This series of 4 photos shows a dissection of the left bundle branch covered by the subaortic muscle. This anatomic structure is present in 20% of the hearts. This band of muscle seems to be put just to protect the left bundle for the injury of the stent during TAVI procedures. Seems also to be in a bad place if this bundle is hypertrophic and generates an intermitent left bundle block. Nobody knows. By pure luck, this is an anatomical website and I have the option to only show not think about what I am showing.
The four potos show a human heart, the left side view with the septum, the left atrium and ventricle. The two papillary muscles of the mitral valve are seen and the anterior mitral valve (AMV) is marked. Th membranous septum (ms) separates the noncoronary from the right coronary (rcs) sinus of the aortic valve.
This is THE relationship of the heart conduction system. The surgeon must imagine –or best- know where is the left bundle in a surgical position guided by this anatomical view.
The surgeon also has to be in view of the (1) left circumflex artery and its relation with the mitral “annulus

Image #66