Myocardial Bridging: a bridge to spasm?

Abstract Introduction Myocardial bridges (MBs) represent a congenital anomaly where a segment of a coronary artery passes through the myocardium, resulting in systolic compression. The role of MBs in causing chest pain has been debated, as coronary blood flow occurs primarily in diastole. MBs are generally considered benign, there is growing evidence implicating them in the pathogenesis of coronary artery spasm (CAS). However, the prevalence of CAS in patients in Europe with MBs, particularly assessed through acetylcholine (ACh) testing, remains poorly defined. Methods We conducted a retrospective analysis of consecutive patients with angina with no obstructive CAD (ANOCA), ischemia with no obstructive CAD (INOCA), or myocardial infarction with no obstructive coronary arteries (MINOCA) undergoing ACh testing between 2021 and 2024 at our centre. Patients with documented MBs on coronary angiography were included. The presence of epicardial CAS, defined as >90% reduction in coronary diameter with symptoms and/or ischemic electrocardiographic changes, was assessed during ACh provocation testing. Clinical characteristics, Fractional flow reserve (FFR), resting full-cycle ratio (RFR), coronary flow reserve (CFR) and the index of microvascular resistance (IMR) were also analyzed. Results From a total of 299 patients who underwent ACh Testing, 21 patients were identified with MBs, (17 Male, 4 Female). The prevalence of focal CAS in the MB among these patients was 90%. None of these patients had abnormal hyperemic (FFR) or non-hyperemic (RFR) measurements. 9 of the 21 patients with MB had increased IMR, and only 1 had a CFR < 2. 1 Patient had both microvascular CAS in addition to focal epicardial CAS. Conclusion This analysis provides valuable insights into the prevalence of CAS in patients with MBs undergoing ACh testing. The findings underscore the importance of considering CAS in the evaluation and management of patients with MBs, particularly during provocative testing. Further prospective studies are warranted to validate these findings and elucidate the clinical implications for risk stratification and treatment strategies in this patient population.