Sihler’s stain visualization of myelinated cardiac plexus fiber attenuation in the AV node and the mitral valve as a result of heart failure

A whole organ staining of myelinated cardiac plexus nerve fibers was conducted to visualize the cardiac innervation pathways in relation to heart failure. This visualization could better inform treatment for heart failure and contributory conditions, including arrhythmia, valve disease, and coronary artery disease. Two pathology-free human cadaveric heart specimens and one acute heart failure human cadaveric heart specimen were acquired as opportunity samples. One pathologyfree specimen was sectioned into three transverse slabs prior to staining, while the remaining pathology free specimen and the acute heart failure specimen were stained whole. Sihler's stain rendered the myocardium semi-translucent red-pink to purple, while the myelinated cardiac plexus fibers were stained a deep violet. Definitive nerve density was found in three major locations: along the coronary vessels, at the mitral valve, and in the ascending aorta, including the aortic valve. The Sihler's nonspecific staining of myelin indicates the presence of sympathetic and/or parasympathetic fibers. The pathology-free and diseased specimens were compared to determine what effect heart failure had on innervation patterns. Notable differences were found in the left anterior descending coronary artery, the atrioventricular (AV) node, the left ventricle, the mitral valve, and the pulmonary trunk. The diseased heart showed attenuated nerve staining in both the AV node and mitral valve, supporting the relationship between parasympathetic withdrawal and heart failure.