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Update on VT Ablation
Abstract & Commentary
By John P. DiMarco, MD, PhD
Source: Sauer WH, et al. Incidence and predictors of mortality following ablation of ventricular tachycardia in patients with an implantable cardioverter-defibrillator. Heart Rhythm. 2010;7:9-14.
This paper details mortality results after ventricular tachycardia (VT) ablation from one of the larger VT ablation sites in the United States, the University of Pennsylvania. Sauer et al report data from all patients with known structural heart disease who underwent ventricular tachycardia ablation in their laboratory between January 1999 and May 2005. All patients had a functional ICD placed either prior to or immediately after the ablation. The authors' protocol included a standard electrophysiologic study, with induction of the tachycardia using programmed electrical stimulation. Electroanatomical and electrogram-based mapping were performed if the ventricular tachycardia was hemodynamically tolerated. If the clinical VT could not be mapped due to hemodynamic instability, a sinus-rhythm voltage map was created. Pace mapping and substrate modification with scar isolation were then used for these hemodynamically unstable VTs. Repeat programmed stimulation was used to determine the acute success of ablation lesions. Procedural success was defined as failure to induce clinically relevant ventricular VT at the end of the ablation procedure. Retrospective analysis of clinical recurrences, ICD therapy, and mortality was then obtained for all patients in the study. Follow-up data at three years was presented.
There were 208 patients in the study group. Of these patients, 144 had healed myocardial infarctions and 64 had nonischemic dilated cardiomyopathy. For the entire group, the mean age was 63.6 years and the left ventricular ejection fraction was 28.6. Fifty-four percent of the patients presented with VT that was not hemodynamically tolerated. Patients underwent a mean of 1.5 ablation sessions per patient, with a range of 1 to 7. At the end of the final procedure, the targeted clinical VT was not inducible after 91% of the procedures. There were seven procedural complications, including three embolic strokes and three pericardial effusions (i.e., perforations) requiring intervention. There were no deaths during the procedure. During long-term follow-up, 89 of the 208 (42.8%) patients died. Ten patients (5%) died within 30 days after VT ablation, and 32% of the cohort died within three years after the ablation procedure. A number of variables were associated with improved survival following VT ablation. Increased age and renal insufficiency were predictors of a poor outcome. Patients who had tolerated VT that permitted mapping and those whose clinical VT could not be induced after ablation had improved survival. Patients who underwent ablation in the first four years of the study had increased mortality compared to those who underwent ablation in the final three years. The authors conclude that this survival rate after VT ablation has improved over time and that predictors of survival can be identified.
This paper summarizes the results of endocardial VT ablation in a very experienced, high-volume center in the United States. The authors show that traditional mapping approaches for tolerated VTs, and substrate modification for poorly tolerated VTs, can yield acceptable results. It is important to note, however, that in the last three years since completion of this study, new approaches to VT ablation have been used with increasing frequency. It is now recognized that epicardial approaches are required to ablate some VTs, particularly in patients with nonischemic cardiomyopathies. Experienced laboratories have also become more aggressive in their patient selection. The use of circulatory assist devices in patients with poorly tolerated VT, or very poor baseline hemodynamics, has enabled traditional mapping and ablation strategies to be used in addition to substrate modification in these patients. Late mortality in these patients is likely to be high even if the VT ablation is successful. This paper shows that VT ablation can be an important adjunct to defibrillator therapy and antiarrhythmic drug therapy. Judicious use of all three modalities is likely to result in the best outcomes.