Background: Absence of cardiac symptoms is not a valid indicator of low cardiac risk in the sedentary patient who is being considered for vascular surgery. Invasive methods of cardiac assessment in such patients are associated with risk and are expensive. This study was carried out to evaluate the utility of pre-operative cardiac risk stratification with dipyridamole myocardial scintigraphy (DMS), in patients to undergo carotid artery surgery.
Study design: From 1991 to 1994, 174 of 266 carotid endarterectomy patients underwent preoperative DMS. The ability of clinical factors and DMS to predict postoperative cardiac morbidity was assessed retrospectively in a nonrandomized fashion.
Results: Forty-seven adverse cardiac events (deaths = 0, myocardial infarction (MI) = 4, congestive heart failure (CHF) = 9, angina = 7, and new dysrhythmias = 27) occurred in 38 (14.3 percent) of 266 patients. Results of DMS were 73 percent normal, 10.3 percent fixed defect, and 16.7 percent reversible defect examinations. Sensitivity and specificity of DMS was 32 and 74 percent for total cardiac morbidity, and 50 and 74 percent for MI. The positive predictive value of DMS for MI, dysrhythmias, CHF, angina, and all cardiac events was 4, 11, 9, zero, and 23 percent, respectively. Negative predictive values were 98, 91, 98, 95, and 82 percent, respectively. Preoperative histories of MI and chest pain were significant independent predictors of adverse cardiac outcomes (p < 0.05) while age greater than 70 years, smoking, hypertension, diabetes mellitus, preoperative arrhythmias, and DMS were not.
Conclusions: Dipyridamole myocardial scintigraphy is an ineffective predictor of adverse cardiac events in patients being evaluated for carotid artery surgery and its routine use is not justified.