A prospective comparison of triple extrastimuli and left ventricular stimulation in studies of ventricular tachycardia induction.

One hundred and one patients with sustained unimorphic ventricular tachycardia underwent programmed ventricular stimulation with one of two protocols. Fifty patients underwent programmed stimulation with protocol A, which consisted of burst overdrive pacing, single, double, and triple extrastimuli at the right ventricular apex, right ventricular outflow tract, or septum, and then at the left ventricular apex. Fifty-one patients underwent programmed stimulation with protocol B, which consisted of burst overdrive pacing, single and double extrastimuli at the right ventricular apex, right ventricular outflow tract or septum, and at the left ventricular apex, followed by triple extrastimuli at these sites. The stimulation protocol was continued until sustained ventricular tachycardia or rapid, polymorphic ventricular tachycardia greater than 10 sec in duration was induced. With protocol A, clinical and nonclinical ventricular tachycardia was induced in 76% and 36% of patients, respectively; with protocol B, clinical and nonclinical ventricular tachycardia was induced in 85% and 38% of patients, respectively. Direct-current countershock for sustained polymorphic ventricular tachycardia was required in 10% of patients studied under protocol A, compared with in 2% of patients studied under protocol B. With protocol A, near-maximal yield of induced clinical (72%) and nonclinical ventricular tachycardia (30%) was attained after the use of triple extrastimuli at the first stimulation site. The yield of stimulation at a second right ventricular site and of left ventricular stimulation was only an additional 2% each. With protocol B, triple extrastimuli increased the yield of induced clinical ventricular tachycardia from 61% to 85%.(ABSTRACT TRUNCATED AT 250 WORDS)