Perfusion-fixation of the heart and its conduction system for ultrastructural studies.

Nine hearts from children who died from noncardiac causes were perfused within 3 h of death with 2.5% glutaraldehyde, 0.1 M sodium cacodylate, pH 7.2, at 4 degrees C. Each heart was perfused continuously for 4 h using a perfusion pressure of 110 mm Hg. The ultrastructural characteristics of the perfused atrial and ventricular myocardium and conduction system, including sinoatrial, atrioventricular node and Purkinje fibers, were studied. These observations were compared with standard published observations on similar tissues. The results demonstrate that the present method yields comparable results and hence provides a simple, yet effective, means for studying ultrastructural aspects of the heart and its conduction system in children. In addition, this method permits satisfactory gross morphologic examination of the organ.