In Reply:-We appreciate the comments by Weigand et al. concerning our use of ventricular fibrillation to facilitate endovascular stent-graft repair of thoracic aortic aneurysms. The use of adenosine is viable for induced asystole during endovascular stent-graft deployment if the time of anticipated deployment is known with a high degree of certainty and if the period of absolute asystole necessary is less than 15-20 s. Longer durations will result in unpredictable breakthrough ventricular escape beats that may compromise stent-graft positioning. In our experience, commercially produced large angioplasty (valvuloplasty) balloons of 30-40 mm in diameter necessitate inflation and deflation times well in excess of 30 s; the exact duration of asystole necessary for successful deployment may be variable and not easily determinable until the time of stent-graft deployment. This need for a prolonged duration of stent-graft deployment is especially necessary during endovascular repair of the thoracic aortic using angioplasty balloon-activated devices (self-expanding endovascular devices do not necessitate this duration of time for deployment). This variability of stent-graft deployment times often is related to the complexity of the anatomy within the vascular segment being repaired. As described in our report, we have required from 55 to 172 s of asystole. Because of interpatient variability in the action of adenosine, there is a risk of escape ventricular beats. Such unanticipated ventricular escape beats would probably adversely effect stent-graft position.
We agree with Weigand et al. that adenosine has some advantages over ventricular fibrillation during endovascular stent-graft deployment, most notable its consistently benign effect on the patient. The purpose of our case report was not to argue for the replacement of adenosine with ventricular fibrillation, but rather to suggest that induced ventricular fibrillation may be another viable method for providing asystole in a subgroup of patients undergoing endovascular repair in which controlled cardiac arrest was mandatory. We agree that further experience will assist in delineating the indications for each of these modalities.
Ronald A. Kahn, M.D.
Michael L. Marin, M.D.
Larry H. Hollier, M.D.
Departments of Anesthesiology and Surgery; The Mount Sinai Medical Center; New York, New York;email@example.com
(Accepted for publication June 10, 1998.)