Contractile Differences in Left and Right Ventricles of Healthy Human Hearts

Abstract

Left ventricle (LV) and right ventricle (RV) differ in embryology, structure and function. Left ventricle originates from the primary heart field while right ventricle originates from the secondary heart field. The two heart fields express different sets of transcription factors and signaling molecules. At the molecular level, the gene expression in response to the pressure loading and failure is different in both ventricles. They also exhibit differences in response to adrenergic stimulation. Adrenergic agonist increase LV contractility but RV contractility may be reduced. Performing different functions, these ventricles have differences in the resistance offered by the systems they pump blood to. The force and tension developed in each ventricle also varies. Although numerous studies have been performed at macroscopic (whole organ) level previously, none (to my knowledge) address the differences at a mesoscopic level, where only a few molecules are investigated. This becomes important, as in macroscopic studies there may be differences due to basic fiber structures, differences in orientation of fibers as well as molecular crowding. These differences were investigated at the level of few molecules by sparsely labeling the myosin lever arm with SeTau 647 Maleimide. The kinetics and distribution of cross-bridges were examined in healthy ex-vivo human ventricles and differences were compared in LV and RV. The results suggest that there is a significance difference in the cross bridge order of left and right ventricles. In particular, the cross bridges of left ventricles were better ordered when compared to those of right ventricles.