Is coronary artery bypass grafting an acceptable alternative to myotomy for the treatment of myocardial bridging?

Abstract

A best evidence topic in cardiothoracic surgery was written according to a structured protocol. The question addressed was 'Is CABG an effective alternative for the treatment of myocardial bridging?' Altogether, only six papers were identified using the reported search that represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes, and results of these papers are tabulated; these studies reported the outcome of myotomy and coronary artery bypass grafting (CABG) for myocardial bridging. All of these studies were retrospective reports of the results of surgical intervention in patients with myocardial bridging. They showed that the incidence of myocardial bridging was less than 1-1.5% in patients with angina requiring angiography, and 7-9% of these patients had refractory angina despite medical treatment and required surgery. The evidence on the treatment of this congenital condition that mainly affects the middle segment of left anterior descending artery is limited, and there are no treatment guidelines currently available. Stenting of the tunnelled segment has shown high failure rates in approximately half of the cases. Current evidence in the literature suggests that surgery is the mainstay treatment for myocardial bridging. Surgery is performed either as supra-arterial myotomy and de-roofing of the muscle bands on- or off-pump, or as coronary artery bypass grafting of the affected coronary artery beyond the tunnelled segment. Although no mortality was reported with either of these operations, surgical myotomy on deep and extensive myocardial bridges carries the risk of entering the right ventricle, bleeding and aneurysm formation. In addition, in a small percentage of the patients undergoing myotomy, angina recurred. Despite the possibility of competitive flow in the native coronary artery after CABG for myocardial bridging, we did not identify any evidence demonstrating graft occlusion after CABG for myocardial bridging. In conclusion, in extensive and deep myocardial bridgings, CABG may be the treatment of choice that carries low risk, limited complications and excellent symptomatic relief.

Surgical Unroofing of Hemodynamically Significant Left Anterior Descending Myocardial Bridges

“…It is also the most stringently evaluated and rigorously defined cohort of myocardial bridge patients available. Published series regarding the surgical or interventional treatment of MBs are limited by inconsistent and subjective evaluation of the pathology creating the possibility of a heterogeneous study population [16][17][18][19]. Furthermore, no previous study utilized a reliable and valid symptom assessment tool, such as the SAQ, to measure differences between the preoperative and postoperative period.…”

“…Coronary artery bypass grafting, with both arterial and venous conduits, has been reported with varying, but limited success. A high percentage of graft failure is noted, more so in the arterial conduits, presumably because of competitive flow [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23].…”

Myocardial Bridging

“…On the one hand, because myotomy attempts to correct the underlying pathology, it may be the treatment of choice for patients who have symptomatic myocardial bridging refractory to medical therapy, ≥75% systolic coronary compression on angiography or evidence of myocardial ischemia or infarction (4). On the other hand, CABG is favored over myotomy in cases of extensive (>25 mm) or deep (>5 mm) myocardial bridges (the risk of myotomy can be considerable), or when the bridged coronary segment fails to decompress completely in diastole (myotomy is unlikely to correct the persistent diastolic compression) (4,8). Importantly, there are no randomized clinical trials comparing intensification of medical therapy to surgical intervention.…”

“…Although myocardial bridges can be found in any epicardial artery, 67-98% occur in the left anterior descending coronary artery (LAD) (5,6). Bridges have been described as superficial or deep based on three observations: 1) they range from 0.3 to 28 mm in depth (4,5), 2) anatomically they consist of either superficial myocardial fibers that traverse over the LAD or deep fibers that encircle the LAD (5,7) and 3) bridges >5 mm deep are less amenable to surgical myotomy (8). The hemodynamic impact of myocardial bridging depends on the thickness and length of the bridge, orientation of the bridge relative to myocardial fibers and presence of loose connective or adipose tissue around the bridged segment.…”

Histological Characteristics of Myocardial Bridge With an Ultrasonic Echolucent Band

“…tional IVUS measurement of systolic arterial compression, may enhance the understanding of this anomaly, provide prognostic information in given patients, and determine the indication and strategy of treatment particularly when unroofing surgery is considered (7-9% of symptomatic MB patients may require surgery due to refractory angina despite medical treatment). 12 For instance, systolic arterial compression can occur without MB, when the coronary segment is located deep within the interventricular gorge. Unroofing surgery is not a treatment option in such cases, which can be readily differentiated on IVUS from arterial compression due to an overlying muscle band.…”