Left Anterior Descending Artery Myocardial Bridging

Abstract

A myocardial bridge (MB) is the term for the muscle overlying the intramyocardial segment of the epicardial coronary artery (referred to as a tunneled artery). Although MBs can be found in any epicardial artery, most of them involve the left anterior descending artery. These congenital coronary anomalies have long been recognized anatomically, and are traditionally considered a benign condition; however, the association between myocardial ischemia and MBs has increased their clinical relevance. This review summarizes the prevalence, pathophysiology, and diagnostic findings, including morphological, functional assessment, and treatment of patients with MB involving the left anterior descending artery, suggesting a pragmatic clinical approach to this entity.

Myocardial bridge: bridging the differential diagnosis

“…There is a growing consensus that the onset of the clinical factors related to myocardial bridge is due to a complex set of physiological factors, categorised by intrinsic and extrinsic factors, rather than by simple anatomy 4. Extrinsic factors include epicardial arterial compression, sympathetically driven myocardial contraction and coronary vasoconstriction 4. Intrinsic factors include interval interactions among aortic pressure, diastolic flow and perfusion time, and transmural perfusion gradients.…”

“…Intrinsic factors include interval interactions among aortic pressure, diastolic flow and perfusion time, and transmural perfusion gradients. Impaired diastolic flow can result in a branch steal phenomenon creating a depressurisation of septal branches leading to an intrabridge decrease in perfusion 4. This results in high systolic wall shear stress proximal to myocardial bridge entrance due to the collision of retrograde and anterograde perfusion leading to constrictive vascular remodelling and early atherosclerosis.…”

“…Additionally, non-dihydropyridine calcium channel blockers are beneficial in instances of coronary vasospasm due to their vasodilatory effects 5 9. Ranolazine, which inhibits cardiac late sodium channel and thus improves myocardial relaxation and perfusion, can be used as monotherapy or in combination with first-line therapies 4. Nitrates are contraindicated as they exacerbate symptoms by reducing intrinsic coronary wall tension and subsequently increase reflex sympathetic stimulation of contractility 3.…”

“…Myocardial bridges produce clinical manifestations by three hypothesised methods: (1) direct compression of the tunnelled coronary artery via myocardial contraction, (2) accelerated atherosclerosis in the proximal segment relative to the myocardial bridge and (3) ‘branch-steal’ phenomenon of systolic retrograde flow and overall flow reduction 4. As a result, multiple case reports suggest symptomatic myocardial bridges may cause angina, myocardial ischaemia, acute coronary syndrome, coronary spasms, exercise-induced dysrhythmias, transient ventricular dysfunction, syncope and even sudden cardiac death 5.…”

Myocardial bridge: If you wait longer you can find it!

“…It can be differentiated on the basis of depth and length of the encasement, with different potential factors favoring symptoms occurrence, such as heart rate, left ventricle (LV) hypertrophy, and coronary atherosclerosis. [34]…”