Elective response to propranolol or verapamil in ischemia on effort

Twenty-four patients with effort angina and positive exercise stress test performed four control exercise stress tests, two tests while taking propranolol (240 mg/day) and two tests while taking verapamil (320 mg/day), in a randomized crossover sequence. For each test the following parameters were measured: time and rate-pressure product at ischemia; intercept and slope of the linear regression between rate-pressure product and minutes of exercise. Group analysis showed that both drugs improved time to ischemia significantly and to the same extent. However, eight patients responded preferentially to verapamil in contrast to 12 patients on propranolol. The remaining four patients responded equally to both drugs. In verapamil responders, verapamil increased time to ischemia by decreasing intercept and increasing rate-pressure product at ischemia. In these patients, propranolol did not increase time to ischemia because of a marked decrease in rate-pressure product at ischemia. In propranolol responders the significant increase in time to ischemia during propranolol was the result of a decrease in intercept and slope. The ineffectiveness of verapamil in these patients was related to a slight decrease in intercept without any increase in rate-pressure product at ischemia. The preferential response to one of the two drugs could not be predicted on the basis of clinical and angiographic features. In conclusion, in patients with effort angina, medical treatment should be personalized and based on a direct and objective verification of a drug's efficacy since different mechanisms can modulate exercise tolerance.