Some aspects of cardiac heterogeneity.

It is remarkable that the heart, which obviously functions as a homogenous pump, shows such a high degree of heterogeneity. There are often contradictory or controversial results as far as transmural gradients are concerned (78). These discrepancies or inconsistencies, however, can at least in part be explained by species differences. Of particular interest is the heterogeneity that is due to the separation into two hearts. In view of the differences in the morphology and function of the left and right heart, it is surprising that the whole organ works in a rather homogenous fashion. In the past, the right heart has received not as much attention as the left heart. This is in particular true for small laboratory animals. It becomes more and more evident that compared to the left ventricle, the right ventricle reacts to various stimuli in a quantitatively different manner. More research on the right heart is therefore needed. Collectively, the data summarized in this article may be interpreted in that the heart not only works as a homogeneous unit, but may even benefit from the heterogeneity of its different parts or subunits under normal as well as under various pathophysiological conditions. Analysis of the processes involved in creating cardiac heterogeneity can provide new insights into the mechanism of adaptation of the heart.