Preoperative dipyridamole thallium imaging and ambulatory electrocardiographic monitoring as a predictor of perioperative cardiac events and long-term outcome.

BACKGROUND: Dipyridamole thallium imaging (DTI) and ambulatory electrocardiography (AEGC) have been advocated as means to stratify risk before vascular surgery. The purpose of this study was to compare the predictive value of both tests in noncardiac surgery patients for perioperative cardiac morbidity and long-term mortality.
METHODS: One hundred eighty patients were referred to the nuclear cardiology laboratory for DTI before noncardiac surgery. In patients with normal electrocardiograms and who consented, an ambulatory electrocardiogram was recorded for 24 h. DTI results were classified as negative, positive, or strongly positive (included in positive). Patients were assessed for a minimum of 12 months, and Kaplan-Meier cardiovascular survival curves were constructed with a log-rank statistic of equality with P < 0.05 significant.
RESULTS: One hundred nine patients had both tests and then underwent surgery, sustaining 10 perioperative cardiac events (cardiac death, myocardial infarction, or symptomatic ischemia). The positive predictive values for DTI (18%) and AECG (25%) were similar, as were the likelihood ratios for positive tests (DTI = 2.1, AECG = 3.3). The likelihood ratios of a negative test were also similar (DTI = 0.45, AECG = 0.48). A strongly positive thallium defect had a somewhat greater likelihood ratio (3.5) for in-hospital events and was the only test result associated with a significantly worse long-term cardiac survival.
CONCLUSIONS: AECG and DTI demonstrated a similar, although lower than initially reported, ability to stratify risk and predict short-term outcome. Only quantitative dipyridamole thallium also had predictive value for long-term prognosis.