The peak (dPower/dt), the maximum value of dPower/dt calculated by differentiation of ventricular power with respect to time, is verified from the physiological studies to be quite useful index indicating the ventricular contractility independent of the pre- and afterloads. However, the index has the disadvantage in the clinical application that it can not be measured by a non-invasive method. In the present study, peak (dPower/dt) could successfully be determined in a non-invasive manner as the product of aortic flow as measured with an ultrasonic pulsed Doppler flowmeter and brachial blood pressure as measured with cuff in the new apparatus. Involved in this study were 21 children, 52 adults with normal cardiac performance and 11 adult patients with coronary artery disease. The measurement of the index was successfully carried out in 28 of 61 adults and especially 16 of 21 children. The results of the study are summarized as follows:
1. Power waveform is similar to blood flow waveform and is little influenced by blood pressure waveform.
2, Peak (dPower/dt) can be determined as product of peak rate of change of aortic flow (peak (dF/dt) ) and mean brachial blood pressure without resorting to measurement of blood pressure waveform.
3. Peak (dPower/dt) was found significantly lower in cases having an ejection fraction less than 50% (93.5 J/sec²) than in those showing an ejection fraction of above 50% (145.3 J/sec²) (p<0.001) .
4. Peak (dPower/dt) normalized with body surface area was not significantly different from 8 years old children (80.2 J/sec²/m²) and 21-34 years old adults (88.0 J/sec²/m²) . According to this index, the cardiac contractility of 8 yearus old children seemed to reach the adult level.
From these findings it is concluded that the non-invasive method of determining a cardiologic parameter, peak (dPower/dt), as an index of cardiac contractility provides a means of salient clinical value.