despite treatment with an antiarrhythmic drug, we suggest catheter-based RFA rather than the addition of a second antiarrhythmic agent. RFA is also an alternative to antiarrhythmic drugs as the initial therapy for SMVT [21,37,38]. In addition, RFA, with or without antiarrhythmic drug therapy, is an option for patients with SMVT who are not candidates for or who refuse ICD implantation. SMVT in patients with a prior MI is usually due to reentry in a circuit created by the heterogeneous electrical properties of residual myocardium in the region of the scar from the infarct. However, other mechanisms such as abnormal automaticity or triggered activity may https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognosi 11/39 7/6/23, 3:39 PM Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis - UpToDate occasionally occur. RFA can alter or eliminate such circuits or foci and prevent VT recurrence in selected patients. (See "Reentry and the development of cardiac arrhythmias".) Our suggested approach to utilizing RFA in the treatment of ventricular arrhythmias is generally consistent with the recommendations of professional society guidelines [1,19,37]: For patients with structural heart disease (such as prior MI, dilated cardiomyopathy, or arrhythmogenic right ventricular cardiomyopathy), catheter ablation is recommended for any of the following conditions: Symptomatic SMVT, including VT terminated by an ICD, that recurs despite antiarrhythmic drug therapy or when antiarrhythmic drugs are not tolerated or not desired Incessant SMVT or VT storm not due to a transient reversible cause Recurrent SMVT and ventricular fibrillation (VF) that is refractory to antiarrhythmic therapy when there is a suspected trigger that can be targeted for ablation For patients with structural heart disease, catheter ablation should be considered for patients with any of the following: One or more episodes of SMVT despite therapy with one or more class I or III antiarrhythmic drugs Recurrent SMVT due to prior MI and expectation for at least one year of survival as an acceptable alternative to amiodarone therapy Hemodynamically tolerated SMVT due to prior MI who have reasonably preserved left ventricular ejection fraction (LVEF >35 percent) even if they have not failed antiarrhythmic drug therapy Catheter ablation techniques A variety of VT ablation techniques have evolved over the years, including ablation focused on abolition of inducible VT based upon the results of activation and entrainment mapping ( waveform 1) versus more extensive ablation of myocardium displaying abnormal electrogram characteristics ("substrate-based ablation"). The technical aspects of catheter ablation for VT are presented separately. (See "Overview of catheter ablation of cardiac arrhythmias".) While no technique has proven to be universally effective or clearly superior, smaller nonrandomized studies have suggested lower rates of VT recurrence following more extensive ablation [39-43]. Subsequently, in a multicenter trial of 118 patients with hemodynamically https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognos 12/39 7/6/23, 3:39 PM Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis - UpToDate tolerated VT and ischemic cardiomyopathy, in which patients were randomized to clinical ablation of inducible VT (60 patients) or substrate-based ablation targeting all "abnormal" electrograms seen on mapping (58 patients) and followed for 12 months, patients in the substrate-based ablation group had significantly fewer VT recurrences (16 versus 48 percent), less need for antiarrhythmic drugs (12 versus 58 percent), and fewer hospitalizations (12 versus 32 percent) compared with patients in the clinical VT ablation group [44]. There was no difference in periprocedural complications between the two approaches; however, 22 patients in the substrate-based ablation group also underwent EP study and induction of VT, raising some concerns that this may have improved the efficacy of the ablation procedure in the substrate- based group. While these data are encouraging, additional data in larger numbers of patients and additional populations are required prior to recommending widespread implementation of the substrate-based ablation technique, even in patients with hemodynamically-tolerated VT. Additionally, a systematic review and meta-analysis of non-randomized trials suggests significantly lower rates of recurrent VT following a combined endocardial/epicardial ablation compared with endocardial ablation alone, in particular among patients with ischemic cardiomyopathy [45]. (See 'Long-term efficacy' below.) Ablation performed via an epicardial approach is another option for select patients with ventricular tachyarrhythmias. Among a cohort of 444 consecutive patients with VT and prior MI who were referred for catheter ablation, 27 patients (6 percent) had successful epicardial ablation of at least one VT after endocardial ablation failed [46]. Some advocate epicardial in addition to endocardial ablation when performing substrate-based ablation. Cardiac magnetic resonance (CMR) imaging with contrast enhancement is also being investigated as a means of identifying critical sites for reentrant ventricular tachyarrhythmias [47]. In one study of 20 patients (mixed nonischemic and ischemic cardiomyopathy) with prior failed endocardial catheter ablation, CMR with late gadolinium enhancement (LGE) imaging was performed, and subsequently ablation strategies were modified based on LGE findings (nine patients underwent epicardial ablation, while 11 underwent repeat endocardial ablation) [48]. At mean follow-up of 17 months, 18 of 22 patients remained free of recurrent VT. Acute procedural success Depending upon a number of factors, acute success rates (defined as lack of inducible VT or termination of incessant VT) for RFA of VT vary from 70 to 90 percent, with a procedure-related mortality of 0.5 percent [19]. Catheter ablation of VT has been applied most often in patients with frequent episodes. Two- thirds of these patients have experienced at least a 75 percent reduction in frequency of VT [19]. https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognos 13/39 7/6/23, 3:39 PM Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis - UpToDate Long-term efficacy Catheter ablation has been evaluated as a therapy to prevent recurrent SMVT with good results in several individual trials [19,49-54]. Depending on the clinical presentation of VT (cardiac arrest versus relative hemodynamic stability), ICDs are usually considered in conjunction with ablation, except in patients with fairly normal LV function who present with stable VT. In the VANISH trial, VT ablation was shown to lower VT storm and appropriate ICD shocks. In this a multicenter, non-blinded study, 259 patients with prior MI and a previously implanted ICD who had at least one episode of VT within the preceding six months while on antiarrhythmic drug therapy were randomly assigned to catheter ablation (132 patients) or escalated antiarrhythmic therapy. Antiarrhythmic therapy was defined as initiating or increasing the dose of amiodarone if the prior dose was less than 300 mg daily, or addition of mexiletine to amiodarone if the prior dose was 300 mg daily or greater (127 patients) [52]. Over a mean follow-up of 28 months, patients in the ablation group had a significantly lower rate of the composite primary outcome of death, VT storm, or appropriate ICD shock (59 versus 69 percent; hazard ratio [HR] 0.72, 95% CI 0.53-0.98). The difference in outcomes was driven by reductions in VT storm and ICD shocks in the ablation group, as there was no significant difference in total mortality between the two groups. There is continuing concern over evidence that ICD shocks, both "appropriate" and "inappropriate," have adverse effects on survival [55]. As a result, earlier use of VT ablation has been proposed as a way to potentially reduce shocks and thereby improve survival. Two trials have suggested that early VT ablation among patients with cardiomyopathy may reduce cardiovascular events, including VT recurrence and ICD shocks [56,57]. One of these trials evaluated VT ablation at the time of ICD placement [56] and the other evaluated VT ablation shortly after a first ICD shock [57]. PAUSE-SCD Among patients with cardiomyopathy (ischemic, nonischemic, or arrythmia- related), early catheter ablation performed at the time of ICD implantation significantly reduced the composite primary outcome of VT recurrence, cardiovascular hospitalization, or death [56]. This trial included 121 patients with cardiomyopathy, SMVT, and an indication for ICD implantation. Participants were randomly assigned to either early VT ablation plus ICD, or medical therapy plus ICD, and were followed for a composite of VT recurrence, cardiovascular hospitalization, or death. Participants assigned to early VT ablation were observed to have fewer primary adverse events compared with the control group (49.3 versus 65.5 percent, HR 0.58 95% CI 0.35-0.96). The observed difference was driven by a reduction in VT recurrence (31.7 versus 50.8 percent), ICD shocks (10 versus 24.6 percent), and antitachycardia pacing (16.2 versus 32.8 percent) in the VT ablation compared with https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognos 14/39 7/6/23, 3:39 PM Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis - UpToDate control group. However, no differences in cardiovascular hospitalization (32 versus. 33.7) or mortality (8.9 versus 8.8 percent) were observed. Complications occurred in 8.3 percent of patients. PARTITA This small trial provides support for performing VT ablation in patients with either ischemic or nonischemic cardiomyopathy after their first ICD shock [57]. The study randomly assigned 47 such patients to either a VT ablation prior to ICD or standard therapy and followed them for the development of death or heart failure (HF) hospitalization. Over a median follow-up of 2.4 years, patients assigned to ablation were less likely to experience death or HF hospitalization (4 versus 42 percent, HR 0.11, 95% CI 0.01-0.85) compared with the control group. The trial was stopped early because it showed early benefit. The ablation group was observed to have fewer deaths (0 versus 33 percent), fewer ICD shocks (9 versus 42 percent), and statistically similar but numerically less HF hospitalizations (4 versus 17 percent). These findings were consistent with two earlier trials of ablation after an initial episode of VT (SMASH-VT and VTACH) [49,53] but differed from the BERLIN VT trial, which did not find benefit for an early VT ablation strategy among patients with ischemic cardiomyopathy [38]. In this study, patients with ischemic cardiomyopathy (left ventricular ejection fraction from 30 to 50 percent) and documented VT were randomly assigned ICD and preventive ablation (76 patients) at the time of enrollment or deferred ablation (83 patients) after three or more appropriate ICD shocks [38]. After a mean follow-up of 13 months, there was no significant difference in the composite primary outcome of death or unplanned hospitalization for VT or HF (33 percent in the early ablation group versus 28 percent in the deferred ablation group), at which point the study was also terminated early for futility. Fewer patients in the early ablation group received appropriate ICD therapy (34 versus 47 percent) or experienced sustained VT (40 versus 48 percent). BERLIN-VT may have had null findings because this study included only patients with ischemic cardiomyopathy (whereas PAUSE-SCD [56]and PARTITA [57] included patients with nonischemic cardiomyopathy). However, because PARTITA was stopped early for benefit, the observed HR may overestimate the efficacy. Consistent with the findings of most individual trials, earlier systematic reviews and meta- analyses have shown that, compared with medical therapy alone, VT ablation generally does not improve mortality but leads to significantly fewer episodes of recurrent VT and VT storm, as well as lower likelihood of an appropriate ICD intervention [20,45,58,59]. As an example, in a 2020 meta-analysis of five randomized trials (635 patients) comparing ablation with medical therapy alone, patients treated with ablation had the following outcomes: https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognos 15/39 7/6/23, 3:39 PM Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis - UpToDate Lower likelihood of appropriate ICD therapies (odds ratio [OR] 0.49; 95% CI 0.28-0.87) and appropriate ICD shocks (OR 0.52; 95% CI 0.28-0.96) Lower likelihood of future VT storm (OR 0.64; 95% CI 0.43-0.95) Lower likelihood of cardiac hospitalization (OR 0.67; 95% CI 0.46-0.97) No significant improvement in all-cause mortality (OR 0.89; 95% CI 0.60-1.34) Complications The potential risks and benefits of the ablation procedure include those risks associated with any invasive electrophysiology (EP) study alone ( table 2), although the overall incidence of complications is higher with ablation, which is a lengthier procedure typically performed in higher-risk patients. In a nationwide sample of 4653 patients who underwent ablation in the United States between 2002 and 2011 for post-MI VT, the overall in-hospital complication rate was 11 percent with in-hospital mortality of 1.6 percent [60]. Generally, risks are lower in experienced operators and centers that perform larger numbers of procedures. These risks are discussed in greater detail separately. (See "Invasive diagnostic cardiac electrophysiology studies", section on 'Complications of invasive cardiac electrophysiology studies'.) As experience with catheter-based RFA accumulates among patients with VT, rates of early mortality and procedural complications appear to be declining. In a registry of 2061 patients with structural heart disease (mean age 62 years, mean LVEF 34 percent; 53 percent ischemic cardiomyopathy) who underwent RFA for VT (including 35 percent with VT storm), procedure- related complications occurred in 127 patients (7 percent), although in-hospital procedure- related mortality occurred in only 12 patients (0.6 percent) [61]. Early all-cause mortality at 31 days occurred in 100 patients (5 percent), with a greater likelihood of early mortality associated with lower LVEF, worse renal function, and pre-ablation VT storm. Among patients for whom data were available on mode of death, the cause was more frequently deemed advancing HF rather than to worsening arrhythmias (39 versus 22 percent). In a different study of 1251 patients who underwent RFA for VT between 2002 and 2013 and were enrolled in the international VT registry, LVEF <30 percent, previous ablation attempt, and presentation with electrical storm were the factors most associated with higher mortality [62]. Patients undergoing catheter ablation are also at risk of hemodynamic decompensation during or after the procedure. Among a single-center cohort of 193 consecutive patients undergoing catheter ablation for scar-related VT, acute hemodynamic decompensation (defined as persistent hypotension in spite of vasopressors requiring mechanical support or discontinuation of the procedure) occurred in 22 patients (11 percent) [63]. Patients with acute hemodynamic decompensation were more likely to be older, have diabetes or chronic obstructive pulmonary disease, have more severe HF, and more often received general anesthesia. In a separate multicenter cohort of 1365 patients (mean age 64 years, mean LVEF 30 percent) with HF https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognos 16/39 7/6/23, 3:39 PM Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis - UpToDate undergoing VT ablation, including 111 patients with NYHA class 4 symptoms, there was no significant difference in the rate of acute complications between patients with NYHA class 2/3 symptoms (7 percent) and those with NYHA class 4 symptoms (10 percent), suggesting that VT ablation is safe for patients with the most severe HF symptoms [64]. In select cases, percutaneous hemodynamic support can be used during catheter ablation for patients at high risk of complications [65]. Other therapies Not all patients will have their VT controlled with antiarrhythmic medications or RFA. In such cases, surgical therapy for VT remains effective in some patients, while energy sources other than radiofrequency are being investigated. Surgical therapy For most patients, because of the proven efficacy of catheter-based RFA and the development of ICDs, surgical treatment of ventricular arrhythmias is infrequently performed. However, surgical treatment of ventricular arrhythmias may be considered in certain subsets of patients with VT/VF: Patients with VT/VF that is refractory to antiarrhythmic therapy, resulting in frequent ICD shocks Patients with VT/VF that is refractory to antiarrhythmic therapy who have failed prior ablation of VT/VF Patients who are unable to tolerate antiarrhythmic therapy Patients requiring surgery for myocardial revascularization Patients with refractory HF and LV aneurysms that may benefit from aneurysm resection and LV reconstruction Although surgical therapies for SMVT are rarely performed today, they do remain a viable therapeutic option for selected patients with SMVT. Arrhythmia surgery is particularly useful when surgical revascularization (coronary artery bypass grafting [CABG]) is also planned, since it offers added hemodynamic benefits, including improvement in LVEF and alleviation of symptoms of HF, especially those requiring CABG and/or LV aneurysmectomy. Surgical ablation using endocardial resection was the mainstay of therapy for recurrent SMVT following MI unresponsive to pharmacologic therapy until the early 1990s, when RF catheter ablation for VT became feasible. A variety of surgical approaches with inconsistent efficacy have been performed, including LV aneurysmectomy, bilateral sympathectomy, encircling endocardial ventriculotomy, and subendocardial resection. Using LV aneurysmectomy as an example, the association of VT with LV aneurysms has been noted since the early 1900s, but aneurysmectomy alone has shown to have limited success in curing VT, presumably due to the fact that VTs may arise from the border of the aneurysm which is rarely excised during conventional https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognos 17/39 7/6/23, 3:39 PM Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis - UpToDate aneurysmectomy [66]. By contrast, long-term control of VT/VF has been excellent when LV aneurysmectomy is combined with LV reconstruction and subendocardial resection guided by VT mapping, with or without cryoablation [67,68]. Cardiac sympathetic denervation (ie, sympathectomy) can be effective as a temporizing strategy in patients with refractory VT and prior failed catheter ablation [69,70]. Stereotactic radiation therapy Stereotactic radiation therapy, in which high doses of radiation are precisely targeted, has been effective and well-tolerated as part of the treatment of some malignancies and has been investigated for VT in some preclinical studies and case reports [71-74]. In a single-center case series of five patients with structural heart disease (three with nonischemic cardiomyopathy, two with ischemic cardiomyopathy) with failed prior radiofrequency ablation (or who were not candidates for ablation) and ongoing VT in spite of two or more antiarrhythmic drugs, episodes of VT decreased following stereotactic radiation therapy [71]. The procedure was generally well-tolerated, with no apparent deterioration of systolic function, HF exacerbations, or other toxicities. Subsequently, in a prospective nonrandomized single arm study of 19 patients (17 for VT, two for premature ventricular complex/contraction [PVC; also referred to a premature ventricular beats or premature ventricular depolarizations]) who underwent stereotactic radiation therapy, median VT (or PVC) burden was markedly reduced, and the procedure was generally safe and well-tolerated (two patients developed radiation pneumonitis, six developed pericardial effusions [five of which were asymptomatic]) [72]. In another series of 10 patients who underwent stereotactic radiation therapy after failed catheter ablation and were followed for a median of 28 months, 8 of 10 patients experienced recurrent VT during follow-up, although the overall VT burden was reduced by 88 percent [73]. Of note, two patients in this series experienced an increased frequency of VT after radiation therapy. Prior to offering this therapy to patients outside of a clinical trial, stereotactic radiation therapy requires additional efficacy and safety evaluation in larger studies. SOCIETY GUIDELINE LINKS Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Ventricular arrhythmias" https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognos 18/39 7/6/23, 3:39 PM Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis - UpToDate and "Society guideline links: Cardiac implantable electronic devices" and "Society guideline links: Catheter ablation of arrhythmias".) INFORMATION FOR PATIENTS UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." th th The Basics patient education pieces are written in plain language, at the 5 to 6 grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more th th sophisticated, and more detailed. These articles are written at the 10 to 12 grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.) Basics topics (see "Patient education: Ventricular tachycardia (The Basics)") SUMMARY AND RECOMMENDATIONS Sustained monomorphic ventricular tachycardia (SMVT) is defined as a regular, wide ( 120 milliseconds) QRS complex tachycardia with uniform and stable QRS morphology at a rate of more than 100 beats per minute that lasts for 30 seconds or longer or causes hemodynamic collapse within 30 seconds. (See 'Introduction' above.) All patients with SMVT should have a brief immediate assessment of the symptoms, vital signs, and level of consciousness to determine if they are hemodynamic stable or unstable. Differentiation between a hemodynamically unstable versus stable patient depends upon hemodynamic compromise, such as hypotension, altered mental status, chest pain, or heart failure (HF). (See 'Initial management' above.) Patients with SMVT who are hemodynamically unstable and pulseless, or who become pulseless during the course of evaluation and treatment, should be managed according to standard advance cardiac life support (ACLS) resuscitation algorithms, with immediate high-energy countershock and cardiopulmonary resuscitation (CPR) ( algorithm 2). Patients should initially be treated with a synchronized 120 to 200 joule shock from a https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognos 19/39 7/6/23, 3:39 PM Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis - UpToDate biphasic defibrillator or a 360 joule shock from a monophasic defibrillator. (See 'Unstable patients' above.) For patients with wide complex tachycardia (WCT) who are hemodynamically unstable, but still responsive with a discernible blood pressure and pulse, we recommend urgent cardioversion (following administration of sedation) (Grade 1B). (See 'Unstable patients' above.) For patients with SMVT who are hemodynamically stable on presentation, after recording a 12-lead ECG we generally prefer to begin with an intravenous antiarrhythmic agent and reserve electrical cardioversion for refractory patients or for those who become unstable ( algorithm 1). (See 'Stable patients' above.) If pharmacologic cardioversion is the chosen approach, we administer intravenous amiodarone, procainamide, or lidocaine. If electrical cardioversion with appropriate procedural sedation is the chosen approach, intravenous analgesics or sedatives should be cautiously administered if the blood pressure will tolerate their use. If the QRS complex and T wave can be distinguished, an attempt at synchronized cardioversion can be performed with a synchronized shock of 100 joules using either a biphasic or monophasic defibrillator. Treatment of underlying conditions associated with VT, such as myocardial ischemia, electrolyte disturbances, drug proarrhythmia, and HF, as well as decreasing the sympathetic facilitation of SMVT, are important components of the acute management of VT. (See 'Treatment of associated conditions' above.) Chronic therapy of patients with SMVT usually requires utilization of multiple therapeutic modalities, including the implantable cardioverter-defibrillator (ICD), antiarrhythmic drugs, radiofrequency catheter ablation, and/or arrhythmia surgery. In the absence of a clearly identifiable and reversible cause for SMVT, nearly all patients with a history of SMVT will be candidates for ICD insertion for secondary prevention of sudden cardiac death, unless the patient refuses or the risks of ICD insertion are felt to outweigh the potential benefits. (See 'ICD therapy' above.) Nearly all patients who experience SMVT have an indication for therapy with a beta blocker, including patients with a prior myocardial infarction, patients with HF and reduced LV systolic function, etc. Beta blockers provide some level of protection against recurrent SMVT, primarily by reducing myocardial oxygen demand and blocking sympathetic input to the heart. (See 'Beta blockers' above.) https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognos 20/39 7/6/23, 3:39 PM Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis - UpToDate Antiarrhythmic drugs may also be used to improve quality of life in patients with frequent SMVT leading to ICD shocks, or in those patients who are not candidates for, or who decline, ICD implantation. Amiodarone has generally been the most effective antiarrhythmic drug for preventing ventricular arrhythmias (and associated ICD shocks). (See 'Antiarrhythmic drugs' above.) For patients with recurrent SMVT resulting in ICD shocks despite treatment with an antiarrhythmic drug, we suggest radiofrequency ablation (RFA) rather than the addition of a second antiarrhythmic agent (Grade 2C). RFA is also an alternative to antiarrhythmic drugs as the initial therapy for SMVT. In addition, RFA, with or without antiarrhythmic drug therapy, is an option for patients with SMVT who are not candidates for or who refuse ICD implantation. (See 'Radiofrequency catheter ablation' above.) ACKNOWLEDGMENT The UpToDate editorial staff acknowledges Leonard Ganz, MD, FHRS, FACC, who contributed to an earlier version of this topic review. Use of UpToDate is subject to the Terms of Use. REFERENCES 1. Al-Khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2018; 72:e91. 2. Link MS, Atkins DL, Passman RS, et al. 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