Temperature distribution within the left ventricular wall of the heart

Abstract The instantaneous local temperature T throughout the left ventricle (LV) wall is obtained by solving the energy balance equation, accounting for the instantaneous spatial heat generation within muscle wall. The distributed oxygen demand as well as time dependent local coronary perfusion, which are based on a previously described mechanical model of the LV, are used as input parameters to the heat equation. Approximations of the local time averaged and the time-dependent temperatures are computed for two types of experimental boundary conditions simulating (a) closed chest heart (given epicardial T ) and (b) an open chest heart (exposed to air with free convection). The effects of the heart rate and the local blood perfusion rate on T are investigated. The local temperature is found to be practically unchanged throughout a cycle, with changes which are typically smaller than 0.005°C during a cycle. However, the temperature varies with the location within the myocardium and attains its maximum value at the mid-layers. For a closed chest heart, an approximation of the instantaneous temperature based on the ‘average’ solution is found. In case of an open chest heart, it is shown how T in the epicardium can define the temperature distribution throughout the entire muscle wall. The calculated results are found to be in fair agreement with experimental studies in dogs.