The Cardiac Pre-ejection Period

The relationship between peak ascending aortic blood-flow acceleration and the cardiac pre-ejection period (PEP) was studied in five chronically prepared dogs. Acceleration was measured as the first derivative of the signal from a flow probe placed around the aortic root. PEP was derived indirectly by subtracting left ventricular ejection time (obtained from a central arterial pressure signal) from the total active electromechanical time (the Q-S2 interval measured from the ECG and heart sounds). Resulting values of PEP were inverted and squared so that they shared a common time unit with acceleration-time−2. Comparison of 1/PEP2 and peak acceleration produced correlation coefficients from 0.74 to 0.96. A linear relationship between these two measurements was maintained over a sixfold change in the inotropic state of the heart. The quotient 1/PEP2 appears to be an easily obtainable, potentially noninvasive expression of the myocardial contractile state.