Detection of severity of coronary artery disease by the ST segment/heart rate relationship in patients on beta-blocker therapy.

Many patients presenting with anginal pain are on beta-blocker therapy and it has been suggested that noninvasive exercise tests for coronary artery disease are adversely affected by such therapy. Recently a new exercise test has been introduced claiming the ability accurately to detect the presence and severity of coronary heart disease in patients with anginal pain; the claim was based on results obtained in patients not undergoing beta-blocker therapy. Therefore using this test, the maximal rate of progression of ST segment depression relative to increases in heart rate during exercise (maximal ST/HR slope) as an index of the severity of myocardial ischaemia, 60 patients on beta-blocker therapy were studied and the results compared with results of coronary arteriography independently obtained. There was a complete agreement, without false results, between the maximal ST/HR slope and the number of significantly diseased coronary arteries. In 21 of these 60 patients the maximal ST/HR slopes obtained before and after beta-blockade were compared; the maximal ST/HR slopes after beta-blockade were not different from those before. It is concluded, that the maximal SR/HR slope can be used reliably to detect the pressure and the severity of coronary heart disease in patients with angina pectoris who are already on beta-blocker therapy.