[Phasic coronary flow velocity pattern characteristics of myocardial bridging: a Doppler guide wire study]

The phasic coronary flow velocity pattern of myocardial bridging was analyzed using a 0.014 inch, 15 MHz Doppler guide wire. Coronary flow velocities and coronary flow reserve at rest and maximum hyperemic time were measured in nine patients with myocardial bridging and 11 normal subjects. Systolic flow reversal followed by prominent early diastolic peak velocity patterns was observed in seven patients (78%) in vessels with myocardial bridging. The systolic time velocity integral was significantly smaller in patients with myocardial bridging than in normal subjects (-1.3 +/- 1.5 vs 4.0 +/- 1.2 cm, p < 0.01), but the diastolic time velocity integral was not significantly different. However, the time velocity integral throughout a cardiac cycle was significantly different between the two groups (12.8 +/- 2.2 vs 18.8 +/- 6.3 cm, p < 0.05). Maximum hyperemic time-averaged peak velocity was significantly lower in patients with myocardial bridging than in normal subjects (40.7 +/- 10.3 vs 57.6 +/- 15.5 cm/sec, p < 0.01), but there was no significant difference in coronary flow reserve between the two groups (2.9 +/- 0.6 vs 3.3 +/- 0.4). Systolic flow reversal followed by prominent early diastolic peak velocity patterns was observed in patients with myocardial bridging. The systolic time velocity integral was significantly smaller in patients with myocardial bridging, so the time velocity integral throughout a cardiac cycle was significantly smaller. There was no significant correlation between coronary flow reserve and ratio of stenosis, and coronary flow reserve was maintained.