Protective effect of beta-blockade on dipyridamole-induced myocardial ischaemia. Role of heart rate.

This study was designed to investigate the effect of heart rate changes on dipyridamole echocardiographic tests in patients with coronary artery disease treated with propranolol. We prospectively studied 12 patients (8 men and 4 women; mean age 56.5 +/- 8.7 years) selected by: (a) angiographic evidence of significant coronary artery disease; (b) adequate echocardiographic window; (c) positive dipyridamole echocardiography test results in baseline conditions (step I); (d) test reproducibility in the absence of treatment; (e) negative dipyridamole echocardiography test results after 7 days of treatment with propranolol (120 mg.day-1) in twice divided doses daily (step II). In all patients treated with propranolol, dipyridamole echocardiographic testing was repeated 24 h after the last negative test. In these patients, transoesophageal atrial pacing was performed at peak dipyridamole infusion to increase heart rate to values similar to those observed at baseline (step III). At baseline, heart rate and rate-pressure product were significantly lower in patients treated with propranolol (-20.3% and -22.5% in group II, P < 0.001 vs step I; -24.3% and -26.4% in group III, P < 0.05 vs step I), but the different treatments did not produce significant differences in systolic and diastolic blood pressure. At peak dipyridamole infusion, heart rate and rate-pressure product increased with either placebo or propranolol treatments with respect to baseline, while remaining significantly lower with propranolol as compared to placebo (-29.6% and -29.5% in step II, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)