Aim: Angina and no obstructive CAD (ANOCA) is common. A potential cause of angina in this patient population is a myocardial bridge (MB). We studied the anatomical and hemodynamic characteristics of an MB in patients with angina and no obstructive CAD.
Methods and Results: Using intravascular ultrasound (IVUS), we identified 184 MBs in 154 patients. We evaluated MB length, arterial compression, and halo thickness. MB muscle index (MMI) was defined as MB length×halo thickness. Hemodynamic testing of the MB was performed using an intracoronary pressure/Doppler flow wire at rest and during dobutamine stress. We defined an abnormal diastolic fractional flow reserve (dFFR) as ≤0.76 during stress. The median MB length was 22.9 mm, arterial compression 30.9%, and halo thickness 0.5mm. The median MMI was 12.1. Endothelial and microvascular dysfunction were present in 85.4% and 22.1%, respectively. At peak dobutamine stress, 94.2% of patients had a dFFR≤0.76 within and/or distal to the MB. MMI was associated with an abnormal dFFR.
Conclusion: In select patients with ANOCA who have an MB by IVUS, a majority have evidence of a hemodynamically significant dFFR during dobutamine stress, suggesting the MB as a cause of their angina. A comprehensive invasive assessment of such patients during coronary angiography provides important diagnostic information that can guide management.