Implications of Myocardial Bridge on Coronary Atherosclerosis and Survival

Abstract

Background: In this study, we aimed to describe the impact of MBs on atherosclerosis and survival, in patients with coronary artery disease (CAD). Methods: We retrospectively studied 1920 consecutive patients who underwent conventional coronary angiography for suspected CAD. Atherosclerotic load (AL), defined as the sum of degrees of stenosis, and general atherosclerotic load (GAL), representing the sum of AL, were compared between patients with MB and a control group without MB; patients in these groups were similar in age and sex. We assessed survival at 10 years after the last enrolled patient. Results: Prevalence of MB was 3.96%, predominantly in the mid-segment of left anterior descendent artery (LAD). In the presence of MB, GAL was lower (158.1 ± 93.7 vs. 205.3 ± 117.9, p = 0.004) with a lesser AL in the proximal (30.3 ± 39.9 vs. 42.9 ± 41.1, p = 0.038) and mid-segments (8.1 ± 20.0 vs. 25.3 ± 35.9, p < 0.001) of LAD. Based on a Multinominal Logistic Regression, we found that the presence of MB on LAD (regardless of its location on this artery) is a protective factor against atherosclerotic lesions, decreasing the probability of significant stenosis, especially of those ≥70%, on the entire artery (B −1.539, OR 4660; 95% CI = 1.873–11.595, p = 0.001) and on each of its segments as well: proximal LAD (B −1.275, OR 0.280; 95% CI = 0.015–5.073; p = 0.038), mid-LAD (B −1.879, OR 6.545; 95% CI = 1.492–28.712; p = 0.013) and distal LAD (B −0.900, OR 2.459, 95% CI = 2.459–2.459, p = 0.032). However, 10-year survival was similar between groups (76.70% vs. 74.30%, p = 0.740). Conclusion: The presence of MB on LAD proved to be a protective factor against atherosclerosis for the entire artery and for each of its segments, but it does not influence long-term survival in patients with CAD.

Anatomical risks and complications associated with myocardial bridging

“…MB milking might also cause ischemia by an 'branch steal' or 'intramural steal' mechanism linked to decreased perfusion pressure of the blood suction and septal branches. In some studies, MB was also shown to be a protective (23,24) or predictive (25)(26)(27) factor of atherosclerosis. Especially, proximal segment of the bridge was considered to be a major risk factor of atherosclerosis (23,24,26,27).…”

“…In some studies, MB was also shown to be a protective (23,24) or predictive (25)(26)(27) factor of atherosclerosis. Especially, proximal segment of the bridge was considered to be a major risk factor of atherosclerosis (23,24,26,27). Overall, MB related symptoms and complications are observed to be highly dependent on various clinical and pathophysiological factors such as age of the patient, degree of systolic narrowing, hear rate or diastolic perfusion time, intrinsic and extrinsic factors (coronary vasoconstriction, sympathetically driven myocardial contraction, transmural perfusion gradients, diastolic flow, arterial/myocardial compression, and aortic pressure), biochemical factors (led to intimal injuries developing into coronary dissection, vasospasticity, and plaque vulnerability/thrombosis), number of tunneled segments, depth of tunneled artery, presence of coronary atherosclerosis, left ventricle (LV) hypertrophy, and the length of the tunneled artery or location of the bridge (21).…”

Editorial for Special Issue “Advance in Diagnostic and Management of Ischemic Heart Disease”

“…An important section of this Special Issue is dedicated to the implications of myocardial bridge in patients with CAD [ 5 ]. The myocardial bridge (MB) represents the muscle fibres that abnormally overlie the intramyocardial passage of an epicardial coronary artery, which consequently becomes tunnelled in its path beneath them.…”

“…Although few isolated MBs have a clinical expression, myocardial ischemia induced by isolated MBs may manifest in significant clinical forms, such as silent ischemia, stable angina, acute coronary syndromes, arrhythmias, and even sudden cardiac death. Darabont et al [ 5 ] studied 1920 consecutive patients who underwent coronary angiographyand identified 76 patients with myocardial bridging. Interestingly, the presence of MB on LAD is not an additional risk factor for coronary atherosclerosis.…”

“…Interestingly, the presence of MB on LAD is not an additional risk factor for coronary atherosclerosis. On the contrary, it proved to be a protective factor against atherosclerosis for the entire artery and for each of its segments, especially in its middle and proximal segments; however, it does not influence 10 year survival in patients with CAD [ 5 ].…”