Initiation of ventricular tachyarrhythmia with programmed stimulation: sensitivity and specificity in an experimental...

Programmed stimulation (PS) is used in the catheterization laboratory and operating room to initiate and study malignant ventricular tachyarrhythmia (VT). The purpose of this study was to evaluate the specificity and sensitivity of PS in short-term studies of 10 normal animals (group A), 10 sham-operated controls (group B), and 10 dogs with chronic myocardial infarction susceptible to inducible VT by an occlusion-reperfusion method (group C). Groups B and C were studied 7 to 14 days after the initial procedure. the pH, PaO2, and PaCO2 were determined and corrected every 30 minutes during the procedure. When bipolar ventricular pacing with three ventricular extrastimuli was used, VT initiation was attempted at 10 normal intramyocardial sites in groups A and B and in close proximity (less than or equal to 1 cm) to areas of infarction in group C. When one ventricular extrastimulus was used during ventricular pacing, VT was induced in dogs with chronic infarctions (3 of 10, 30%, group C). Using two extrastimuli, however, VT was inducible in 4 of 10 (40%) of group A, 6 of 10 60%) of group B, and all 10 (100%) of group C. With three extrastimuli, all 30 dogs had inducible VT. Overall, PS with one extrastimulus was highly specific in 100% but insensitive in 30%. With two extrastimuli the sensitivity increased to 100%, but the specificity fell to 50%. Finally, with three extrastimuli the sensitivity was also 100%, but the specificity decreased to 0%. PS remains an invaluable technique in diagnosing and assessing therapy for patients with VT. The diagnostic implications of this test await more precise pathophysiologic elucidation of arrhythmic mechanisms.