Pan-Asia United States PrEvention of Sudden Cardiac Death Catheter Ablation Trial (PAUSE-SCD): rationale and study design

Ventricular Tachycardia Ablation Guided by Functional Substrate Mapping: Practices and Outcomes

Catheter ablation of ventricular tachycardia has demonstrated its important role in the treatment of ventricular tachycardia in patients with structural cardiomyopathy. Conventional mapping techniques used to define the critical isthmus, such as activation mapping and entrainment, are limited by the non-inducibility of the clinical tachycardia or its poor hemodynamic tolerance. To overcome these limitations, a voltage mapping strategy based on bipolar electrograms peak to peak analysis was developed, but a low specificity (30%) for VT isthmus has been described with this approach. Functional mapping strategy relies on the analysis of the characteristics of the electrograms but also their propagation patterns and their response to extra-stimulus or alternative pacing wavefronts to define the targets for ablation. With this review, we aim to summarize the different functional mapping strategies described to date to identify ventricular arrhythmic substrate in patients with structural heart disease.

First-Line Catheter Ablation of Monomorphic Ventricular Tachycardia in Cardiomyopathy Concurrent with Defibrillator Implantation: The PAUSE-SCD Randomized Trial

Background: Catheter ablation as first-line therapy for ventricular tachycardia (VT) at the time of implantable cardioverter defibrillator (ICD) implantation has not been adopted into clinical guidelines. Also, there is an unmet clinical need to prospectively examine the role of VT ablation in patients with non-ischemic cardiomyopathy (NICM), an increasingly prevalent population referred for advanced therapies globally. Methods: We conducted an international, multi-center, randomized controlled trial enrolling 180 patients with cardiomyopathy and monomorphic VT with an indication for implantable cardioverter defibrillator (ICD) implantation to assess the role of early, first-line ablation therapy. A total of 121 patients were randomized (1:1) to ablation + an ICD versus conventional medical therapy + an ICD. Patients who refused ICD (n=47) were followed in a prospective registry after stand-alone ablation treatment. The primary outcome was a composite endpoint of VT recurrence, cardiovascular hospitalization, or death. Results: Randomized patients had a mean age of 55 years old (IQR 46-64) and left ventricular ejection fraction of 40 % (IQR 30-49 %); 81 % were male. The underlying heart disease was ischemic cardiomyopathy (ICM) in 35 %, NICM in 30 %, and arrhythmogenic cardiomyopathy (ARVC) in 35 %. Ablation was performed a median of 2 days prior to ICD implantation (IQR 5 days prior to 14 days after). At 31-months, the primary outcome occurred in 49.3 %of the ablation group and 65.5 % in the control group (HR 0.58, 95 % CI, 0.35-0.96; P=0.04). The observed difference was driven by a reduction in VT recurrence in the ablation arm (HR 0.51 [95 %CI, 0.29-0.90 ]; P=0.02). A statistically significant reduction in both ICD shocks (10.0 vs 24.6 %; p=0.03) and anti-tachycardia pacing (16.2 % vs 32.8 %; p=0.04) was observed in patients who underwent ablation compared with control. No differences in cardiovascular hospitalization (32.0 % vs. 33.7 %; HR 0.82 [95 % CI, 0.43-1.56 ]; P=0.55) or mortality (8.9% vs 8.8 %, HR 1.40 [95 %CI, 0.38-5.22 ]; P=0.62]) were observed. Ablation-related complications occurred in 8.3 % of patients. Conclusions: Among patients with cardiomyopathy of varied etiologies, early catheter ablation performed at the time of ICD implantation significantly reduced the composite primary outcome of VT recurrence, cardiovascular hospitalization, or death. These findings were driven by a reduction in ICD therapies.

Contemporary Management of Complex Ventricular Arrhythmias

Percutaneous catheter ablation is an effective and safe therapy that can eliminate ventricular tachycardia, reducing the risks of both recurrent arrhythmia and shock therapies from a defibrillator. Successful ablation requires accurate identification of arrhythmic substrate and the effective delivery of energy to the targeted tissue. A thorough pre-procedural assessment is needed before considered 3D electroanatomical mapping can be performed. In contemporary practice, this must combine traditional electrophysiological techniques, such as activation and entrainment mapping, with more novel physiological mapping techniques for which there is an ever-increasing evidence base. Novel techniques to maximise energy delivery to the tissue must also be considered and balanced against their associated risks of complication. This review provides a comprehensive appraisal of contemporary practice and the evidence base that supports recent developments in mapping and ablation, while also considering potential future developments in the field.

[Update on ablation of ventricular tachyarrhythmias]

Catheter ablation of ventricular tachycardia (VT) is performed with increasing frequency in clinical practice. Whereas the reported success rates of idiopathic VT are high, catheter ablation of VT in patients with structural heart disease with its scar-related re-entry mechanism may remain a challenge especially if deep intramyocardial or epicardial portions exist. The integration of modern cardiac imaging, new functional mapping strategies and catheter technologies allow optimized identification and characterization of the critical arrhythmogenic substrate and hence a more targeted VT ablation. The extent to which these innovations will have the potential to improve VT ablation success rates will be determined by future studies.

Management of ventricular tachycardia in patients with ischaemic cardiomyopathy: contemporary armamentarium

Worldwide, ∼4 million people die from sudden cardiac death every year caused in more than half of the cases by ischaemic cardiomyopathy (ICM). Prevention of sudden cardiac death after myocardial infarction by implantation of a cardioverter-defibrillator (ICD) is the most common, even though not curative, therapy to date. Optimized ICD programming should be strived for in order to decrease the incidence of ICD interventions. Catheter ablation reduces the recurrence of ventricular tachycardias (VTs) and is an important adjunct to sole ICD-based treatment or pharmacological antiarrhythmic therapy in patients with ICM, as conclusively demonstrated by seven randomized controlled trials (RCTs) in the last two decades. However, none of the conducted trials was powered to reveal a survival benefit for ablated patients as compared to controls. Whereas thorough consideration of an early approach is necessary following two recent RCTs (PAUSE-SCD, BERLIN VT), catheter ablation is particularly recommended in patients with recurrent VT after ICD therapy. In this context, novel, pathophysiologically driven ablation strategies referring to deep morphological and functional substrate phenotyping based on high-resolution mapping and three-dimensional visualization of scars appear promising. Emerging concepts like sympathetic cardiac denervation as well as radioablation might expand the therapeutical armamentarium especially in patients with therapy-refractory VT. Randomized controlled trials are warranted and on the way to investigate how these translate into improved patient outcome. This review summarizes therapeutic strategies currently available for the prevention of VT recurrences, the optimal timing of applicability, and highlights future perspectives after a PAUSE in BERLIN.