ATRIOVENTRICULAR PACING DOES NOT INCREASE INFARCT SIZE IN THE IN-SITURABBIT HEART

OBJECTIVE: To examine the hypothesis that an altered left ventricular depolarization sequence may augment infarct size. METHODS: Twenty-one New Zealand male rabbits were anesthetized and ventilated. The chest w as opened and two electrodes were placed on the right atrium and ventr icle. The rabbits were then randomized to atrial (n=7), atrioventricul ar (AV) sequential (n=7) or no (n=7) pacing. The pacing rate was 20 be ats/min higher than the sinus rate. After 1 min of pacing, the left: c oronary artery was occluded by a snare. After 30 mins, the snare was r eleased and pacing was stopped. After 120 mins of reperfusion the expe riment was terminated. Normal areas and areas at risk were delineated, infarct size was measured and the infarcted areas and areas at risk w ere planimetered. RESULTS: All results were expressed in cubic centime tres, and the ratio of the infarcted area to area at risk was calculat ed as a percentage (%I:R). The double product during ischemia was 21,5 46+/-2300 in controls, 23,000+/-3005 in rabbits with atrial pacing and 24,418+/-4253 in rabbits with AV pacing (F=1.33, P=0.28), and %I:R wa s 41.4+/-19.8, 43.9+/-15.4 and 38.4+/-18.4 (F=0.16, P=0.84), respectiv ely. CONCLUSIONS: An altered left ventricular depolarization sequence in rabbit hearts does not increase infarct size.