Anatomical Basis for the Cardiac Interventional Electrophysiologist

Figure 3

(a) Frontal view of the heart in a cadaver that has been dissected to show the course of the phrenic nerves relative to the atria and left ventricle. The anticipated location of the sinus node outlined with dots on yellow background. The double-headed arrow represents the sectioning plane used for making the sections through the sinus node and the terminal crest shown in the histological sections. (b, c) Histological sections with picrosirius red stain and polarized light showing variations in locations of the sinus node relative to the epicardial and endocardial surfaces and sizes of the terminal crest. Note nodal extensions (arrows) to superior caval vein, terminal crest, and epicardium. (d) With Masson’s trichrome stain is recognizable a nodal extension to terminal crest by its fibrous matrix (green). (e) Histological section of the nodal body (Masson’s trichrome stain). Note the contour of the node towards the neighboring myocardium (asterisks). Ao = aorta, LPN = left phrenic nerve, and LV = left ventricle. PT = pulmonary trunk, RAA = right atrial appendage, RPN = right phrenic nerve, RV = right ventricle, SCV = superior cava vein, TC = terminal crest, and TV = tricuspid valve.