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Epicardial Ablation Experience
Abstract & Commentary
By John P. DiMarco, MD, PhD
Source: Sacher F, et al. Epicardial ventricular tachycardia ablation. J Am Coll Cardiol. 2010;55:2366-2372.
In this study, Sacher and colleagues, from three well-know ablation centers, report their experience with epicardial ventricular tachycardia (VT) ablation. During the period from 2001 to 2007, 913 VT ablations were performed in the three centers. Of these, 156 (17%) involved epicardial mapping or ablation. Cardiac diagnoses included: ischemic cardiomyopathy in 51 patients, nonischemic cardiomyopathy in 39 patients, arrhythmogenic right ventricular cardiomyopathy in 14 patients, miscellaneous cardiomyopathies in 13 patients, and 17 patients with no structural heart disease. Pericardial access was obtained using either a percutaneous subxiphoid puncture or, in patients where this was not possible, a surgical subxiphoid or lateral incision. In a few patients who were to undergo associated cardiac surgery, a median sternotomy was used. Ablation was performed using radiofrequency catheters. In the latter portions of the study, the Biosense Webster ThermaCool 3.5 mm tip irrigated catheter was the standard ablation tool. Coronary arteriography was used to avoid damage to the coronary arteries. High output pacing was performed before ablation on the lateral wall to exclude phrenic nerve injury.
A total of 156 epicardial ablation mapping or ablation procedures were performed in 134 patients. Access to the pericardial space was successful in 136 of 151 attempts. The most common reason for failure was a history of prior cardiac surgery. Major complications were observed acutely or before discharge after 14 of the 156 procedures (9%). However, only eight of these were strictly related to the epicardial approach. There were seven patients who had epicardial bleeding and one patient who had an asymptomatic coronary artery stenosis. Six of the 14 complications were related to concomitant endocardial ablation. These included: pulmonary emboli (2), cardiogenic shock, pericardial effusion, AV block, and bilateral groin hematomas (2). Right ventricular puncture without significant bleeding was observed during an additional 23 procedures. Most patients developed chest pain as a result of pericardial inflammation and required nonsteroidal antiarrhythmic drugs. Delayed reactions included a major pericardial inflammatory reaction, one delayed tamponade, and an acute inferior myocardial infarction two weeks after the procedure. The total acute and delayed major complication rate was 7%.
The authors concluded that epicardial ablation was a valuable adjunct in 13% of patients referred for VT ablation. Although the risk for acute and delayed major complications is significant, they seem justifiable by the absence of therapeutic alternatives for this population.
Over the last several years, it has been recognized that epicardial catheter ablation has been able to control monomorphic VT in some patients with failed endocardial ablation attempts. This is particularly true when the VT occurs in the setting of a nonischemic cardiomyopathy. This paper demonstrates that epicardial VT ablation is possible, but that the procedure carries substantial risks. It would be helpful if the authors had described their success rate so that the reader might weigh risks vs. benefits. In another report from the Boston group that contributed many of the patients included in this paper (J Cardiovasc Electrophysiol. 2010;21:406-411), combined endocardial and epicardial ablation eliminated all inducible VT in 50% and the target VT in another 30%. These results appear to justify the added risks associated with epicardial procedures even in experienced hands.