We evaluated the feasibility, safety, and efficacy of sequential pulse countershock (SqCS) delivered solely through two endocardial
catheters for the termination of
ventricular tachycardia (VT) and fibrillation (VF) in patients undergoing electrophysiology studies (EPS). Thirty-four patients (31
men, 3 women) with a mean age of 56.8 +/- 10.1 years were studied. Etiology of VT/VF was
ischemic heart disease (n = 26),
cardiomyopathy (4) repaired
tetralogy of Fallot (n = 1), heart transplant (n = 1), and no identifiable
heart disease (n = 2).
Catheters were positioned successfully in 29 patients. These were positioned in the right ventricular apex (RVA) and the coronary sinus (CS), respectively. The RVA
electrode served as the common cathode for both pulses. The two
electrodes located near the right atrium/superior vena cava junction served as
anode for pulse 1 while the distal CS
electrodes served as
anode for pulse 2. Twenty-nine induced VT episodes with cycle length (CL) 220-370 msec were treated. SqCS successfully terminated 15 VT (100-500V) while 14 were accelerated or degenerated to VF. VTCL was longer in successful SqCS episodes than in those that were accelerated (285 +/- 17.3 vs 245 +/- 30.8 msec, P less than .003). Of 26 VF episodes, 21 were terminated with SqCS (500-900V) and 5 were terminated by transthoracic rescue shocks. On 2 occasions, failure to defibrillate was attributable to poor
catheter position at the time of
shock. No complications occurred. We conclude that SqCS delivered solely between endocardial
catheter electrodes is feasible and effective using energy doses within the range of existing
implantable cardioverter defibrillators.