Novel use of HFUS to identify myocardial bridge

This cardiac case highlights a very interesting paper called: “Epicardial Ultrasound in a Case of Myocardial Bridge and Apical Hypertrophic Cardiomyopathy” by Lindsey Whalen, Stephen Davies, Karen Singh, and Gorav Ailawadi.

In this case, the surgical team used High-Frequency Ultrasound (HFUS) to identify the myocardial bridge and confirm resolution of the compression. Furthermore, epicardial ultrasound was used for guiding the degree of apical resection on the decompressed heart.

Abstract

A 59-year-old male with a history of unstable angina was diagnosed with a myocardial bridge of the left anterior descending artery (LAD) and apical variant hypertrophic cardiomyopathy (AHCM). He underwent unroofing of the myocardial bridge and a left ventricular apical myectomy. Intraoperatively, epicardial ultrasound was used to identify the myocardial bridge with systolic compression of the LAD and confirm the resolution of this compression postoperatively (Image 1).

Image 1: A) A cardiac catheterization image indicates compression (arrow) of the left anterior descending artery (LAD) due to a myocardial bridge.
B) A frame of the Medistim video during systole shows the lumen of the LAD (arrow) is compressed by myocardial bridge above (arrowhead).
C) A frame of the Medistim video post-myectomy shows the LAD (arrow) again in systole, now with a patent lumen with no residual muscle above the vessel.

Furthermore, epicardial ultrasound was used for guiding the degree of apical resection of the decompressed heart (Image 2).

Image 2: A) The pre-apical myectomy TEE mid-esophageal 2 chamber view shows hypertrophied apical myocardium with a classic spade-shaped LV cavity in diastole.
B) A Medistim probe image reveals the thickened apical myocardium (arrow) overriding the narrowed LV chamber (thin line).
C) The post-CPB TEE mid-esophageal 2 chamber view shows an underfilled LV with a slightly higher estimated end-diastolic volume, as compared to pre-CPB imaging. The shape of the LV apical cavity appears normal after surgical reduction of the apical myocardium.

This novel use of intraoperative epicardial ultrasound can help guide surgeons preoperatively and confirm results immediately after an operation.

Summary

Similar to the real time feedback cardiologists get when performing coronary or valvular procedures on the beating heart, epicardial ultrasound gives the surgeon useful real-time guidance intraoperatively that may provide a safer and more effective result.

How the Medistim™ MiraQ was used

The surgical team used HFUS to examine the LAD trajectory and left ventricle apical myocardial thickness. The L15 Ultrasound Imaging probe helped identify the LAD under a layer of epicardial adipose tissue and traced the LAD more proximally to locate the myocardial bridge. The LAD was almost fully blocked during systole but open during diastole (Video 1).

At the end of the procedure Imaging of the LAD was repeated and showed a patent vessel in both systole and diastole (Video 2).

The L15 Ultrasound Imaging probe was also used to help guide the resection of the hypertrophic apex. After coring out the apical septum and walls the HFUS was used to confirm good residual left ventricle wall thickness (Video 3).

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Reference

Epicardial Ultrasound in a Case of Myocardial Bridge and Apical Hypertrophic Cardiomyopathy

Lindsey Whalen, Stephen Davies, Karen Singh, et al. Epicardial Ultrasound in a Case of Myocardial Bridge and Apical Hypertrophic Cardiomyopathy. J Card Surg. 2020 Aug;35(8):2041-2043.

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