Off-Pump Myocardial Bridge Unroofing

Workup 

The patient was a twenty-nine-year-old man who presented us with a seven-year history of episodic chest pain that radiated to the left neck and arm. The pain was associated with exertion, and only mild improvement of symptoms were noted with medication. He underwent a stress echocardiogram that revealed septal buckling and apical sparing during stress. A CT coronary angiogram confirmed the presence of the myocardial bridge (MB) over the left anterior descending (LAD) coronary artery. It measured 27.6mm from the left anterior descending/left circumflex bifurcation and 24.3mm in length. Jailed septal branches were also noted within the bridge. 

The patient underwent an invasive angiography utilizing intravascular ultrasonography (IVUS) to measure systolic arterial compression, minimal lumen area, myocardial bridge length, and the maximal plaque burden upstream from the bridge entrance. The IVUS map also noted the relationship of the myocardial bridge to diagonal and septal coronary artery branches. 

Here are some measurements related to the case: 

• Systolic arterial compression: 49% 
• Minimal lumen area: 5.8mm^2 
• Myocardial bridge length: 24.3mm 
• Maximal plaque burden: 24.5% located 24.7mm proximal to the myocardial bridge 

The hemodynamic significance of the myocardial bridge was then tested by measuring the diastolic fractional flow reserve (dFFR) utilizing a dobutamine challenge. A dFFR of 0.76 or less is considered hemodynamically significant. The dFFR was 0.57. 

Surgical Technique 

Prior to the operation, a peripheral nerve block was performed at the first thoracic level. Nimbus catheter pumps were placed bilaterally administering lidocaine 0.5% at 15mls q120 minutes. 

A median sternotomy was then performed, and the pericardium was opened in inverted T fashion. Then the heart was positioned to expose the anterior surface of the heart, and the LAD was identified epicardially where it exited the MB distally. A Beaver blade was used to divide the epicardium overlying the LAD where it emerged from the myocardium and the epicardial fat distal to the MB. Upon entering the surgical plane, immediately anterior to the coronary artery, tenotomy scissors were utilized to divide the overlying epicardial fat and MB, moving in a distal to proximal direction in 1mm to 2mm increments until the entire bridge had been released. Epicardial venous bleeding was then controlled with a combination of Bovie cautery, clips, and suture ligation. Upon completion of the unroofing, the length of the unroofed artery was measured to compare with measurements obtained from the IVUS map and CT images. A 24-French Blake drain was then placed and left in the mediastinum. Then, the pericardium was loosely reapproximated over the aorta, and the chest wall was closed in the standard fashion. 

Post-Op Hospital Course and Follow-Up 

The patient was extubated postoperatively and admitted to the floor. The next day the chest tube and nerve block catheters were removed. He was discharged from the hospital the following day. The patient was seen in clinic nine days after the procedure and was recovering well. His chest pain had resolved, and he was able to walk five miles in a day. 

References

1. Hostiuc, S, Negoi, I, Rusu, MC, Hostiuc, M. Myocardial bridging: a meta-analysis of prevalence. J Forensic Sci. 2018;63:1176–1185.
2. Liu, G, Qu, Y, Chen, X. Measurements of myocardial bridges on computed tomography predict presence of clinical symptoms and outcomes of adverse heart events: a retrospective study in a large population from China. Acta Radiol. 2017;58:1068–1076.
3. Loukas, M, Curry, B, Bowers, M. The relationship of myocardial bridges to coronary artery dominance in the adult human heart. J Anat. 2006;209:43–50.
4. Corban, MT, Hung, OY, Eshtehardi, P. Myocardial bridging: contemporary understanding of pathophysiology with implications for diagnostic and therapeutic strategies. J Am Coll Cardiol. 2014;63:2346–2355.
5. Ge, J, Jeremias, A, Rupp, A. New signs characteristic of myocardial bridging demonstrated by intracoronary ultrasound and Doppler. Eur Heart J. 1999;20:1707–1716.
6. Boyd JH, Pargaonkar VS, Scoville DH, et al. Surgical Unroofing of Hemodynamically Significant Left Anterior Descending Myocardial Bridges. Ann Thorac Surg. 2017;103(5):1443-1450. doi:10.1016/j.athoracsur.2016.08.035

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