Abnormal ST Response Research Articles

Can serial exercise testing improve the prediction of coronary events in asymptomatic individuals?

An abnormal ST segment response to treadmill exercise has a low predictive value for future coronary events (angina pectoris, nonfatal myocardial infarction, or cardiac death) in apparently healthy individuals. To determine whether the conversion from a normal to an abnormal ST segment response might identify individuals at high risk for a future coronary event, we analyzed the results of serial exercise tests performed at 2-4-year intervals in 726 male and female volunteers, aged 22-84 years (mean, 55.1 years), from the Baltimore Longitudinal Study of Aging (BLSA). All subjects were free of cardiovascular disease at entry by history, physical examination, and resting 12-lead electrocardiogram. Over a mean overall follow-up of 7.4 years, coronary events occurred in 34 of 178 (19.1%) of those with an abnormal ST response to exercise versus 30 of 548 (5.5%) in those with a normal response (p = 0.001). Angina pectoris was the most common presenting coronary event regardless of ST segment exercise response. Among individuals with an abnormal ST segment response, the incidence of events was virtually identical between those with an initially abnormal response (group 1) and those who converted from a normal to an abnormal response (group 2), 19.8% versus 18.5%. After adjustment for standard coronary risk factors by proportional hazards regression analysis, the risk of a coronary event relative to subjects with persistently normal ST segment responses (group 3) remained nearly identical in the two groups, 2.72 in group 1 (p less than 0.003) and 2.80 in group 2 (p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise-induced ST depression in the diagnosis of coronary artery disease. A meta-analysis.

To evaluate the variability in the reported diagnostic accuracy of the exercise electrocardiogram, we applied meta-analysis to 147 consecutively published reports comparing exercise-induced ST depression with coronary angiography. These reports involved 24,074 patients who underwent both tests. Population characteristics and technical and methodologic factors, including publication year, number of electrocardiographic leads, exercise protocol, use of hyperventilation, definition of an abnormal ST response, exclusion of certain subgroups, and blinding of test interpretation were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity, 68%; range, 23-100%; SD, 16%; and mean specificity, 77%; range, 17-100%; SD, 17%). The four study characteristics found to be significantly and independently related to sensitivity were the treatment of equivocal test results, comparison with a "better" test such as thallium scintigraphy, exclusion of patients on digitalis, and publication year. The four variables found to be significantly and independently related to specificity were the treatment of upsloping ST depressions, the exclusion of subjects with prior infarction or left bundle branch block, and the use of preexercise hyperventilation. Stepwise linear regression explained less than 35% of the variance in sensitivities and specificities reported in the 147 publications. There is wide variability in the reported accuracy of the exercise electrocardiogram. This variability is not explained by information reported in the medical literature.

Prognosis and thallium-201 scintigraphy in patients admitted with chest pain without confirmed acute myocardial infarction.

Exercise and rest thallium scintigraphy and exercise electrocardiography were performed after discharge in 158 patients aged less than 76 years admitted with chest pain in whom a suspected diagnosis of acute myocardial infarction had not been confirmed. During a follow up of 12-24 months (median 14 months) there were 10 cardiac events--that is, non-fatal acute myocardial infarction or cardiac deaths. Transient thallium defects and abnormal ST response (that is ST segment deviation or uninterpretable ST segment) during exercise were correlated significantly with an unfavourable prognosis. One hundred and four patients with neither of these characteristics were at lower risk of a cardiac event than the 19 patients with both of these characteristics. The percentages of patients in these two groups without a cardiac event after one year were 98.1 and 78.8 respectively. Thallium scintigraphy, alone or in combination with exercise electrocardiography, can be used to identify groups at high and low risk of future cardiac events, in patients with chest pain in whom acute myocardial infarction is suspected but not found.

Prognostic value of exercise electrocardiogram in men at high risk of future coronary heart disease: Multiple risk factor intervention trial experience

The prognostic value of the exercise electrocardiogram was examined in the 6,438 usual care men of the Multiple Risk Factor Intervention Trial in relation to fatal and nonfatal coronary heart disease events, rest electrocardiographic abnormalities and coronary heart disease risk factors. An abnormal response to exercise, defined as an ST depression integral of 16 microV-s or more, was observed in 12.2% of the men. There was a nearly fourfold increase in 7 year coronary mortality among men with an abnormal response to exercise compared with men with a normal ST segment in exercise (risk ratio 3.8, 95% confidence limits 2.5 to 5.5). The risk ratio for coronary death, adjusted for age, diastolic blood pressure, serum cholesterol and smoking status at baseline was 3.5, and the corresponding adjusted risk ratio for death from all causes was 1.6. A similar trend toward excess coronary events was seen for angina pectoris (risk ratio of 1.6). The trend was not significant for nonfatal myocardial infarction. Multivariate analyses indicated that the ST depression integral was a strong independent predictor of future coronary death (p less than 0.001). Men with an abnormal electrocardiogram at rest (mainly high amplitude R waves) and with an abnormal ST response to exercise had an over sixfold relative risk for coronary death compared with men with an abnormal electrocardiogram at rest and a normal ST response to exercise. These results suggest that exercise testing may be indicated for improved risk assessment and the assessment of the significance of minor rest electrocardiographic abnormalities in middle-aged men with elevated levels of coronary heart disease risk factors.

Computed ST forces of Frank and bipolar exercise electrocardiograms

1. 1. Simultaneous CB 5 bipolar and Frank X, Y, and Z orthogonal ECG leads were recorded during a standardized exercise test on 36 ambulatory individuals. From analysis of direct-writing the CB 5 bipolar lead at the moment of cessation of exercise, 11 were classified by visual interpretation with an abnormal ST response, and 28 with a normal ST response to maximally tolerated exercise. An objective computer method confirmed these subjective clinical differentiations. Classification of responses from X, Y, and Z orthogonal leads was not more reliable than that from the CB 5 bipolar lead. 2. 2. Multivariate analysis of normal and abnormal ECG responses grouped together showed the highest correlation between spatial and bipolar ST forces at the ST 2 locus at rest and during most of the recovery and at ST 1 locus during strenuous exercise and immediate recovery. During the second and third minute of recovery, there was no correlation between spatial and bipolar ST 3 forces. 3. 3. Most of the ST 2 information related to the bipolar lead was located in the X lead of the Frank lead electrocardiogram. A satisfactory correlation between observed bipolar ST 2 and predicted bipolar ST 2 forces (computed from X, Y, Z, frontal, and spatial measurements of the Frank lead ECG) was obtained by external checking in other patients. 4. 4. A single bipolar precordial lead appears to be as reliable for purposes of classifying ECG responses to maximal exercise as the more comprehensive Frank lead system.