Use of a multielectrode “basket” catheter for endocardial mapping of ventricular tachycardia

Abstract

Successful ablation of sustained ventricular tachycardia (VT) following myocardial infarction (MI) depends on an accurate analysis of the arrhythmic substrate. A post-MI porcine model of sustained VT was created by injecting agarose gel beads (75–150 μm) into the mid-left anterior descending coronary artery following percutaneous transluminal coronary angiographic balloon occlusion in 96 animals. When animals returned for induction and analysis of VT 4–6 weeks post-MI, VT could be induced in 42–61 (68%) of surviving animals; VT cycle length was 179 ± 25 ms at baseline and 230 ± 43 ms following intravenous procainamide ( P < .001). Endocardial mapping using a multielectrode “basket” catheter (Constellation, EP Technologies, Sunnyvale CA) was performed in 38 animals. The catheter consists of 64 electrodes symmetrically arranged on eight self-expanding struts. Unipolar pacing was successful from 78 ± 15% of the electrodes at 3 mA and from an additional 13 ± 7% at 10 mA. Ventricular tachycardia activation mapping obtained from 32 bipolar pairs recorded earliest ventricular activity 40 ± 23 ms prior to QRS onset. Isolated mid-diastolic potentials were recorded from 26 animals. Further analysis demonstrated reset response with single premature beats in 6 of 12 classic entrainment in 19, and concealed entrainment in 10. Radiofrequency (RF) ablation was attempted in 12 animals. Target sites for RF ablation of VT were guided by the results of mapping with the basket catheter, which pointed to a zone of slow conduction. The RF energy was delivered to the tip of an 8-mm ablation probe directed to the target site by a custom discrete navigation device, which assessed electrode orientation. Power was regulated to maintain a tip temperature of 70–80°C for 60 seconds. Ablation was successful in terminating VT and preventing reinduction of the target VT in 11 of 12 animals. It was concluded that multielectrode basket catheter assists in the rapid analysis of sustained VT following MI and provides important data for successful ablation.