Myocardial Depression

Previous studies from this laboratory described myocardial depression in an arterially perfused rabbit interventricular septum following perfusion with acute septic plasma. Calcium is critical for maintenance of cardiac contractility on a beat-to-beat basis. We have investigated calcium flux in the septal tissue to determine whether altered calcium flux explains the impaired cardiac function during sepsis. Twenty-two rabbit septa were perfused with control and septic perfusate (cryo-precipitated plasma + RBCs) and calcium flux determined in seven experiments. Perfusate cations (Ca++, Na+, K+, and H+) were measured, tissue function and arterial pressure were monitored. Developed tension decreased 46%, acceleration of tension change fell 42%, and arterial pressure decreased 26%, all highly significant. All septa recovered after return to control perfusate. The septic perfusate Ca++ was significantly lower than control perfusate, while K+ and H+ were significantly elevated. Ion flux studies, however, could not demonstrate altered calcium flux associated with the depressed contractility.