The direct traumatic effects of coronary artery bypass surgery may counter-balance the expected improvement of myocardial function in the early postoperative period. In 55 patients, the regional shortening fraction was measured over 12 months using radiopaque epicardial markers pairs implanted during surgery in the newly perfused regions. The time course of cardiothoracic ratio, heart rate and cuff blood pressure was documented. All patients were catheterized before surgery and 1 year afterwards. There is an initial depression in myocardial function lasting up to 3 months after surgery which is not directionally related to changes in loading conditions or chronotropic state, but most likely to recovery of the myocardium from perioperative injury. At 1 year after surgery the overall ventricular function is unchanged. The evaluation of ventricular function after coronary artery bypass grafting should be performed no sooner than 3 months after surgery to avoid this transient period of depressed myocardial performance.

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European Surgical Research: clinical and experimental surgery
Erasmus MC: University Medical Center Rotterdam