Sixteen male patients with typical
angina pectoris secondary to
coronary atherosclerosis performed two daily standardized exercise tests during two consecutive days. Three hours before each exercise they received placebo or 400 mg
practolol administered orally in double-blind fashion in order to complete a cross-over design.
Practolol significantly prolonged the exercise duration by 30.6% and delayed the appearance time of ischaemic electrocardiographic changes by 67.7%. Maximal heart rate, systolic pressure, and pressure-rate product were also reduced after medication. In order to investigate further the effects of this beta blocking agent, myocardial function and metabolism at rest and during supine exercise were assessed in 12 male patients with
coronary artery disease before and after
practolol 30 mg, iv. At rest,
practolol produced a decrease in tension-time index (18%), cardiac index (17%), heart rate (10%), and
stroke index (7%). A significant reduction was also observed in resting
stroke work index (14%) and systolic and mean aortic pressure (6%). Left ventricular end-diastolic pressure remained unchanged. During supine exercise, only time-tension index (12%), heart rate (12%), and cardiac index (10%) were significantly reduced after the beta blocking agent.
Practolol did not significantly change the arterial
glucose,
lactate,
inorganic phosphate,
potassium,
calcium,
magnesium, pH, PCO2, or PO2. The beta blocking agent did not modify the myocardial extraction of any of these substrates at rest or during exercise. In the dosage used in both studies,
practolol significantly improved the exercise tolerance and reduced the ischaemic manifestations. The efficacy of
practolol in
angina pectoris may result mostly from its ability to decrease heart rate and systolic pressure during exercise.