[Effect of beta adrenergic blocking drugs on the prognostic value of ST-segment depression during exercise electrocardiogram testing].

Exercise testing has been shown to be predictive for future cardiac events in patients with established diagnosis of coronary heart disease. Exercise test parameters associated with poor prognosis may be unreliable if patient is receiving beta adrenergic agents. The purpose of this study was: 1) to compare the results of exercise testing performed before and during beta blocking therapy, and 2) to determine the role of beta blockers in the prognostic significance of the ST-segment response recorded during exercise testing. The study population consisted of 518 patients (mean age 52 +/- 7 years) with coronary heart disease. The diagnosis was based on the presence of one of the following three criteria: 1) typical history and significant ST-segment depression on resting or exercise electrocardiogram, 2) history of myocardial infarction, 3) significant coronary angiographic abnormalities. In all patients symptom-limited exercise test was performed before and two weeks after the onset of beta blocker therapy. The data from the first and second tests were estimated for significance of differences between the mean values with following results: maximal heart rate--135 +/- 21 and 123 +/- 19 bpm (p less than 0.001), maximal work load achieved--98 +/- 43 and 109 +/- 44 W (p less than 0.001), maximal systolic blood pressure--171 +/- 28 and 163 +/- 26 mmHg (p less than 0.001). Occurrence of characteristic ST-segment depression was more frequent during the first than during the second test (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)