Identifying patients with symptomatic carotid artery disease at high and low risk of severe myocardial infarction and cardiac death

The extent of cardiac investigation required in patients with coexistent symptomatic carotid and cardiac disease is unsettled. This study compared the outlook for patients symptomatic from carotid stenosis with and without a history of symptomatic ischemic heart disease (IHD). The risk of combined outcome of severe myocardial infarction and cardiac death was evaluated in patients from the North American Symptomatic Carotid Endarterectomy Trial. A total of 1124 patients had a history of symptomatic IHD and 1691 did not. The median age was 66 years; 70% were male. With history of IHD at entry, the 5-year risk of combined outcome of severe myocardial infarction and cardiac death was 16.5% (95% CI, 13.9 to 19.0). Without history at entry, risk was 6.7% (95% CI, 5.1 to 8.3). Risk of unheralded severe MI and cardiac death was only 3.3%. One hundred ninety-four patients had > or =4 of the following risk factors: age > or =75 years, history of diabetes, history of hypertension, smoking in past year, left ventricular hypertrophy on ECG, myocardial infarction on ECG, or creatinine >115 micromol/L. The 5-year risk of severe myocardial infarction or cardiac death increased to 33.9% for patients with > or =4 risk factors and a history of IHD and to 23.5% for those without history of IHD. Most patients with symptomatic carotid stenosis without symptomatic IHD had a low risk of severe myocardial infarction and cardiac death. With many risk factors, these patients had a risk high enough to warrant cardiac investigations.