Relating mechanics, blood flow and mass transport in the cardiac muscle

Abstract Myocardial mechanics, perfusion and across-capillary mass transport are functionally related. The effects of these interacting phenomena on the performance of the left ventricle (LV) are investigated here. The effect of fluid balance on the diastolic and systolic intramyocardial pressures ( IMP ) and the interstitial and myocardial volumes as well as the global ventricular mechanics are of particular interest. The LV is approximated by a cylindrical geometry, containing blood vessels imbedded in the interstitial fluid and a fibrous matrix with active and passive elements. The coronary circulation is described by pressure dependent resistance-capacitance analog elements. Fluid and mass transport are calculated assuming an ideal semipermeable capillary wall and the lymphatic drainage depends linearly on the IMP . Changes in lymphatic flow are used to simulate edema formation, and its effects on myocardial mechanics and coronary flow. The empty beating and isovolumic contracting hearts are studied under constant coronary perfusion pressures. The model successfully predicts the corresponding changes of the coronary flow, the IMP , the LV pressure and the ventricular compliance. The simulated effects of a transient contractile dysfunction on the dynamics of fluid transport and coronary flow are in agreement with experimental data.