Significance of the Anatomical Properties of a Myocardial Bridge in Coronary Heart Disease

Abstract

he myocardial bridge (MB) is an anatomical variant that often covers part of the left anterior descending coronary artery (LAD). 1 It occurs almost exclusively in the mid-portion of the LAD (Figure 1). 2,3 Muscular contraction of the MB itself alters blood flow within the LAD, as demonstrated by coronary angiography, and influences the distribution of hemodynamic stress. [3][4][5] It is widely accepted that an MB sometimes causes coronary heart disease (CHD), 2,5,6 either from direct compression of the MB at cardiac systole or by enhancement of the natural progression of coronary atherosclerosis in the LAD segment proximal to the MB. 2,5,7 Both mechanisms are closely associated with changes in hemodynamic stress driven by the force of the MB contraction through a combination of anatomical properties, such as the location, length, and thickness of the MB. 3,7,8 This review focuses on the relationship between the presence of an MB in the LAD and the occurrence of CHD, specifically addressing the importance of the anatomical properties of the MB as the common root for the 2 distinct mechanisms. In addition, therapeutic approaches to CHD caused by an MB are summarized, along with their outcomes. A myocardial bridge (MB), partially covering the coronary artery, is a congenital anatomical variant usually present in the left anterior descending coronary artery (LAD). MB causes coronary heart disease (CHD) by 2 distinct mechanisms influenced by the anatomical properties of the MB, such as its length, thickness, and location. One is direct MB compression of the LAD at cardiac systole, resulting in delayed arterial relaxation at diastole, reduced blood flow reserve, and decreased blood perfusion. The other is enhancement of coronary atherosclerosis causing stenosis of the LAD proximal to the MB, occurring because of endothelial injury arising from the abnormal hemodynamics provoked by retrograde blood flow up toward the left coronary ostium at cardiac systole. The magnitude of the effect of the 2 distinct mechanisms of the MB on LAD blood flow is prescribed by a common root of the MB-muscle mass volume generated by those properties. Furthermore, the anatomical properties of the MB are closely associated with the choice of treatment and therapeutic outcome in CHD patients having an MB. Thus, the anatomical properties of an MB should be considered in the diagnosis and management of CHD patients with this anomaly. (Circ J 2011; 75: 1559 - 1566

Functional Versus Anatomic Assessment of Myocardial Bridging by Intravascular Ultrasound: Impact of Arterial Compression on Proximal Atherosclerotic Plaque

“…In particular, the sample size was not large enough to deny the possible correlations between anatomic MB properties and proximal atherosclerotic plaque burden. Second, the rate of MB appears higher in the current study compared with past angiographic reports (prevalence 0.4–16%) in the literature 20. This might be attributed to the higher image resolution of IVUS and its ability to directly visualize MB muscle or may suggest that MB itself is a substantial contributor to anginal symptoms without obstructive coronary artery disease.…”

“…Another study using a catheter‐based pressure measurement system demonstrated that the intracoronary pressure within the LAD segment proximal to the MB was significantly higher than the aortic blood pressure, suggesting potential augmentation of the intimal injury at this segment 9. Finally, solid mechanical forces that result from the motion and deformation of the coronary tree and myocardial material properties may lead to a heterogeneous stress field at this segment 6, 9, 20, 21…”

Congenital coronary artery anomalies in adult population detected using dual source ECG-gated CTA in a single institution

“…However, the relationship between MB anomaly and increased cardiovascular morbidity is still unclear. According to previous reports [21,30], the MB may cause coronary heart disease by two mechanisms. First, by a direct systolic compression of the tunnelled segment and second by the enhanced atherosclerotic plaque formation occurring because of alteration of haemodynamic factors, mainly in the vessel segment proximal to the bridge.…”

“…First, by a direct systolic compression of the tunnelled segment and second by the enhanced atherosclerotic plaque formation occurring because of alteration of haemodynamic factors, mainly in the vessel segment proximal to the bridge. The length, the depth and the location of the MB have been associated with the mechanisms above [21,30]. Therefore, MB is classified as superficial or deep, depending on the thickness of the covering muscular layer (≤ 1 mm or > 1 mm) [26].…”

Angiographic prevalence of myocardial bridging İn our department

“…Biz bu çalışmamızda, koroner anjiografi yapılan hastalardaki MB prevalansını araştırmayı amaçladık. (20). Nadir olarakta sağ koroner arter ve Cx arterde de görülebilmektedir.…”