METOPROLOL AFTER VASCULAR SURGERY (MAVS)

INTRODUCTION In vascular surgery, $-blockers are increasingly used to prevent peri-operative cardiac complications. This is a report of a RCT on the peri-operative use of metoprolol. METHODS After REB approval, patients undergoing abdominal aortic surgery, infra-inguinal or extraanatomical revascularization were recruited to a double-blind RCT of peri-operative metoprolol versus placebo. Consenting eligible patients were randomized to either IV/oral metoprolol or placebo 2 hours pre-op. Study medication was continued IV q6h or po bid until hospital discharge or maximum 5 days post-op. The primary outcome on an intent-to-treat basis was the 30-day post-op composite incidence of non-fatal MI; unstable angina; new CHF; new atrial or ventricular dysrhythmia requiring treatment; or cardiac death. RESULTS 497 patients consented and were randomized: 247 metoprolol and 250 placebo. The groups were balanced in demographics and pre-op co-morbidities. Early study drug discontinuation was 12% in placebo and 13% in metoprolol patients. One or more events in the primary outcome cluster occurred in 30 (12.0%) placebo and 25 (10.1%) metoprolol patients. The risk difference, -1.9% (CI -7.6% to 4.0%), was not significant (p=0.40). The observed effects in the primary cluster are shown (Table). Intra-operatively, more metoprolol patients had bradycardia requiring treatment (53/247 vs 19/250, p=0.00001) and hypotension requiring treatment (26/250 vs 84/247, p=0.0046). DISCUSSION This is the largest peri-operative $-blocker RCT completed to-date. An unblinded study 1 on 112 patients found a 10-fold reduction in MI and cardiac mortality. Our study was double-blinded and our patients were considered moderate/high risk. Another study reported 17-32% cardiovascular event rate2. It was under-powered to detect 30-day treatment effects although an effect beyond 6 months was noted. Our event rate was lower than previous reports, decreasing the study’s calculated power to detect 50% RRR from 80% to about 40%. In summary, our preliminary 30-day results did not support a clinically useful metoprolol effect in reducing the cardiac event rate in these vascular patients. The 6-month and longer-term follow-ups have yet to be completed.