ISCHEMIA DURING AMBULATORY MONITORING AS A PROGNOSTIC INDICATOR IN PATIENTS WITH STABLE CORONARY-ARTERY DISEASE

Objective.-To assess long-term prognostic significance of transient is chemia in patients with documented coronary artery disease and stable symptoms and to examine the relation between transient ischemia and th e site of angiographic disease progression following acute cardiac eve nts. Design.-Cohort study with a mean+/-SD follow-up of 51.5+/-23.8 mo nths. Setting.--Ambulatory patients with stable coronary artery diseas e, assigned to medical therapy. Patients.-A total 221 patients (173 me n; mean age, 60.8 years) were recruited, Of the 221 patients, 101 (45. 7%) had single-vessel, 86 (38.9%) had 2-vessel, and 34 (15.4%) had 3-v essel disease. A total of 135 had a positive exercise test for ischemi a, and mean+/-SD resting left ventricular ejection fraction (LVEF) was 49.8%+/-11.4%. Using conventional criteria, patients were prospective ly stratified as low risk for continued medical therapy (single-vessel disease, 2-vessel disease with negative exercise test, or LVEF greate r than or equal to 40%; n=189 [85.5%]) or high risk for continued medi cal therapy (multivessel disease with ischemia and/or left ventricular dysfunction; n=32 [14.5%]). Interventions.-Ambulalory ST-segment moni toring, treadmill exercise testing, radionuclide ventriculography, and coronary angiography. Main Outcome Measures.-Demographic, clinical, a mbulatory monitoring, treadmill exercise, and left ventricular functio n variables as independent predictors of acute (cardiac death, myocard ial infarction, or unstable angina) or all (including revascularizatio n) cardiac events in the overall and the low-risk population. Results. -None of the clinical or noninvasive measures of ischemia were of prog nostic significance in the overall or the low-risk group. The only sig nificant independent predictor of outcome in all patients for all even ts, including revascularization, was the number of diseased vessels (c hi(2)=13.5 [df=1]; P<.001). Exclusion of vessel disease resulted in co nventional risk stratification as the most significant predictor of ou tcome from all events in all patients (chi(2)=10.3 [df=1]; P=.001). In the low-risk group, the number of diseased vessels was the only predi ctor for all events (chi(2)=4.6; P=.03). For acute cardiac events, non e of the variables tested were of prognostic significance. Based on th e frequency of events in the low-risk patients, a 2-fold increase in t he rate of cardiac events in patients with transient ischemia compared with those without transient ischemia during ambulatory monitoring co uld be excluded with greater than 85% power and alpha of .05. Of 30 pa tients suffering acute nonfatal cardiac events during follow-up, angio graphy was performed in 27, revealing significant progression of coron ary disease in 24 (88.8%) and the development of new significant lesio ns al sites remote from previously significant lesions in 20 (74%) cas es. These new lesions were equally likely to occur in those with or wi thout transient ischemia at initial assessment. Conclusions.-Acute car diac events in predominantly low-risk stable angina patients with conf irmed coronary disease are unpredictable, and those more likely to suf fer such an event cannot be identified by the detection of ambulatory ischemia. Acute nonfatal cardiac events result predominantly from the development of significant new coronary lesions, not initially severe enough to cause ischemia. Patients categorized as high risk for long-t erm medical therapy have an increased rate of cardiac events (mainly r evascularization) when compared with low-risk patients.