Effect of propranolol on indices of intermittent myocardial ischemia, assessed by exercise testing and ambulatory st‐segment monitoring

Seventy three patients (63 males and 10 females) aged 41–75 years with established stable exertional angina pectoris were studied in a double-blind fashion to confirm the efficacy of 80 mg propranolol administered three times daily and also to examine its effect on ST-segment changes in the electrocardiogram by ambulatory ST-segment monitoring and exercise testing using on-line computer analysis. During ambulatory monitoring, episodes of ST-segment depression in lead CM5 were significantly reduced from 6.5±0.7 during placebo to 3.4±0.6 during propranolol therapy (p<0.001). The total duration of ST-segment depression was also significantly reduced and the maximal depth of ST-segment depression improved from 2.6±0.2 mm during placebo to 1.7±0.2 mm during propranolol therapy (p<0.001). The mean ± SEM exercise time of 5.5±0.2 minutes on placebo increased to 8.6±0.4 minutes on propranolol 240 mg daily (p<0.001). The 1 mm ST-segment depression time of 3.5±0.2 minutes on placebo in lead CM5 was prolonged to 6.2±0.3 minutes during propranolol therapy (p<0.001). Propranolol treatment significantly reduced the resting and maximal heart rates (p<0.001). The maximal ST-segment depression during exercise in lead CM5 was reduced from 2.3±0.1 mm on placebo to 1.9±0.1 mm with propranolol (p<0.01). Similarly, the rate-pressure product at peak exercise of 188±5 units on placebo was reduced to 144±3 units with propranolol (p<0.001). Eleven patients were rendered angina free during treadmill testing. Two patients were withdrawn due to adverse effects. In conclusion, propranolol is confirmed to be an effective antianginal agent which improves the ST-segment changes during controlled as well as uncontrolled conditions and acts by lowering the heart rate and rate-pressure product.