DISTURBED INTRACORONARY HEMODYNAMICS IN MYOCARDIAL BRIDGING - EARLY NORMALIZATION BY INTRACORONARY STENT PLACEMENT

Background The purpose of this study was to evaluate the hemodynamic m echanisms leading to myocardial ischemia in patients with myocardial b ridging. Myocardial bridging is known to induce angina and even severe myocardial ischemia. Methods and Results In 12 symptomatic patients w ith myocardial bridges, quantitative coronary angiography was performe d to obtain systolic/diastolic vessel diameters within the bridged seg ments. Coronary flow velocities, flow reserve, and pressures were dete rmined with a 0.014-in Doppler and a 0.014-in pressure microtransducer . In 3 symptomatic patients, coronary stents were implanted and hemody namic measurements were repeated immediately and after 7 weeks. An in vitro validation of the pressure measurements was performed. Angiograp hy revealed a systolic diameter reduction of 80.6+/-9.2% and a persist ent diastolic reduction of 35.3+/-11% within the bridged segment. Dias tolic flow velocities (cm/s) were increased (31.5+/-14.3 within versus 17.3+/-5.7 proximal and 15.2+/-6.3 distal, P<.001). Coronary flow res erve distal to the bridge was 2.5+/-0.5. There was an increased peak s ystolic pressure within the bridged segment (171+/-48 versus 113+/-10 mmHg proximal, P<.001). Stent placement abolished the phasic lumen com pression, the diastolic flow abnormalities, the intracoronary peak sys tolic pressure, and clinical symptoms. Coronary flow reserve improved to 3.8+/-0.3. Conclusions Coronary hemodynamics in myocardial bridges are characterized by a phasic systolic vessel compression with a local ized peak pressure, persistent diastolic diameter reduction, increased blood flow velocities, retrograde flow, and a reduced flow reserve. T hese alterations may explain the occurrence of symptoms and ischemia i n these patients. Intracoronary stent placement abolished all hemodyna mic abnormalities and may improve clinical symptoms in otherwise unsuc cessfully treated patients with myocardial bridges.