Hybrid therapy for ventricular arrhythmia management

Ventricular Tachycardia Ablation Endpoints: Moving Beyond Noninducibility

In patients with structural heart disease and ventricular tachycardia (VT) undergoing catheter ablation, the response to programmed electrical stimulation (PES) at the end of the procedure has been traditionally used to evaluate the acute success and predict long-term outcomes. Although noninducibility at PES has been extensively investigated and validated in clinical trials and large multicenter registries, its performance in predicting long-term freedom from VT is suboptimal. In addition, PES has inherent limitations related to the influence of background antiarrhythmic drug therapy, periprocedural use of anesthesia, and the heterogeneity in PES protocols. The increased utilization of substrate-based ablation approaches that focus on ablation of abnormal electrograms identified with mapping in sinus or paced rhythm has been paralleled by a need for additional procedural endpoints beyond VT noninducibility at PES. This article critically appraises the relative merits and limitations of different procedural endpoints according to different ablation techniques for catheter ablation of scar-related VT.

Scar nonexcitability using simultaneous pacing for substrate ablation of ventricular tachycardia

OBJECTIVES

To describe an expedited strategy of simultaneous high-output pacing during radiofrequency ablation to achieve scar homogenization and electrical inexcitability as an approach for substrate ablation for scar-related ventricular tachycardia (VT).

BACKGROUND

Scar homogenization with additional testing for electrical inexcitability is known endpoints for catheter ablation, but achieving both can be time consuming. We describe a strategy of simultaneous pacing during radiofrequency ablation to expedite this approach.

METHODS AND RESULTS

Ten patients (age 74 ± 6 years; all men, (LV) ejection fraction of 33% ± 8%, ischemic cardiomyopathy, 9; VT storm, 7) underwent scar homogenization with electrical inexcitability to pacing (10 mA, 9 ms pulse width), as well as noninducibility of any VT as an acute procedural endpoint. Thirty-four VTs were inducible in 10 patients with a total of 1127 ablation lesions applied. Median ablation lesions per patient were 97 (interquartile range [IQR]_25-75 71-151), and the total ablation time was 49 minutes (IQR_25-75 45-56 minutes) with average duration per lesion of 32.2 seconds (IQR_25-75 25.8-37.8 seconds). Average power was 33 W (IQR_25-75 32-38 W), average contact force was 13 g (IQR_25-75 11.9-14.6 g) with a median impedance drop of 9.6 Ω/lesion (IQR_25-75 8.1-10.0 Ω). There were no ventricular fibrillation episodes using this strategy. The median procedure time was 246 minutes (IQR_25-75 214-293 minutes). Acute procedural success was seen in nine patients with 97% of VTs noninducible.

CONCLUSION

Simultaneous ablation with high output pacing to achieve scar inexcitability, when combined with scar homogenization and noninducibility of any VT may be an expeditious, safe, and effective technique for catheter ablation.

Strategies to Reduce Recurrent Shocks Due to Ventricular Arrhythmias in Patients with an Implanted Cardioverter-Defibrillator

Ventricular arrhythmias are a therapeutic challenge, owing to their relatively unpredictable and deadly nature. Many patients are treated with an implantable cardioverter-defibrillator for either primary or secondary prevention of ventricular arrhythmias, meaning those who are at high risk of versus those who have experienced ventricular arrhythmias or sudden cardiac arrest, respectively. Despite the life-saving benefit, ICD comes with the risk of recurrent shocks for both appropriate and inappropriate rhythms. Patients with recurrent shocks have a poor quality of life and increased mortality rates. In this article, we review data for optimal device settings, medical management and radiofrequency ablation strategies to minimise the frequency of ICD shock, with a focus on treatment of ventricular arrhythmias, to reduce patient morbidity and mortality, and to maximise wellbeing and quality of life.

Substrate mapping for unstable ventricular tachycardia

The primary goal of catheter ablation of scar-related ventricular tachycardia (VT) is the interruption of critical areas of slow conduction responsible for the development and maintenance of the reentrant VT circuit. Most patients with scar-related VT present with unstable arrhythmias that are not amenable to interrogation from multiple sites to define the VT circuit based on the intracardiac activation sequence and the response to entrainment mapping. In order to effectively target unstable VTs, a number of ablation approaches have been described with the aim of targeting the abnormal substrate defined with mapping in sinus or paced rhythm. Some of these strategies (eg, late potential and local abnormal ventricular activity ablation or scar homogenization) target the entire abnormal substrate harboring abnormal electrograms, defined with a variety of different criteria. Scar dechanneling, linear ablation through sites matching VT with pacing, and the core isolation approach focus on more discrete regions within the abnormal substrate that have been proven relevant to the clinical and/or inducible arrhythmias by means of physiologic maneuvers, although this does not necessarily translate to fewer radiofrequency lesions to achieve the procedural end-point. Observational studies evaluating different substrate-based ablation techniques have reported fairly uniform arrhythmia-free survivals at short- and mid-term follow-up, although direct comparisons between different techniques are lacking. In this article, we summarize the different state-of-the-art substrate mapping and ablation approaches for targeting unstable VT, with a particular focus on the relative merits and limitations of the described techniques.

Noninvasive programmed ventricular stimulation early after ventricular tachycardia ablation to predict risk of late recurrence

OBJECTIVES

The goal of this study was to evaluate the ability of noninvasive programmed stimulation (NIPS) after ventricular tachycardia (VT) ablation to identify patients at high risk of recurrence.

BACKGROUND

Optimal endpoints for VT ablation are not well defined.

METHODS

Of 200 consecutive patients with VT and structural heart disease undergoing ablation, 11 had clinical VT inducible at the end of ablation and 11 recurred spontaneously. Of the remaining 178 patients, 132 underwent NIPS through their implantable cardioverter-defibrillator 3.1 ± 2.1 days after ablation. At 2 drive cycle lengths, single, double, and triple right ventricular extrastimuli were delivered to refractoriness. Clinical VT was defined by comparison with 12-lead electrocardiograms and stored implantable cardioverter-defibrillator electrograms from spontaneous VT episodes. Patients were followed for 1 year.

RESULTS

Fifty-nine patients (44.7%) had no VT inducible at NIPS; 49 (37.1%) had inducible nonclinical VT only; and 24 (18.2%) had inducible clinical VT. Patients with inducible clinical VT at NIPS had markedly decreased 1-year VT-free survival compared to those in whom no VT was inducible (<30% vs. >80%; p = 0.001), including 33% recurring with VT storm. Patients with inducible nonclinical VT only, had intermediate 1-year VT-free survival (65%).

CONCLUSIONS

When patients with VT and structural heart disease have no VT or nonclinical VT only inducible at the end of ablation or their condition is too unstable to undergo final programmed stimulation, NIPS should be considered in the following days to further define risk of recurrence. If clinical VT is inducible at NIPS, repeat ablation may be considered because recurrence over the following year is high.

Ventricular Tachycardia/Ventricular Fibrillation Ablation in the Setting of Ischemic Heart Disease

Recurrent ventricular tachycardia (VT) in the setting of coronary artery disease is frequently a life-threatening electrophysiologic emergency. Even in patients with an implantable defibrillator, recurrent VT is frequently accompanied by repeated and disabling shock therapy. Catheter ablative therapy offers the ability to provide immediate control of recurrent VT. Long-term elimination of VT should be anticipated in most patients. This article reviews the strategies, tools, techniques, and expected outcome for catheter ablation of stable and unstable ventricular arrhythmias in the setting ischemic heart disease.

Advances in ablation therapy for complex arrhythmias: atrial fibrillation and ventricular tachycardia

Catheter ablation has evolved over the past two decades to become first-line therapy for many cardiac arrhythmias. Multiple advances in the technology and understanding of radiofrequency ablation have allowed this technique to blossom into one of the most powerful therapeutic tools available to the electrophysiologist, and have opened a new chapter in the diagnosis and management of clinical arrhythmias. Catheter ablation often eliminates the need for chronic drug therapy and can result in significant long-term cost savings. As catheter technology continues to improve, and newer, more effective energy delivery systems are developed, the applicability of catheter-based therapy will continue to expand. This review addresses some of the more commonly encountered clinical arrhythmias and the recent developments in the treatment of these arrhythmias from a catheter-based standpoint.