Insights into the mechanism of sustained ventricular tachycardia after myocardial infarction in a closed chest porcine model using a multielectrode "basket" catheter.
BACKGROUND
Accurate analysis of the arrhythmia substrate is important for successful radiofrequency ablation of sustained ventricular tachycardia (VT) after myocardial infarction (MI).


RESULTS
A multielectrode "basket" catheter capable of endocardial recording and pacing was inserted percutaneously into the left ventricle of post-MI swine for analysis of the mechanism of sustained VT. Sustained VT was induced in 42 of 61 pigs that survived an acute MI produced by percutaneous transluminal coronary angioplasty balloon occlusion of the left anterior descending coronary artery and injection of agarose gel beads. A multielectrode "basket" catheter (Constellation) with 64 electrodes was inserted in 35 of these animals for analysis of the VT. Induced VT had a cycle length of 179 +/- 25 msec at control and 230 +/- 43 msec after administration of intravenous procainamide. Presystolic electrical activity was recorded from at least 1 of 32 bipolar pairs of electrodes at a mean 40.7 +/- 23.6 msec prior to QRS onset. Isolated mid-diastolic potentials were recorded in 26 of 35 animals. In 22 animals, there were multiple isolated potentials recorded from adjacent electrode pairs. Isochronal maps demonstrated that these potentials returned to the systolic site of origin. Resetting of sustained VT by single premature ventricular stimuli was observed in 6 of 12 animals. Entrainment with overdrive pacing was seen in 19 of 26 animals with induced VT. Concealed entrainment was observed in ten animals. The mean stimulus to QRS interval was 45 +/- 28 msec. Concealed entrainment was observed from adjacent electrode pairs with different stimulus to QRS intervals.


CONCLUSIONS
These data suggest that sustained VT in this model is due to reentry with an excitable gap. A multielectrode "basket" catheter is useful for analyzing the zone of slow conduction participating in the tachycardia circuit. Such analysis may provide useful information to guide successful catheter ablation of sustained VT after MI.
Greenspon
A J
AJ
Department of Medicine, Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA. Arnold.Greenspon@mail.tju.edu
Hsu
S S
SS
Borge
R
R
Smith
M F
MF
Eldar
M
M
D000818:Animals; D004562:Electrocardiography / Q000295:instrumentation; D004567:Electrodes, Implanted; D004867:Equipment Design; D009203:Myocardial Infarction / Q000150:complications*; D010138:Pacemaker, Artificial; D013552:Swine; D017180:Tachycardia, Ventricular / Q000209:etiology* / Q000503:physiopathology*; D013997:Time Factors