Catheter Ablation of Ventricular Tachycardia as Adjuvant Therapy With an Implantable Cardioverter-Defibrillator

ABSTRACT & COMMENTARY

Synopsis: Catheter ablation is the procedure of choice in patients with recurrent slow ventricular tachycardia after ICD therapy.

Source: Strickberger SA, et al. Circulation 1997;96: 1525-1531.

Strickberger and colleagues describe the acute and long-term results of catheter ablation of ventricular tachycardia in patients in whom the success of implantable cardioverter defibrillator (ICD) therapy has been limited by frequent episodes of tachycardia. Twenty-one patients with coronary artery disease formed the study group. Their mean left ventricular ejection fraction was 0.22 ± 0.08. All patients were receiving one or more oral or intravenous antiarrhythmic drugs with 16 of them receiving amiodarone. Prior to the ablation procedure, patients had received 25 ± 88 ICD therapies—either shocks or antitachycardia pacing—per month. Patients initially underwent programmed ventricular stimulation and monomorphic ventricular tachycardia mapping. In the two patients with hemodynamically unstable tachycardia, only pace mapping could be used. Before the ablation procedure, 26 different ventricular tachycardias (VT) had been identified as responsible for frequent ICD discharges in these 20 patients. During the mapping procedure, a total of 46 ventricular tachycardias were targeted for ablation. Of these 46, 36 (78%) were successfully ablated in 16 of 21 patients (76%). Due to drug therapy, the tachycardias were relatively slow with a mean cycle length of 455 ± 93 m/sec. During the ablation procedure, patients received 12 ± 9 radiofrequency (RF) energy applications. Complete heart block was the only acute complication, and this was noted in a patient whose ventricular tachycardia arose from the high LV septum. After the ablation procedure, there was a dramatic decrease from 134 ± 338 ICD therapies per month to 0.5 ± 1.1 ICD therapies per month during follow-up. Only two patients died during 11.8 ± 10 months of follow-up. One of these deaths was due to congestive heart failure. The other death occurred in a patient in whom the ablation procedure had been unsuccessful. The latter patient died after a surgical ablation attempt using a map-guided endocardial resection. Quality of life was also measured using a specially designed questionnaire. There was a marked improvement in quality of life reported by those patients who had a successful ablation. Strickberger et al conclude that RF ablation of VT in CAD patients with ICDs is a reasonable approach to reducing ICD discharges and improving quality of life.

COMMENT BY JOHN P. DiMARCO, MD, PhD

Patients who have received an ICD frequently develop more frequent episodes of VT. Antiarrhythmic drug therapy may slow the tachycardia and make it better tolerated but may not decrease the frequency of episodes. Antitachycardia pacing can terminate many episodes of tachycardia without producing discomfort, but, eventually, the tachycardia may either accelerate with pacing and, therefore, require shock therapy or become incessant with resulting hemodynamic compromise. As the tachycardias become more frequent, congestive heart failure may worsen, and the need for frequent unpleasant shock therapies is a significant factor in decreasing a patient’s quality of life.

In such patients, there are often few other options other than attempts at ablation. This paper illustrates some of the potential benefits and problems of this procedure. It is important to recognize that virtually all such patients have multiple morphologic tachycardias, and it is frequently not possible to identify, map, and ablate them all. Patients during the procedure may switch back and forth from one to the other—making mapping difficult. However, in many patients, a single tachycardia can be identified that is responsible for the majority of symptoms, and, if this tachycardia can be successfully ablated, the frequency of ICD therapy can be dramatically reduced. Once the number of ICD therapies required is low enough so that the patient can tolerate the therapies and is not hemodynamically compromised by the incessant nature of the tachycardia, he or she can often return to a virtually normal lifestyle.

The high success rate reported by Strickberger et al in this paper suggests that catheter ablation is the procedure of choice in patients with recurrent slow VT after ICD therapy. Unless there is a very discrete aneurysm that would be suitable for surgical resection, this approach should be safer and less risky than an attempt at surgical therapy.