Comparison in the same patient of two programmed ventricular stimulation protocols to induce ventricular tachycardia.

In 24 consecutive patients with documented ventricular tachycardia (VT) (22 patients) or fibrillation (VF) (2 patients), results of 2 programmed ventricular stimulation protocols to initiate VT/VF were prospectively studied. Seventeen patients had VT/VF after a healed myocardial infarction (MI) and 7 patients had idiopathic VT. In both protocols (designated 1 and 2), the right ventricular (RV) apex was paced at 100 beats/min, using a maximum of 2 ventricular premature complexes (VPCs) given at twice diastolic threshold. This protocol had a sensitivity of 25%. In protocol 1, the pacing site was changed to the RV outflow tract and the previous steps were repeated; in protocol 2, the pacing rate was increased to 120 and 140 beats/min at the RV apex, also using a maximum of 2 VPCs. The next step in protocol 1 consisted of increase of current strength to 20 mA and repeating previous steps at the RV apex and RV outflow tract, with a maximum of 2 VPCs; in the next step in protocol 2, three VPCs were used during sinus rhythm and pacing was performed at rates of 100, 120 and 140 beats/min. In protocol 1, therefore, only stimulation site and current strength were changed, while in protocol 2 only pacing rate and number of VPCs were modified. Protocol 1 had a sensitivity of 54% and protocol 2 a sensitivity of 83%. The sensitivity of protocol 2 was statistically higher than that of protocol 1 (p less than 0.05). In the group of patients with VT after MI, the sensitivity was 66% for protocol 1 and 93% for protocol 2.(ABSTRACT TRUNCATED AT 250 WORDS)