Altering hemodynamic conditions and contractile state adjusted the duration of each phase of left ventricular systole in denervated dog hearts.
The duration of left ventricular systole phases dynamically adjusts to changing hemodynamic conditions and myocardial contractile state.
The effects of altering stroke volume, aortic pressure and heart rate on the duration of each phase of left ventricular systole were investigated in a denervated dog heart. Augmenting stroke volume was found to prolong ejection, shorten the isovolumic period and had little or no effect on the duration of total systole. Elevating mean aortic blood pressure shortened ejection time, prolonged the isovolumic phase and either had no effect or decreased slightly the duration of total systole. Increasing heart rate at constant aortic pressure and stroke volume reduced the duration of all phases of systole. Digitalis and norepinephrine shortened all phases of systole. These findings demonstrate that the duration of each phase of left ventricular systole is dependent upon existing hemodynamic conditions as well as on the contractile state of the myocardium. By means of intrinsic mechanisms the ventricle exhibits the remarkable capability of being able to adjust the duration of each phase of systole in a manner appropriate to changing hemodynamic conditions.
Wallace et al. (1963) studied Hemodynamic conditions in left ventricular systole. Altering stroke volume, aortic pressure, heart rate, digitalis, and norepinephrine was evaluated on Duration of each phase of left ventricular systole. Altering hemodynamic conditions and contractile state adjusted the duration of each phase of left ventricular systole in denervated dog hearts.