RESUMEN
BACKGROUND: A relationship between coronary artery spasm (CAS) and myocardial bridge (MB) has been noticed. This study was designed to investigate the differences of stress tests and symptoms between CAS patients with or without MB. METHODS: Two hundred and sixteen patients with atypical chest pain who underwent coronary angiography and acetylcholine provocation test were divided into MB group (n=68) and nonmyocardial bridge group (NMB, n=148). The results of acetylcholine test, treadmill exercise electrocardiography, myocardial scintigraphy, and levels of plasma endothelin-1 and nitric oxide were compared between the two groups. RESULTS: Among these atypical chest pain patients, CAS was induced by acetylcholine in 85% MB patients and 53% NMB patients (P<0.001). A positive exercise electrocardiogram was identified in 71% MB patients and 8% NMB patients (P<0.001). Myocardial scintigraphy revealed ischemic changes in 67% MB patients and 9% NMB patients (P<0.001) and reverse redistribution in 87 and 69% (P<0.01), respectively. MB patients experienced exertional chest pain as well as at rest more frequently than NMB patients. Endothelin-1 levels were elevated in MB group complicated with CAS (P<0.01), whereas nitric oxide levels were reduced in the same cohort (P<0.05) compared with NMB group. CONCLUSION: MB might predispose to CAS in which endothelial dysfunction may play a part. CAS patients with MB usually present mixed chest pain and positive stress tests as well as reversal redistribution on myocardial scintigraphy whereas CAS patients without MB displayed chest pain at rest, negative stress test and reversal redistribution.