Preferential conduction in the atria: clinical implications

There are areas in the heart, and especially the atrial walls, where cardiomyocytes are aggregated together in a parallel fashion, producing preferential pathways for conduction. Although aggregated together, however, the cardiomyocytes lack the insulation that is the characteristic feature of the 'specialized' ventricular conduction system. This review presents the anatomical and histological evidence that emphasizes the fundamental differences between preferential conduction across the atrial walls, as opposed to 'specialized' activation of the ventricular myocardium. With the advent of novel techniques, it may well prove possible to identify particular features of the histologically indistinct cardiomyocytes making up the atrial walls that influence their speed of conduction and hence perhaps underscore a mode of 'functional' specialization, but as yet such evidence remains lacking.