Right ventricular epicardial arrhythmogenic substrate in long-QT syndrome patients at risk of sudden death.

AIMS: The long-QT syndrome (LQTS) represents a leading cause of sudden cardiac death (SCD). The aim of this study was to assess the presence of an underlying electroanatomical arrhythmogenic substrate in high-risk LQTS patients. METHODS AND RESULTS: The present study enrolled 11 consecutive LQTS patients who had experienced frequent implantable cardioverter-defibrillator (ICD discharges triggered by ventricular fibrillation (VF). We acquired electroanatomical biventricular maps of both endo and epicardial regions for all patients and analyzed electrograms sampled from several myocardial regions. Abnormal electrical activities were targeted and eliminated by the means of radiofrequency catheter ablation. VF episodes caused a median of four ICD discharges in eleven patients (6 male, 54.5%; mean age 44.0 ± 7.8 years, range 22-53) prior to our mapping and ablation procedures. The average QTc interval was 500.0 ± 30.2 ms. Endo-epicardial biventricular maps displayed abnormally fragmented, low-voltage (0.9 ± 0.2 mV) and prolonged electrograms (89.9 ± 24.1 ms) exclusively localized in the right ventricular epicardium. We found electrical abnormalities extending over a mean epicardial area of 15.7 ± 3.1 cm2. Catheter ablation of the abnormal epicardial area completely suppressed malignant arrhythmias over a mean 12 months of follow-up (median VF episodes before vs. after ablation, 4 vs. 0; P = 0.003). After the procedure, the QTc interval measured in a 12-lead ECG analysis shortened to a mean of 461.8 ± 23.6 ms (P = 0.004). CONCLUSION: This study reveals that, among high-risk LQTS patients, regions localized in the epicardium of the right ventricle harbour structural electrophysiological abnormalities. Elimination of these abnormal electrical activities successfully prevented malignant ventricular arrhythmia recurrences.

Impact of Dietary Factors on Brugada Syndrome and Long QT Syndrome.

A healthy regime is fundamental for the prevention of cardiovascular diseases (CVD). In inherited channelopathies, such as Brugada syndrome (BrS) and Long QT syndrome (LQTS), unfortunately, sudden cardiac death could be the first sign for patients affected by these syndromes. Several known factors are used to stratify the risk of developing cardiac arrhythmias, although none are determinative. The risk factors can be affected by adjusting lifestyle habits, such as a particular diet, impacting the risk of arrhythmogenic events and mortality. To date, the importance of understanding the relationship between diet and inherited channelopathies has been underrated. Therefore, we describe herein the effects of dietary factors on the development of arrhythmia in patients affected by BrS and LQTS. Modifying the diet might not be enough to fully prevent arrhythmias, but it can help lower the risk.

Non-paroxysmal atrial fibrillation mapping: characterization of the electrophysiological substrate using a novel integrated mapping technique.

AIMS: Clinical outcomes after radiofrequency catheter ablation (RFCA) remain suboptimal in the treatment of non-paroxysmal atrial fibrillation (AF). Electrophysiological mapping may improve understanding of the underlying mechanisms. To describe the arrhythmia substrate in patients with persistent (Pers) and long-standing persistent (LSPers) AF, undergoing RFCA, using an integrated mechanism mapping technique. METHODS AND RESULTS: Patients underwent high-density electroanatomical mapping before and after catheter ablation. Integrated maps characterized electrogram (EGM) cycle length (CL) in regions with repetitive-regular (RR) activations, stable wavefront propagation, fragmentation, and peak-to-peak bipolar voltage. Among 83 patients (72% male, 60 ± 11 years old), RR activations were identified in 376 regions (mean CL 180 ± 31 ms). PersAF patients (n = 43) showed more RR sites per patient (5.3 ± 2.4 vs. 3.7 ± 2.1, P = 0.002) with faster CL (166 ± 29 vs. 190 ± 29 ms; P < 0.001) and smaller surface area of fragmented EGMs (15 ± 14% vs. 27 ± 17%, P < 0.001) compared with LSPersAF. The post-ablation map in 50 patients remaining in AF, documented reduction of the RR activities per patient (1.5 ± 0.7 vs. 3.7 ± 1.4, P < 0.001) and area of fragmentation (22 ± 17% vs. 8 ± 9%, P < 0.001). Atrial fibrillation termination during ablation occurred at RR sites (0.48 ± 0.24 mV; 170.5 ± 20.2 ms CL) in 31/33 patients (94%). At the latest follow-up, arrhythmia freedom was higher among patients receiving ablation >75% of RR sites (Q4 82.6%, Q3 63.1%, Q2 35.1%, and Q1 0%; P < 0.001). CONCLUSION: The integrated mapping technique allowed characterization of multiple arrhythmic substrates in non-paroxysmal AF patients. This technique might serve as tool for a substrate-targeted ablation approach.

Electrical Substrate Elimination in 135 Consecutive Patients With Brugada Syndrome.

BACKGROUND: There is emerging evidence that localization and elimination of abnormal electric activity in the epicardial right ventricular outflow tract may be beneficial in patients with Brugada syndrome. METHODS AND RESULTS: A total of 135 symptomatic Brugada syndrome patients having implantable cardiac defibrillator were enrolled: 63 (group 1) having documented ventricular tachycardia (VT)/ventricular fibrillation (VF) and Brugada syndrome-related symptoms, and 72 (group 2) having inducible VT/VF without ECG documentation at the time of symptoms. About 27 patients of group 1 experienced multiple implantable cardiac defibrillator shocks for recurrent VT/VF episodes. Three-dimensional maps before and after ajmaline determined the arrhythmogenic electrophysiological substrate (AES) as characterized by prolonged fragmented ventricular potentials. Primary end point was identification and elimination of AES leading to ECG pattern normalization and VT/VF noninducibility. Extensive areas of AES were found in the right ventricle epicardium, which were wider in group 1 (P=0.007). AES increased after ajmaline in both groups (P<0.001) and was larger in men (P=0.008). The increase of type-1 ST-segment elevation correlated with AES expansion (r=0.682, P<0.001). Radiofrequency ablation eliminated AES leading to ECG normalization and VT/VF noninducibility in all patients. During a median follow-up of 10 months, the ECG remained normal even after ajmaline in all except 2 patients who underwent a repeated effective procedure for recurrent VF. CONCLUSIONS: In Brugada syndrome, AES is commonly located in the right ventricle epicardium and ajmaline exposes its extent and distribution, which is correlated with the degree of coved ST-elevation. AES elimination by radiofrequency ablation results in ECG normalization and VT/VF noninducibility. Substrate-based ablation is effective in potentially eliminating the arrhythmic consequences of this genetic disease. CLINICAL TRIAL REGISTRATION: URL: https://clinicaltrials.gov. Unique identifier: NCT02641431.

Electrophysiology testing and catheter ablation are helpful when evaluating asymptomatic patients with Wolff-Parkinson-White pattern: the pro perspective.

Important advances in the natural history and diagnosis of, and therapy for, asymptomatic Wolff-Parkinson-White (WPW) syndrome have been made in the last decade by our group. These data have necessitated revisiting current practice guidelines to decide on the optimal management of the asymptomatic WPW population. There has also been an emphasis on identifying initially asymptomatic individuals who are at risk by nationwide screening programs using the electrocardiogram for prophylactic catheter ablation to prevent the lifetime risk of sudden cardiac death, particularly in young asymptomatic people, because only a subgroup of them is at high risk, requiring early catheter ablation.

Brugada Syndrome Phenotype Elimination by Epicardial Substrate Ablation.

BACKGROUND: Whether Brugada syndrome (BrS) depends on functional epicardial substrates, which may be definitively eliminated by radiofrequency ablation, remains unknown. METHODS AND RESULTS: Patients with BrS underwent epicardial mapping to identify areas of abnormal electrograms as target for radiofrequency ablation. Substrate identification consisted in mapping right ventricle epicardial surface before and after flecainide (2 mg/kg per 10 minutes). After radiofrequency ablation, flecainide and remap confirmed elimination of abnormal substrate, BrS ECG pattern, and ventricular tachycardia/ventricular fibrillation inducibility. Flecainide testing was performed at each follow-up visits ≤6 months. Fourteen patients with BrS, median age 39 years (30.3-42.3) with implantable cardioverter-defibrillator were enrolled. Low-voltage areas (<1.5 mV) were commonly identified on the anterior right free wall and right ventricular outflow tract, which increased after flecainide from 17.6 cm(2) (12.1-24.2) to 28.5 cm(2) (21.6-30.2; P=0.001). Similarly, areas with abnormal electrograms increased after flecainide from 19.0 (17.5-23.6) to 27.3 cm(2) (24.0-31.2; P=0.001). After 23.8 minutes (18.1-28.5) of radiofrequency ablation, abnormal electrograms disappeared, whereas low-voltage areas were replaced by scar areas (<0.5 mV) of 25.9 cm(2) (19.6-31.0). Substrate elimination resulted in BrS ECG pattern disappearance and no ventricular tachycardia/ventricular fibrillation inducibility without complications. After a median follow-up of 5 months (3.8-5.3), ECG remained normal despite flecainide. CONCLUSIONS: In patients with BrS, there is a relationship between abnormal ECG pattern, the extent of abnormal epicardial substrate, and ventricular tachycardia/ventricular fibrillation inducibility. Ablation of the substrate identified in the presence of flecainide can eliminate the BrS phenotype and warrants further study.

The natural history of asymptomatic ventricular pre-excitation a long-term prospective follow-up study of 184 asymptomatic children.

OBJECTIVES: The aim of this study was to describe the natural history of asymptomatic ventricular pre-excitation in children and to determine predictors of potentially life-threatening arrhythmic events. BACKGROUND: Sudden death can be the first clinical manifestation in asymptomatic children with ventricular pre-excitation, but reduction of its incidence by prophylactic ablation requires the identification of subjects at high risk. METHODS: Between 1995 and 2005 we prospectively collected clinical and electrophysiologic data from 184 children (66% male; median age 10 years; range 8 to 12 years) with asymptomatic ventricular pre-excitation on the electrocardiogram. After electrophysiologic testing, subjects were followed as outpatients taking no medications. The primary end point of the study was the occurrence of arrhythmic events. Predictors of potentially life-threatening arrhythmias were analyzed. RESULTS: Over a median follow-up of 57 months (min/max 32/90 months) after electrophysiologic testing, 133 children (mean age 10 years; range 8 to 12 years) did not experience arrhythmic events, remaining totally asymptomatic, while 51 children had within 20 months (min/max 8/60 months) a first arrhythmic event, which was potentially life-threatening in 19 of them (mean age 10 years; range 10 to 14 years). Life-threatening tachyarrhythmias resulted in cardiac arrest (3 patients), syncope (3 patients), atypical symptoms (8 patients), or minimal symptoms (5 patients). Univariate analysis identified tachyarrhythmia inducibility (p < 0.001), anterograde refractory period of accessory pathways (APERP)

Sudden death and ventricular preexcitation: is it necessary to treat the asymptomatic patients?

Currently, asymptomatic ventricular preexcitation, which has been put at rest for many decades, remains a clinical challenge as there are no predictors of sudden death, which can be the first clinical presentation of the syndrome. Identification of risk factors for sudden death is important, considering the availability of a definitive treatment. Now, as radiofrequency catheter ablation of accessory pathways has reported success rates approaching 100 percent without major complications in many centers worldwide, it becomes unacceptable that even one asymptomatic individual with WPW will die or will experience life-threatening arrhythmic events. In our extensive experience a short anterograde refractory period of accessory pathways, inducibility of sustained tachyarrhythmias and the presence of multiple accessory pathways are the strongest predictors of life-threatening arrhythmias and sudden death. Therefore, it is not yet justified that, after an incidental diagnosis of WPW syndrome has been made, no risk stratification by invasive testing is done. Subjects at high risk, particularly if young or adolescent, should be identified and then ablated in the same session as they can develop lethal arrhythmic events within a few years and this is our current practice. Recently, we sent a questionnaire to investigate clinical practices over a large number of centers around the world about asymptomatic ventricular preexcitation. A total of 100 replies were received and the results demonstrate that there is worldwide agreement in performing invasive electrophysiologic testing and prophylactic ablation in selected subjects. These findings provide strong evidence to revisit current guidelines, which appropriately in the absence of evidence had been conservative.

Endocardial impedance mapping during circumferential pulmonary vein ablation of atrial fibrillation differentiates between atrial and venous tissue.

BACKGROUND: Circumferential pulmonary vein ablation (CPVA) is an effective treatment for atrial fibrillation (AF). Accurate left atrial (LA) mapping is essential for creating lesions at the LA-pulmonary vein (PV) junction, avoiding PV stenosis. OBJECTIVES: The purpose of this study was to establish whether endocardial impedance varies within the LA and PVs and whether it is a useful tool for mapping and ablation. METHODS: Pilot Phase: Three-dimensional LA maps were created using CARTO. Impedance (Z) was measured using a radiofrequency generator at multiple points in the LA, PV ostia (PVO), and deep PVs in 79 patients undergoing their first AF ablation (group 1) and 29 patients undergoing repeat CPVA (group 2). Prospective Phase: In an additional 20 patients, using pilot phase data, one operator defined catheter tip location as either LA or PVO based on CARTO and fluoroscopy. A second operator blinded to CARTO simultaneously did the same based on impedance at 15 +/- 4 points per patient. RESULTS: Group 1: Z(LA) was 99.4 +/- 9.0 omega. Z(PVO) was higher (109.2 +/- 8.5 omega), rising further as the catheter advanced into deep PV (137 omega +/- 18). Z(PVO) differed from Z(LA) by 9 +/- 4 omega. Group 2 had a lower Z(LA) and Z(PVO) compared with group 1 (P <.05). Impedance monitoring differentiated between LA and PVO, with 91% specificity and sensitivity, 96% positive predictive value, and 81% negative predictive value. At 3-month follow-up, no patients had evidence of PV stenosis on magnetic resonance imaging. CONCLUSION: Impedance mapping reliably identifies the LA-PV transitional zone, facilitating AF ablation, and its use is associated with a low incidence of PV stenosis.

Atrial fibrillation ablation: state of the art.

Among several catheter-based strategies for curing atrial fibrillation (AF), 2 approaches have emerged as dominant strategies in current clinical practice: ostial segmental disconnection of all pulmonary veins (PVs) from the adjacent atrial tissue and circumferential PV ablation, first reported by our laboratory in Milan. The cure for AF by circumferential PV ablation has had a dramatic impact on morbidity, quality of life, and even mortality in patients with the most frequent cardiac arrhythmia. The last 10 years of AF ablation are characterized by a better understanding of AF mechanisms as well as by new and evolving concepts associated with innovation in technologies. We recently demonstrated, for the first time, the role of vagal denervation in enhancing long-term benefits from circumferential PV ablation. Unlike other strategies, our strategy was associated with high success rates in both paroxysmal and chronic AF. As a result, our initial approach did not substantially change over time, and now we have long-term results after >3 years of follow-up. Recently, we demonstrated the safety and feasibility of remote magnetic navigation of a soft magnetic-tip catheter within the left atrium, even at challenging sites for both mapping and ablation in patients with AF. Use of a robotic navigation system has begun a new era in interventional cardiac electrophysiology-without risk of major complications, such as cardiac tamponade or atrioesophageal fistula, even in less experienced laboratories.

Radiofrequency ablation in children with asymptomatic Wolff-Parkinson-White syndrome.

BACKGROUND: Ventricular fibrillation can be the presenting arrhythmia in children with asymptomatic Wolff-Parkinson-White syndrome. Deaths due to this arrhythmia are potentially preventable. METHODS: We performed a randomized study in which prophylactic radiofrequency catheter ablation of accessory pathways was compared with no ablation in asymptomatic children (age range, 5 to 12 years) with the Wolff-Parkinson-White syndrome who were at high risk for arrhythmias. The primary end point was the occurrence of arrhythmic events during follow-up. RESULTS: Of the 165 eligible children, 60 were determined to be at high risk for arrhythmias. After randomization, but before any ablation had been performed, the parents withdrew 13 children from the study. Of the remaining children, 20 underwent prophylactic ablation and 27 had no treatment. The characteristics of the two groups were similar. There were three ablation-related complications, one of which led to hospitalization. During follow-up, 1 child in the ablation group (5 percent) and 12 in the control group (44 percent) had arrhythmic events. Two children in the control group had ventricular fibrillation, and one died suddenly. The cumulative rate of arrhythmic events was lower among children at high risk who underwent ablation than among those at high risk who did not. The reduction in risk associated with ablation remained significant after adjustment in a Cox regression analysis. In both the ablation and the control groups, the independent predictors of arrhythmic events were the absence of prophylactic ablation and the presence of multiple accessory pathways. CONCLUSIONS: In asymptomatic, high-risk children with the Wolff-Parkinson-White syndrome, prophylactic catheter ablation performed by an experienced operator reduces the risk of life-threatening arrhythmias.

Left atrial tachycardia after circumferential pulmonary vein ablation for atrial fibrillation: electroanatomic characterization and treatment.

OBJECTIVES: The purpose of this study was to evaluate the electroanatomic characteristics of left atrial tachycardia (AT) in a series of patients who underwent circumferential pulmonary vein ablation (CPVA) and to describe the ablation strategy and clinical outcome. BACKGROUND: Circumferential pulmonary vein ablation is an effective treatment for atrial fibrillation. A potential midterm complication is the development of left AT. There are only isolated reports describing mapping and ablation of such arrhythmias. METHODS: Thirteen patients (age 57.4 +/- 8.9 years, five female) underwent mapping and ablation of 14 left ATs via an electroanatomic mapping system a mean of 2.6 +/- 1.6 months after CPVA. RESULTS: Three patients were characterized as having focal AT (cycle length: 266 +/- 35.9 ms). Of 11 macro-re-entrant tachycardias studied in the remaining 10 patients (cycle length: 275 +/- 75 ms), 5 showed single-loop and 6 dual-loop circuits. Re-entrant circuits used the mitral isthmus, the posterior wall, or gaps on previous encircling lines. Such gaps and all three foci occurred anterior to the left superior pulmonary vein or at the septal aspect of the right pulmonary veins. Thirteen of 14 tachycardias (93%) were successfully ablated. CONCLUSIONS: Left AT after CPVA can be due to a macro-re-entrant or focal mechanism. Re-entry occurs most commonly across the mitral isthmus, the posterior wall, or gaps on previous ablation lines. Such gaps and foci occur most commonly at the anterior aspect of the left superior pulmonary vein and at the septal aspect of the right pulmonary veins. These arrhythmias can be successfully mapped and ablated with an electroanatomic mapping system.

Cardiac contractility modulation by non-excitatory electrical currents. The new frontier for electrical therapy of heart failure.

Heart failure (HF) may complicate ischemic heart disease in both its acute and chronic manifestations, representing a prevalent health problem throughout the world. Development of therapies to improve heart function, relieve symptoms, reduce hospitalizations and improve survival is a high priority in cardiovascular medicine. The available pharmacological strategies, including angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, beta-blockers, and aldosterone receptor antagonists have recently been complemented by new electrical therapy, including implantable cardioverter-defibrillators for "MADIT II" patients and cardiac resynchronization for the 30% of HF patients with concomitant intraventricular conduction delay. The wide variety of available HF medications provides ample evidence that we have not yet succeeded in this effort. Safe and effective inotropic electrical therapy could be a useful addition to our therapeutic armamentarium in an attempt to correct Ca2+ fluxes abnormalities during the cardiac action potential. Cardiac contractility modulation (CCM) by means of non-excitatory electrical currents delivered during the action potential plateau has been shown to acutely enhance systolic function in humans with HF. Herewith, we report on our preliminary experience with CCM therapy for patients with HF, providing fundamental notions to characterize the rationale of this novel form of therapy. Briefly, CCM therapy appears to be safe and feasible. Proarrhythmic effects of this novel therapy seem unlikely. Preliminary data indicate that CCM gradually and significantly improves systolic performance, symptoms and functional status. The technique would appear to be attractive as an additive treatment for severe HF. Controlled randomized studies are needed to validate this novel concept.

First human chronic experience with cardiac contractility modulation by nonexcitatory electrical currents for treating systolic heart failure: mid-term safety and efficacy results from a multicenter study.

INTRODUCTION: Conventional electrical therapies for heart failure (HF) encompass defibrillation and ventricular resynchronization for patients at high risk for lethal arrhythmias and/or with inhomogeneous ventricular contraction. Cardiac contractility modulation (CCM) by means of nonexcitatory electrical currents delivered during the action potential plateau has been shown to acutely enhance systolic function in humans with HF. The aim of this multicenter study was to assess the chronic safety and preliminary efficacy of an implantable device delivering this novel form of electrical therapy. METHODS AND RESULTS: Thirteen patients with drug-resistant HF (New York Heart Association [NYHA] class III) were consecutively implanted with a device (OPTIMIZER II) delivering CCM biphasic square-wave pulses (20 ms, 5.8-7.7 V, 30 ms after detection of local activation) through two right ventricular leads screwed into the right aspect of the interventricular septum. CCM signals were delivered 3 hours daily over 8 weeks (3-hour phase) and 7 hours daily over the next 24 weeks (7-hour phase). Safety and feasibility of this novel therapy were regarded as primary endpoints. Preliminary clinical efficacy, -as expressed by changes in ejection fraction (EF), NYHA class, 6-minute walking test (6-MWT), peak O(2) uptake (peak VO(2)), and Minnesota Living with HF Questionnaire (MLWHFQ), was assessed at baseline and at the end of each phase. At the end of follow-up (8.8 +/- 0.2 months), all patients were alive, without heart transplantation or need for left ventricular assist device. Serial 24-hour Holter analysis revealed no proarrhythmic effect. No devices malfunctioned or failed for any reason other than end-of-battery life. Throughout the two study phases, EF improved from 22.7 +/- 7% to 28.7 +/- 7% and 37 +/- 13% (P = 0.004), 6-MWT from 418 +/- 99 m to 477 +/- 96 m and 510 +/- 107 m (P = 0.002), MLWHFQ from 36 +/- 21 to 18 +/- 12 and 7 +/- 6 (P = 0.002), peak VO(2) from 13.7 +/- 1.1 to 14.9 +/- 1.9 to 16.2 +/- 2.4 (P = 0.037), and NYHA class from 3 to 1.8 +/- 0.4 to 1.5 +/- 0.7 (P < 0.001). CONCLUSION: CCM therapy appears to be safe and feasible. Proarrhythmic effects of this novel therapy seem unlikely. Preliminary data indicate that CCM gradually and significantly improves systolic performance, symptoms, and functional status. CCM therapy for 7 hours per day is associated with greater dispersion near the mean, emphasizing the need to individually tailor CCM delivery duration. The technique appears to be attractive as an additive treatment for severe HF. Controlled randomized studies are needed to validate this novel concept.

A randomized study of prophylactic catheter ablation in asymptomatic patients with the Wolff-Parkinson-White syndrome.

BACKGROUND: Young age and inducibility of atrioventricular reciprocating tachycardia or atrial fibrillation during invasive electrophysiological testing identify asymptomatic patients with a Wolff-Parkinson-White pattern on the electrocardiogram as being at high risk for arrhythmic events. We tested the hypothesis that prophylactic catheter ablation of accessory pathways would provide meaningful and durable benefits as compared with no treatment in such patients. METHODS: From 1997 to 2002, among 224 eligible asymptomatic patients with the Wolff-Parkinson-White syndrome, patients at high risk for arrhythmias were randomly assigned to radio-frequency catheter ablation of accessory pathways (37 patients) or no treatment (35 patients). The end point was the occurrence of arrhythmic events over a five-year follow-up period. RESULTS: Patients assigned to ablation had base-line characteristics that were similar to those of the controls. Two patients in the ablation group (5 percent) and 21 in the control group (60 percent) had arrhythmic events. One control patient had ventricular fibrillation as the presenting arrhythmia. The five-year Kaplan-Meier estimates of the incidence of arrhythmic events were 7 percent among patients who underwent ablation and 77 percent among the controls (P<0.001 by the log-rank test); the risk reduction with ablation was 92 percent (relative risk, 0.08; 95 percent confidence interval, 0.02 to 0.33; P<0.001). CONCLUSIONS: Prophylactic accessory-pathway ablation markedly reduces the frequency of arrhythmic events in asymptomatic patients with the Wolff-Parkinson-White syndrome who are at high risk for such events.

Sudden death due to atrial fibrillation in hypertrophic cardiomyopathy: a predictable event in a young patient.

This case refers to a 39-year-old woman with hypertrophic cardiomyopathy (HCM) and family history of sudden death (SD). In 1985, high rate atrial stimulation induced VF. In 1996 an ICD was implanted and she remained without arrhythmic events until November 2000 when the device reported one episode of atrial fibrillation degenerating into VF and terminated by the ICD. The VF induction mechanism recorded by the ICD was similar to that observed in 1985. The high incidence of atrial tachyarrhythmias in HCM renders cases like this at higher risk of SD. The predictive role of incremental atrial stimulation merits highlighting in future studies.