Non-invasive evaluation of left ventricular power output by simultaneous recordings of applanation tonometry and echocardiographic Doppler signals

Ventricular hydraulic power is defined as the instantaneous product of flow and pressure at the aortic root. This paper describes a system for non-invasive determination of LV power output based on simultaneous acquisition of applanation tonometry for aortic blood pressure (BP) evaluation and echo-Doppler signals for flow measurement. Acquisition is performed with a dedicated A/D system allowing on-line visualisation of Doppler power spectra and calibrated tonometric signals (using mean and diastolic cuff BP at the brachial level). Aortic BP is estimated either using an aorto-radial transfer function, either untransformed carotid BP. This method has been investigated in 10 normal volunteers. Visualisation of calibrated data during acquisition allowed recordings with a low variability (mean standard deviation of reconstructed systolic BP<5 mmHg). The expected increase in systolic BP was observed from carotid to radial sites. The mean peak power was 6±2 W