Contractile function and rhythmicity of cardiac preparations from Escherichia coli endotoxin-shocked guinea pigs

Isovolumic left ventricular (LV) preparations were isolated from guinea pigs 16-18 hr after IP injection of either saline (control groups) or 4 mg/kg of Escherichia coli endotoxin (shock groups). The tissues were then subjected to mechanical performance comparisons in a carefully regulated coronary perfusion system. Endotoxicosis consistently resulted in myocardial contractile dysfunction as evidenced by significantly low values for LV systolic pressure and maximal rates of LV pressure rise (+dP/dtmax) and fall (-dP/dtmax). There was a distinct tendency for spontaneous tachybradydysrhythmias in the shock groups, but the LV contractile deficit was not dependent upon beating frequency. Also, LV function curves (systolic pressure vs end-diastolic pressure) generated by shock hearts were shifted downward and to the right of control curves, in the direction of inotropic failure. Thus, cardiodynamic adjustments during endotoxin shock may reflect and be limited by underlying dysfunction intrinsic to the heart itself; by 16-18 hr, the resulting functional changes in LV myocardium are manifested in an isolated environment and do not depend on depressive constraints operative in the intact host.