Hemodynamic determinants of coronary constriction in human myocardial bridges

To study the physiopathology of myocardial bridges, we assessed the degree of systolic coronary artery constriction (%SC) in different hemodynamic situations in six patients submitted for coronary angiograms. There was an increase of %SC (p less than 0.05) with sodium nitroprusside (NP), no modification during fast atrial stimulation (AS), and a decrease (p less than 0.05) during noradrenaline infusion (Nor). Hemodynamic studies indicate an inverse relation (p less than 0.05) between %SC and systolic and diastolic aortic pressure and left ventricular dP/dt. There was no correlation between changes in %SC and changes in Vmax or heart rate. Thus we conclude that changes in systemic arterial pressure and coronary perfusion pressure may significantly affect the degree of severity of myocardial bridges, possibly through an influence upon intraluminal coronary pressure and an intramyocardial tension relationship.