Relation between severity of myocardial bridge and vasospasm

Myocardial bridge (MB) has been reported to induce cardiac complications including coronary vasospasm. Although MB has some anatomical and morphological variations, the association of these variations with vasospasm is unclear. The aim of this study was to investigate the relation between morphological severity of MB and vasospasm induced by acetylcholine (ACh) provocation test.

A total of 392 patients without coronary stent in the left anterior descending artery (LAD) undergoing intracoronary ACh provocation test were included. Angiographic coronary artery vasospasm was defined as total or subtotal occlusion induced by ACh provocation. MB was identified on coronary angiography as a milking effect. Total bridged length and maximum percent systolic compression of MB in the LAD were analyzed quantitatively.

MBs in the LAD were identified in 140 patients (36%), mostly in the mid segment. Patients with MB in the LAD had greater number of provoked vasospasm in the LAD and positive ACh provocation test compared to those without. The bridged length positively correlated with percent systolic compression of MB (r=0.37, p<0.001). In the receiver operating characteristic curve analysis, both bridged length and percent systolic compression of MB significantly predicted the provoked LAD spasm (AUC 0.74, p<0.001, and AUC 0.68, p<0.001). Multivariate regression analysis demonstrated these factors as independent predictors for provoked LAD spasm.

MB, especially morphologically severe MB, may induce greater coronary vasospasm.