Unroofing of Myocardial Bridging Combined with Septal Myectomy in Hypertrophic Cardiomyopathy: When and How?

Myocardial bridging (MB) describes systolic compression of the epicardial coronary arteries by the surrounding ventricular myocardium. It may affect more than one vessel, but it most often affects the LAD (67–98%). Symptoms may range from none to angina to myocardial infarction or even sudden death. It has been reported in up to 30 percent of patients of hypertrophic cardiomyopathy (HCM). MB may be superficial or deep. Schwartz classification includes three types: Type A (incidental finding on angiography), Type B (ischemia on stress test, and Type C (altered intracoronary hemodynamics).

Myriad tests are used to diagnose MB. This includes coronary angiography, intravascular ultrasound, intracoronary doppler and pressures measurements, multislice computed tomography, cardiac magnetic resonance imaging, and contrast stress echocardiogram.

There are no clear guidelines for indications of unroofing in those with HCM; however, the presence of symptoms—especially angina—constitutes a strong indication for unroofing combined with septal myectomy. Unroofing is the recommended treatment of choice for MB. Coronary artery bypass grafting is not an optimal option as graft patency is low. Coronary artery stenting has risk of stent fracture and restenosis.

Several technical tips and pitfalls are critical when performing unroofing. It is advisable to perform the procedure on the arrested heart. It is important to properly identify the coronary artery via cardioplegic administration, use of intraoperative fluorescent angiography with indocyanine green, and moving from the non-intramyocardial to the intramyocardial segments. It is not advised to directly incise the myocardium on top of the intramyocardial coronary artery as it may result in injury of the coronary artery or ventricular free wall perforation. A combination of Potts scissors and electrocautery are useful for dissection.

This video presents a case of a ten-year-old boy with Noonan syndrome who underwent left ventricular septal myectomy at a different institution and presented with chest pain that occurred with exertion. The chest pain led to repeated hospitalization, and an exercise test was terminated because of the chest pain. Coronary angiography showed significant and long deep myocardial bridge affecting the left anterior descending (LAD) coronary artery.

A repeat sternotomy was performed, and the LAD was completely unroofed. The patient recovered from surgery and has been free from chest pain for the duration of his follow-up.

References

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2. Wang S, Wang S, Lai Y, et al. Midterm results of different treatment methods for myocardial bridging in patients after septal myectomy. Journal of cardiac surgery. 2021; Vol.36 (2): 501-8

3. Said SM, Dearani JA, Burkhart HM, Schaff HV. Surgical management of congenital coronary arterial anomalies in adults. Cardiol Young. 2010;20:68-85.

4. Said SM, Marey G, Hiremath GM. Unroofing of Myocardial Bridging After Septal Myectomy in a Child With Noonan Syndrome. World J Pediatr Congenit Heart Surg. 2021 Sep;12(5):659-660