The value of perioperative clinical indexes and dipyridamole thallium scintigraphy for the prediction of myocardial infarction and cardiac death in patients undergoing vascular surgery.

Abstract

Dipyridamole thallium scintigraphy has previously been shown to have predictive value for both perioperative and late cardiac events in patients undergoing vascular surgery. However, despite the prognostic utility of this technique, the relative importance of clinical factors and scintigraphic information is not well known. The purpose of this study was to evaluate the value of commonly used clinical risk indexes, composed of historic variables, and dipyridamole thallium scintigraphy for predicting perioperative cardiac event-free survival rates. Clinical and scintigraphic variables in 360 patients undergoing vascular surgery were analyzed for their predictive utility for perioperative and late (up to 5 years) cardiac events (nonfatal myocardial infarction or cardiac death) by means of chart review and telephone contact. Patients were correctly categorized as being at low, moderate, or high risk for perioperative cardiac events based on two clinical indexes. Thallium redistribution, however, was a more powerful predictor of cardiac events than these indexes. Even in a clinically low-risk patient cohort, the odds ratio for an event increased by 6- to 8-fold (p < 0.05) if thallium redistribution was noted. These indexes also demonstrated prognostic utility for late cardiac event-free survival rates by life-table analysis (p < 0.001). The presence of a fixed thallium defect was associated with an increased risk of late cardiac events (p < 0.01). When stratified by risk index, in those patients at moderate to high risk who had a fixed defect the odds ratio increased by 3.9- to 5.4-fold (p < 0.001). Likewise, the low-risk subgroup had a 3.9- to 8.2-fold increase in the risk of a late cardiac event when a fixed perfusion defect was present. Preoperative clinical indexes are predictive of both perioperative and late cardiac events in patients undergoing vascular surgery. However, dipyridamole thallium scintigraphy is more powerful prognostically than these clinical indexes and provides supplemental value to clinical risk stratification.