[The ST/HR slope and coronary stenoses].

BACKGROUND

The heart rate adjustment of ST depression (ST/HR Slope) has been shown by some authors to markedly improve the accuracy of treadmill exercise electrocardiogram for identifying and quantifying coronary artery disease. However, other authors have obtained different results. In the present study the results of our exercise electrocardiography laboratory are compared with the data obtained from the literature.

METHODS

Fifty patients (46 males and 4 females, age range 60 +/- 7 years) with suspect or certain coronary artery disease were referred for a routine treadmill exercise electrocardiogram, and subsequently underwent cardiac catheterization and selective coronary cineangiography to assess the severity of coronary obstruction. All patients exercised according to a recently reported modification of the standard Bruce protocol, proposed by Kligfield et al, for a more accurate evaluation of the ST/HR Slope, which was calculated in real time by a computerized system. Patients with coexisting valvular heart disease, cardiomyopathy, left bundle-branch block on the resting ECG, myocardial infarction within 8 weeks, diabetes mellitus, hypertensive response during exercise testing (diastolic blood pressure > 95 mm Hg and/or systolic blood pressure > 190 mm Hg), abnormalities or variations of the coronary arteries, were excluded from this study.

RESULTS

This method correctly identified 13 of 14 patients with multivessel coronary artery disease and 35 of 36 with less severe disease: one patient was false negative and another one false positive. Thus, in our exercise electrocardiography laboratory this approach shows a sensitivity of 93%, a specificity of 97%, a positive predictive value of 93% and a negative predictive value of 97% for the detection of severe coronary disease.

CONCLUSIONS

These findings suggest that, in patients selected as in this study, the ST/HR slope is a good method which improves the clinical usefulness of the treadmill exercise electrocardiogram in coronary artery disease.