Endotype distribution and response to tailored medical therapy in patients with myocardial bridging and ischaemia with non-obstructive coronary arteries

Introduction Myocardial bridging (MB) is an acknowledged epicardial structural mechanism of myocardial ischaemia and associated to ischaemia and non-obstructive coronary arteries (INOCA). Beta-blockers are the most frequently used and recommended drugs for the management of symptomatic MB according to current guidelines and expert consensus. Purpose The aims of this subanalysis are to describe the prevalence of INOCA endotypes among patients with MB and to evaluate their responsiveness to tailored medical therapy in terms of symptoms and quality of life improvement. Materials and methods The analysis was performed on data from the INOCA-IT Registry, which consecutively enrolled patients with angina and/or inducible myocardial ischemia, without obstructive coronary artery disease (CAD), who underwent full invasive coronary functional assessment including acetylcholine provocative testing. This subanalysis investigates the prevalence of INOCA endotypes amongst patients with MB at coronary angiography, and the impact of a stratified therapeutic approach on angina severity and on quality of life via the Seattle Angina Questionnaire (SAQ) and EQ-5D-5L questionnaire at baseline and at 12-months clinical follow-up. Results Of 213 patients included in the registry, 38 (17.8%) had a documented MB. Baseline characteristics such as typical cardiovascular risk factors, atrial fibrillation and chronic kidney disease were comparable to general INOCA patients, as well as the characteristics of angina upon presentation (atypical angina: 7.9% in MB vs 11.4% in no-MB, p=0.525; unstable angina: 5.3% vs 8%, respectively, p=0.562) and the severity assessed via the Canadian Cardiovascular Society (CCS) class (p for overall comparison 0.656). At baseline, 47.3% of MB patients were on beta blockers (BB), whereas 5.3% were taking non-dihydropyridinic calcium channel blockers (NH-CCB). As displayed in Figure 1 the distribution of different INOCA endotypes was significantly different between patients with and without MB. The most frequent endotype amongst patients with MB was the combination of epicardial spasm (ES) and coronary microvascular dysfunction (CMD), whereas microvascular spasm (MVS) was the rarest (44.7% and 2.6 %, respectively). Therefore, amongst MB patients, 63.2% were treated with first-line NH-CCB, whereas only 23.7% with BB. Tailored medical therapy was effective in improving both the chest pain symptoms in terms of CCS class and SAQ summary score (p<0.001 – Figure 2). Regarding quality of life, the pain and discomfort and usual activity domains of the EQ-5D-5L questionnaire showed improvements, as well as the EuroQol Visual Analogue Scale (EQ VAS). Conclusions MB was detected in 17.8% of patients in the INOCA-IT Registry and the combination of CMD and EP was the most frequent endotype. Tailored medical therapy effectively improved symptoms and quality of life at follow-up.