Road-Map to Epicardial Approach for Catheter Ablation of Ventricular Tachycardia in Structural Heart Disease: Results From a 10-Year Tertiary-Center Experience.

BACKGROUND: Epicardial approach in ventricular tachycardia (VT) ablation is still regarded as a second-step strategy, due to the risk of complications. We evaluated the frequency that epicardial ablation targets were identified and ablation performed following pericardial access compared with unnecessary pericardial access for different VT causes and potential markers of epicardial VT. METHODS: All VT ablation procedures including epicardial approach over a 10-year period were included. First-line epicardial approach was indicated in arrhythmogenic right ventricular cardiomyopathy (ARVC) and postmyocarditis VT; in patients with idiopathic dilated cardiomyopathy (IDCM) and postmyocardial infarction, indications resulted from available imaging techniques or 12-lead VT morphology. The epicardial approach was considered useful if epicardial ablation was performed after epicardial mapping. Feasibility, complications, and long-term outcome were reported. RESULTS: Four hundred and eighty-eight subjects with a median age of 60 years (interquartile range, 47-65) and of left ventricle ejection fraction 41% (interquartile range, 30-55) underwent 626 epicardial VT ablations. Percutaneous access had a success rate of 92.2% and a complication rate of 3.6%. Overall, epicardial approach was, respectively, indicated to 11.8% of postmyocardial infarction patients, 49.5% in IDCM, 94% in myocarditis, and 90.7% in ARVC. Epicardial ablation at the first ablation attempt was performed in 9.3% of postmyocardial infarction patients, 28.8% in IDCM, 86.5% in myocarditis, and 81.3% in patients with ARVC. In first-line epicardial group, ARVC and myocarditis showed the highest odds for epicardial ablation (OR, 4.057 [95% CI, 1.299-8.937]; P=0.007; OR, 3.971 [95% CI, 1.376-11.465]; P=0.005, respectively). IDCM independently predicted unnecessary epicardial approach (OR, 2.7 [95% CI, 1.7-4.3]; P<0.001). After a follow-up of 41 months (interquartile range, 19-64), patients with IDCM experienced higher rate of recurrences and mortality compared with other causes. CONCLUSIONS: Epicardial approach is integral part of ablation armamentarium regardless of the VT cause, with high feasibility and low complication rate in experienced centers. Our data support its use at first ablation attempt in VTs related to ARVC and myocarditis.

Active Arrhythmia Pattern: A Novel Predictor of ICD Shocks-A Subanalysis From the PARTITA Study.

BACKGROUND: In the PARTITA trial (Does Timing of Ventricular Tachycardia Ablation Affect Prognosis in Patients With an Implantable Cardioverter Defibrillator?), antitachycardia pacing (ATP) predicted the occurrence of implantable cardioverter defibrillator (ICD) shocks. Catheter ablation of ventricular tachycardia after the first shock reduced the risk of death or worsening heart failure. A threshold of ATPs that might warrant an ablation procedure before ICD shocks is unknown. Our aim was to identify a threshold of ATPs and clinical features that predict the occurrence of shocks and cardiovascular events. METHODS: We analyzed data from 517 patients in phase A of the PARTITA study. We used classification and regression tree analysis to develop and test a risk stratification model based on arrhythmia patterns and clinical data to predict ICD shocks. Secondary end points were worsening heart failure and cardiovascular hospitalization. RESULTS: Classification and regression tree classified patients into 6 leaves by increasing shock probability. Patients treated with ≥5 ATPs in 6 months (active arrhythmia pattern) had the highest risk of ICD shocks (93% and 86%, training and testing samples, respectively). Patients without ATPs had the lowest (1% and 2%). Other predictors included left ventricle ejection fraction<35%, age of <60 years, and obesity. Survival analysis revealed a higher risk of worsening heart failure (hazard ratio, 5.45 [95% CI, 1.62-18.4]; P=0.006) and cardiovascular hospitalization (hazard ratio, 7.29 [95% CI, 3.66-14.5]; P<0.001) for patients with an active arrhythmia pattern compared with those without ATPs. CONCLUSIONS: Patients with an active arrhythmia pattern (≥5 ATPs in 6 months) are associated with an increased risk of ICD shocks, as well as heart failure hospitalization and cardiovascular hospitalization. These data suggest that additional treatments may be helpful to this high-risk group as a preventive strategy to reduce the incidence of major events. Further prospective randomized trials are needed to confirm the benefits of early ventricular tachycardia ablation in this setting.

Long-Term Follow-Up of Catheter Ablation for Premature Ventricular Complexes in the Modern Era: The Importance of Localization and Substrate.

Background: Large-scale studies evaluating long-term recurrence rates in both idiopathic and non-idiopathic PVC catheter ablation (CA) patients have not been reported. Objective: To evaluate the efficacy and safety of idiopathic and non-idiopathic PVC CA, investigating the predictors of acute and long-term efficacy. Methods: This retrospective multicentric study included 439 patients who underwent PVC CA at three institutions from April-2015 to December-2021. Clinical success at 6 months' follow-up, defined as a reduction of at least 80% of the pre-procedural PVC burden, was deemed the primary outcome. The secondary aims of the study were: clinical success at the last available follow-up, predictors of arrhythmic recurrences at long-term follow-up, and safety outcomes. Results: The median age was 51 years, with 24.9% patients being affected suffering from structural heart disease. The median pre-procedural PVC burden was 20.1%. PVCs originating from the RVOT were the most common index PVC observed (29.1%), followed by coronary cusp (CC) and non-outflow tract (OT) LV PVCs (23.1% and 19.0%). The primary outcome at 6 months was reached in 85.1% cases, with a significant reduction in the 24 h% PVC burden (−91.4% [−83.4; −96.7], p < 0.001); long-term efficacy was observed in 82.1% of cases at almost 3-year follow-up. The presence of underlying structural heart disease and non-OT LV region origin (aHR 1.77 [1.07−2.93], p = 0.027 and aHR = 1.96 [1.22−3.14], p = 0.005) was independently associated with recurrences. Conclusion: CA of both idiopathic and non-idiopathic PVCs showed a very good acute and long-term procedural success rate, with an overall low complication. Predictors of arrhythmic recurrence at follow-up were underlying structural heart disease and non-OT LV origin.

Patients with Cardiac Implantable Electronic Device Undergoing Radiation Therapy: Insights from a Ten-Year Tertiary Center Experience.

BACKGROUND: The number of patients with cardiac implantable electronic devices (CIEDs) receiving radiotherapy (RT) is increasing. The management of CIED-carriers undergoing RT is challenging and requires a collaborative multidisciplinary approach. AIM: The aim of the study is to report the real-world, ten-year experience of a tertiary multidisciplinary teaching hospital. METHODS: We conducted an observational, real-world, retrospective, single-center study, enrolling all CIED-carriers who underwent RT at the San Raffaele University Hospital, between June 2010 and December 2021. All devices were MRI-conditional. The devices were programmed to an asynchronous pacing mode for patients who had an intrinsic heart rate of less than 40 beats per minute. An inhibited pacing mode was used for all other patients. All tachyarrhythmia device functions were temporarily disabled. After each RT session, the CIED were reprogrammed to the original settings. Outcomes included adverse events and changes in the variables that indicate lead and device functions. RESULTS: Between June 2010 and December 2021, 107 patients were enrolled, among which 63 (58.9%) were pacemaker carriers and 44 (41.1%) were ICD carriers. Patients were subjected to a mean of 16.4 (±10.7) RT sessions. The most represented tumors in our cohort were prostate cancer (12; 11%), breast cancer (10; 9%) and lung cancer (28; 26%). No statistically significant changes in device parameters were recorded before and after radiotherapy. Generator failures, power-on resets, changes in pacing threshold or sensing requiring system revision or programming changes, battery depletions, pacing inhibitions and inappropriate therapies did not occur in our cohort of patients during a ten-year time span period. Atrial arrhythmias were recorded during RT session in 14 patients (13.1%) and ventricular arrhythmias were observed at device interrogation in 10 patients (9.9%). CONCLUSIONS: Changes in device parameters and arrhythmia occurrence were infrequent, and none resulted in a clinically significant adverse event.

Significance of abnormal and late ventricular signals in ventricular tachycardia ablation of ischemic and nonischemic cardiomyopathies.

BACKGROUND: Abnormal ventricular signals (AVS) are the cornerstone of substrate-based ventricular tachycardia (VT) ablation in sinus rhythm. Signal characterization of AVS in ischemic and nonischemic cardiomyopathies has never been performed. OBJECTIVE: The purpose of this study was to describe ventricular signal abnormalities in 3 different pathologies and examine their association with the diastolic component of VT circuits. METHODS: A total of 45 patients (15 ischemic cardiomyopathy [ICM], 15 arrhythmogenic cardiomyopathy [ACM], 15 dilated cardiomyopathy [DCM]) who had undergone VT ablation with >50% of the diastolic pathway of the VT circuit recorded were studied. AVS were classified into late potentials (LPs) and continuous fractionated ventricular signals (CFVS), and their characteristics and correlation with the diastolic pathway of VT circuits were analyzed. RESULTS: Seventy-five VT circuits were analyzed. Bipolar scars were greatest in ICM endocardially (53 cm2 ICM vs 36 cm2 ACM vs 25 cm2 DCM; P = .010) and in ACM epicardially (98 cm2 ACM vs 25 cm2 ICM vs 24 cm2 DCM; P = .005). Location of the VT diastolic interval coincided with AVS location in 54% of VTs in ICM, 89% in ACM, and 72% in DCM (P = .036). There was a trend toward a greater association of diastolic intervals coinciding with LPs than with CFVS (78% vs 57%; P = .052) (69% diastolic intervals in ICM coincided with LPs, 33% with CFVS; P = .063). All patients (100%) with CFVS in ACM had VT diastolic components arising from CFVS (33% ICM, 64% DCM; P = .049). Positive predictive value for LPs vs CFVS was 77.8% vs 56.7%, and sensitivity was 67.3% vs 32.7%, respectively. CONCLUSION: The nature of abnormal signals in different cardiomyopathies reflects underlying pathology. LPs rather than CFVS seem to be more linked to diastolic components of VT circuits, especially in ICM. LPs have greater sensitivity and specificity for VT; however, CFVS may be of more relevance in ACM.

Bi-atrial characterization of the electrical substrate in patients with atrial fibrillation.

BACKGROUND: Little is known regarding the characterization of electrical substrate in both atria in patients with atrial fibrillation (AF). METHODS: Eight consecutive patients undergoing AF ablation (five paroxysmal, three persistent) underwent electrical substrate characterization during sinus rhythm. Mapping of the left (LA) and right atrium (RA) was performed with the use of the HD Grid catheter (Abbott). Bipolar voltage maps were analyzed to search for low voltage areas (LVA), the following electrophysiological phenomena were assessed: (1) slow conduction corridors, and (2) lines of block. EGMs were characterized to search for fractionation. Electrical characteristics were compared between atria and between paroxysmal versus persistent AF patients. RESULTS: In the RA, LVAs were present in 60% of patients with paroxysmal AF and 100% of patients with persistent AF. In the LA, LVAs were present in 40% of patients with paroxysmal AF and 66% of patients with persistent AF. The areas of LVA in the RA and LA were 4.8±7.3 cm2 and 7.8±13.6 cm2 in patients with paroxysmal AF versus 11.7±3.0 cm2 and 2.1±1.8 cm2 in patients with persistent AF. In the RA, slow conduction corridors were present in 40.0% (paroxysmal AF) versus 66.7% (persistent AF) whereas in the LA, slow conduction corridors occurred in 20.0% versus 33.3% respectively (p = ns). EGM analysis showed more fractionation in persistent AF patients than paroxysmal (RA: persistent AF 10.8 vs. paroxysmal AF 4.7%, p = .036, LA: 10.3 vs. 4.1%, p = .108). CONCLUSION: Bi-atrial involvement is present in patients with paroxysmal and persistent AF. This is expressed by low voltage areas and slow conduction corridors whose extension progresses as the arrhythmia becomes persistent. This electrophysiological substrate demonstrates the important interplay with the pulmonary vein triggers to constitute the substrate for persistent arrhythmia.

One-year mortality after implantable defibrillator implantation: do risk stratification models help improving clinical practice?

PURPOSE: The purpose of this study was to assess the available mortality risk stratification models for implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy defibrillator (CRT-D) patients. METHODS: We conducted a review of mortality risk stratification models and tested their ability to improve prediction of 1-year survival after implant in a database of patients who received a remotely controlled ICD/CRT-D device during routine care and included in the independent Home Monitoring Expert Alliance registry. RESULTS: We identified ten predicting models published in peer-reviewed journals between 2000 and 2021 (Parkash, PACE, MADIT, aCCI, CHA2DS2-VASc quartiles, CIDS, FADES, Sjoblom, AAACC, and MADIT-ICD non-arrhythmic mortality score) that could be tested in our database as based on common demographic, clinical, echocardiographic, electrocardiographic, and laboratory variables. Our cohort included 1,911 patients with left ventricular dysfunction (median age 71, 18.3% female) from sites not using any risk stratification score for systematic patient screening. Patients received an ICD (53.8%) or CRT-D (46.2%) between 2011 and 2017, after standard physician evaluation. There were 56 deaths within 1-year post-implant, with an all-cause mortality rate of 2.9% (95% confidence interval [CI], 2.3-3.8%). Four predicting models (Parkash, MADIT, AAACC, and MADIT-ICD non-arrhythmic mortality score) were significantly associated with increased risk of 1-year mortality with hazard ratios ranging from 3.75 (CI, 1.31-10.7) to 6.53 (CI 1.52-28.0, p ≤ 0.014 for all four). Positive predictive values of 1-year mortality were below 25% for all models. CONCLUSION: In our analysis, the models we tested conferred modest incremental predicting power to ordinary screening methods.

Check the Need-Prevalence and Outcome after Transvenous Cardiac Implantable Electric Device Extraction without Reimplantation.

BACKGROUND: after transvenous lead extraction (TLE) of cardiac implantable electric devices (CIEDs), some patients may not benefit from device reimplantation. This study sought to analyse predictors and long-term outcome of patients after TLE with vs. without reimplantation in a high-volume centre. METHODS: all patients undergoing TLE at our centre between January 2010 and November 2015 were included into this analysis. RESULTS: a total of 223 patients (median age 70 years, 22.0% female) were included into the study. Cardiac resynchronization therapy-defibrillator (CRT-D) was the most common device (40.4%) followed by pacemaker (PM) (31.4%), implantable cardioverter-defibrillator (ICD) (26.9%), and cardiac resynchronization therapy-PM (CRT-P) (1.4%). TLE was performed due to infection (55.6%), malfunction (35.9%), system upgrade (6.7%) or other causes (1.8%). In 14.8%, no reimplantation was performed after TLE. At a median follow-up of 41 months, no preventable arrhythmia-related events were documented in the no-reimplantation group, but 11.8% received a new CIED after 17-84 months. While there was no difference in short-term survival, five-year survival was significantly lower in the no-reimplantation group (78.3% vs. 94.7%, p = 0.014). CONCLUSIONS: in patients undergoing TLE, a re-evaluation of the indication for reimplantation is safe and effective. Reimplantation was not related to preventable arrhythmia events, but all-cause survival was lower.

Cardiac resynchronization therapy defibrillators in patients with permanent atrial fibrillation.

AIMS: There are conflicting data on the benefit of cardiac resynchronization therapy (CRT) in heart failure (HF) patients with permanent atrial fibrillation (AF). We aimed to compare patient outcomes according to the presence or absence of permanent AF at device implantation. METHODS AND RESULTS: We retrospectively analysed remote monitoring data from 1141 CRT defibrillators. Propensity score with inverse-probability weighting method was used to balance AF and sinus rhythm (SR) groups. Analysis endpoints included total mortality, appropriate defibrillation shocks, and CRT percentage. There were 229 patients (20.1%) in the AF group and 912 patients (79.9%) in the SR group. Compared with SR patients, AF patients were older (median age, 77 vs. 72 years, P < 0.001), more frequently male (82.5% vs. 75.5%, P = 0.02), and had higher heart rate (75.7 vs. 71.0 b.p.m., P < 0.001). Of the 229 AF patients, 162 (70.7%) received suboptimal CRT (<98%) and 67 (29.3%) had adequate CRT (≥98%). During a median follow-up of 24 months, total mortality did not differ between AF and SR groups (propensity-score-weighted hazard ratio, HR 1.32 [95% confidence interval, 0.82-2.15], P = 0.25). The risk of appropriate shocks was significantly higher in the AF group with <98% CRT than in the SR group (weighted-HR, 1.99 [1.21-3.26], P = 0.006) and was similar in the AF group with ≥98% CRT versus the SR group (1.29 [0.66-2.53], P = 0.45). During follow-up, sinus rhythm was recovered in 23 patients in the AF group (10%) after a median time of 106 (42-256) days. The rate of sinus rhythm recovery in the AF group was 4.5 (95% CI, 2.8-6.7) per 100 patient-years; the rate of permanent AF occurrence in the SR group was 2.5 (95% CI, 1.9-3.3) per 100 patient-years. CONCLUSIONS: Although mortality was similar across patient groups, patients with permanent AF and suboptimal CRT had twofold higher risk of appropriate shocks than SR patients or AF patients with CRT ≥ 98%.

Heart-team hybrid approach to persistent atrial fibrillation with dilated atria: the added value of continuous rhythm monitoring.

OBJECTIVES: To assess by a continuous implantable rhythm monitoring (ILR) the mid-term outcomes of a staged-hybrid approach for patients with persistent/long-standing persistent atrial fibrillation (AF) and dilated atria. METHODS: Fifty patients [age 57 (standard deviation, SD: 8.3), previous catheter ablation 66%, AF history 6.5 (2-12) years, left ventricular ejection fraction 56 (SD: 7.9)%, left atrial volume index 44 (38-56) ml/m2] with persistent (44%) or long-standing persistent (56%) AF, underwent a 2-staged hybrid ablation (thoracoscopic epicardial procedure with Cobra-Fusion system and transcatheter Rhythmia mapping with endocardial touch-up of gaps). All patients received an ILR. RESULTS: No hospital deaths and no stroke occurred. Follow-up was 98% complete [median 22 (11-34) months]. The 2-year arrhythmia-free survival off class I-III antiarrhythmic drugs/electrical cardioversion/redo catheter ablation and the arrhythmia control (maintenance of sinus rhythm with or without antiarrhythmic drugs/electrical cardioversion) were 65 (SD: 7.1)% and 82 (SD: 5.8)%, respectively. The occurrence of AF in the blanking period was identified as an independent predictor of AF recurrence (odds ratio 26.6, 95% confidence interval 5.3, 132.3; P < 0.001). At longitudinal analysis, the predicted prevalence of sinus rhythm and sinus rhythm off class I-III antiarrhythmic drugs/electrical cardioversion/redo catheter ablation was 82% and 69% at 2 years, respectively. Among patients with recurrence, 50% had short-lasting asymptomatic episodes, identified only by ILR monitoring. The proportion of patients with AF burden ≤1% was 82% and 91% at 1 and 2 years, respectively, and in these cases, left atrial volume index decreased from 46 (SD: 12) ml/m2 to 41 (SD: 11) ml/m2 (P = 0.026). CONCLUSIONS: A staged hybrid approach yields promising results in selected patients with persistent/long-standing persistent AF and dilated left atrium who are at very high risk of AF recurrence. The use of ILR in this setting should become a standard to optimize patient management.

Characterization of cardiac electrogram signals in atrial arrhythmias.

Despite significant advancements in 3D cardiac mapping systems utilized in daily electrophysiology practices, the characterization of atrial substrate remains crucial for the comprehension of supraventricular arrhythmias. During mapping, intracardiac electrograms (EGM) provide specific information that the cardiac electrophysiologist is required to rapidly interpret during the course of a procedure in order to perform an effective ablation. In this review, EGM characteristics collected during sinus rhythm (SR) in patients with paroxysmal atrial fibrillation (pAF) are analyzed, focusing on amplitude, duration and fractionation. Additionally, EGMs recorded during atrial fibrillation (AF), including complex fractionated atrial EGMs (CFAE), may also provide precious information. A complete understanding of their significance remains lacking, and as such, we aimed to further explore the role of CFAE in strategies for ablation of persistent AF. Considering focal atrial tachycardias (AT), current cardiac mapping systems provide excellent tools that can guide the operator to the site of earliest activation. However, only careful analysis of the EGM, distinguishing low amplitude high frequency signals, can reliably identify the absolute best site for RF. Evaluating macro-reentrant atrial tachycardia circuits, specific EGM signatures correspond to particular electrophysiological phenomena: the careful recognition of these EGM patterns may in fact reveal the best site of ablation. In the near future, mathematical models, integrating patient-specific data, such as cardiac geometry and electrical conduction properties, may further characterize the substrate and predict future (potential) reentrant circuits.

Etiology is a predictor of recurrence after catheter ablation of ventricular arrhythmias in pediatric patients.

BACKGROUND: Ventricular arrhythmias (VAs) are rare in pediatric patients, especially in absence of structural heart disease (SHD). Few data are available regarding the invasive VAs treatment with catheter ablation (CA) in pediatric patients and predictors of outcomes have not been fully investigated. OBJECTIVE: To describe the clinical presentation, procedural characteristics, and outcomes in pediatric patients undergoing CA for VAs. METHODS: Eighty-one consecutive pediatric patients (58 male [72%], 15.5 ± 2.2 years) treated by CA for ventricular tachycardia (VT) or premature ventricular beats (PVBs) were retrospectively evaluated. Study endpoints were VAs recurrence and mortality for any cause. RESULTS: Ninety-five procedures were performed in 81 patients, 52 (55%) PVBs and 43 (45%) VT ablations. During a follow-up of 35.0 months (interquartile range = 13.0-71.0), 14 patients (14.7%) had a VA recurrence: 11 (33.3%) patients treated with CA for VT and 3 (6.2%) patients treated for PVBs (p < .001). One patient (1%) died 26 months after the procedure during an electrical storm. Patients with SHD had higher VAs recurrence rate, as compared with idiopathic VAs (pairwise log-rank p < .001). Patients treated with CA for VT had higher VA recurrence rate, as compared with PVB patients (pairwise log-rank p = .002). At Cox multivariate analysis only SHD was an independent predictor of VAs recurrence (hazard ratio = 5.56, 95% confidence interval = 2.68-11.54, p < .001). CONCLUSION: CA of VAs is effective and safe in a pediatric population. CA of idiopathic and fascicular VAs are associated with lower recurrence rate, than VAs in the setting of SHD.

Inflammation as a Predictor of Recurrent Ventricular Tachycardia After Ablation in Patients With Myocarditis.

BACKGROUND: Little is known about the risk stratification of patients with myocarditis undergoing ventricular tachycardia (VT) ablation. OBJECTIVES: This study sought to describe VT ablation results and identify factors associated with arrhythmia recurrences in a cohort of patients with myocarditis. METHODS: The authors enrolled 125 consecutive patients with myocarditis, undergoing VT ablation. Before ablation, disease stage was evaluated, to identify active (AM) versus previous myocarditis (PM). The primary study endpoint was assessment of VT recurrences by 12-month follow-up. Predictors of VT recurrences were retrospectively identified. RESULTS: All patients (age 51 ± 14 years, 91% men, left ventricular ejection fraction 52% ± 9%) had history of myocarditis diagnosed by endomyocardial biopsy (59%) and/or cardiac magnetic resonance (90%). Furthermore, all had multiple episodes of drug-refractory VTs. Multimodal pre-procedural staging identified 47 patients with AM (38%) and 78 patients with PM (62%). All patients showed low-voltage areas (LVA) at electroanatomical map (97% epicardial or endoepicardial); of them, 25 (20%) had wide borderzone (WBZ, constituting >50% of the whole LVA). VT recurrences were documented in 25 patients (20%) by 12 months, and in 43 (34%) by last follow-up (median 63 months; interquartile range: 39 to 87). At multivariable analysis, AM stage was the only predictor of VT recurrences by 12 months (hazard ratio: 9.5; 95% confidence interval: 2.6 to 35.3; p < 0.001), whereas both AM stage and WBZ were associated with arrhythmia recurrences anytime during follow-up. No VT episodes were found after redo ablation was performed in 23 patients during PM stage. CONCLUSION: Our findings suggest that VT ablation should be avoided during AM, but is often of benefit for recurrent VT after the acute phase of myocarditis.

Complete Electroanatomic Imaging of the Diastolic Pathway Is Associated With Improved Freedom From Ventricular Tachycardia Recurrence.

BACKGROUND: The development of multielectrode mapping catheters has expanded the spectrum of mappable ventricular tachycardias (VTs). Full diastolic pathway recording has been associated with a high rate of VT termination during radiofrequency ablation as well as noninducibility at study end. However, the role of diastolic pathway mapping on VT recurrence has yet to be clearly elucidated. We aimed to explore the role of complete diastolic pathway activation mapping on VT recurrence. METHODS: Eighty-five consecutive patients who underwent VT ablation guided by high-density mapping were enrolled. During activation mapping, the presence of electrical activity in all segments of diastole defined the evidence of having had recorded the whole diastolic interval. Patients were categorized as having recorded the full diastolic pathway, partial diastolic pathway, or no diastolic pathway map performed. Recurrences of VT were defined as appropriate implantable cardioverter defibrillator therapies or on the basis of ECG-documented arrhythmia. RESULTS: Eighty-five patients were included. Complete recording of the diastolic pathway was achieved in 36/85 (42.4%) patients. Partial recording of the diastolic pathway of the clinical VT was achieved in 24/85 (28.2%) patients. No recording of the diastolic pathway of the clinical VT was feasible in 25/85 patients (29.4%). At a mean of 12.8 months, freedom from VT recurrence was 67% in the overall cohort. At a mean of 12.8 months, freedom from VT recurrence was 88%, 50%, and 55% in patients who had full diastolic activity recorded, partial diastolic activity recorded, or underwent substrate modification, respectively; the observed differences were statistically significant (P=0.02). CONCLUSIONS: Mapping of the entire diastolic pathway was associated with a higher freedom from VT recurrence as compared with partial diastolic pathway recording and substrate modification. The use of multielectrode mapping catheters in recording diastolic activity may help predict those VTs employing intramural circuits and further optimize ablation strategies.

Long-Term Outcome After Ventricular Tachycardia Ablation in Nonischemic Cardiomyopathy: Late Potential Abolition and VT Noninducibility.

BACKGROUND: In patients with an ischemic cardiomyopathy (ICM), the combination of late potential (LP) abolition and postprocedural ventricular tachycardia (VT) noninducibility is known to be the desirable end point for a successful long-term outcome after VT ablation. We investigated whether LP abolition and VT noninducibilty have a similar impact on the outcomes of patients with non-ICMs (NICM) undergoing VT ablation. METHODS: A total of 403 patients with NICM (523 procedures) who underwent a VT ablation from 2010 to 2016 were included. The procedure end points were the LP abolition (if the LPs were absent, other ablation strategies were undertaken) and the VT noninducibilty. RESULTS: The underlying structural heart disease consisted of dilated cardiomyopathy (DCM, 49%), arrhythmogenic right ventricular dysplasia (ARVD, 17%), postmyocarditis (14%), valvular heart disease (8%), congenital heart disease (2%), hypertrophic cardiomyopathy (2%), and others (5%). The epicardial access was performed in 57% of the patients. At baseline, the LPs were present in 60% of the patients and a VT was either inducible or sustained/incessant in 85% of the cases. At the end of the procedure, the LP abolition was achieved in 79% of the cases and VT noninducibility in 80%. After a multivariable analysis, the combination of LP abolition and VT noninducibilty was independently associated with free survival from VT (hazard ratio, 0.45 [95% CI, 0.29-0.69], P=0.0002) and cardiac death (hazard ratio, 0.38 [95% CI, 0.18-0.74], P=0.005). The benefit of the LP abolition on preventing the VT recurrence in patients with ARVD and postmyocarditis appeared superior to that observed for those with DCM. CONCLUSIONS: In patients with NICM undergoing VT ablation, the strategy of LP abolition and VT noninducibilty were associated with better outcomes in terms of long-term VT recurrences and cardiac survival. Graphic Abstract: A graphic abstract is available for this article.

High-Density Characterization of the Ventricular Electrical Substrate During Sinus Rhythm in Post-Myocardial Infarction Patients.

OBJECTIVES: The aim of this study was to characterize, during sinus rhythm, the electric activation abnormalities in post-myocardial infarction patients undergoing ablation of ventricular tachycardia (VT) in order to identify specific signatures of those abnormal electrograms (EGMs). BACKGROUND: In the setting of VT ablation, substrate characterization hinges on the identification of local abnormal ventricular activity (LAVA) and late potentials (LPs) that are considered to be related to the VT circuit. METHODS: Patients scheduled for VT ablation underwent high-density ventricular substrate mapping. The substrate map during sinus rhythm was then compared with the activation maps of the clinical VT. Abnormal EGMs (LAVA and LPs) during sinus rhythm were characterized according to their configuration, duration, and amplitude and distinguished as belonging to bystander region or to the re-entrant circuit. Underlying electrophysiological mechanisms (wave-front collision, slow conduction) were identified on the activation maps and assigned to corresponding EGMs. RESULTS: Ten patients satisfied the criteria to be enrolled in the study. A mean of 5 ± 1 slow-conduction areas and 4 ± 2 wave-front collisions were identified. LAVA was due to slow conduction in 60.5%, followed by wave-front collision (17.5%). LPs were caused by slow conduction in 52% of cases and by wave-front collision in 43% of cases. During sinus rhythm, entrance and exit sites were characterized by LAVA, while at the VT isthmus, only LPs were identified. Cutoff values of duration <24.5 ms (95% sensitivity and 99% specificity) and amplitude <0.14 mV (90% sensitivity and 48.1% specificity) discriminated those LPs belonging to the circuit from those playing a bystander role. CONCLUSIONS: In the setting of post-myocardial infarction cardiomyopathy, specific EGM signatures are expressions of distinct electrophysiological phenomena. LAVA and LPs may play a bystander or an active role in the VT circuit, but only LPs with low amplitude and short duration predicted the VT isthmus.

Bipolar radiofrequency ablation for ventricular tachycardias originating from the interventricular septum: Safety and efficacy in a pilot cohort study.

BACKGROUND: Interest has grown in recent years in bipolar radiofrequency ablation (B-RFA). However, indications and outcome in patients with ventricular tachycardia (VT) are still to be defined. OBJECTIVE: The purpose of this study was to describe patient selection, safety and effectiveness of B-RFA, in a pilot cohort study of patients with nonischemic dilated cardiomyopathy (NIDCM) and drug-refractory VT. METHODS: We enrolled 21 patients with NIDCM (mean age 66±10 years; 18/21 (86%) men; left ventricular ejection fraction 35%±14%; 100% redo procedures) scheduled for a B-RFA procedure because of drug-refractory VT of suspected septal (interventricular septum [IVS]) origin. After electroanatomic mapping by using the CARTO®3 system, B-RFA was performed in all patients. Short- and long-term outcomes, including procedural success, major complications, and occurrence of major ventricular arrhythmias (MVAs), were evaluated at 25±8 months of follow-up (FU). RESULTS: Endocardial mapping showed IVS scar in all patients and extra-IVS in 7 patients (33%). B-RFA was performed at an average power of 33 W, for 60-90 seconds, over a 4.1 cm2 area, with 13±3 mm distance between catheters tips. The impedance drop was 27±4 Ω. The primary end point of noninducibility of the target clinical VT was obtained in 20 patients (95%). During FU, MVAs were documented in 7 patients (33%). FU MVAs occurred in all (100%) patients with extra-IVS localizations (7 of 7) or inflammatory nonischemic cardiomyopathy etiology (2 of 2). IVS thinning (tip-to-tip catheter distance < 5 mm) represented the only anatomical limitation to B-RFA. CONCLUSION: B-RFA is feasible in patients with NIDCM and drug-refractory VT of septal origin. Extra-IVS substrate and inflammatory NIDCM etiology were associated with an adverse outcome.

The COVID-19 challenge to cardiac electrophysiologists: optimizing resources at a referral center.

PURPOSE: To describe how a referral center for cardiac electrophysiology (EP) rapidly changed to comply with the ongoing COVID-19 healthcare emergency. METHODS: We present retrospective data about the modification of daily activities at our EP unit, following the pandemic outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in Italy. In particular, in the context of a pre-existing "hub-and-spoke" network, we describe how procedure types and volumes have changed in the last 3 months. RESULTS: Since our institution was selected as a COVID-19 referral center, the entire in-hospital activity was reorganized to assist more than 1000 COVID-positive cases. Only urgent EP procedures, including ventricular tachycardia ablation and extraction of infected devices, were both maintained and optimized to meet the needs of external hospitals. In addition, most of the non-urgent EP procedures were postponed. Finally, following prompt internal reorganization, both outpatient clinics and on-call services underwent significant modification, by integrating telemedicine support whenever applicable. CONCLUSION: We presented the fast reorganization of an EP referral center during the ongoing COVID-19 healthcare emergency. Our hub-and-spoke model may be useful for other centers, aiming at a cost-effective management of resources in the context of a global crisis.

Grid Mapping Catheter for Ventricular Tachycardia Ablation.

BACKGROUND: A new grid mapping catheter (GMC)-allowing for bipolar recordings of the electrograms in each orthogonal direction-became available. The aim of the current study is to evaluate the utility of the GMC in creating substrate and ventricular tachycardia (VT) activation maps during VT ablation procedures. METHODS: From December 2017 to July 2018, 41 consecutive patients undergoing a VT ablation procedure using a GMC were studied. During the substrate mapping, 3 different maps were created using the 3 GMC bipolar configurations (along the spline, across the spline, HD wave solution); the low voltage area and late potential areas were compared. In case of inducible VTs, the GMC was used to create the VT activation maps focusing on the diastolic interval. The relation between diastolic activities during VT and substrate abnormality during sinus rhythm was also investigated. RESULTS: The median low-voltage area drawn by the HD wave configuration was 28.9 cm2, 13% and 15% smaller than the low-voltage areas identified by the along and across configuration, respectively (33.1 and 33.9 cm2; P<0.0001). The late potential areas obtained with the 3 GMC configuration did not differ (P>0.05). VT activation mappings using the GMC were performed in 40 VTs, visualizing the full diastolic pathway in 22 (55%) of them. While the latest late potential areas were included in VT diastolic pathway in 17 VTs, the other 6 VTs showed mismatching of them. Identifying the full diastolic pathway led to a higher ongoing VT termination rate during the ablation than in case of partial recordings (88% versus 45%; P=0.03); furthermore, in the former situation, the noninducibility of the targeted VTs was achieved in all cases. CONCLUSIONS: The GMC is a useful tool for performing substrate and VT activation mappings during the VT ablation procedure, precisely identifying the low-voltage areas and quickly visualizing the diastolic pathways.