Procedural and Intermediate-term Results of the Electroanatomical-guided Cardioneuroablation for the Treatment of Supra-Hisian Second- or Advanced-degree Atrioventricular Block: the PIRECNA multicentre registry.

AIMS: Prior case series showed promising results for cardioneuroablation in patients with vagally induced atrioventricular blocks (VAVBs). We aimed to examine the acute procedural characteristics and intermediate-term outcomes of electroanatomical-guided cardioneuroablation (EACNA) in patients with VAVB. METHODS AND RESULTS: This international multicentre retrospective registry included data collected from 20 centres. Patients presenting with symptomatic paroxysmal or persistent VAVB were included in the study. All patients underwent EACNA. Procedural success was defined by the acute reversal of atrioventricular blocks (AVBs) and complete abolition of atropine response. The primary outcome was occurrence of syncope and daytime second- or advanced-degree AVB on serial prolonged electrocardiogram monitoring during follow-up. A total of 130 patients underwent EACNA. Acute procedural success was achieved in 96.2% of the cases. During a median follow-up of 300 days (150, 496), the primary outcome occurred in 17/125 (14%) cases with acute procedural success (recurrence of AVB in 9 and new syncope in 8 cases). Operator experience and use of extracardiac vagal stimulation were similar for patients with and without primary outcomes. A history of atrial fibrillation, hypertension, and coronary artery disease was associated with a higher primary outcome occurrence. Only four patients with primary outcome required pacemaker placement during follow-up. CONCLUSION: This is the largest multicentre study demonstrating the feasibility of EACNA with encouraging intermediate-term outcomes in selected patients with VAVB. Studies investigating the effect on burden of daytime symptoms caused by the AVB are required to confirm these findings.

Linear epicardial cryoablation effects in a porcine model: Lesion characteristics and vascular risk.

INTRODUCTION: Cryoablation in open-chest surgical interventions for ventricular arrhythmias has been reported with reasonable procedural outcomes. However, the characteristics of cryoablation lesions on the ventricular myocardium are not well defined. The purpose of the present study was to determine the tissue and vascular effects of a linear epicardial cryoablation probe in a porcine animal model. METHODS: Five adult Yorkshire swine underwent median sternotomy and application of linear cryoablation lesions using a malleable aluminum linear cryoablation probe of varying duration (2, 3, 4, and 5 min), including one lesion placed intentionally over the left anterior descending coronary (LAD) artery. Histological analysis was performed. RESULTS: Maximum lesion depth was approximately 1.0 cm with 3 min freezes, with no significant increase in depth achieved with longer lesions. No transmural lesions were achieved. No large vessel epicardial coronary artery injuries were seen to the LAD; however, surprisingly, remote isolated interventricular septal injury was seen in all animals, suggestive of possible compromise of smaller coronary arterial vessels. CONCLUSION: Single application freezes with an aluminum linear cryoablation probe can create homogeneous ablative lesions over the ventricular myocardium with a maximum depth of approximately 1.0 cm. No large vessel injury occurred with direct lesion application of the LAD; however, small coronary vessels may be at risk.

Catheter ablation of ventricular tachycardia in patients with prior cardiac surgery: An analysis from the International VT Ablation Center Collaborative Group.

INTRODUCTION: Patients with prior cardiac surgery may represent a subgroup of patients with ventricular tachycardia (VT) that may be more difficult to control with catheter ablation. METHODS: We evaluated 1901 patients with ischemic and nonischemic cardiomyopathy who underwent VT ablation at 12 centers. Clinical characteristics and VT radiofrequency ablation procedural outcomes were assessed and compared between those with and without prior cardiac surgery. Kaplan-Meier analysis was used to estimate freedom from recurrent VT and survival. RESULTS: There were 578 subjects (30.4%) with prior cardiac surgery identified in the cohort. Those with prior cardiac surgery were older (66.4 ± 11.0 years vs. 60.5 ± 13.9 years, p < .01), with lower left ventricular ejection fraction (30.2 ± 11.5% vs. 34.8 ± 13.6%, p < .01) and more ischemic heart disease (82.5% vs. 39.3%, p < .01) but less likely to undergo epicardial mapping or ablation (9.0% vs. 38.1%, p<.01) compared to those without prior surgery. When epicardial mapping was performed, a significantly greater proportion required surgical intervention for access (19/52 [36.5%] vs. 14/504 [2.8%]; p < .01). Procedural complications, including epicardial access-related complications, were lower (5.7% vs. 7.0%, p < .01) in patients with versus without prior cardiac surgery. VT-free survival (75.1% vs. 74.1%, p = .805) and survival (86.5% vs. 87.9%, p = .397) were not different between those with and without prior heart surgery, regardless of etiology of cardiomyopathy. VT recurrence was associated with increased mortality in patients with and without prior cardiac surgery. CONCLUSION: Despite different clinical characteristics and fewer epicardial procedures, the safety and efficacy of VT ablation in patients with prior cardiac surgery is similar to others in this cohort. The incremental yield of epicardial mapping in predominant ischemic cardiomyopathy population prior heart surgery may be low but appears safe in experienced centers.

Recurrent ventricular tachycardia after cardiac sympathetic denervation: Prolonged cycle length with improved hemodynamic tolerance and ablation outcomes.

INTRODUCTION: Cardiac sympathetic denervation (CSD) is utilized for the management of ventricular tachycardia (VT) in structural heart disease when refractory to radiofrequency ablation (RFA) or when patient/VT characteristics are not conducive to RFA. METHODS: We studied consecutive patients who underwent CSD at our institution from 2009 to 2018 with VT requiring repeat RFA post-CSD. Patient demographics, VT/procedural characteristics, and outcomes were assessed. RESULTS: Ninety-six patients had CSD, 16 patients underwent RFA for VT post-CSD. There were 15 male and 1 female patients with mean age of 54.2 ± 13.2 years. Fourteen patients had nonischemic cardiomyopathy. A mean of 2.0 ± 0.8 RFAs for VT was unsuccessful before the patient undergoing CSD. The median time between CSD and RFA was 104 days (interquartile range [IQR] = 15-241). The clinical VT cycle length was significantly increased after CSD both spontaneously on ECG and/or ICD interrogation (355 ± 73 ms pre-CSD vs. 422 ± 94 ms post-CSD, p = .001) and intraprocedurally (406 ± 86 ms pre-CSD vs. 457 ± 88 ms post-CSD, p = .03). Two patients had polymorphic and 14 had monomorphic VT (MMVT) pre-CSD, and all patients had MMVT post-CSD. The proportion of mappable, hemodynamically stable VTs increased from 35% during pre-CSD RFA to 58% during post-CSD RFA (p = .038). At median follow-up of 413 days (IQR = 43-1840) after RFA, eight patients had no further VT. CONCLUSION: RFA for recurrent MMVT post-CSD is a reasonable treatment option with intermediate-term clinical success in 50% of patients. Clinical VT cycle length was significantly increased after CSD with associated improvement in mappable, hemodynamically tolerated VT during RFA.

Premature ventricular contraction diurnal profiles predict distinct clinical characteristics and beta-blocker responses.

INTRODUCTION: Frequent premature ventricular complexes (PVCs) can lead to symptoms, such as cardiomyopathy and increased mortality. Beta-blockers are recommended as first-line therapy to reduce PVC burden; however, the response is unpredictable. The objective of this study is to determine whether PVC diurnal-variability patterns are associated with different clinical profiles and predict drug response. METHODS: Consecutive patients with frequent PVCs (burden ≥ 1%), referred for Holter monitoring between 2014 and 2016, were included. Follow-up Holters, when available, were assessed after beta-blocker initiation to assess response (≥50% reduction). Patients were divided into three groups on the basis of relationship between hourly PVC count and mean HR during each of the 24 Holter hours: (1) fast-HR-dependent-PVC (F-HR-PVC) for positive correlation (Pearson, P < 0.05), (2) slow-HR-dependent-PVC (S-HR-PVC) for a negative, and (3) independent-HR-PVC (I-HR-PVC) when no correlation was found. RESULTS: Of the 416 patients included, 50.2% had F-HR-PVC, 35.6% I-HR-PVC, and 14.2% S-HR-PVC with distinct clinical profiles. Beta-blocker therapy was successful in 34.0% patients overall: patients with F-HR-PVC had a decrease in PVC burden (18.8 ± 10.4% to 9.3 ± 6.6%, P < 0.0001; 62% success), I-HR-PVC had no change (18.4 ± 17.9% to 20.6 ± 17.9%, P = 0.175; 0% success), whereas S-HR-PVC had an increase in burden (14.6 ± 15.3% to 20.8 ± 13.8%, P = 0.016; 0% success). The correlation coefficient was the only predictor of beta-blocker success (AUC = 0.84, sensitivity = 100%, specificity = 67.7%; r ≥ 0.4). CONCLUSIONS: A simple analysis of Holter PVC diurnal variability may provide incremental value to guide clinical PVC management. Only patients displaying a F-HR-PVC profile benefited from beta-blockers. An alternative strategy should be considered for others, as beta-blockers may have no effect or can even be harmful.

Ventricular Tachycardia Ablation in the Presence of Left Ventricular Thrombus: Safety and Efficacy.

INTRODUCTION: The safety of ventricular tachycardia (VT) ablation in patients with laminated left ventricular (LV) thrombus has not been examined. METHODS: Patients with laminated LV thrombus on transthoracic echocardiogram who underwent scar-mediated VT ablation at two centers from 2010 to 2013 were retrospectively analyzed. All patients had failed medical therapy. Acute procedural outcomes, complications, and clinical outcomes at 1 year were assessed. RESULTS: Eight patients (four ischemic, four nonischemic cardiomyopathy) underwent VT ablation in the presence of laminated intracavitary thrombus. Six out of eight (75%) had electrical storm (ES). The mapping and ablation approach was LV endocardial-only in three patients, epicardial-only in two, combined epicardial-RV endocardial in two, and combined epicardial-LV endocardial in one. Major complication (ischemic stroke) occurred in one patient 9 days post-procedure. There was no procedural mortality. Complete acute procedural success (noninducibility of any VT after ablation) was achieved in five (63%), and partial success (ablation of only clinical VT) in an additional three (37%). At 1 year, freedom from VT and survival were achieved in six (75%) and seven (88%) patients, respectively. CONCLUSION: Initial data suggest that ablation of VT in the presence of intracavitary thrombus is feasible, is associated with a similar success rate to historical studies in patients without thrombus, and has an acceptable risk of complications given the high-risk nature of patients with ES. Further data are needed; however, the presence of a laminated thrombus should not necessarily preclude ablation in patients who have failed medical therapy for VT in whom ablation is otherwise indicated.

A New Combined Parameter to Predict Premature Ventricular Complexes Induced Cardiomyopathy: Impact and Recognition of Epicardial Origin.

INTRODUCTION: Reversible premature ventricular complexes-induced cardiomyopathy (PVC-CMP) is a well-described, multi-factorial entity. Single predictors, such as PVC burden or QRS duration, may not apply equally to all patients in contemporary unselected populations including patients with structural heart disease (SHD) or with particular origin such as epicardial (EPI) PVC. We sought to evaluate clinical criteria associated with PVC-CMP notably focusing on the EPI origin impact and ECG recognition and the value of a new composite predictor of PVC-CMP, the PVC-CMP-Index. METHODS AND RESULTS: We studied 107 consecutive patients (69 men; mean age = 56 ± 16 years) with frequent PVC (23.1 ± 11.5%) referred for PVC ablation. Thirty-six patients (33.6%) had an underlying SHD and 25 patients (23.4%) an EPI PVC origin. After a mean follow-up of 22.7 ± 15.3 months, 72.9% achieved a long-term successful ablation and 54.2% had PVC-CMP. PVC-CMP prevalence was significantly higher in patients with an EPI compared to endocardial PVC focus (84.0% vs. 45.1%, respectively, P < 0.001). EPI PVC origin (OR = 68.7 IC95% [3.5-1363], P = 0.005), as well as SHD (OR = 12.3 IC95% [1.6-92.6], P = 0.015), was independent predictor of PVC-CMP. While PVC burden (AUC = 0.78) or PVC-QRS width (AUC = 0.68) independently predicted PVC-CMP, the PVC-CMP-Index (values ≥39) defined as: PVC burden (0-1) × PVC-QRS width (milliseconds) × a constant C (1.28 for SHD or 2 for ECG suggesting EPI origin based on our ECG 3-step algorithm), highly correlated with PVC-CMP (AUC = 0.91, sensitivity = 93%, specificity = 80%). CONCLUSION: We developed a new index, which incorporates PVC burden, QRS width, and presence of SHD or suspected EPI origin that best predicted PVC-CMP.

Heart Failure Secondary to Chagas Disease: an Emerging Problem in Non-endemic Areas.

Chagas disease affects millions of people worldwide. Though the majority of infected individuals remain asymptomatic, approximately 30 % of patients progress to develop cardiac manifestations and eventual heart failure. While vectorial transmission occurs predominantly in South America, Central America, and Mexico, millions of people originally from these endemic regions immigrate to non-endemic countries in North America, Europe, and Asia. Outside of rare specialized centers, health-care providers lack experience diagnosing and treating this disease. This lack of experience likely leads to far fewer Chagas disease patients being diagnosed than what actually exist in non-endemic countries, with subsequent adverse effect on patient outcomes and health-care expenses. Underdiagnosis increases the risk of developing cardiomyopathy, associated heart failure, and life-threatening ventricular arrhythmias as the disease progresses.

Multidetector Computed Tomography Assessment of Anatomical Ventricular Tachycardia Isthmuses in Repaired Tetralogy of Fallot.

BACKGROUND: Tetralogy of Fallot (TOF) is associated with risk for sustained monomorphic ventricular tachycardia (VT). Preemptive electrophysiology study before transcatheter pulmonary valve placement is increasing, but the value of MDCT for anatomical VT isthmus assessment is unknown. OBJECTIVES: The purpose of this study was to determine the impact of multidetector computed tomography (MDCT) in the evaluation of sustained monomorphic VT for repaired TOF. METHODS: Consecutive pre-transcatheter pulmonary valve MDCT studies were identified, and anatomical isthmus dimensions were measured. For a subset of patients with preemptive electrophysiology study, MDCT features were compared with electroanatomical maps. RESULTS: A total of 61 repaired TOFs with MDCT were identified (mean 35 ± 14 years, 58% men) with MDCT electroanatomical map pairs in 35 (57%). Calcification corresponding to patch material was present in 46 (75%) and was used to measure anatomical VT isthmuses. MDCT wall thickness correlated positively with number of ablation lesions and varied with functional isthmus properties (blocked isthmus 2.6 mm [Q1, Q3: 2.1, 4.0 mm], slow conduction 4.8 mm [Q1, Q3: 3.3, 6.0 mm], and normal conduction 5.6 mm [Q1, Q3: 3.9, 8.3 mm]; P < 0.001). A large conal branch was present in 6 (10%) and a major coronary anomaly was discovered in 3 (5%). Median ablation lesion distance was closer to the right vs the left coronary artery (10 mm vs 15 mm; P = 0.01) with lesion-to-coronary distance <5 mm in 3 patients. CONCLUSIONS: MDCT identifies anatomical structures relevant to catheter ablation for repaired TOF. Wall thickness at commonly targeted anatomical VT isthmuses is associated with functional isthmus properties and increased thermal energy delivery.

Cardioneuroablation for the management of patients with recurrent vasovagal syncope and symptomatic bradyarrhythmias: the CNA-FWRD Registry.

BACKGROUND: Cardioneuroablation has been emerging as a potential treatment alternative in appropriately selected patients with cardioinhibitory vasovagal syncope (VVS) and functional AV block (AVB). However the majority of available evidence has been derived from retrospective cohort studies performed by experienced operators. METHODS: The Cardioneuroablation for the Management of Patients with Recurrent Vasovagal Syncope and Symptomatic Bradyarrhythmias (CNA-FWRD) Registry is a multicenter prospective registry with cross-over design evaluating acute and long-term outcomes of VVS and AVB patients treated by conservative therapy and CNA. RESULTS: The study is a prospective observational registry with cross-over design for analysis of outcomes between a control group (i.e., behavioral and medical therapy only) and intervention group (Cardioneuroablation). Primary and secondary outcomes will only be assessed after enrollment in the registry. The follow-up period will be 3 years after enrollment. CONCLUSIONS: There remains a lack of prospective multicentered data for long-term outcomes comparing conservative therapy to radiofrequency CNA procedures particularly for key outcomes including recurrence of syncope, AV block, durable impact of disruption of the autonomic nervous system, and long-term complications after CNA. The CNA-FWRD registry has the potential to help fill this information gap.

Our approach to minimize risk of epicardial access: standard techniques with the addition of electroanatomic mapping guidance.

Epicardial mapping and ablation is increasingly being performed for the treatment of complex arrhythmias. Right ventricular (RV) puncture remains the most common complication, with damage to surrounding non-cardiac structures also a concern. We describe the standard techniques used in our lab essential for safe epicardial access, as well as a novel technique incorporating electroanatomic mapping (EAM) guidance. In a series of 8 patients referred for ventricular tachycardia ablation, an RV endocardial voltage map was created using EAM systems. EAM images were fused with preprocedure CT scans when available. A 17G Tuohy needle was integrated with the EAM system by attaching the needle to sterile electrode clamps. EAM location points were used in conjunction with standard access techniques until epicardial access was obtained. Epicardial access was successfully obtained in 8/8 (100%) patients. Successful access without RV puncture was achieved in 7/8 (88%) cases. This proof of concept study demonstrates that EAM systems can be used as an adjunct to standard access techniques to visualize and facilitate pericardial access.

Transmural "Scar-to-Scar" Reentrant Ventricular Tachycardia.

We describe a scar-related reentrant ventricular tachycardia circuit with a proximal segment in an endocardial basal septal scar and an exit in a region of slow conduction in a non-overlapping region of epicardial basal lateral scar. The 12-lead EKG demonstrates criteria for a basal lateral epicardial VT, however the same morphology could be produced with a longer stim-latency with pace mapping or VT induction from the endocardial septal region of scar. A significant segment of myocardium demonstrated no endocardial or epicardial scar on electroanatomic mapping, suggesting the presence of a mid-myocardial isthmus. Further evidence was provided by assessment of unipolar settings. The epicardial VT that initially appeared to originate from the basal lateral epicardial region, was successfully treated with radiofrequency ablation of the lateral aspect of the endocardial septal scar.

Revisiting the Anatomy of the Left Ventricular Summit.

The left ventricular summit corresponds to the epicardial side of the basal superior free wall, extending from the base of the left coronary aortic sinus. The summit composes the floor of the compartment surrounded by the aortic root, infundibulum, pulmonary root, and left atrial appendage. The compartment is filled with thick adipose tissue, carrying the coronary vessels. Thus, the treatment of ventricular tachycardia originating from the summit is challenging, and three-dimensional understanding of this complicated region is fundamental. We revisit the clinical anatomy of the left ventricular summit with original images from the Wallace A. McAlpine collection.

Clinical predictors and implications of cardiac inflammation detected on positron emission tomography (PET) in patients referred for premature ventricular complex (PVC) ablation.

BACKGROUND: Positron emission tomography computed tomography (PET-CT) is not routinely used for premature ventricular complexes (PVCs). Whether specific clinical factors are associated with abnormal PET-CT results is not clear. METHODS: The treatment courses and baseline characteristics of consecutive patients in a single center between 2012 and 2021, age > 18 years old, and who received 18F-fluorodeoxyglucose (FDG) PET-CT imaging for evaluation of PVCs were retrospectively analyzed. RESULTS: A total of 102 patients was included. Of these, 27 patients (26.4%) had abnormal PET-CT and 61 (59.8%) had normal imaging. Abnormal PET-CT findings were associated with non-sustained ventricular tachycardia (NSVT) (95.2% vs. 52.6%, p = 0.001), higher number of PVC morphologies (2.29 ± 0.7 vs. 1.31 ± 0.6, p < 0.001), greater PVC coupling interval dispersion (72.47 ± 66.4 ms vs. 13.42 ± 17.9 ms, p < 0.001), and greater likelihood of fast heart rate dependent PVCs (78.5% vs. 38.2%, p = 0.017). Fourteen (51.8%) patients had an abnormal PET-CT and abnormal late gadolinium enhancement (LGE). Patients with abnormal PET-CT were more frequently treated with immunosuppression (81.4% vs. 3.2%, p < .0001) than with catheter ablation (11.1% vs. 45.9%, p = 0.002) compared to the normal PET-CT group. Over a median follow-up of 862 days (IQR 134, 1407), PVC burden decreased in both groups [from 23 ± 16% to 9 ± 10% (p < 0.001) in abnormal PET-CT group and from 21 ± 15% to 7 ± 10% (p < 0.001) in normal PET-CT group]. CONCLUSIONS: Abnormal PET-CT findings were more commonly associated with NSVT, multiform PVCs, greater PVC coupling interval dispersion, and fast heart rate dependent PVCs. LGE was not sensitive for detecting inflammation. Immunosuppression was effective in managing PVCs with abnormal PET-CT.

Ischemia-induced ventricular proarrhythmia and cardiovascular autonomic dysreflexia after cardioneuroablation.

BACKGROUND: Cardioneuroablation (CNA) is an attractive treatment of vasovagal syncope. Its long-term efficacy and safety remain unknown. OBJECTIVE: The purpose of this study was to develop a chronic porcine model of CNA to examine the susceptibility to ventricular tachyarrhythmia (ventricular tachycardia/ventricular fibrillation [VT/VF]) and cardiac autonomic function after CNA. METHODS: A percutaneous CNA model was developed by ablation of left- and right-sided ganglionated plexi (n = 5), confirmed by histology. Reproducible bilateral vagal denervation was confirmed after CNA by extracardiac vagal nerve stimulation (VNS) and histology. Chronic studies included 16 pigs randomized to CNA (n = 8) and sham ablation (n = 8, Control). After 6 weeks, animals underwent hemodynamic studies, assessment of cardiac sympathetic and parasympathetic function using sympathetic chain stimulation and direct VNS, respectively, and proarrhythmic potential after left anterior descending (LAD) coronary artery ligation. RESULTS: After CNA, extracardiac VNS responses remained abolished for 6 weeks despite ganglia remaining in ablated ganglionated plexi. In the CNA group, direct VNS resulted in paradoxical increases in blood pressure, but not in sham-ablated animals (CNA group vs sham group: 8.36% ± 7.0% vs -4.83% ± 8.7%, respectively; P = .009). Left sympathetic chain stimulation (8 Hz) induced significant corrected QT interval prolongation in the CNA group vs the sham group (11.23% ± 4.0% vs 1.49% ± 4.0%, respectively; P < .001). VT/VF after LAD ligation was more prevalent and occurred earlier in the CNA group than in the control group (61.44 ± 73.7 seconds vs 245.11 ± 104.0 seconds, respectively; P = .002). CONCLUSION: Cardiac vagal denervation is maintained long-term after CNA in a porcine model. However, chronic CNA was associated with cardiovascular dysreflexia, diminished cardioprotective effects of cardiac vagal tone, and increased susceptibility to VT/VF in ischemia. These potential long-term negative effects of CNA suggest the need for rigorous clinical studies on CNA.

Sudden cardiac arrest in athletes and strategies to optimize preparedness.

Sudden cardiac arrest (SCA) is the leading cause of death in young athletes. Despite efforts to improve preparedness for cardiac emergencies, the incidence of out-of-hospital cardiac arrests in athletes remains high, and bystander awareness and readiness for SCA support are inadequate. Initiatives such as designing an emergency action plan (EAP) and mandating training in cardiopulmonary resuscitation (CPR) and automated external defibrillator use (AED) for team members and personnel can contribute to improved survival rates in SCA cases. This review provides an overview of SCA in athletes, focusing on identifying populations at the highest risk and evaluating the effectiveness of different screening practices in detecting conditions that may lead to SCA. We summarize current practices and recommendations for improving the response to SCA events, and we highlight the need for ongoing efforts to optimize preparedness through the implementation of EAPs and the training of individuals in CPR and AED use. Additionally, we propose a call to action to increase awareness and training in EAP development, CPR, and AED use for team members and personnel. To improve outcomes of SCA cases in athletes, it is crucial to enhance bystander awareness and preparedness for cardiac emergencies. Implementing EAPs and providing training in CPR and AED use for team members and personnel are essential steps toward improving survival rates in SCA cases.

The derivative of tissue activation as a marker of arrhythmogenic myocardium.

BACKGROUND: Mapping techniques to identify diseased myocardial substrate during ventricular tachycardia ablation procedures remain limited. OBJECTIVE: We hypothesized that tissue derivative of the voltage with respect to time (dV/dt), the slope of the unipolar ventricular electrogram registered by local ventricular activation, represents a unique parameter for identifying potential arrhythmogenic tissue in the ischemic scar border zone. METHODS: Using high-resolution electrical mapping, we examined dV/dt characteristics in the border zone of animals after chronic myocardial infarction (MI). RESULTS: Minimum dV/dt (dV/dtmin) in MI animals was less than that in control animals (-344.7 ± 68.7 in controls vs -174.2 ± 104.5 in MI; P < .001) and related to ventricular fibrosis. In MI animals, dV/dtmin values were divided into high (≤-200 µV/ms) and low (>-200 µV/ms) dV/dtmin. Low dV/dtmin regions harbored arrhythmogenic substrates that were characterized by (1) high responsiveness to sympathetic stimulation, (2) presence of late potentials, and (3) lower unipolar and bipolar voltage amplitudes. CONCLUSION: Our data indicate that dV/dtmin is a unique parameter for identifying arrhythmogenic myocardium and may add a useful metric to conventional mapping strategies.

Ventricular Parasystole in Cardiomyopathy Patients: A Link Between His-Purkinje System Damage and Ventricular Fibrillation.

BACKGROUND: The clinical relevance and prognostic implications of ventricular parasystole are unknown. OBJECTIVES: This study sought to assess the prevalence of ventricular parasystole in patients with implantable cardioverter-defibrillators (ICDs) and ventricular parasystole's association with ventricular arrhythmias and conduction system abnormalities. METHODS: This study retrospectively evaluated patients who underwent ICD interrogation at a single center between June 1, 2019, and August 31, 2020, and reviewed all available ICD and electrocardiogram data. This study identified patients with ventricular parasystole and compared the prevalence of ventricular fibrillation (VF), ventricular tachycardia (VT), and new conduction system abnormalities in those with ≥5 years of intrinsic QRS-complex electrocardiograms to those without parasystole. RESULTS: This study included 374 patients (age 57 ± 21 years, 72% male, 45% nonischemic, 32% ischemic cardiomyopathy), of which, 104 (28%) had VT only, 39 (10%) VF only, and 10 (3%) both VT/VF. Ventricular parasystole was identified in 33 patients (9%); parasystolic foci were predominantly from the His-Purkinje system. Compared with those without parasystole, patients with parasystole had a significantly higher rate of VF (36% vs 11%; P < 0.01), but not VT (42% vs 29%; P = 0.12). Patients with parasystole, compared with those without parasystole, had a higher prevalence of new conduction abnormalities, particularly progressive intraventricular conduction delay (11 of 18 [61%] vs 12 of 83 [14%]; P < 0.01) and new right bundle branch block (4 of 18 [22%] vs 1 of 83 [1%]; P < 0.01). CONCLUSIONS: Ventricular parasystole was strongly associated with new conduction system abnormalities and VF in patients who have cardiomyopathy with ICDs, suggesting a potential link between VF and His-Purkinje damage in this patient population.