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

Abstract

Paients (101) with sustained unimorphic ventricular tachycardia underwent programmed ventricular stimulation with 1 of 2 protocols. Patients (50) 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. Patients (51) 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 > 10 s 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 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 1st stimulation site. The yield of stimulation at a 2nd 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%. In patients with sustained unimorphic ventricular tachycardia undergoing programmed ventricular stimulation, the use of triple extrastimuli at the 1st stimulation site (protocol A) resulted in a high yield of induced clinical ventricular tachycardia early in the protocol, but at the cost of a significant yield of nonclinical ventricular tachycardia. In the patient who has documented ventricular tachycardia, protocol A may be suitable since the nonclinical arrhythmias that are induced will be readily identifiable as such. The initial use of burst overdrive pacing, and single and double extrastimuli in the right ventricle (protocol B) will obviate the need for triple extrastimuli and left ventricular stimulation in 53% of patients, and result in a low yield of nonclinical arrhythmias, especially those that are polymorphic (4%). Protocol B may therefore be preferable in patients with sustained but undocumented ventricular tachycardia, to minimize uncertainty regarding the clinical significance of induced tachycardia. Triple extrastimuli will still be required to induce clinical ventricular tachycardia in 24% of patients, and the overall yield of nonclinical ventricular tachycardia is similar with protocols A and B.