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Type A patients with coronary artery disease (CAD) tend to ignore or underreport symptoms, especially during challenging tasks such as the treadmill exercise test. To determine whether type A CAD patients might be more likely than type B patients to have silent ischemia during exercise and consequently a worse prognosis, 403 patients with stable CAD who had significant coronary disease on angiography, a positive Bruce protocol treadmill test and a structured interview to assess type A behavior were studied. Median follow-up time was 6 years. Type A patients were more likely to experience silent ischemia during exercise than were type B patients (35 vs 25%, p = 0.05). Patients with silent ischemia during exercise had a history of fewer anginal episodes/week, and type A patients with silent ischemia were less likely to have had a history of typical angina. However, using the Cox model, there were no significant differences in survival between type A patients and B patients with silent ischemia (4-year survival 86 vs 79%, p = 0.44) and no significant differences in survival between type A patients with silent ischemia and type A patients with symptomatic ischemia (6-year survival 86 vs 80%, p = 0.59). Similar results were obtained for infarction-free survival. Type A patients are more likely than type B patients to have silent ischemia during exercise, but long-term survival is not affected.
BACKGROUND - The treadmill exercise test identifies patients with different degrees of risk of death from cardiovascular events. We devised a prognostic score, based on the results of treadmill exercise testing, that accurately predicts outcome among inpatients referred for cardiac catheterization. This study was designed to determine whether this score could also accurately predict prognosis in unselected outpatients.
METHODS - We prospectively studied 613 consecutive outpatients with suspected coronary disease who were referred for exercise testing between 1983 and 1985. Follow-up was 98 percent complete at four years. The treadmill score was calculated as follows: duration of exercise in minutes--(5 x the maximal ST-segment deviation during or after exercise, in millimeters)--(4 x the treadmill angina index). The numerical treadmill angina index was 0 for no angina, 1 for nonlimiting angina, and 2 for exercise-limiting angina. Treadmill scores ranged from -25 (indicating the highest risk) to +15 (indicating the lowest risk).
RESULTS - Predicted outcomes for the outpatients, based on their treadmill scores, agreed closely with the observed outcomes. The score accurately separated patients who subsequently died from those who lived for four years (area under the receiver-operating-characteristic curve = 0.849). The treadmill score was a better discriminator than the clinical data and was even more useful for outpatients than it had been for inpatients. Approximately two thirds of the outpatients had treadmill scores indicating low risk (greater than or equal to +5), reflecting longer exercise times and little or no ST-segment deviation, and their four-year survival rate was 99 percent (average annual mortality rate, 0.25 percent). Four percent of the outpatients had scores indicating high risk (less than -10), reflecting shorter exercise times and more severe ST-segment deviation; their four-year survival rate was 79 percent (average annual mortality rate, 5 percent).
CONCLUSIONS - The treadmill score is a useful and valid tool that can help clinicians determine prognosis and decide whether to refer outpatients with suspected coronary disease for cardiac catheterization. In this study, it was a better predictor of outcome than the clinical assessment.