Objective: To assess the effect of beta blocker on blood flow velocity and reserve on the intramural coronary artery of patients with myocardial bridging.
Methods: In 8 patients with myocardial bridge, intracoronary Doppler was performed before and after esmolol was given intravenously. The basic average peak velocity (bAPV), hyperaemic average peak velocity (hAPV) of blood flow, and coronary flow reserve (CFR) proximal and distal to the mural myocardial bridging was measured and compared.
Results: After esmolol injection, the mural coronary diameter systolic reduction decreased from (58.0 +/- 14.7)% to (26.0 +/- 9.8)% (P < 0.01); the bAPV proximal and distal to myocardial bridging separately decreased from (19.4 +/- 4.9) cm/s and (18.4 +/- 3.6) cm/s to (4.7 +/- 3.9) cm/s (P < 0.01) and (15.1 +/- 1.5) cm/s (P < 0.05). Under hyperemization, esmolol changed the hAPV of proximal and distal to myocardial bridging separately from (54.1 +/- 14.9) cm/s and (44.7 +/- 9.4) cm/s to (49.7 +/- 16.4) cm/s and (48.9 +/- 10.1) cm/s (all P > 0.05); thus, the value of CFR both proximal and distal to myocardial bridge increased separately from 2.8 +/- 0.3 and 2.5 +/- 0.5 to 3.4 +/- 0.5 and 3.2 +/- 0.6 (all P < 0.01).
Conclusion: Esmolol can decreased the compression of the intramural coronary artery and increased the CFR to normal level of it.