The importance of clinical subsets in interpreting maximal treadmill exercise test results: the role of multiple-lead ECG systems.

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Abstract
Men (200) with normal ECGs at rest had maximum treadmill tests using 14 ECG leads 1 day before their coronary arteriogram. The prevalence of coronary stenoses .gtoreq. 70% was 86% in 87 men with typical angina, 65% in 64 men with probable angina, and 28% in 49 men with nonspecific chest pain (P < 0.001). Among the 117 men who had coronary disease and probable or typical angina, there was more 3-vessel (32% vs 7%; P = 0.06) and proximal left coronary disease (41% vs 14%; P < 0.05) than among the 14 men with coronary lesions and nonspecific chest pain. Prevalence, extent and location of coronary stenoses were different among the clinical subsets. The predictive value of a positive test in any one of 14 leads was 45% (9 of 20) in men with nonspecific chest pain vs 82% (36 of 44) in men with probable angina and 100% (65 of 65) in men with typical angina (P < 0.001). The predictive value of a negative test in 14 leads was 83% (24 of 29) in men with nonspecific chest pain vs 70% (14 of 20) in men with probable angina and 55% (12 of 22) in men with typical angina (NS). In men with probable or typical angina, 92% (33 of 36) of those with a positive test and treadmill work time .ltoreq. 360 s had multivessel disease; only 1 man in 40 with a negative test in 14 leads and treadmill work time > 540 s had 3-vessel disease. The diagnostic impact of maximal treadmill testing using 14 ECG leads is greatest in men with typical and probable angina. In these 2 clinical subsets the presence or absence of horizontal or downsloping ST-segment depression .gtoreq. 1 mm, ST-segment elevation .gtoreq. 1 mm, or a slowly upsloping ST-segment depression .gtoreq. 2 mm at 0.08 s after the J point in any of 14 leads is highly predictive of multivessel disease when used in conjunction with treadmill work time. The predictive value of maximal treadmill testing using 14 ECG leads in men with nonspecific chest pain is less useful. The lower predictive value of a positive test occurs because this clinical subset has less severe coronary disease and a lower prevalence of disease than men with anginal symptoms. Recording a single lead such as CM5 would suffice for the majority of patients in this subset using either horizontal or downsloping ST-segment depression .gtoreq. 1 mm or ST-segment elevation .gtoreq. 1 mm as criteria for positivity.