BACKGROUND: Myocardial injury is strongly associated with excess morbidity and mortality after noncardiac surgery. Higher heart rate may result in perioperative myocardial injury through demand-supply mismatch. Alternatively, higher heart rates may reflect autonomic dysfunction that promotes myocardial injury independently of heart rate. The specific hyperpolarisation-activated, cyclic nucleotide-gated (HCN)-4 (funny) channel inhibitor ivabradine slows the heart rate without altering autonomic control, blood pressure, or myocardial contractility. We hypothesise that individuals with autonomic dysfunction may benefit most from ivabradine reducing heart rate control to minimise myocardial injury-associated morbidity. METHODS: This triple-blind, international, multicentre, randomised, placebo-controlled, parallel group randomised trial will recruit 350 patients, aged ≥55 yr, with cardiovascular risk factors for myocardial injury during elective noncardiac surgery. To achieve the target heart rate <
70 beats min CONCLUSIONS: This phase 2b study will explore whether targeted heart rate control reduces morbidity after surgery, using ivabradine to selectively slow the heart rate without altering perioperative autonomic control. CLINICAL TRIAL REGISTRATION: ISRCTN12903789.