The putative contribution of mechanosensitive fibroblasts to mechanically induced electrophysiological disturbances observed in ischemically damaged or scarred tissue has yet to be elucidated experimentally. Damaged tissue is expected to display reduced contractility and to contribute less to ventricular muscle shortening. Measurements in human patients with angiographically documented regional ventricular ischemia, performed by high temporal resolution magnetic resonance tissue tagging, have shown decreased mechanical function within regions of ischemically damaged tissue. Seventy-five per cent of these patients showed ‘paradoxical deformation’, defined as distension rather than contraction of the damaged myocardium during systole . We hypothesized that this type of localized stretch stimulus could initiate MEF in mechanically less active regions during cardiac contraction .To investigate the potential impact of mechanosensitive connective tissue, stretch was applied in the model to fibroblasts exclusively. In the model a fibrotic region of between 20 and 35 cells in diameter was implemented into the centre of a network of over 16,000 cardiomyocytes, which imposed a hyperpolarizing – and therefore functionally anti-arrhythmic – load on the damaged tissue. The simulations demonstrate that mechanical stimulation of the fibroblasts is capable of triggering local depolarization, local action potentials and, if size of fibroblast-rich region and stretch amplitude are big enough, generalized ventricular excitation. The minimum size for such response to occur is alarmingly low. A region as small as 30 cells in diameter may constitute a focus for mechanically induced ectopic excitation. It is worthwhile to remember that such a region would occupy a surface area of less than 1 mm . Experimental investigations into the electrophysiological substrate of disturbances in ventricular rhythm, performed in vitro and in vivo, have already shown that comparatively small regions may be capable of triggering ventricular tachycardia . These very small regions of damaged cardiac tissue could conceivably constitute a histological substrate for the origin of sudden cardiac death. You will always come across generic viagra online at a pharmacy that will offer best deals.