Depressed function of isolated hearts from hyperdynamic septic rats

The aim of this study was to determine if hearts removed from rats in sustained hypermetabolic sepsis possessed normal physiological reserves as defined by Frank-Starling curves. The resting cardiac output of these hearts is elevated in vivo and this is mediated by an increased heart rate. In this study mechanical function was assessed under in vitro conditions in which preload could be varied and controlled. Isolated perfused working hearts from septic animals showed depressed cardiac performance, both in terms of peak systolic pressure development and cardiac output, over a range of left atrial filling pressures. In spite of this depressed function, most hearts from septic animals were able to recover cardiac output and pressure development following an acute ischemic episode. Thus, a loss of myocardial reserve is demonstrable in hearts isolated from septic rats, even though mean arterial blood pressure, cardiac output, and coronary blood flow are well maintained in vivo. This dysfunction is primarily evidenced by an inability to respond appropriately to increased preloads.