incremental cost-effectiveness of ICD by years of life added* (example). *Figure based on formula: Incremental cost-effectiveness ratio = $50000/QALYs. CE indicated cost effectiveness, ICD, implantable cardioverter-defibrillator; LYA, life year added; and QALYs, quality-adjusted life-years. CLINICAL STATEMENTS AND GUIDELINES 18. EVIDENCE GAPS AND FUTURE RESEARCH NEEDS Despite the numerous advances in risk stratification for SCD and prevention and treatment of SCD and VA, many gaps in knowledge remain. These gaps include: Identification of patients who are most likely to benefit from an ICD among all ICD-eligible patients. The role of novel markers (including genetic and imaging markers) and combinations of markers should be studied. Characterizing the role of the ICD in patient sub- groups not well-represented in the pivotal ICD trials. Such subgroups include patients 80 years of age and those with kidney disease, espe- cially patients with ESRD on dialysis, or multiple comorbidities. Methods to identify and treat patients at high indi- vidual risk for SCD who are not identified by cur- rent ICD eligibility criteria, including those who are within 40 days of an MI. Defining the role of the ICD in patients with HCM, arrhythmogenic right ventricular cardiomyopathy, cardiac sarcoidosis, and inherited cardiac chan- nelopathies in prospective studies (preferably RCT). Determining the best approach to patients due for elective ICD generator replacement due to battery depletion, but who may now be at low risk for SCA, such as if significant LVEF improvement has occurred. Obtaining more data on the efficacy and effec- tiveness of the subcutaneous implantable cardio- verter-defibrillator, compared with transvenous ICDs and on the extent of testing required, and its use with other novel technologies, including lead- less pacemakers. Conducting RCTs on catheter ablation of VT in ischemic heart disease and cardiomyopathies that evaluates procedural end points, mortality, arrhythmia suppression, QoL, and costs. Improving identification of individuals without sig- nificant ventricular dysfunction who are at risk of SCD. Identifying mechanisms and risk factors for SCD in patients with HFpEF. Improving emergency response to out-of-hospital cardiac arrest. Developing better methods for identifying and ablating the arrhythmia substrate in structural heart disease. Developing better risk stratification of diseases and syndromes associated with sudden death, includ- ing ischemic heart disease, NICM, adult congenital heart disease, and Brugada syndrome. Identifying what causes different types of long QT syndrome, catecholaminergic polymorphic ven- tricular tachycardia, Brugada syndrome, HCM, and arrhythmogenic right ventricular cardiomyopathy and advancing the genotype-phenotype relation- ships, genotype-dependent risk, and genotype- based tailoring of therapies for patients with inherited cardiomyopathies and inherited channelopathies. Defining the most appropriate and beneficial use of wearable cardioverter-defibrillators. Developing methods to identify and treat patients at high personal risk for SCD who are not identi- fied by current ICD eligibility criteria. Defining the role of CMR in enhancing risk strati- fication for SCD. Increasing research funding in this area, through ex- isting and new mechanisms is critically important. Some have proposed research funding strategies that would offer business incentives to the insurance industries, while providing support for unresolved research goals. Such approaches should be tested. ACC/AHA TASK FORCE MEMBERS GlennN.Levine,MD,FACC,FAHA,Chair;PatrickT.O Gara, MD, MACC, FAHA, Chair-Elect; Jonathan L. Halperin, MD, FACC, FAHA, Immediate Past Chair*; Sana M. Al-Khatib, MD, MHS, FACC, FAHA; Joshua A. Beckman, MD, MS, FAHA; Kim K. Birtcher, MS, PharmD, AACC; Biykem Boz- kurt, MD, PhD, FACC, FAHA*; Ralph G. Brindis, MD, MPH, MACC*; Joaquin E. Cigarroa, MD, FACC; Anita Deswal, MD, MPH, FACC, FAHA; Lesley H. Curtis, PhD, FAHA*; Lee A. Fleisher, MD, FACC, FAHA; Federico Gentile, MD, FACC; Samuel Gidding, MD, FAHA*; Zachary D. Goldberger, MD, MS, FACC, FAHA; Mark A. Hlatky, MD, FACC, FAHA; John Ikonomidis, MD, PhD, FAHA; Jos A. Joglar, MD, FACC, FAHA; Laura Mauri, MD, MSc, FAHA; Barbara Rie- gel, PhD, RN, FAHA; Susan J. Pressler, PhD, RN, FAHA*; Duminda N. Wijeysundera, MD, PhD PRESIDENTS AND STAFF American College of Cardiology Mary Norine Walsh, MD, FACC, President Shalom Jacobovitz, Chief Executive Officer William J. Oetgen, MD, MBA, FACC, Executive Vice President, Science, Education, Quality, and Publishing Amelia Scholtz, PhD, Publications Manager, Science, Education, Quality, and Publishing American College of Cardiology/ American Heart Association Katherine A. Sheehan, PhD, Director, Guideline Strategy and Operations *Former Task Force member; current member during the writing effort. CLINICAL STATEMENTS AND GUIDELINES Abdul R. Abdullah, MD, Science and Medicine Advisor Sam Shahid, MBBS, MPH, Associate Science and Medicine Advisor American Heart Association John J. Warner, MD, President Nancy Brown, Chief Executive Officer Rose Marie Robertson, MD, FAHA, Chief Science and Medicine Officer Gayle R. Whitman, PhD, RN, FAHA, FAAN, Senior Vice President, Office of Science Operations Prashant Nedungadi, PhD, Associate Science and Medicine Advisor, Office of Science Operations Jody Hundley, Production and Operations Manager, Scientific Publications, Office of Science Operations ARTICLE INFORMATION This document was approved by the American College of Cardiology Clinical Policy Approval Committee, the American Heart Association Science Advi- sory and Coordinating Committee, and the Heart Rhythm Society in Sep- tember 2017, and the American Heart Association Executive Committee in October 2017. The Comprehensive RWI Data Supplement table is available with this article at https://www.ahajournals.org/doi/suppl/10.1161/CIR.0000000000000549. A Data Supplement is available with this article at https://www.ahajournals. org/doi/suppl/10.1161/CIR.0000000000000549. This article has been copublished in the Journal of the American College of Cardiology and HeartRhythm. Copies: This document is available on the World Wide Web sites of the American College of Cardiology (www.acc.org), the American Heart Associa- tion (professional.heart.org), and the Heart Rhythm Society (www.hrsonline. org). A copy of the document is available at http://professional.heart.org/ statements by using either Search for Guidelines & Statements or the Browse by Topic area. To purchase additional reprints, call 843-216-2533 or e-mail kelle.ramsay@wolterskluwer.com. The expert peer review of AHA-commissioned documents (eg, scientific statements, clinical practice guidelines, systematic reviews) is conducted by the AHA Office of Science Operations. For more on AHA statements and guide- lines development, visit https://professional.heart.org/statements. Select the Guidelines & Statements drop-down menu near the top of the webpage, then click Publication Development. 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