Histopathologic studies of the conduction system in marked left-axis deviation

Abstract

The histopothologic changes of the left ventricular (LV) conduction system were studied in 11 autopsy cases with, marked left-axis deviation (LAD). In all cases the LV conduction system was fanlike and spread broadly over the left septal surface. However, the sizes and sites of the histopathologic lesions varied. In 2 cases the lesions were small and localized at, the initial portion of the LV conduction system, wereas in 9 cases the lesions were located more peripherally and were more extensive, especially in 2 cases in which the lesions were mainly localized in the apical third of the LV conduction system. These differences in the sizes of lesions were believed to be due to the anatomic structure of the conduction system. At the initial portion of the LV conduction system, cells were oriented longitudinally with collagen partitions, which presumably resulted in functionally longitudinal dissociation. The variability in the lesions in these patients may explain why prognosis in terms of development of complete heart block is not always poor in patients with LAD and right bundle branch block.