Perioperative myocardial ischaemia, heart rate and arrhythmia in patients undergoing thoracotomy: an observational study

We have studied myocardial ischaemia, heart rate and arrhythmia in 82 patie nts undergoing elective thoracotomy. Myocardial ischaemia was detected usin g a microprocessor-based surveillance system programmed to record leads V2 and V5. Patients were monitored on the day before and for up to 72 h after surgery. The total monitoring time was 5158 h. The incidence of silent myoc ardial ischaemia before operation was 11% (nine of 82). This increased to 2 4% (20 of 82) after operation. Postoperative myocardial ischaemia was assoc iated with preoperative myocardial ischaemia in six patients. Before operat ion, the mean duration of myocardial ischaemia was 0.31 min per hour of mon itoring. After operation, this increased to 1.36 min per hour of monitoring (P<0.05). For the whole population, mean heart rate before operation was 7 4 beat min(-1) and increased to 84 beat min(-1) after operation (P<0.01). P atients with ischaemia had a mean heart rate of 92.8 beat min(-1) after ope ration compared with those with no ischaemia whose mean heart rate was unch anged at 81.8 beat min(-1) (P<0.05). The incidence of atrial tachyarrhythmi a increased from one patient before operation to 12 patients after operatio n (P<0.01). Atrial tachyarrhythmia was not associated with postoperative my ocardial ischaemia. Nine patients had an adverse operative outcome; two had non-fatal myocardial infarction and seven died. Postoperative myocardial i schaemia was associated with adverse outcomes (P<0.05).