PROTECTIVE EFFECT OF BETA-BLOCKADE ON DIPYRIDAMOLE-INDUCED MYOCARDIAL-ISCHEMIA

This study was designed to investigate the effect of heart changes on dipyridamole echocardiographic tests in patients with coronary artery disease treated with propranolol. We prospectively studied 12 patients 98 men and 4 women; mean age 56.5 +/- 8.7 years) selected by: (a) ang iographic evidence of significant coronary artery disease; (b) adequat e echocardiographic window; (c) positive dipyridamole echocardiography test results in baseline conditions (step I); (d) test reproductibili ty in the absence of treatment; (e) negative dipyridamole echocardiogr aphy test results after 7 days of treatment with propranolol (120 mg.d ay(-1)) in twice divided doses daily (step II). In all patients treate d with propranolol, dipyridamole echocardiographic testing was repeate d 24 h after the last negative test. In these patients, transoesophage al atrial pacing was performed at peak dipyridamole infusion to increa se heart rate to values similar to those observed at baseline (step II I). At baseline, heart rate and rate-pressure product were significant ly lower in patients treated with propranolol (-20.3% and -22.5% in gr oup II, P<0.001 vs step I; -24.3% and -26.4% in group III, P<.005 vs s tep I), but the different treatments did not produce significant diffe rences in systolic and diastolic blood pressure. At peak dipyridamole infusion, heart rate and rate-pressure product increased with either p lacebo or propranolol treatments with respect to baseline, while remai ning significantly lower with propranolol as compared to placebo (-29. 6% and -29.5% in step II, P<0.001). During treatment with propranolol plus transoesophageal pacing to maintain heart rate at values attained with placebo, the rate-pressure product did not change significantly with respect to placebo, nor did systolic blood pressure. Transoesopha geal atrial pacing performed during propranolol treatment to restore h eart rate to baseline values did not affect the dipyridamole echocardi ographic test in eight patients (group I), and induced transient wall abnormalities in four patients (group II) (P-ns). Our date suggest tha t the anti-ischaemic effect of propranolol in man is not correlated on ly to reduction of heart rate.