Ventricular Tachycardia Ablation: Should We Be Impelled to Do More?^∗Free Access

Introduction

Catheter ablation of ventricular tachycardia (VT) in patients with structural heart disease is a difficult business. These patients are often very sick, and the onset of VT portends a poor prognosis, with high rates of arrhythmic and heart failure–related death (1). Yet catheter ablation of VT is an effective and relatively safe treatment option for patients with VT, particularly VT refractory to antiarrhythmic therapy (2–4). Advances in our understanding of the pathophysiology of VT, coupled with technological innovation, have meant that electrophysiologists can now tackle more difficult arrhythmias occurring in patients with more severe disease. Most VT in structural heart disease is hemodynamically unstable, and we need strategies to treat these arrhythmias (5). Many patients, especially those with nonischemic cardiomyopathies, have complex scar substrates that may be epicardial or intramural. It would seem intuitive that technology that converts hemodynamically unstable VT to mappable VT should increase procedural success and reduce risk.

Minimally invasive hemodynamic support devices should be just such devices, permitting mapping of hemodynamically unstable VT, better organ perfusion, and ultimately greater patient safety. Yet the optimal patient and procedural indications for hemodynamic support to assist VT ablation have not been determined, and the technology is costly (6). It is likely that the technology will be chosen by physicians only for the sickest patients at the highest risk of adverse outcomes, thus resulting in an impression that the technology increases risk.

In this issue of JACC: Clinical Electrophysiology, Turagam et al. (7) from the International VT Ablation Center Collaborative Group report on their experience with hemodynamic support for VT ablation. This is one of the largest reported series, with 105 patients receiving hemodynamic support from a cohort of 1,655 patients at 12 experienced centers. Not surprisingly, the patients who received hemodynamic support had more severe heart disease, as well as a higher comorbidity burden. In adjusted, multivariate analyses, there was no obvious benefit to hemodynamic support, with similar rates of acute elimination of the clinical VT and recurrent VT at 12 months. These results are not dissimilar to those of the other large, single-center cohort study of hemodynamic support for VT ablation (8).

Although no obvious clinical benefit was shown, the risk of complications and death in the current study was high, and it gives cause for concern (7). As with any observational study involving critically ill patients, unmeasured confounders assuredly exist and likely explain, in part, both the inability to demonstrate clinical superiority and some of the increased risk of complications. The large comparison group places the observed results in context, but it should not be considered to have similar risk. The operators’ choice to use hemodynamic support in these patients differentiates this group from the rest of the cohort, thereby limiting the inference of a causal link between the intervention and clinical outcomes.

In the current study (7) and the other reported large, single-center experience (8), the proportion of patients who had undergone prior ablation was surprisingly low (slightly more than 50% and slightly <30%, respectively). This may reflect the realities of VT ablation undertaken at large referral centers, yet it also indicates that hemodynamic support is being chosen for first procedures. What selection criteria are most appropriate to identify patients likely to have improved outcomes with support? Are there some patients for whom it carries greater invasiveness and greater risk?

Insertion of the hemodynamic support device is the easy part. However, the pre-procedural, intraprocedural, and post-procedural management of such patients is complex (9). Even a minor complication in such patients can lead to a catastrophic outcome. Using these devices in VT ablation means that the infrastructure must be in place to support these patients, particularly outside the electrophysiology laboratory.

For some patients, ablation techniques solely targeted at substrate likely to be arrhythmogenic can be effective, by limiting or avoiding VT inductions with ablation performance predominantly in sinus rhythm (10–14). Advances in multipolar mapping catheters and mapping software have enhanced our ability to identify surrogates of VT circuits in sinus and to assess the efficacy of ablation (15,16). These techniques, although not without limitations, can be performed with minimal hemodynamic insult to the patient and with no additional vascular access or indwelling device. It is possible that advanced cardiac imaging, with or without personalized modeling strategies (17) and with precision delivery of targeted endocardial, epicardial, or intramural ablation lesions, may someday enhance substrate-based techniques sufficiently to obviate arrhythmia induction entirely.

The report by Turagam et al. (7) provides useful clinical information on outcomes that can be anticipated with catheter ablation of the some of the highest-risk patients with VT. How do we translate this information into clinical utility or use it to guide future research meaningfully? For the moment, the appropriate clinical indications for hemodynamic support remain unclear. We need better validated predictors of hemodynamic embarrassment during VT ablation. The collective experience of the International VT Ablation Center Collaborative Group and other high-volume sites may help define clinical equipoise and generate knowledge about anticipated recurrence, survival, and complication rates. This knowledge should inform prospective studies that can determine whether the cost and risk of hemodynamic support are outweighed by improvements in clinical outcomes.

The data available thus far do not demonstrate a clear benefit of this intervention, but absence of evidence of benefit is not evidence of absence of benefit (18). The decision to use intraprocedural hemodynamic support during catheter ablation of VT requires astute clinical judgment. Definitive data to identify whether this approach truly increases our ability safely to treat patients in the most unstable condition will require either a very well matched comparison group or a prospective randomized study.

Footnotes