Postoperative myocardial ischemia: etiology of cardiac morbidity or manifestation of underlying disease?

STUDY OBJECTIVE

To determine the relationship between postoperative ST segment changes and clinically apparent cardiac morbidity in noncardiac surgery patients.

DESIGN

Prospective, cohort study.

SETTING

General inpatient and intensive care units at a tertiary care hospital.

PATIENTS

145 high-risk noncardiac surgery patients.

MEASUREMENTS AND MAIN RESULTS

Patients were monitored for ST segment changes using ambulatory electrocardiographic (ECG) recorders from the end of the surgical period for up to the third postoperative day. Patients were evaluated for a clinically apparent cardiac event (cardiac death or myocardial infarction) by daily 12-lead ECGs, and CK-MB isoenzymes, as clinically indicated. Nine patients sustained a clinically apparent cardiac event, 7 of whom had a cardiac event during the period in which they were monitored by ambulatory ECG. All 7 patients who sustained a cardiac event during the monitoring period had at least one episode of myocardial ischemia, which persisted for a minimum of 30 minutes either prior to or at the same time of the event, with no morbidity occurring in the group of patients who had only short durations of myocardial ischemia. Three of the patients with events had continuous ST segment changes, while the other patients had transient ST segment changes.

CONCLUSIONS

These observations suggest that clinically apparent cardiac events are associated with prolonged ST segment changes detected on ambulatory ECG recorders. The cardiac ischemia leading to prolonged postoperative ST segment changes may itself result in cardiac morbidity, or it may be a reflection of underlying pathophysiology.