Prolonged postoperative myocardial ischaemia and infarction in vascular surgery performed under regional anaesthesia

The importance of prolonged postoperative myocardial ischaemia in cardiac outcome has recently been emphasised. The present study examines the correlation between perioperative ischaemia and myocardial infarction (MI) in patients undergoing peripheral vascular surgery (PVS) under regional anaesthesia. One-hundred-and-forty consecutive peripheral vascular operations under regional anaesthesia were prospectively analysed, using Hotter monitoring for perioperative myocardial ischaemia (defined as down sloping or horizontal ST-segment depression of ≥ 1mm) and postoperative cardiac outcome. The study was approved after informed consent. There were 82 carotid endarterectomies under cervical block and 58 infrainguinal bypass procedures under continuous spinal or epidural anaesthesia. IHD was present in 53.6% cases: previous MI - 38%; angina pectoris - 33%; previous CABG/PTCA - 24%. Holter monitoring started about 20 hours before surgery and continued for 45 hours. After surgery patients were followed for signs of cardiac complications; daily 12 lead ECG; 6 hourly CK-MB isoenzymes during the first 24 postoperative hours and later whenever indicated. MI diagnosis was based on chest pain, permanent new, ECG changes and CK-MB elevation. There was no 30-day mortality. Postoperative MI occurred in seven patients (5%). Five of the postoperative MI were non-Q-wave infarctions. The majority (71%) of the adverse cardiac events started within 24 hours of surgery, and the latest occurred 52 and 72 hours post surgery. In 65 cases (46.4%) there were 259 episodes of significant STdepression. In 75 (53.6%) cases ischaemic episodes were not detected. Patients with postoperative cardiac events had significantly more and longer ischaemic episodes in all three perioperative periods than those without such events. However, only the cumulative ischaemia duration in the postoperative period remained associated with adverse cardiac outcome when subjected to multivariate logistic regression analysis (p < 0.03).