Myocardial bridge evaluation towards personalized medicine: study design and preliminary results of the RIALTO registry.

ABSTRACT

Myocardial bridge (MB) is the most frequent inborn coronary artery variant in which a portion of the myocardium overlies an epicardial coronary artery segment. Although MB has long been considered a benign entity, a growing body of evidence has suggested its association with angina and adverse cardiac events. However, to date, no data on long-term prognosis are available, nor on therapies improving cardiovascular outcomes. We are currently conducting an ambispective, observational, multicentre, study in which we enrol patients with a clinical indication to undergo coronary angiography (CA) and evidence of MB, aiming to describe the incidence of symptoms and cardiovascular events at baseline and at long-term follow-up (FUP). The role of invasive full-physiology assessment in modifying the discharge therapy and eventually the perceived quality of life and the incidence of major cardiovascular events will be analysed. Basal clinical-instrumental data of eligible and consenting patients have been acquired after CA; FUP was performed 6, 12, and 24 months after the angiographic diagnosis of MB. The primary endpoint of the study is the incidence of major adverse cardiovascular events (MACE), defined as the composite of cardiac death, myocardial infarction, cardiac hospitalization, and target vessel revascularization; the secondary endpoints are the rate of patients with Seattle Angina Questionnaire (SAQ) summary score <70 and the incidence of MACE in patients undergoing invasive intracoronary assessment. Among patients undergone FUP visits, we recorded 31 MACE at 6 months (11.6%), 16 MACE at 12 months (6.5%), and 26 MACE at 24 months (13.5%). The rate of patients with SAQ <70 is 18.8% at 6 months, 20.6% at 12 months, and 21.8% at 24 months. To evaluate the prognostic role of invasive intracoronary assessment, we compared MB patients who underwent only angiographic evaluation (Angio group) to those who underwent acetylcholine (ACH) provocative test with indication to calcium-channel blockers (CCBs) at discharge (Angio + ACH + CCBs group) and those who underwent functional assessment with fractional flow reserve (FFR) with indication to beta-blockers (BBs) at discharge (Angio + FFR + BBs group). After 2 years of FUP, the rate of MACE was significantly reduced in both Angio + ACH + CCBs group (6 vs. 25%, P = 0.029) and Angio + FFR + BBs group (3 vs. 25%, P = 0.005) compared with Angio group. The preliminary results of our study showed that MB may be a cause of angina and adverse cardiac events in patients referred to CA for suspected coronary artery disease (CAD). Full-physiology assessment unmasking MB-related ischaemia mechanisms, allowed to guide the treatment, personalizing the clinical management, improving the quality of life, and cardiovascular outcomes in patients with MB.