For example, patients with ASD who underwent surgery before the age of 25 years had better long-term outcomes and a lower incidence of atrial arrhythmias than those who underwent surgery later in life.475 Closure of significant atrial septal defects in adults even later in life improves morbidity and survival476 but is associated with new (7%) or recurrent (60%) AT.475 Arrhythmias still can be treated successfully when they develop later after surgical corrections; catheter ablation of atrial arrhythmias associated with ASD repair is highly successful, with acute success rates reported as 93% to 100%.449,458,477 Therefore, patients with unoperated significant ASD and arrhythmias should undergo ablation of the AT, as well as closure of the ASD. The choice of catheter versus surgical approaches to therapy is determined by anatomic features of the ASD likely to be successfully addressed with a catheter approach. No randomized comparison trials of catheter versus surgical closure of ASD combined with arrhythmia intervention have been reported. Surgical closure of large ASDs combined with arrhythmia surgery for AT or fibrillation can be safely performed, with 6.5% occurrence of AF reported during 2 years of follow-up.478 IIa B-NR Intravenous ibutilide or procainamide can be effective for acute treatment in ACHD patients and atrial flutter who are See Online Data Supplement 20. A small observational study reported that intravenous ibutilide was successful in conversion of 71% of acute episodes of atrial flutter in ACHD patients; torsades de pointes or nonsustained VT was reported in 2.7% of episodes.468 Pretreatment with magnesium may reduce the incidence of postibutilide ventricular arrhythmias. Small studies support the use of intravenous procainamide as adjunctive therapy for acute therapy of atrial flutter because it improves efficacy of pacing conversion of atrial flutter.466,467 IIa B-NR Atrial pacing can be effective for acute treatment in ACHD patients and SVT who are hemodynamically stable and anticoagulated as per current guidelines for antithrombotic therapy in patients with AF.466,469 472 See Online Data Supplement 20. Small observational studies support the efficacy of atrial pacing to successfully terminate 54% to 82% of acute episodes of AT or atrial Atrial pacing is an effective alternative, particularly when concerns about the use of antiarrhythmic medications or significant sinus node dysfunction exist. IIa B-NR Elective synchronized cardioversion can be useful for acute termination of AT or atrial flutter in ACHD patients when acute pharmacological therapy is ineffective or contraindicated.460 See Online Data Supplement 20. ACHD patients are at increased risk of congestive heart failure and/or atrial thrombus formation with prolonged episodes of AT or atrial flutter. Pharmacological conversion in patients with complex anatomy, ventricular dysfunction, or prolonged QTc intervals may result in significant proarrhythmia or acute hemodynamic deterioration. Early assessment for cardiac thrombus with transesophageal echocardiogram followed by synchronized cardioversion may be preferable to prolonged or multiple attempts to achieve pharmacological cardioversion. Because of frequent coexistent sinus node dysfunction and ventricular dysfunction, the need for chronotropic or inotropic intervention should be anticipated, with appropriate personnel and support present. Modification of electrode pad placement may be necessary, by using an anterior-posterior configuration in patients with marked atrial enlargement or positioning strategically according to the individual arrhythmia and anatomic substrate, including consideration of the possibility of dextrocardia. IIb B-NR Oral dofetilide or sotalol may be reasonable for acute treatment in ACHD patients and AT and/or atrial flutter who are See Online Data Supplement 20. Small observational studies support the use of oral dofetilide474 to acutely convert AT to sinus rhythm in 70% to 85% of episodes of acute AT or atrial flutter. Proarrhythmic events are more commonly reported with dofetilide. One small study of 20 patients reported that 10% experienced torsades de pointes after dofetilide474 ; both proarrhythmic events occurred in patients with single-ventricle physiology. The risk of proarrhythmia or worsening ventricular function requires arrhythmia monitoring with use. Recommendations for Acute Treatment of SVT in ACHD Patients (Continued) COR LOE Recommendations IIa B-NR Preoperative catheter ablation or intraoperative surgical ablation of accessory pathways or AT is reasonable in patients with SVT who are undergoing surgical repair of Ebstein anomaly.479 485 See Online Data Supplement 20. The prevalence of SVT among patients with Ebstein anomaly was 33% in 1 large series, the highest noted among ACHD and increased with age. AT, atrial flutter, or AF develops in 50% of patients with Ebstein anomaly and significant tricuspid regurgitation. Right-sided accessory pathways are present in 15% to 30% of patients with Ebstein anomaly and may be multiple in up to 29% of those patients. Catheter ablation of accessory pathways in patients with Ebstein anomaly is associated with lower success rates than for other populations, acute success rate of 75% to 89% of procedures, with acute recurrence in 25% In a series of 83 adults undergoing arrhythmia surgery at the time of surgical repair of Ebstein anomaly, accessory pathways were present in 32%, and atrial flutter/fibrillation was noted in 54%,483 with no recurrence of AP after surgery. Successful surgical ablation of accessory pathways has been reported in 92% to 100%.483,484 In a series of patients undergoing right atrial maze procedures or isthmus ablation for atrial flutter/fibrillation in association with repair of Ebstein anomaly, freedom from recurrent flutter/fibrillation was 75% during 34 months of follow-up.483 In a comparison study of combined operative arrhythmia surgery with repair, versus catheter ablation followed by surgical repair, the combined approach was effective in 94% of cases versus 76% of patients treated with the catheter approach alone.484 In a series of patients undergoing repair of Ebstein anomaly, patients who underwent preoperative EP study with intraoperative ablation of arrhythmia substrate had lower risk of SCD than patients without In patients with Ebstein anomaly undergoing planned surgical intervention, an integrated approach of arrhythmia intervention has been demonstrated to be safe and effective. IIa B-NR 2. Oral beta blockers or sotalol therapy can be useful for prevention of recurrent AT or atrial flutter in ACHD patients.218,447,486 See Online Data Supplement 20. Beta blockers may decrease catecholamine-related triggers and provide AV nodal blockade during recurrent atrial arrhythmias. One study of adults with transposition of the great arteries and prior atrial switch repairs with implanted defibrillators demonstrated SVT preceding VT in 50% of patients; use of beta-blocker medications in this population was associated with decreased incidence of appropriate defibrillator shocks.486 Observational studies on the use of sotalol in ACHD patients report freedom from recurrent AT in 41% to 46% of patients during short-term follow-up.218,487,488 Use of either medication in the setting of significant sinus node dysfunction may exacerbate bradycardia and requires careful monitoring. Initiation of sotalol in this population is recommended during inpatient monitoring for proarrhythmia for 48 to 72 hours. IIa B-NR 3. Catheter ablation is reasonable for treatment of recurrent symptomatic SVT in ACHD patients.330,449,452,454,457,458,489 492 See Online Data Supplement 20. Multiple observational and multicenter studies have demon strated acute success rates between 65% and 100% for treatment of SVT associated with ACHD.452,454,455,457,489,493,494 Acute success rates vary by tachycardia mechanism and type of congenital heart disease and repair. Success rates are highest for SVT associated with AVNRT (>80%),490,494 accessory pathways (75% to 89% among patients with Ebstein or focal AT (80% to 100%).492,494,495 Success rates for catheter ablation of AT or atrial flutter are significantly lower than that reported in patients without ACHD, with overall 65% to 82% acute success in mixed anatomic substrates,452,454,455,457,493,494 but success rates have improved with advanced mapping and ablation techniques.494 Acute success rates in ablation of AT or atrial flutter varies significantly by type of congenital heart disease, ranging from 93% to 100% in patients with repaired ASD,330,449,458 85% to 100% in atrial baffle repairs of transposition of the great arteries,490,492 and 54% to 75% of univentricular heart or Fontan repairs.457,490,495 Older age and presence of univentricular heart physiology was associated with decreased acute success rates in a series of 193 ablations of AT.457 Recurrent AT has been reported in 20% to 85% of patients during short-term follow-up, with development of AF reported in 7% to 30% of patients.330,449,454,493 Recurrent SVT may represent the same or a new reentrant circuit, and arrhythmia burden may be decreased by ablation procedures. Ablation procedures in patients with complex congenital heart disease are best performed in centers with advanced mapping techniques and expertise in congenital heart disease.25,29,496 IIa B-NR 4. Surgical ablation of AT or atrial flutter can be effective in ACHD patients undergoing planned surgical repair.497 508 See Online Data Supplement 20. In patients with symptomatic SVT undergoing planned surgical repairs of structural heart disease or ischemic heart disease, observation studies report that arrhythmia surgery can be integrated into the operation with high efficacy and without increased surgical morbidity.497 500 In populations including those with tetralogy of Fallot/double-outlet right ventricle, tricuspid valve repairs, and ASD, rates of freedom from recurrent AT or atrial flutter have been reported as 73% to 93% without antiarrhythmic medications during medium-term follow-up of 2.5 to 10 years. Catheter ablation may be attempted in specialized centersbefore surgical Fontan repair. There are no RCTs comparing efficacy of catheter versus surgical ablation of AT or atrial flutter in patients with prior Fontan repairs. The incidence of AT or atrial flutter in patients with prior Fontan repairs approaches 60% and increases with advancing age. Catheter ablation success rates in this subset of patients are lower than for other lesions,457 with acute success in 54% to 75%, and with recurrent AT in 27% to 50% of patients within 2 to 4 years490,495 ; death or transplantation was reported in 27% during follow-up. Several observational studies of surgical resection and ablation for AT or atrial flutter associated with Fontan conversion reported rates of freedom from AT of 12% to 16% during follow-up extending to 8 years501 505 ; death or transplantation was reported in 6% to 14% during follow-up. Performance of a modified right atrial maze procedure versus CTI ablation was associated with lower recurrence rates.501 Alternatively, surgical repairs without arrhythmia intervention are associated with high recurrence rates of AT. Arrhythmia surgery can be combined with hemodynamic surgical revision with low mortality rate and improved medium-term freedom from arrhythmia recurrence and deathin this population. IIb B-NR Atrial pacing may be reasonable to decrease recurrences of AT or atrial flutter in ACHD patients and sinus node See Online Data Supplement 20. Small observational studies support the use of atrial pacing in patients with recurrent AT or atrial flutter to reduce the frequency of tachycardia episodes. The pacing rate is programmed to maintain atrial pacing for the majority of the time in patients with sinus node dysfunction, significantly reducing tachycardia recurrences to 11% in 1 study.509,510 In addition, the implanted pacemaker can be used for termination of recurrent episodes of AT or atrial flutter.472 Recommendations for Ongoing Management of SVT in ACHD Patients (Continued) COR LOE Recommendations Page et al 2015 ACC/AHA/HRS SVT Guideline e553 Pregnancy may confer an increased susceptibility to a variety of arrhythmias, even in the absence of underlying heart Pregnancy is also associated with an increased risk of arrhythmia exacerbation, such as more frequent and refractory tachycardia episodes, in patients with a pre-existing An important consideration is that adverse maternal and fetal outcomes have been reported as a result of SVT in pregnancy.515 Although there is potential tox- icity to the fetus with certain pharmacological and nonphar- macological therapies, safe options exist to allow for treating most cases of maternal SVT effectively. The literature on therapeutic options for the management of arrhythmias in pregnancy is generally limited to single case reports or small series and favors the use of older antiarrhyth- mic agents because of more abundant reports on the safe use of these drugs. Experience with use of drugs in pregnancy also comes from treating a variety of maternal and fetal condi- tions, not maternal SVT alone. Although all medications have potential side effects to both the mother and the fetus at any stage of pregnancy, if possible, drugs should be avoided in the first trimester, when risk of congenital malformations is great- est. The lowest recommended dose should be used initially, accompanied by regular monitoring of clinical response. 9.3.1. Acute Treatment: Recommendations IIb B-NR 2. Oral dofetilide may be reasonable for prevention of recurrent AT or atrial flutter in ACHD patients.447,474,487,488 See Online Data Supplement 20. Two small observational studies on the use of oral dofetilide for ACHD patients report a high rate of acute conversion of AT or atrial flutter, with longer-term efficacy of the drug (defined by either complete suppression or partial improvement of symptoms) ranging from 70% to 85%. The benefit was tempered by an association with torsades de pointes in 10%.471,484 Although many patients continued to experience recurrence, these episodes were better tolerated and were of limited duration.471,484 Because of the potential risk of proarrhythmia, dofetilide is usually a second-line medication after failure of beta blockers and sotalol. Initiation of oral dofetilide is recommended during 72-hour inpatient monitoring. IIb B-NR Amiodarone may be reasonable for prevention of recurrent AT or atrial flutter in ACHD patients for whom other medications and catheter ablation are ineffective or contraindicated.447 See Online Data Supplement 20. An observational study reported efficacy of amiodarone in maintaining sinus rhythm, although side effects were noted frequently, including thyroid disorders or AV block.447 The risk of significant side effects increases with chronic use and with higher dosages; using the minimal effective chronic dosage is recommended. Observational studies reported thyroid disorders in 13% to 36% of ACHD patients receiving amiodarone; risk factors for thyrotoxicosis include female sex, cyanotic heart disease, low body mass index, prior Fontan procedure, or dosages >200 mg daily.511,512 Amiodarone is recommended for short-term use or for patients for whom alternative therapy is not an option for prevention of recurrent AT. III: Harm B-NR 1. Flecainide should not be administered for treatment of SVT in ACHD patients and significant ventricular dysfunction.419 See Online Data Supplement 20. There are no RCTs on the use of flecainide in ACHD patients and ventricular dysfunction. One retrospective study collected data on 579 young patients, 369 of whom received flecainide for the treatment of SVT. Efficacy for the treatment of SVT was 71%. Among 12 patients with cardiac arrest while receiving flecainide for SVT, 8 had congenital heart disease, and 7 of 8 had either mild to moderate ventricular dysfunction or systemic right- or single-ventricle anatomy. The risk associated with flecainide treatment of SVT associated with congenital heart disease appears to be highest among patients with complex heart disease or ventricular dysfunction. Recommendations for Ongoing Management of SVT in ACHD Patients (Continued) COR LOE Recommendations Recommendations for Acute Treatment of SVT in Pregnant Patients COR LOE Recommendations I C-LD 1. Vagal maneuvers are recommended for acute treatment in pregnant patients with SVT.235,516 See Online Data Supplement 20. For acute conversion of SVT, vagal maneuvers, including Valsalva and carotid sinus massage, can be performed quickly and should be the first-line intervention to terminate SVT. These maneuvers should be performed with the patient in the supine position. Vagal maneuvers typically will not be effective if the rhythm does not involve the AV node as a requisite component of a reentrant circuit. There is no gold standard for proper Valsalva maneuver technique, but in general, the patient raises intrathoracic pressure by bearing down against a closed glottis for 10 to 30 seconds, equivalent to at least 30 Carotid massage is performed after absence of bruit has been confirmed by auscultation, by applying steady pressure over the right or left carotid sinus for 5 to 10 seconds.83,84 Another vagal maneuver based on the classic diving reflex consists of applying an ice-cold, wet towel to the ; in a laboratory setting, facial immersion in water at 10 C (50 F) has proved effective in terminating tachycardia, as well.86 One study involving 148 nonpregnant patients with SVT demonstrated that Valsalva was more successful than carotid sinus massage, and switching from 1 technique to the other resulted in an overall success rate of 27.7%.82 The practice of applying pressure to the eyeball is potentially dangerous and has been abandoned. I C-LD 2. Adenosine is recommended for acute treatment in pregnant patients with SVT.516 See Online Data Supplement 20. When vagal maneuvers fail to terminate SVT, adenosine is a first-line drug option for pregnant patients.516 Adverse effects to the fetus would not be expected, given that it is unlikely the drug will reach the fetal circulation because of adenosine s short half-life.517 Maternal side effects, such as chest discomfort and flushing, are usually transient. The initial dose for adenosine is 6-mg rapid bolus IV. If this is ineffective, up to 2 subsequent infusions of 12 mg may be administered. Higher doses of adenosine may be necessary in some cases; safe administration of up to 24 mg has been reported.518 I C-LD Synchronized cardioversion is recommended for acute treatment in pregnant patients with hemodynamically unstable SVT when pharmacological therapy is ineffective or contraindicated.516 See Online Data Supplement 20. Synchronized cardioversion has been reported to be safe at all stages of pregnancy. The electrode pads should be applied such that the energy source and trajectory are directed away from the uterus.519 Fetal monitoring during cardioversion (if time allows) and during the immediate postcardioversion period is recommended.519 Energy dosing for pregnant patients should be the same as in nonpregnant patients.520 9.3.2. Ongoing Management: Recommendations IIa C-LD Intravenous metoprolol or propranolol is reasonable for acute treatment in pregnant patients with SVT when adenosine is ineffective or contraindicated.516 See Online Data Supplement 20. Beta-adrenergic blocking drugs are considered the first-line option for a variety of arrhythmias in pregnancy because there are extensive reports on their safe use from treating a variety of maternal conditions over many decades. A slow infusion would be less likely to cause IIb C-LD Intravenous verapamil may be reasonable for acute treatment in pregnant patients with SVT when adenosine and beta blockers are ineffective or contraindicated.516 See Online Data Supplement 20. Intravenous verapamil has been used effectively for the acute treatment of SVT in pregnant women; however, there is a higher risk of maternal hypotension with intravenous verapamil than with adenosine.516 Reports on diltiazem use for acute SVT termination in pregnancy are more limited than for verapamil, yet similar effects are expected.517 IIb C-LD 2. Intravenous procainamide may be reasonable for acute treatment in pregnant patients with SVT.522 See Online Data Supplement 20. Intravenous procainamide has been used safely to treat a variety of maternal and fetal supraventricular and ventricular arrhythmias and can be effective when used for acute conversion.517,522 Procainamide is generally best avoided as long-term therapy because it can cause a lupus- like syndrome, unless other options are contraindicated or ineffective. IIb C-LD Intravenous amiodarone may be considered for acute treatment in pregnant patients with potentially life-threatening SVT when other therapies are ineffective or contraindicated.517,523 See Online Data Supplement 20. Although intravenous amiodarone has been administered safely during pregnancy, multiple adverse effects to the fetus have also been An important concern is the possibility of fetal hypothyroidism, reported in approximately 17% of cases.517,523 With an intravenous infusion for short-term use, side effects would be less of a concern, given that most toxicities are related to cumulative drug dose. Recommendations for Acute Treatment of SVT in Pregnant Patients (Continued) COR LOE Recommendations Recommendations for Ongoing Management of SVT in Pregnant Patients COR LOE Recommendations IIa C-LD The following drugs, alone or in combination, can be effective for ongoing management in pregnant patients with highly symptomatic SVT: See Online Data Supplement 20. If possible, antiarrhythmic drugs should be avoided in the first trimester, when risk of congenital malformations is greatest. Almost no reports exist on the use of newer antiarrhythmic drugs (such as dofetilide) during pregnancy, yet their use may be justified if the benefits outweigh the risk. The lowest recommended dose should be used initially, with dose adjustments made according to clinical response. For oral chronic prophylaxis, drugs such as metoprolol, propranolol, and digoxin are considered safe first-line agents because of their longer record of safety, yet caution is advised, given that therapy with beta blockers has been associated with intrauterine growth retardation.517,524 This effect appears to be especially pronounced with atenolol, especially in mothers who received atenolol earlier in gestational age and who were treated for longer duration.525 Flecainide and propafenone have been used effectively to treat a variety of maternal and fetal tachycardias, yet they are reserved for patients who have no underlying structural heart disease or ischemic heart disease.113 IIb C-LD Catheter ablation may be reasonable in pregnant patients with highly symptomatic, recurrent, drug-refractory SVT with efforts toward minimizing radiation exposure.526,527 See Online Data Supplement 20. The risk of radiation exposure to the fetus is a concern with catheter ablation in pregnant patients, because high-dose ionizing radiation has been linked to excess malignancy and congenital malformations.528 However, the fetal radiation dose for most common cardiovascular interventions is not likely to exceed the 50-mGy negligible-risk threshold dose for excess malignancy.529 One study that used phantoms to simulate pregnancy estimated a low lifetime risk of malignancies from radiation exposure to the conceptus during a typical ablation procedure.527 Furthermore, with current technologies such as electroanatomic mapping systems, catheter ablation procedures using minimal or even zero fluoroscopy have been described in pregnant women.526 Thus, if a catheter ablation procedure is required in a pregnant woman, radiation-reduction technologies should be used, and the procedure should be avoided in the first trimester when the teratogenic risk is greatest.528 Of note, shielding the fetus by covering the mother with a lead apron does not eliminate radiation to the fetus because most of the radiation to the fetus comes from scatter. IIb C-LD Oral amiodarone may be considered for ongoing management in pregnant patients when treatment of highly symptomatic, recurrent SVT is required and other therapies are ineffective or contraindicated.517,523 See Online Data Supplement 20. Although oral amiodarone has been administered safely during pregnancy, multiple adverse effects to the fetus have also been reported.523 An important concern is the possibility of fetal hypothyroidism, reported in approximately 17% of cases.517,523 Therefore, fetal monitoring for development of goiter with ultrasound and for signs of clinical hypothyroidism is advised. In addition, amiodarone has the potential for direct neurotoxicity, which may lead to neurodevelopmental abnormalities.523 Page et al 2015 ACC/AHA/HRS SVT Guideline e555 9.4. SVT in Older Populations 9.4.1. Acute Treatment and Ongoing Management: Recommendation The natural history of SVT is steadily changing because most patients with SVT undergo ablation at a younger age, but in general, the relative proportion of AT is higher in older popu- lations, and AVNRT is more prevalent than AVRT among patients undergoing ablation.49 Atypical atrial flutter and mac- roreentrant AT are on the rise as consequences of increasing AF ablation in this patient population, yet there are limited outcome data from RCTs for this segment of the population. Therapeutic decisions should be balanced between the over- all risks and benefits of the invasive nature of ablation versus long-term commitment to pharmacological therapy. 10. Quality-of-Life Considerations Patients with SVT may experience recurring symptoms that negatively impact their quality of life. Episodes of tachy- cardia can cause lightheadedness and syncope, which can become an obstacle to the performance of usual activities of daily living (eg, driving).72 However, there are minimal data on the effect of treatment on the quality of life for patients with SVT. In 1 study that evaluated patients with SVT who underwent ablation or received medical therapy, questionnaires such as the 36-Item Short-Form Health Survey revealed improved quality-of-life scores in several categories, including physical role functioning (perceived disability from physical limitations), general health percep- tions (perceived physical and mental health), and emotional role functioning (perceived disability from emotional limi- These improvements, measured at 1 to 5 years of follow-up, were greater in patients who underwent abla- tion than in those treated with medical therapy. Other lit- erature, using domains from the 36-Item Short-Form Health and other quality- of-life questionnaires,544 546 suggests that quality of life is improved after ablation for PSVT. However, these data carry important limitations, par- ticularly a lack of an appropriate control group, small sam- ple sizes, and referral bias. Furthermore, patients affected by PSVT carry different experiences. Therefore, firm con- clusions cannot be drawn about the effect on quality of life provided by medical or ablation therapy, and no recommen- dations are provided. See Online Data Supplement 22 for additional data on quality-of-life considerations. Given the rising costs of health care, there is a growing enthusiasm for incorporating economic appraisals of avail- able therapies and resources into guidelines. The 2014 ACC/AHA Statement on Cost/Value Methodology in Clinical Practice Guidelines and Performance Measures 6 called for development of Level of Value categories to accompany COR and LOE in future guidelines. Although basing recommendations on a cost-effectiveness approach to therapy is an important goal for the current and future healthcare economy, it also poses considerable challenges. For example, the cost of therapy, available technology, and practice patterns are highly dynamic, and there may Recommendations for Acute Treatment and Ongoing Management of SVT in Older Populations COR LOE Recommendation I B-NR Diagnostic and therapeutic approaches to SVT should be individualized in patients more than 75 years of age to incorporate age, comorbid illness, physical and cognitive functions, patient preferences, and severity of symptoms.66,67,530 538 See Online Data Supplement 20. Data have consistently demonstrated that ablation is highly successful (>95%) in selected older patients.66,67,531 536 Outcomes from 48 medical centers in Germany were reported among 3234 consecutive patients undergoing AVNRT ablation from 2007 to 2010; of the total, Acute success was achieved in 98.5% of the older patient group, similar to the 2 younger patient groups (98.7% for the group <50 years of age; 98.8% for the group 50 to 75 years of age). In this study, complication rates were low; hemodynamically stable pericardial effusion was observed in 2 of 259 patients (0.8%), and no pacemakers were needed in the older patient group. Similarly, additional studies from older patient cohorts have consistently shown that older patients have more comorbid medical conditions, have a higher incidence of structural heart disease or ischemic heart disease, and have more severe symptoms associated with A few studies have shown that complications may be slightly higher in older patients than in younger patients, although the overall complications are low and acceptable.530,538,539 These ablation outcome data should be balanced with the risks and benefits of pharmacological therapy when therapeutic options are reviewed with older patients. Figure 22. Acute treatment of SVT in ACHD patients. Colors correspond to Class of Recommendation in Table 1; drugs listed alphabetically. *For rhythms that break or recur spontaneously, synchronized cardioversion is not appropriate. ACHD indicates adult congenital heart disease; IV, intravenous; and SVT, supra- ventricular tachycardia. be some cost associated with unintended harm or compli- cations that result from any intervention. Furthermore, the approach toward evaluating the burden of cost in the litera- ture is based on varied perspectives (eg, individual, third party, stakeholder, societal). The small body of literature evaluating cost-effectiveness strategies in PSVT has traditionally centered on an evalua- tion of medical therapy versus catheter ablation. A rigorous cost-effectiveness Markov model was conducted in 2000 to compare radiofrequency ablation to medical management with generic metoprolol from the societal perspective.105 The estimated population consisted of patients with AVNRT (approximately 65%) and AVRT. On the basis of this simula- tion, the authors concluded that, for symptomatic patients with monthly episodes of PSVT, radiofrequency ablation was the more effective and less expensive strategy when compared with medical therapy. An observational cohort study of patients with atrial flutter supported early ablation to significantly reduce hospital-based healthcare utilization and the risk of AF.547 These studies, along with other older literature, favor cath- eter ablation over medical therapy as the more cost-effective approach to treating PSVT and atrial flutter. However, the results of these studies were based on cost data and practice patterns that do not apply to the current environment and prac- tice. Therefore, no recommendations are provided. See Online Data Supplement 23 for additional data on cost-effectiveness. 12. Shared Decision Making It is important that the patient be included in clinical decision- making processes, with consideration of his/her preferences and goals for therapy, as well as his/her unique physical, psychological, and social situation. In selected cases, per- sonalized, self-directed interventions can be developed in partnership with the patient, such as vagal maneuvers and pill-in-the-pocket drug therapy. Shared decision making is especially important for patients with SVT. As seen in this guideline, SVT treatment can be nuanced and requires expert knowledge of EP pro- cesses and treatment options. Treatment options are highly specific to the exact type of arrhythmia and can depend on certain characteristics of a particular arrhythmia (eg, whether there is pre-excitation). The various choices for therapy, including drugs, cardioversion, invasive treatment, or a combination thereof, can be confusing to the patient, so a detailed explanation of the benefits and risks must be included in the conversation. Patients are encouraged to ask questions with time allot- ted for caregivers to respond. Providing a relaxed atmosphere, anticipating patient concerns, and encouraging patients to keep a notebook with questions could facilitate productive conversations. It is also important that clinicians use lay terminology to explain treatment options to their patients. This involves a clear explanation of the risks and benefits of each recom- mendation, including how other comorbidities may impact each treatment option. Discussions with other physicians and healthcare providers caring for the patient will provide the broadest picture available. A full discussion about decisions for subsequent care and any further instructions is important to reinforce these issues before the patient leaves the healthcare setting. It is the responsibility of the physician and healthcare team to provide the patient with the best possible understand- ing of all management options in terms of risks, benefits, and potential effects on quality of life. 13. Evidence Gaps and Future Research Needs SVTs, even with the exclusion of AF, are among the most common arrhythmias that require medical interven- tion. The decade before the publication of the 2003 ACC/ AHA/ESC Guidelines for the Management of Patients With was characterized by major shifts in understanding of the mechanism for SVT, as well as a sea change in management (because of catheter abla- tion). Since the early 2000s, there have been many iterative but important advances in pharmacological and invasive management for SVT. Catheter ablation is even better estab- lished, with a high degree of success and low complication rate, especially for the most common types of SVT, such as AVNRT and AVRT. Drug options, on the other hand, are rela- tively unchanged since publication of the 2003 guideline, per- haps relating to ongoing concern about potential adverse side effects of antiarrhythmic agents. Areas of uncertainty remain, including interventions for which advanced technology is less important. For example, vagal maneuvers are recommended in many circumstances as first-line intervention in patients with SVT, but they are often ineffective. Furthermore, there is great variation in the way these maneuvers are administered. Therefore, research on the best technique of vagal maneuvers, with dis- semination of the findings, is necessary. Clinical trials on Figure 23. Ongoing management of SVT in ACHD patients. Colors correspond to Class of Recommendation in Table 1; drugs listed alpha- betically. ACHD indicates adult congenital heart disease; intra-op, intraoperative; pre-op, preopera- tive; and SVT, supraventricular tachycardia. Page et al 2015 ACC/AHA/HRS SVT Guideline e557 antiarrhythmic drugs for SVT have been limited, and data are often extrapolated from studies that primarily focused on management of patients with AF. The efficacy of a variety of drugs is likely to differ according to the tachycardia mech- anism, and therefore differentiating the best drug for each individual arrhythmia is necessary; for example, the efficacy of class III agents might be markedly different in patients with AF than in patients with atrial flutter. Limited data exist on the optimal management of less common types of SVTs, such as junctional tachycardia and multifocal AT. Therefore, in view of significant gaps that remain with regard to opti- mal management of patients with SVT, we must consider the role of electronic medical records, registries, and national datasets to better acquire observational data when trials are not available or feasible. Multicenter registry studies would allow for expansion of our knowledge on the best pharma- cological and nonpharmacological approaches to treat these arrhythmias. In collaboration with national societies, the National Institutes of Health, and the US Food and Drug Administration, registries could be developed across selected centers to gather important information on safety and long- term outcomes where data are lacking (just as such registries are being developed for AF ablation). Mandatory postmarket surveillance data collection on new drugs for SVT could also be considered by the US Food and Drug Administration as a condition for drug approval. The mechanism and primary etiology of IST remains to be defined advances here would provide a first step on finding better therapies for this disorder. It should be noted that medi- cal advances have resulted in an increase in the number of patients with SVT in specific populations, such as in patients after ablation (especially AF), ACHD patients, and patients of advanced age. As the numbers of these often-complicated patients grow, opportunities arise to perform clinical research to guide future recommendations. New pharmacological therapies are needed, especially for SVT in patients for whom ablation is not an option or has been unsuccessful. Newer drugs that selectively target atrial channels currently under investigation for patients with AF should be investigated for management of AT. Both mapping and ablation techniques need to be further investigated to maximize the likelihood of successful ablation with minimal risk. In the outpatient setting, the added value of new personal monitoring and implantable devices needs to be assessed, and studies of the impact of shared decision making with patients on outcomes are needed for personal monitoring innovations. Finally, we encourage investigation of quality-of-life improve- ment strategies, in addition to cost-effectiveness studies, for the management of SVT. Presidents and Staff American College of Cardiology Kim A. Williams, Sr, MD, FACC, FAHA, President Shalom Jacobovitz, Chief Executive Officer William J. Oetgen, MD, MBA, FACC, Executive Vice President, Science, Education, and Quality Amelia Scholtz, PhD, Publications Manager, Science, Education, and Quality American College of Cardiology/American Heart Association Lisa Bradfield, CAE, Director, Guidelines and Clinical Policy Abdul R. Abdullah, MD, Associate Science and Medicine Advisor Alexa Papaila, Project Manager, Science and Clinical Policy American Heart Association Mark A. Creager, MD, FACC, FAHA, President Nancy Brown, Chief Executive Officer Rose Marie Robertson, MD, FAHA, Chief Science Officer Gayle R. Whitman, PhD, RN, FAHA, FAAN, Senior Vice President, Office of Science Operations Marco Di Buono, PhD, Vice President, Science, Research, and Professional Education Jody Hundley, Production Manager, Scientific Publications, Office of Science Operations Acknowledgments We thank Dr. Daniel B. Mark for his invaluable assistance in review- ing studies relating to quality of life and cost-effectiveness. His research and insight informed much of the discussion on these topics. We also thank Dr. Sarah A. Spinler for her contributions with regard to antiarrhythmic drug therapy. References 1. Committee on Standards for Developing Trustworthy Clinical Practice Guidelines, Institute of Medicine (US). Clinical Practice Guidelines We Can Trust. Washington, DC: National Academies Press, 2011. 2. 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