PERSPECTIVE Catheter ablation for treatment of tachyarrhythmias: present role and potential promise

DELIVERY OF high-energy direct-current shocks through electrode catheters for treatment of patients with cardiac arrhythmias was first introduced in 1981 Since that time, this experimental technique has be-come established as a therapeutic tool for selected pa-tients. This essay will review the basic biophysical effects of such shocks, summarize the present clinical indications for this therapy, and speculate on the future directions for interventional electrophysiology. Biophysical effects of catheter electroshocks. The deliv-ery of 200 to 400 J of stored energy through an elec-trode catheter results in 2000 to 3000 V potentials at the electrode surface. If the discharge is delivered into a saline solution, an explosive flash develops.2 This electrical energy is at least partially converted to heat. In addition, the explosion produces concussion waves exceeding 1 to 2 atmospheres of pressure.2 Finally, the intense electrical charge may disrupt cellular integri-ty.3 Thus, local injury after delivered shocks may re-sult from thermal electrocoagulation of tissue, ' strong concussive shock waves,2 or membrane damage due to the intense electrical field.3 One other factor should be emphasized. The structural integrity of the electrode catheter materials to withstand shocks of this magni-tude must be assured.4 Most conventional direct-cur-rent defibrillators deliver capacitor discharge over 5 to 10 msec, with peak voltage achieved within 1 to 2 msec. Delivery of 1000 to 3000 V to one electrode of a multipolar electrode catheter may result in insulation breakdown with shunting of current to other electrodes and hence less delivered energy to the tissues. These factors will obviously influence the safety and efficacy of this approach. The histologic effects of catheter-delivered shocks have been described5 6 and we have previously de-scribed the evolutionary histology after catheter-deliv-ered shock in the normal canine heart. Anodal and cathodal discharge produce qualitatively simila