Background: Myocardial bridging is the most common congenital coronary anomaly. It is infrequently associated with myocardial ischemia, however, it is difficult to assess the functional significance of this lesion due to its dynamic nature. We performed this study to assess the hemodynamic relevance of myocardial bridges using a pressure wire. Methods: From Jan 2004 to Jul 2006, 24 patients with lone myocardial bridging lesions were consecutively enrolled (systolic compression >50% by visual estimation). Baseline angiogram was obtained after intracoronary nitroglycerine administration and angiographic data of diastolic and systolic phases were obtained. Then fractional flow reserve (FFR) and pressure parameters were measured. Diastolic FFR was calculated by off-line analysis. Cut-off values for functional significance of FFR and diastolic FFR were 0.75 and 0.76. Dobutamine stress–FFR (DS-FFR) was performed with intravenous dobutamine infusion while keeping the pressure wire across the lesion (n=13). Hyperemia was induced by intracoronary adenosine infusion. Results: Mean age was 60짹9 years and 63% were male. Baseline systolic percent stenosis and lesion length of myocardial bridging were 70짹16% and 24짹7mm. Baseline FFR was 0.92짹0.05 and diastolic FFR, 0.89짹0.07 (p=0.006). No lesion was functionally significant according to baseline FFR/diastolic FFR. After dobutamine infusion, percent stenosis and lesion length were aggravated and diastolic FFR was lowered. However, FFR was not changed (Table). Two lesions became functionally significant after dobutamine infusion. Conclusion: Dobutamine increased the morphologic and functional significance of myocardial bridging. Diastolic FFR should be used in functional assessment of myocardial bridging.