Mechano-Electric Feedback in the Heart: Evidence from Intracellular Microelectrode Recordings on Multicellular Preparations and Single Cells from Healthy and Diseased Tissue

We report on studies applying intracellular microelectrode recordings and whole-cell current measurements to investigate the effect of mechanical stretch on the electrical properties of cells from normal and diseased heart. Imposing physical stretch on atrial and ventricular tissue specimens elicited stretch-induced depolarizations (SID) of cardiomyocytes. Extra-action potentials occurred in the multicellular tissue preparations when the SIDs reached a threshold potential. Isolated cardiomyocytes responded to stretch with membrane depolarization, prolongation of their action potential (AP) and extra-APs that correlated with the amplitude of a non-selective stretch-activated current (I). At negative potentials, I was negative and carried by a transmembrane influx of Na ions, which induced diastolic depolarization or SID. Whilst the reaction of cardiomyocytes to mechanical stretch was independent of their spatial orientation (edgewise or broadwise), their response to compression was different and determined by the relative position of each cell. The sensitivity of the AP to mechanical stretch was significantly increased in hypertrophied myocardium, and this could be related to the expression of SACs.