Roderick Tung

A Critical Appraisal of Implantable Cardioverter-Defibrillator Therapy for the Prevention of Sudden Cardiac Death

The indications for implantable cardioverter-defibrillators (ICDs) for the prevention of sudden cardiac death have rapidly expanded over the past 10 years. Clinical trial data have quickly been implemented into guidelines without critical reassessment of the strengths and limitations of the evidence. ICD therapy has inherent risks including infection, unnecessary shocks, potential for proarrhythmia, device malfunction, highly publicized manufacturer advisories, and procedural complications, which can adversely affect morbidity and quality of life. A reappraisal of the benefits and potential hazards of ICD therapy will enable physicians to a have a more mutually informed and balanced dialogue with their patients.

Characterization of the Arrhythmogenic Substrate in Ischemic and Nonischemic Cardiomyopathy: Implications for Catheter Ablation of Hemodynamically Unstable Ventricular Tachycardia

OBJECTIVES The purpose of this study was to compare the characteristics and prevalence of late potentials (LP) in patients with nonischemic cardiomyopathy (NICM) and ischemic cardiomyopathy (ICM) etiologies and evaluate their value as targets for catheter ablation. BACKGROUND LP are frequently found in post-myocardial infarction scars and are useful ablation targets. The relative prevalence and characteristics of LP in patients with NICM is not well understood. METHODS Thirty-three patients with structural heart disease (NICM, n = 16; ICM, n = 17) referred for catheter ablation of ventricular tachycardia were studied. Electroanatomic mapping was performed endocardially (n = 33) and epicardially (n = 19). The LP were defined as low voltage electrograms (<1.5 mV) with onset after the QRS interval. Very late potentials (vLP) were defined as electrograms with onset >100 ms after the QRS. RESULTS We sampled an average of 564 +/- 449 points and 726 +/- 483 points in the left ventricle endocardium and epicardium, respectively. Mean total low voltage area in patients with ICM was 101 +/- 55 cm(2) and 56 +/- 33 cm(2), endocardial and epicardial, respectively, compared with NICM of 55 +/- 41 cm(2) and 53 +/- 28 cm(2), respectively. Within the total low voltage area, vLP were observed more frequently in ICM than in NICM in endocardium (4.1% vs. 1.3%; p = 0.0003) and epicardium (4.3% vs. 2.1%, p = 0.035). An LP-targeted ablation strategy was effective in ICM patients (82% nonrecurrence at 12 +/- 10 months of follow-up), whereas NICM patients had less favorable outcomes (50% at 15 +/- 13 months of follow-up). CONCLUSIONS The contribution of scar to the electrophysiological abnormalities targeted for ablation of unstable ventricular tachycardia differs between ICM and NICM. An approach incorporating LP ablation and pace-mapping had limited success in patients with NICM compared with ICM, and alternative ablation strategies should be considered.

Ablation of Ventricular Arrhythmias in Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy: Arrhythmia-Free Survival after Endo-Epicardial Substrate Based Mapping and Ablation

Background— In patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy, freedom from ventricular arrhythmias (VAs) after endocardial ablation is limited. We compared the long-term freedom from recurrent VAs by using endocardial-alone ablation versus endo-epicardial substrate-based ablation. Methods and Results— Forty-nine patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy undergoing ablation of ventricular tachycardia (VT) were divided into 2 groups: endocardial-alone ablation (group 1, n=23) and endo-epicardial ablation (group 2, n=26). All patients had an implantable cardioverter-defibrillator (ICD). Conventional and 3D mappings were used to determine the mechanism of induced VTs and to identify area of “scar” or “abnormal” myocardium. All critical sites responsible for VTs and points with “abnormal” potential were targeted for ablation from endocardium (group 1) or from both endocardium and epicardium (group 2). The procedural end point was noninducibility of sustained, monomorphic VT with isoproterenol. The presence of frequent premature ventricular contractions at the end of ablation was recorded. Patients were followed up by ECG, Holter, and ICD interrogation. After a follow-up of at least 3 years, freedom from VAs or ICD therapy was 52.2% (12/23) in group 1 and 84.6% (22/26) in group 2 (P=0.029), with 21.7% (5/23) and 69.2% (18/26) patients off antiarrhythmic drugs (P<0.001), respectively. Compared with patients with no premature ventricular contractions after ablation, patients with frequent premature ventricular contractions after ablation were more likely to have VA recurrence/ICD therapy [3/33 (9%) versus 12/16 (75%); log-rank P<0.001]. Conclusions— An endo-epicardial–based ablation strategy achieves higher long-term freedom from recurrent VAs off antiarrhythmic therapy in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy when compared with endocardial-alone ablation. The presence of ≥10 premature ventricular contractions per minute after ablation is associated with more VA recurrence.Background— In patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy, freedom from ventricular arrhythmias (VAs) after endocardial ablation is limited. We compared the long-term freedom from recurrent VAs by using endocardial-alone ablation versus endo-epicardial substrate-based ablation. Methods and Results— Forty-nine patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy undergoing ablation of ventricular tachycardia (VT) were divided into 2 groups: endocardial-alone ablation (group 1, n=23) and endo-epicardial ablation (group 2, n=26). All patients had an implantable cardioverter-defibrillator (ICD). Conventional and 3D mappings were used to determine the mechanism of induced VTs and to identify area of “scar” or “abnormal” myocardium. All critical sites responsible for VTs and points with “abnormal” potential were targeted for ablation from endocardium (group 1) or from both endocardium and epicardium (group 2). The procedural end point was noninducibility of sustained, monomorphic VT with isoproterenol. The presence of frequent premature ventricular contractions at the end of ablation was recorded. Patients were followed up by ECG, Holter, and ICD interrogation. After a follow-up of at least 3 years, freedom from VAs or ICD therapy was 52.2% (12/23) in group 1 and 84.6% (22/26) in group 2 ( P =0.029), with 21.7% (5/23) and 69.2% (18/26) patients off antiarrhythmic drugs ( P <0.001), respectively. Compared with patients with no premature ventricular contractions after ablation, patients with frequent premature ventricular contractions after ablation were more likely to have VA recurrence/ICD therapy [3/33 (9%) versus 12/16 (75%); log-rank P <0.001]. Conclusions— An endo-epicardial–based ablation strategy achieves higher long-term freedom from recurrent VAs off antiarrhythmic therapy in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy when compared with endocardial-alone ablation. The presence of ≥10 premature ventricular contractions per minute after ablation is associated with more VA recurrence.

Narrative Review: Drug-Eluting Stents for the Management of Restenosis: A Critical Appraisal of the Evidence

Since their approval in April 2003, drug-eluting stents have revolutionized the practice of interventional cardiology. Currently, more than 85% of all coronary interventions in the United States are performed with drug-eluting stents (1). Two pivotal trials, Sirolimus-Eluting Balloon Expandable Stent in the Treatment of Patients With De Novo Native Coronary Artery Lesions (SIRIUS) (2) and Treatment of De Novo Coronary Disease Using a Single Paclitaxel Eluting Stent (TAXUS)-IV (3), demonstrated striking reductions in angiographic restenosis and revascularization rates with sirolimus- and paclitaxel-eluting stents, respectively. The current U.S. Food and Drug Administrationapproved indication for drug-eluting stents is for discrete, de novo lesions in native vessels with reference vessel diameters of 2.5 mm to 3.5 mm (4). Nevertheless, the unrestricted implementation of drug-eluting stents seems to be widely accepted in contemporary interventional clinical practice. This widespread adoption has largely been driven by nonrandomized registry experience and has been fueled by enthusiastic dissemination and acceptance of data, aggressive marketing, and unbridled expectations of patients. At our institution (Cedars-Sinai Medical Center, Los Angeles, California), 2975 drug-eluting stents were used in a 2-year period (May 2003 to April 2005), representing nearly 95% of all coronary interventions. While drug-eluting stents are clearly effective in reducing the knotty problem of restenosis, they cost nearly 3- to 4-fold more than bare metal stents. The unrestricted, off-label use of drug-eluting stents has important implications for health care delivery systems. The benefits of this new technology must be appraised for optimal utilization in clinical practice. Accordingly, we searched the MEDLINE database for articles published from January 1999 to November 2005 by using the following terms: drug-eluting stents, bare metal stents, restenosis, stent thrombosis, and cost-effectiveness. We focused on pivotal randomized trials and pertinent registry studies to explore key issues relating to drug-eluting stents. We offer a critical appraisal that challenges the mainstream interpretation of the data on several grounds (Table 1). Table 1. Summary of Critical Appraisal Have Trials Overestimated the Clinical Benefits of Drug-Eluting Stents? The impressive results on restenosis and repeated revascularization in the pivotal drug-eluting stent trials may have been overestimated for many reasons. First, careful examination reveals inordinately high restenosis or target vessel revascularization rates in the bare metal stent control groupnearly 50% higher than that observed in contemporary randomized trials and in real-world clinical experience (Table 2). The inferior performance of bare metal stents may be explained by the use of thick-strut stents: Bx VELOCITY (140 m; Cordis Corp., Miami Lakes, Florida) in the SIRIUS trial and Express (130 m; Boston Scientific, Natick, Massachusetts) in the TAXUS-IV trial, both of which are associated with a high restenosis rate. Use of thick-strut stents that yield a higher risk for restenosis (17), in small-diameter lesions (<3.0 mm in SIRIUS) where the risk for restenosis is often magnified, may have inflated the restenosis and revascularization rates with bare metal stents in these trials. Had the trials used the best available benchmarkthin-strut stents, such as PALMAZ-SCHATZ (62 m; Cordis Corp.) used in the Evaluation of Platelet IIb/IIIa Inhibitor for Stenting (EPISTENT) and Stent-Primary Angioplasty in Myocardial Infarction (Stent-PAMI) trials or MULTI-LINK DUET (91 m; Guidant Corp., Santa Clara, California) used in the Controlled Abciximab and Device Investigation to Lower Late Angioplasty Complications (CADILLAC) study, instead of a suboptimal bare metal stentthey may have determined a more reliable estimate of the true restenosis reduction rate with a drug-eluting stent. Thus, the impressive restenosis reduction rate observed in the pivotal trials may, in fact, be exaggerated because of the inferior performance of the control bare metal stent compared with the superior performance of the drug-eluting stent. Table 2. Target Vessel Revascularization Rates with Bare Metal Stents in Recent Trials* Second, protocol-mandated angiography in drug-eluting stent trials may have overestimated the need for revascularization. The analysis of event-free survival on the basis of target lesion revascularization in the SIRIUS trial (Figure 1) demonstrates a sudden increase of 8.3 percentage points immediately after angiography at 8 months in the bare metal stent group (from 13.1% at 7.5 months to 21.4% at 9 months) compared with 2.9 percentage points in the sirolimus-eluting stent group (from 6.0% at 7.5 months to 8.9% at 9 months). In contrast, no such increase was observed in patients who did not undergo protocol-mandated angiography (18). The 6-month target vessel revascularization rate of 7.8% in the Basel Stent Kosten Effektivitts Trial (BASKET) (6), which did not allow protocol-driven angiography, provides additional evidence that supports this. Thus, protocol-mandated angiography may have biased revascularization against the bare metal stent group through the well-described oculostenotic reflex, thereby contributing to an overestimation of benefit with drug-eluting stents. Figure 1. Influence of protocol-mandated angiography on target lesion revascularization. TLR MACE TVF n top n bottom Third, the clinical relevance of surrogate angiographic outcomes, such as binary restenosis or late lumen loss (a surrogate for neointimal proliferation), which primarily account for the superiority of drug-eluting stents, is unclear. While a mean late loss of 0.17 mm or 0.39 mm reported with drug-eluting stents (2, 3) is an incremental advantage over the late loss of 0.6 mm to 1.2 mm reported with bare metal stents (16, 19), the clinical relevance of this difference is not known. Figure 2 depicts data from the 4 largest randomized drug-eluting stent trials to point out several important facts. Figure 2. Relationship between angiographic variables and clinical outcomes. top middle bottom n n n n P Despite a more than 2-fold difference in late loss with the TAXUS stent (Boston Scientific) compared with the CYPHER stent (Cordis Corp.), rates of restenosis (8.9% vs. 7.9%) and target lesion revascularization (3.0% vs. 4.1%) did not differ. Ellis and colleagues (20) have attributed this to a possible curvilinear relationship between late loss and target lesion revascularization. Late loss of 0.0 mm to 1.0 mm may lie on a relatively flat portion of the curve, with high revascularization rates (>15% to 20%) not expected until late loss values appear on steeper parts of the curve (>1.2 mm to 1.5 mm); these are seldom seen with optimal clinical-grade bare metal stents (16, 19). A steep gradient (>4-fold difference) in late loss between the ACHIEVE stent (Guidant Corp.) (used in the Drug-Eluting Coronary Stent System in the Treatment of Patients With De Novo Native Coronary Lesions [DELIVER]) and CYPHER was not associated with substantial differences in major adverse cardiac events (10.3% vs. 7.1%) or target vessel failure (11.9% vs. 8.6%), suggesting a curvilinear relationship between late loss and clinical outcomes as well. These findings highlight a lack of consistent translation of cosmetic angiographic benefits to improvement in clinical outcomes. Bare metal stent late losses of 1.0 mm in SIRIUS and 0.92 mm in TAXUS-IV reflect a mean minimum lumen diameter (postprocedural minimum lumen diameterlate loss) of 1.69 mm and 1.74 mm, respectively, or diameter stenosis (1[minimum lumen diameter/reference vessel diameter]100) of 36% and 35%, respectively. These values are unlikely to be associated with flow-limiting stenosis causing angina or ischemia, which typically occurs at a minimum lumen diameter less than 1.0 mm to 1.5 mm or diameter stenosis greater than 70%. Given the near-normal distribution of late loss with bare metal stents (19), these numbers are difficult to reconcile with the high proportion (>75% to 80%) of revascularizations that were performed because of anginal symptoms in SIRIUS (18) or because of ischemia in TAXUS-IV (3). Fourth, the revascularization benefit with drug-eluting stents is attenuated in high-risk patients and lesion cohorts (diabetes; the acute coronary syndromes, including ST-segment elevation myocardial infarction [MI]; left main disease; bifurcation lesions; smaller-diameter lesions and longer lesions; several stents or overlapping stents; chronic total occlusions; and vein grafts). For example, the risk reduction in target vessel revascularization decreases from 67% in SIRIUS (19.2% to 6.4%) (2) and 60% in TAXUS-IV (12.0% to 4.7%) (3) in nonhigh-risk cohorts to 41% in BASKET (7.8% to 4.6%) (6) and 30% in TAXUS-V (17.3% to 12.1%) (7) in high-risk cohorts. Similar attenuation of reductions in target lesion revascularization (73% to 45%) and major adverse cardiac events (43% to 29%) is also observed with drug-eluting stents in TAXUS-V compared with TAXUS-IV (Figure 2). Despite these reduced benefits with drug-eluting stents, avoiding repeated procedures or bypass surgery may be clinically worthwhile in high-risk patients. Finally, disease progression (which may be responsible for more than one third of repeated revascularizations at 1 year and 4 times the number of adverse clinical outcomes beyond the first year compared with clinical restenosis [21]) may substantially mitigate the long-term benefits of drug-eluting stents. Have Trials Underestimated Adverse Events, Such as Stent Thrombosis? Unlike restenosis, thrombosis is a rare but potentially life-threatening complication of coronary stents (22-26). Stent thrombosis usually occurs before reendothelialization (healing) has been completed. Stent thrombosis rarely occurs (and, therefore, dual antiplatelet therapy is rarely required) beyond

Quantitative Analysis of Localized Sources Identified by Focal Impulse and Rotor Modulation Mapping in Atrial Fibrillation

Background—New approaches to ablation of atrial fibrillation (AF) include focal impulse and rotor modulation (FIRM) mapping, and initial results reported with this technique have been favorable. We sought to independently evaluate the approach by analyzing quantitative characteristics of atrial electrograms used to identify rotors and describe acute procedural outcomes of FIRM-guided ablation. Methods and Results—All FIRM-guided ablation procedures (n=24; 50% paroxysmal) at University of California, Los Angeles Medical Center were included for analysis. During AF, unipolar atrial electrograms collected from a 64-pole basket catheter were used to construct phase maps and identify putative AF sources. These sites were targeted for ablation, in conjunction with pulmonary vein isolation in most patients (n=19; 79%). All patients had rotors identified (mean, 2.3±0.9 per patient; 72% in left atrium). Prespecified acute procedural end point was achieved in 12 of 24 (50%) patients: AF termination (n=1), organization (n=3), or >10% slowing of AF cycle length (n=8). Basket electrodes were within 1 cm of 54% of left atrial surface area, and a mean of 31 electrodes per patient showed interpretable atrial electrograms. Offline analysis revealed no differences between rotor and distant sites in dominant frequency or Shannon entropy. Electroanatomic mapping showed no rotational activation at FIRM-identified rotor sites in 23 of 24 patients (96%). Conclusions—FIRM-identified rotor sites did not exhibit quantitative atrial electrogram characteristics expected from rotors and did not differ quantitatively from surrounding tissue. Catheter ablation at these sites, in conjunction with pulmonary vein isolation, resulted in AF termination or organization in a minority of patients (4/24; 17%). Further validation of this approach is necessary.

FREEDOM FROM RECURRENT VENTRICULAR TACHYCARDIA AFTER CATHETER ABLATION IS ASSOCIATED WITH IMPROVED SURVIVAL IN PATIENTS WITH STRUCTURAL HEART DISEASE: AN INTERNATIONAL VT ABLATION CENTER COLLABORATIVE GROUP STUDY

BACKGROUND The impact of catheter ablation of ventricular tachycardia (VT) on all-cause mortality remains unknown. OBJECTIVE The purpose of this study was to examine the association between VT recurrence after ablation and survival in patients with scar-related VT. METHODS Analysis of 2061 patients with structural heart disease referred for catheter ablation of scar-related VT from 12 international centers was performed. Data on clinical and procedural variables, VT recurrence, and mortality were analyzed. Kaplan-Meier analysis was used to estimate freedom from recurrent VT, transplant, and death. Cox proportional hazards frailty models were used to analyze the effect of risk factors on VT recurrence and mortality. RESULTS One-year freedom from VT recurrence was 70% (72% in ischemic and 68% in nonischemic cardiomyopathy). Fifty-seven patients (3%) underwent cardiac transplantation, and 216 (10%) died during follow-up. At 1 year, the estimated rate of transplant and/or mortality was 15% (same for ischemic and nonischemic cardiomyopathy). Transplant-free survival was significantly higher in patients without VT recurrence than in those with recurrence (90% vs 71%, P<.001). In multivariable analysis, recurrence of VT after ablation showed the highest risk for transplant and/or mortality [hazard ratio 6.9 (95% CI 5.3-9.0), P<.001]. In patients with ejection fraction <30% and across all New York Heart Association functional classes, improved transplant-free survival was seen in those without VT recurrence. CONCLUSION Catheter ablation of VT in patients with structural heart disease results in 70% freedom from VT recurrence, with an overall transplant and/or mortality rate of 15% at 1 year. Freedom from VT recurrence is associated with improved transplant-free survival, independent of heart failure severity.

Long-term clinical outcomes of focal impulse and rotor modulation for treatment of atrial fibrillation: A multicenter experience

BACKGROUND New approaches to ablation of atrial fibrillation (AF) include focal impulse and rotor modulation (FIRM). Studies of this technology with short-term follow-up have shown favorable outcomes. OBJECTIVE The purpose of this study was to characterize the long-term results of FIRM ablation in a cohort of patients treated at 2 academic medical centers. METHODS All FIRM-guided ablation procedures (n = 43) at UCLA Medical Center and Virginia Commonwealth University Medical Center performed between January 2012 and October 2013 were included for analysis. During AF, FIRM software constructed phase maps from unipolar atrial electrograms to identify putative AF sources. These sites were targeted for ablation, along with pulmonary vein isolation in 77% of patients. RESULTS AF was paroxysmal in 56%, and 67% had prior AF ablation. All patients had rotors identified (mean 2.6 ± 1.2 per patient, 77% in LA). Prespecified acute procedural end-point was achieved in 47% of patients (n = 20): AF termination in 4, organization in 7, >10% slowing of AF cycle length in 9. Acute complications occurred in 4 patients (9.3%). At 18 ± 7 months of follow-up, 37% were free from documented recurrent AF after a 3-month blanking period; 21% were free from documented atrial tachyarrhythmias and off antiarrhythmic drugs. Multivariate analysis did not reveal any significant predictors of AF recurrence, including pattern of AF, acute procedural success, or prior failed ablation. CONCLUSION Long-term clinical results after FIRM ablation in this cohort of patients showed poor efficacy, different from previously published studies. Randomized studies are needed to evaluate the efficacy and clinical utility of this ablation approach for treating AF.

Bilateral Cardiac Sympathetic Denervation for the Management of Electrical Storm

To the Editor: The sympathetic nervous system plays an important role in ventricular arrhythmogenesis. Left cardiac sympathetic denervation (LCSD) decreases the incidence of ventricular arrhythmias (VAs) and sudden cardiac death in patients with severe VAs ([1,2][1]). However, when LCSD is

Incidence of pulmonary vein conduction recovery in patients without clinical recurrence after ablation of paroxysmal atrial fibrillation: Mechanistic implications

BACKGROUND Pulmonary vein (PV) isolation has become the mainstay acute procedural end point for paroxysmal atrial fibrillation (AF) ablation. OBJECTIVE To examine the incidence of conduction recovery in the PVs in patients without clinical recurrence of AF after paroxysmal AF ablation. METHODS From August 2008 to March 2011, 392 patients with drug-refractory PAF underwent catheter ablation in our center, a wide area circumferential ablation approach guided with a circular mapping catheter was performed with the intended endpoint of entrance block in all PVs. 276 (70.4%) of them were free from recurrence at one year follow-up, and 32 of them were enrolled to assess the incidence of PV reconnection. Forty-three patients with clinical recurrence after ablation were analyzed for comparison. The regions of gap were mapped and characterized in all of the reconnected PVs. RESULTS Among patients without recurrence, recovery of PV conduction was observed in 29 of 32 (90.6%) patients: 10/32 (31.2%) reconnection in 4 veins, 7/32 (21.9%) in 3 veins, 10/32 (31.2%) in 2 veins, and 2/32 (6.2%) in 1 vein. No anatomic propensity was seen because reconnection was evenly distributed throughout all veins (left superior pulmonary vein 21, left inferior pulmonary vein 20, right superior pulmonary vein 19, and right inferior pulmonary vein 23). When compared to patients with recurrence, no significant differences were seen in the proportion of patients with reconnection (P = 1.0) or in left atrium-PV intervals (73.4 ± 43.3 ms vs 61.9 ± 31.8 ms; P > .05). CONCLUSION A high incidence of PV reconnection was similarly observed in patients with and without recurrence of AF, suggesting that sustained PV isolation may not be required for freedom from clinical recurrence of AF.

Epicardial ablation of ventricular tachycardia: An institutional experience of safety and efficacy

BACKGROUND Epicardial ablation has been shown to be a useful adjunct for treatment of ventricular tachycardia (VT). OBJECTIVE To report the trends, safety, and efficacy of epicardial mapping and ablation at a single center over an 8-year period. METHODS Patients referred for VT ablation (June 2004 to July 2011) were divided into 3 groups: ischemic cardiomyopathy (ICM), nonischemic cardiomyopathy (NICM), and idiopathic ventricular arrhythmias (VA). Patients with scar-mediated VT who underwent combined epicardial and endocardial (epi-endo) mapping and ablation were compared with those who underwent endocardial-only (endo-only) ablation with regard to patient characteristics, acute procedural success, 6- and 12-month clinical outcomes. RESULTS Among 144 patients referred for VT ablation, 95 patients underwent 109 epicardial procedures (94% access rate). Major complications were seen in 8 patients (8.8%) with pericardial bleeding (>80 cm(3)) in 6 cases (6.7%), although no tamponade, surgical intervention, or procedural mortality was seen. Patients with ICM who underwent a combined epi-endo ablation had improved freedom from VT compared with those who underwent endo-only ablation at 12 months (85% vs 56%; P = .03). In patients with NICM, no differences were seen between those who underwent epi-endo ablation and those who underwent endo-only ablation at 12 months (36% vs 33%; P = 1.0). In idiopathic VA, only 2 of 17 patients were successfully ablated from the epicardium. CONCLUSIONS In this large tertiary single-center experience, complication rates are acceptably low and improved clinical outcomes were associated with epi-endo ablation in patients with ICM. Patients with NICM represent a growing referred population, although clinical recurrence remains high despite epicardial ablation. Epicardial ablation has a low yield in idiopathic VA.