Appropriate and inappropriate shocks in hypertrophic cardiomyopathy patients with subcutaneous implantable cardioverter-defibrillators: An international multicenter study

BACKGROUND

Subcutaneous implantable cardioverter-defibrillators (S-ICDs) are attractive for preventing sudden cardiac death in hypertrophic cardiomyopathy (HCM) as they mitigate risks of transvenous leads in young patients. However, S-ICDs may be associated with increased inappropriate shock (IAS) in HCM patients.

OBJECTIVE

The purpose of this study was to assess the incidence and predictors of appropriate shock and IAS in a contemporary HCM S-ICD cohort.

METHODS

We collected electrocardiographic and clinical data from HCM patients who underwent S-ICD implantation at 4 centers. Etiologies of all S-ICD shocks were adjudicated. We used Firth penalized logistic regression to derive adjusted odds ratios (aORs) for predictors of IAS.

RESULTS

Eighty-eight HCM patients received S-ICDs (81 for primary and 7 for secondary prevention) with a mean follow-up of 2.7 years. Five patients (5.7%) had 9 IAS episodes (3.8 IAS per 100 patient-years) most often because of sinus tachycardia and/or T-wave oversensing. Independent predictors of IAS were higher 12-lead electrocardiographic R-wave amplitude (aOR 2.55 per 1 mV; 95% confidence interval 1.15-6.38) and abnormal T-wave inversions (aOR 0.16; 95% confidence interval 0.02-0.97). There were 2 appropriate shocks in 7 secondary prevention patients and none in 81 primary prevention patients, despite 96% meeting Enhanced American College of Cardiology/American Heart Association criteria and the mean European HCM Risk-SCD score predicting 5.7% 5-year risk. No patients had sudden death or untreated sustained ventricular arrhythmias.

CONCLUSION

In this multicenter HCM S-ICD study, IAS were rare and appropriate shocks confined to secondary prevention patients. The R-wave amplitude increased IAS risk, whereas T-wave inversions were protective. HCM primary prevention implantable cardioverter-defibrillator guidelines overestimated the risk of appropriate shocks in our cohort.

Impact of a nurse-led limited risk factor modification program on arrhythmia outcomes in patients with atrial fibrillation undergoing catheter ablation

BACKGROUND

We have previously demonstrated the feasibility of a nurse-led risk factor modification (RFM) program for improving weight loss and obstructive sleep apnea (OSA) care among patients with atrial fibrillation (AF).

OBJECTIVE

We now report its impact on arrhythmia outcomes in a subgroup of patients undergoing catheter ablation.

METHODS

Participating patients with obesity and/or need for OSA management (high risk per Berlin Questionnaire or untreated OSA) underwent in-person consultation and monthly telephone calls with the nurse for up to 1 year. Arrhythmias were assessed by office ECGs and ≥2 wearable monitors. Outcomes, defined as Arrhythmia control (0-6 self-terminating recurrences, with ≤1 cardioversion for nonparoxysmal AF) and Freedom from arrhythmias (no recurrences on or off antiarrhythmic drugs), were compared at 1 year between patients undergoing catheter ablation who enrolled and declined RFM.

RESULTS

Between 1 November 2016 and 1 April 2018, 195 patients enrolled and 196 declined RFM (body mass index, 35.1 ± 6.7 vs 34.3 ± 6.3 kg/m² ; 50% vs 50% paroxysmal AF; P = NS). At 1 year, enrolled patients demonstrated significant weight loss (4.7% ± 5.3% vs 0.3% ± 4.4% in declined patients; P < .0001) and improved OSA care (78% [n = 43] of patients diagnosed with OSA began treatment). However, outcomes were similar between enrolled and declined patients undergoing ablation (arrhythmia control in 80% [n = 48] vs 79% [n = 38]; freedom from arrhythmia in 58% [n = 35] vs 71% [n = 34]; P = NS).

CONCLUSION

Despite improving weight loss and OSA care, our nurse-led RFM program did not impact 1-year arrhythmia outcomes in patients with AF undergoing catheter ablation.

Characterization of Structural Changes in Arrhythmogenic Right Ventricular Cardiomyopathy With Recurrent Ventricular Tachycardia After Ablation: Insights From Repeat Electroanatomic Voltage Mapping

BACKGROUND

Data characterizing structural changes of arrhythmogenic right ventricular (RV) cardiomyopathy are limited.

METHODS

Patients presenting with left bundle branch block ventricular tachycardia in the setting of arrhythmogenic RV cardiomyopathy with procedures separated by at least 9 months were included.

RESULTS

Nineteen consecutive patients (84% males; mean age 39±15 years [range, 20-76 years]) were included. All 19 patients underwent 2 detailed sinus rhythm electroanatomic endocardial voltage maps (average 385±177 points per map; range, 93-847 points). Time interval between the initial and repeat ablation procedures was mean 50±37 months (range, 9-162). No significant progression of voltage was observed (bipolar: 38 cm² [interquartile range (IQR), 25-54] versus 53 cm² [IQR, 25-65], P=0.09; unipolar: 116 cm² [IQR, 61-209] versus 159 cm² [IQR, 73-204], P=0.36) for the entire study group. There was a significant increase in RV volumes (percentage increase, 28%; 206 mL [IQR, 170-253] versus 263 mL [IQR, 204-294], P<0.001) for the entire study population. Larger scars at baseline but not changes over time were associated with a significant increase in RV volume (bipolar: Spearman ρ, 0.6965, P=0.006; unipolar: Spearman ρ, 0.5743, P=0.03). Most patients with progressive RV dilatation (8/14, 57%) had moderate (2 patients) or severe (6 patients) tricuspid regurgitation recorded at either initial or repeat ablation procedure.

CONCLUSIONS

In patients with arrhythmogenic RV cardiomyopathy presenting with recurrent ventricular tachycardia, >10% increase in RV endocardial surface area of bipolar voltage consistent with scar is uncommon during the intermediate term. Most recurrent ventricular tachycardias are localized to regions of prior defined scar. Voltage indexed scar area at baseline but not changes in scar over time is associated with progressive increase in RV size and is consistent with adverse remodeling but not scar progression. Marked tricuspid regurgitation is frequently present in patients with arrhythmogenic RV cardiomyopathy who have progressive RV dilation.

Septal Versus Lateral Mitral Isthmus Ablation for Treatment of Mitral Annular Flutter

OBJECTIVES

This study sought to compare efficacy and safety of the septal mitral isthmus line (SMIL) with that of the lateral mitral isthmus line (LMIL) for treatment of mitral annular flutter (MAF).

BACKGROUND

MAF is the most common left atrial macro-re-entrant organized atrial tachycardia (OAT) occurring after catheter ablation of atrial fibrillation. The 2 most common lesion sets for treating MAF include linear ablation from the anteroseptal mitral annulus to the right superior pulmonary vein (SMIL) and from the lateral mitral annulus to left inferior pulmonary vein (LMIL).

METHODS

The study included all mitral isthmus ablations performed at the Hospital of the University of Pennsylvania in 2016 and 2017. Acute procedural results and long-term arrhythmia-free survival were compared between groups.

RESULTS

Of 114 total MILs, conduction block was achieved across 73 (93.6%) SMILs compared with 29 (80.6%) LMILs (p = 0.05). Although the length of the SMIL was longer (48.9 ± 12.8 cm vs. 38.7 ± 12.8 cm; p = 0.001), time required to achieve block was shorter (25.2 ± 15.9 min vs. 36.6 ± 21.3 min; p = 0.03). Coronary sinus ablation was required in 58.3% of LMILs due to inability to achieve conduction block with left atrial ablation alone. In multivariate analysis, only failure to achieve acute MIL block remained significantly associated with subsequent OAT recurrence (hazard ratio: 6.39; 95% confidence interval: 1.37 to 29.9; p = 0.02).

CONCLUSIONS

The SMIL requires less time to complete and more frequently results in acute MIL block than the LMIL. Additionally, ablation is rarely required outside the left atrium. Failure to achieve acute MIL block is strongly associated with subsequent OAT recurrence.

A Nurse-Led Limited Risk Factor Modification Program to Address Obesity and Obstructive Sleep Apnea in Atrial Fibrillation Patients

Background

Obesity and obstructive sleep apnea (OSA) are associated with atrial fibrillation (AF), yet these conditions remain inadequately treated. We report on the feasibility and efficacy of a nurse‐led risk factor modification program utilizing a pragmatic approach to address obesity and OSA in AF patients.

Methods and Results

AF patients with obesity (body mass index ≥30 kg/m²) and/or the need for OSA management (high risk per Berlin Questionnaire or untreated OSA) were voluntarily enrolled for risk factor modification, which comprised patient education, lifestyle modification, coordination with specialists, and longitudinal management. Weight loss and OSA treatment were monitored by monthly follow‐up calls and/or continuous positive airway pressure (CPAP) unit downloads. Quality of life and arrhythmia symptoms were assessed with the SF‐36 and AF Severity Scale at baseline and at 6 months. From November 1, 2016 to October 31, 2017, 252 patients (age 63±11 years; 71% male; 57% paroxysmal AF) were enrolled, 189 for obesity and 93 for OSA. Obese patients who enrolled lost significantly greater percent body weight than those who declined (3% versus 0.3%; P<0.05). Among 93 patients enrolled for OSA, 70 completed sleep studies, OSA was confirmed in 50, and the majority (76%) started CPAP therapy. All components of quality of life and arrhythmia symptoms improved significantly from baseline to 6 months among enrolled patients.

Conclusions

A nurse‐led risk factor modification program is a potentially sustainable and generalizable model that can improve weight loss and OSA in AF patients, translating into improved quality of life and arrhythmia symptoms.

Incidence of Left Atrial Appendage Triggers in Patients With Atrial Fibrillation Undergoing Catheter Ablation

OBJECTIVE

This study sought to investigate incidence of left atrial appendage (LAA) triggers of atrial fibrillation (AF) and/or organized atrial tachycardias (OAT) in patients undergoing AF ablation and to evaluate outcomes after ablation.

BACKGROUND

Although LAA isolation is being increasingly performed during AF ablation, the true incidence of LAA triggers for AF remains unclear.

METHODS

All patients with LAA triggers of AF and/or OAT during AF ablation from 2001 to 2017 were included. LAA triggers were defined as atrial premature depolarizations from the LAA, which initiated sustained AF and/or OAT.

RESULTS

Out of 7,129 patients undergoing AF ablation over 16 years, LAA triggers were observed in 21 (0.3%) subjects (age 60 ± 9 years; 57% males; 52% persistent AF). Twenty (95%) patients were undergoing repeat ablation. The LAA was the only nonpulmonary vein trigger in 3 patients; the remaining 18 patients had both LAA and other nonpulmonary vein triggers. LAA triggers were eliminated in all patients (focal ablation in 19 patients; LAA isolation in 2 patients). Twelve months after ablation, 47.6% remained free from recurrent arrhythmia. After overall follow-up of 5.0 ± 3.6 years (median: 3.7 years; interquartile range: 1.4 to 8.9 years), 38.1% were arrhythmia-free. All 3 patients with triggers limited to the LAA remained free of AF recurrence. One patient undergoing LAA isolation developed LAA thrombus during follow-up.

CONCLUSIONS

The incidence of true LAA triggers is very low (0.3%). Most patients with LAA triggers have additional nonpulmonary vein triggers, and despite elimination of LAA triggers, long-term arrhythmia recurrence rates remain high. Potential risks of empiric LAA isolation during AF ablation (especially first-time AF ablation) may outweigh benefits.

Improvement in ventricular function with rhythm control of atrial arrhythmias may delay the need for atrioventricular valve surgery in adults with congenital heart disease

OBJECTIVE

Atrial arrhythmias and atrioventricular valve regurgitation (AVVR) are common causes of morbidity among adults with congenital heart disease (ACHD). The impact of rhythm control on AVVR in this population is unknown. We sought to determine whether a rhythm control strategy is associated with greater freedom from AV valve surgery than a rate control strategy.

DESIGN

Patients evaluated by both ACHD and electrophysiology specialists at a single academic center were screened for atrial arrhythmias and at least moderate-severe AVVR. Clinical and electrographic data were abstracted. All echocardiograms were interpreted by a single echocardiographer blinded to treatment strategy. Patients were followed until AV valve surgery, heart transplantation, death, or last clinical follow-up.

RESULTS

Rhythm control was attempted in 9 of 24 identified patients. Among these nine patients, arrhythmias were eliminated in three and reduced from persistent to paroxysmal in another three. In the rhythm control group, mean left ventricular ejection fraction improved from 54.4 ± 12.4% to 60.0 ± 11.5% (P = .02) and mean right ventricular systolic function increased nearly one grade (P = .02). AVVR did not decrease significantly. No significant change in left or right ventricular systolic function, or AVVR was observed among the 15 patients treated with rate control. Four-year survival free of AV valve operation and heart transplant was 88% in the rhythm control group and 31% in the rate control group (P = .04).

CONCLUSIONS

In ACHD patients with atrial arrhythmias and at least moderate-severe AVVR, a rhythm control strategy was associated with improved biventricular systolic function. This improvement in ventricular function and symptoms may allow valve surgery to be deferred.

Abstract 562: Comprehensive Arteriovenous Metabolomics in the Human Heart

Introduction: Despite broad interest in the role of metabolism in the pathogenesis of heart failure, a definitive account of fuel use by the beating human heart in situ is lacking. We therefore determined the uptake and release of over 270 metabolites by simultaneous sampling of arterial, coronary sinus, and femoral venous blood in 100 patients.

Methods: We enrolled 100 patients (60% male, 12% diabetic, age = 63.6 +/- 13.5 years, BMI = 29.75 +/- 6.1, EF = 57.14 +/- 6.48) undergoing ablation of atrial fibrillation. We used liquid chromatography-mass spectrometry to quantify over 270 metabolites in plasma from coronary sinus, femoral vein, and arterial blood. We also measured O 2 and CO 2 concentration, as well as atrial pressure.

Results: We detected uptake or release of 77 metabolites by the heart and 136 metabolites across the leg (p <0.05 after Benjamini-Hochberg correction). We determined the cardiac extraction of all major fuel sources, including 29 fatty acids, 11 amino acids, lactate, acetoacetate, and 3-hydroxybutyrate. Several patterns emerge: first, while the leg extracts glucose (FV/A = 0.95, q = 4.7x10-14) and releases lactate (FV/A = 1.11, q = 2.87x10-14), the heart extracts lactate (CS/A = 0.95, q = 3.77x10-9) and neither extracts nor secretes glucose. Second, while the leg releases nearly all fatty acid and amino acid species, the heart consumes most fatty acids and certain non-essential amino acids. Third, extraction of unsaturated acylcarnitines correlates with left atrial pressure (p<0.01). Finally, we find a significant positive correlation between myocardial O2 consumption and extraction of ketones (p < 0.01), but not other major cardiac fuels.

Conclusion: We present the most comprehensive study to date of metabolite use and secretion by the human heart. We find the heart to be an avid consumer of fatty acids and ketone bodies, but less so of glucose and essential amino acids. Consumption of ketones increases with O2 consumption, suggesting that ketones may be a preferential fuel source under high work loads. Extraction of certain acylcarnitines increases with left atrial pressure, indicating metabolic reprogramming under high filling pressures. In summary, we provide the first comprehensive model of fuel use by the beating human heart in situ.

Comparison of the Ventricular Tachycardia Circuit Between Patients With Ischemic and Nonischemic Cardiomyopathies

Background:

There has been increasing awareness of the 3-dimensional nature of ventricular tachycardia (VT) circuits. VT circuits in patients with ischemic cardiomyopathies (ICM) and non-ICM (NICM) may differ in this regard.

Methods:

Among patients with structural heart disease and at least 1 hemodynamically tolerated VT undergoing ablation, we retrospectively analyzed responses to all entrainment maneuvers.

Results:

Of 445 patients (ICM 228, NICM 217) undergoing VT ablation, detailed entrainment mapping of at least 1 tolerated VT was performed in 111 patients (ICM 71, NICM 40). Of 89 ICM VTs, the isthmus could be identified by endocardial entrainment in 55 (62%), compared with only 8 of 47 (17%) NICM VTs ( P <0.01). With combined endocardial and epicardial mapping, the isthmus could be identified in 56 (63%) ICM VTs and 12 (26%) NICM VTs ( P <0.01), whereas any critical component (defined as entrance, isthmus or exit) could be identified in 76 (85%) ICM VTs and 37 (79%) NICM VTs ( P =0.3). Complete success (no inducible VT at the end of ablation, 82% versus 65%, P =0.04) and 1-year, single-procedure VT-free survival (82% versus 55%, P <0.01) were both higher among patients with ICM.

Conclusions:

Among mappable ICM VTs, critical circuit components can usually be identified on the endocardium. In contrast, among mappable NICM VTs, although some critical component can typically be identified with the addition of epicardial mapping, the isthmus is less commonly identified, possibly due to midmyocardial location.

Electrocardiographic and Electrophysiologic Characteristics of Idiopathic Ventricular Arrhythmias Originating From the Basal Inferoseptal Left Ventricle

OBJECTIVES

This study sought to characterize ventricular arrhythmia (VA) ablated from the basal inferoseptal left ventricular endocardium (BIS-LVe) and identify electrocardiographic characteristics to differentiate from inferobasal crux (IBC) VA.

BACKGROUND

The inferior basal septum is an uncommon source of idiopathic VAs, which can arise from its endocardial or epicardial (crux) aspect. Because the latter are often targeted from the coronary venous system or epicardium, distinguishing between the 2 is important for successful ablation.

METHODS

Consecutive patients undergoing ablation of idiopathic VA from the BIS-LVe or IBC from 2009 to 2018 were identified and clinical characteristics and electrocardiographs of VA were compared.

RESULTS

Of 931 patients undergoing idiopathic VA ablation, Virginia was eliminated from the BIS-LVe in 19 patients (2%) (17 male, age 63.7 ± 9.2 years, LV ejection fraction: 45.0 ± 9.3%). QRS complexes typically manifested right bundle branch block morphology with "reverse V₂ pattern break" and left superior axis (more negative in lead III than II). VA elimination was achieved after median of 2 lesions (interquartile range [IQR]: 1-6; range 1 to 20) (radiofrequency ablation time: 123 s [IQR: 75-311]). Compared with 7 patients with IBC VA (3 male, age 51.9 ± 20.1 years, LV ejection fraction: 51.4 ± 17.7%), BIS-LVe VA less frequently had initial negative forces (QS pattern) in leads II, III, and/or aVF (p < 0.001), R-S ratio <1 in lead V₁ (p = 0.005), and notching in lead II (p = 0.006) were narrower (QRS duration: 178.2 ± 22.4 vs. 221.1 ± 41.9 ms; p = 0.04) and more frequently had maximum deflection index of <0.55 (p < 0.001).

CONCLUSIONS

The BIS-LVe region is an uncommon source of idiopathic VA. Distinguishing these from IBC VA is important for procedural planning and ablation success.

The Heart Rhythm Society/American College of Physicians Atrial Fibrillation Screening and Education Initiative

BACKGROUND

The prevalence of both atrial fibrillation (AF) and stroke is increasing. Stroke is common in AF and can have devastating consequences, especially when AF is unrecognized and anticoagulation is not initiated.

OBJECTIVE

The purpose of this study was to demonstrate the feasibility and yield, both in identifying previously undiagnosed AF and in educating patients and caregivers about AF, of systematic screening events in internal medicine practices using a mobile electrocardiogram device (Kardia/AliveCor iECG).

METHODS

With support from the Heart Rhythm Society and the American College of Physicians, 5 internal medicine practices performed systematic screening and education of patients at higher risk of AF using the Kardia/AliveCor device and a variety of educational materials. Patients screened as "unclassified" or "possible AF" were referred for further evaluation. Patients and providers (physicians, nurses, and allied professionals) assessed the screening process.

RESULTS

A total of 772 patients were screened. The mean age was 65.2 ± 15.4 years, and 281 (28.2%) were 75 years or older. The majority, 521 (67.5%), were female, and 586 (75.7%) had a CHA₂DS₂-VASc score of ≥2. Six hundred seventy patients (86.8%) were screened as "normal," 85 (11.0%) as "unclassified," and 17 (2.2%) as "possible AF." Participants demonstrated a significant knowledge deficit about stroke and AF before the screening events, and the majority felt that their awareness of these issues increased significantly as a result of their participation.

CONCLUSION

This collaborative Heart Rhythm Society/American College of Physicians systematic screening effort using the Kardia/AliveCor device was feasible. Although it resulted in a relatively modest yield of "unclassified" or "possible AF" screens, it had significant educational benefit to participants and caregivers. The diagnostic yield of future programs could be enriched by including more elderly patients and those with more risk factors for AF and stroke. A greater duration or frequency of monitoring would likely increase sensitivity but be more complicated and costlier to administer. Future events should include on-site confirmatory testing with a 12-lead electrocardiogram. Devices such as the Kardia/AliveCor monitor may enhance patient engagement in screening programs.

Papillary muscle ventricular arrhythmias in patients with arrhythmic mitral valve prolapse: Electrophysiologic substrate and catheter ablation outcomes

BACKGROUND

Mitral valve prolapse (MVP) is a common valve condition and has been associated with sudden cardiac death. Premature ventricular contractions (PVCs) from the papillary muscles (PMs) may play a role as triggers for ventricular fibrillation (VF) in these patients.

OBJECTIVES

To characterize the electrophysiological substrate and outcomes of catheter ablation in patients with MVP and PM PVCs.

METHODS

Of 597 patients undergoing ablation of ventricular arrhythmias during the period 2012-2015, we identified 25 patients with MVP and PVCs mapped to the PMs (64% female). PVC-triggered VF was the presentation in 4 patients and a fifth patient died suddenly during follow-up. The left ventricle ejection fraction (LVEF) was 50.5% ± 11.8% and PVC burden was 24.4% ± 13.1%. A cardiac magnetic resonance imaging was performed in nine cases and areas of late gadolinium enhancement were found in four of them. A detailed LV voltage map was performed in 11 patients, three of which exhibited bipolar voltage abnormalities. Complete PVC elimination was achieved in 19 (76%) patients and a significant reduction in PVC burden was observed in two (8%). In patients in which the ablation was successful, the PVC burden decreased from 20.4% ± 10.8% to 6.3% ± 9.5% (P = 0.001). In 5/6 patients with depressed LVEF and successful ablation, the LV function improved postablation. No significant differences were identified between patients with and without VF.

CONCLUSIONS

PM PVCs are a source of VF in patients with MVP and can induce PVC-mediated cardiomyopathy that reverses after PVC suppression. Catheter ablation is highly successful with more than 80% PVC elimination or burden reduction.

"As Needed" nonvitamin K antagonist oral anticoagulants for infrequent atrial fibrillation episodes following atrial fibrillation ablation guided by diligent pulse monitoring: A feasibility study

INTRODUCTION

After atrial fibrillation (AF) ablation, oral anticoagulation (OAC) is recommended if stroke risk as assessed by CHA₂ DS ₂ -VASc score is high. However, patients without AF are often reluctant to take daily OAC. We describe outcome using as needed nonvitamin K antagonist (NOACs) guided by pulse monitoring to detect AF following successful ablation.

METHODS AND RESULTS

We identified 99 patients (84% male, age 64 ± 8 years), CHA₂ DS ₂ -VASc score greater than or equal to 1 in men and greater than or equal to 2 in women (median 2, range 1-6), capable of pulse assessment twice daily and no AF on extended monitoring after AF ablation. All patients were instructed to start NOAC if AF >1 hour or recurrent shorter episodes. Duration of NOAC use after restart was typically 2 to 4 weeks. After 30 ± 14 months (total 244 patient-years), 22 patients (22%) transitioned to daily NOAC because of noncompliance with pulse assessment or patient preference (six patients) or because of suspected or documented AF episode(s) in 16 (16%) patients. Of the remaining 77 (78%), 14 (14%) used NOACs but did not transition back to daily use, most (10 patients) with single use (seven patients) or non-AF rhythm (three patients) documented. There was only one thromboembolic event (0.4%/yr of follow-up) in patient without AF and one mild bleeding event (epistaxis).

CONCLUSION

The use of as needed NOACs when AF is suspected with pulse monitoring is effective and safe to maintain low risk of stroke and bleeding after successful ablation. Transition back to daily NOAC use should be anticipated in about one quarter of patients.

Long-term outcome and mode of recurrence following noninducibility during noninvasive programmed stimulation after ventricular tachycardia ablation

BACKGROUND

Noninducibility of ventricular tachycardia (VT) at noninvasive programmed stimulation performed shortly following ablation (negative NIPS) predicts low risk of the medium-term recurrence. This study aimed to evaluate long-term rate and mode of recurrence following negative NIPS.

METHODS

We extended follow-up on patients in whom no VT could be induced at NIPS following ablation between 2008 and 2010. Recurrent VTs were categorized as "Original clinical" if they matched VT that had occurred spontaneously prior to the index ablation; "Original nonclinical" if they matched VT that was induced during the index ablation but had not occurred spontaneously; or "New." Among those undergoing repeat ablation, the area ablated to treat the recurrent VT was categorized as "Targeted initial scar" if it was targeted during the index procedure; "Untargeted initial scar" if it was present but not targeted during the index procedure; or "New scar" if it was not present during the index procedure.

RESULTS

Of 60 patients with negative NIPS, 18 (30%) had recurrent VT and nine underwent repeat ablation over (4.1 ± 3.2) years follow-up. Of 23 recurrent VTs, 18 (78%) were "New." During repeat ablations, six (46%) of the 13 recurrent VTs were ablated in "untargeted initial scar" and four (31%) in "new scar."

CONCLUSIONS

When spontaneous or inducible VTs are eliminated with ablation and no longer inducible during NIPS, these VTs are unlikely to recur during long-term follow-up. More commonly, new VTs occur, which are either associated with areas of scar not present or not targeted during the initial ablation.

Three-dimensional myocardial scar characterization from the endocardium: Usefulness of endocardial unipolar electroanatomic mapping

Epicardial ablation may be required to eliminate ventricular tachycardia (VT) in patients with underlying structural heart disease. The decision to gain epicardial access is frequently based on the suspicion of an epicardial origin for the VT and/or presence of an arrhythmogenic substrate. Epicardial pathology and VT is frequently present in patients with nonischemic right and/or left cardiomyopathies even in the setting of modest or no endocardial bipolar voltage substrate. In this setting, unipolar voltage mapping from the endocardium serves to help identify midmyocardial and/or epicardial VT substrate. The additional value of endocardial unipolar mapping includes its usefulness to predict the clinical outcome after VT ablation, to determine the irreversibility of myocardial disease, and to guide endomyocardial biopsy procedures to specific areas of intramural scarring. In this review, we aim to provide a guide to the use of endocardial unipolar mapping and its appropriate interpretation in a variety of clinical situations.

Utility of ripple mapping for identification of slow conduction channels during ventricular tachycardia ablation in the setting of arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Ripple mapping displays every deflection of a bipolar electrogram and enables the visualization of conduction channels (RMCC) within postinfarction ventricular scar to guide ventricular tachycardia (VT) ablation. The utility of RMCC identification for facilitation of VT ablation in the setting of arrhythmogenic right ventricular cardiomyopathy (ARVC) has not been described.

OBJECTIVE

We sought to (a) identify the slow conduction channels in the endocardial/epicardial scar by ripple mapping and (b) retrospectively analyze whether the elimination of RMCC is associated with improved VT-free survival, in ARVC patients.

METHODS

High-density right ventricular endocardial and epicardial electrograms were collected using the CARTO 3 system in sinus rhythm or ventricular pacing and reviewed for RMCC. Low-voltage zones and abnormal myocardium in the epicardium were identified by using standardized late-gadolinium-enhanced (LGE) magnetic resonance imaging (MRI) signal intensity (SI) z-scores.

RESULTS

A cohort of 20 ARVC patients that had undergone simultaneous high-density right ventricular endocardial and epicardial electrogram mapping was identified (age 44 ± 13 years). Epicardial scar, defined as bipolar voltage less than 1.0 mV, occupied 47.6% (interquartile range [IQR], 30.9-63.7) of the total epicardial surface area and was larger than endocardial scar, defined as bipolar voltage less than 1.5 mV, which occupied 11.2% (IQR, 4.2 ± 17.8) of the endocardium (P < 0.01). A median 1.5 RMCC, defined as continuous corridors of sequential late activation within scar, were identified per patient (IQR, 1-3), most of which were epicardial. The median ratio of RMCC ablated was 1 (IQR, 0.6-1). During a median follow-up of 44 months (IQR, 11-49), the ratio of RMCC ablated was associated with freedom from recurrent VT (hazard ratio, 0.01; P = 0.049). Among nine patients with adequate MRI, 73% of RMCC were localized in LGE regions, 24% were adjacent to an area with LGE, and 3% were in regions without LGE.

CONCLUSION

Slow conduction channels within endocardial or epicardial ARVC scar were delineated clearly by ripple mapping and corresponded to critical isthmus sites during entrainment. Complete elimination of RMCC was associated with freedom from VT.