The ventricular conduction system - ultrastructure and function

Sudden cardiac death associated with hypoplasia of the coronary arteries and conduction system alteration

We present a case of sudden cardiac death in a 24-year-old woman with evidence of hypoplasia of the left anterior descending (LAD) and posterior descending (PDA) coronary arteries. These vessels averaged 0.7 mm in internal diameter combined, in contrast to an average of 2.4 mm in control coronary arteries (p < 0.001). The myocardium exhibited areas of acute and chronic ischemic change. Also, the cardiac conduction system (CCS) had diffuse cellular enlargement, believed to be secondary to ischemia. The cells of the sinoatrial node (SAN) and the Purkinje cells of the proximal right bundle branch (RBB) averaged 28.5 and 25.6 microns, respectively. These were significantly larger than the SAN cells (21.6 microns, p = 0.002) and larger than the Purkinje cells (15.9 microns, p = 0.012) of control cases. We report that hypoplastic coronary artery disease is a cause of sudden death, is associated with varying degrees of ischemic change in the heart, and can be associated with condition system alteration.

The development of Purkinje fibres and ordinary myocytes in the bovine fetal heart. An ultrastructural study

A comparative ultrastructural study of bovine Purkinje fibres and ordinary myocytes during fetal development has been undertaken. Differences between the two cell types with respect to the intercalated disc, amount of myofibrils, arrangement of mitochondria, amount of glycogen and formation of T-tubules became apparent gradually. In all stages studied an abundance of intermediate filaments was typical for the Purkinje fibres. Myofibrillar M-bands developed at an earlier stage in Purkinje fibres than in ordinary myocytes. Myofilament-polyribosome complexes typical of adult cow Purkinje fibres were not observed in the fetal hearts. Only in late fetal stages were leptofibrils observed in both cell types. We conclude that in the bovine heart Purkinje fibres develop along a different pathway from ordinary myocytes.