Analysis of Left Ventricular Pressure Pulses and Characteristics of Catheter-Manometer System

Abstract

Dynamic response of the fluid-filled catheter-manometer system was assessed by means of sinusoidal and rectangular pressure generator. The frequency response curves were found to be independent of the amplitude of the input sinusoidal pressure waves. Thus the evidence indicated that the catheter-manometer system was essentially linear. The performance of the catheter-manometer system suggested that it could be treated as an equivalent second order system at low frequencies. Typical pressure from various left ventricular pulses of the dogs obtained from a catheter-tip manometer were digitized and analyzed by Fourier analysis on a digital computer in order to determine the modulus of each harmonics and the number of harmonics necessary to construct accurate pressure waves. It was shown that resynthesis of the pressure recorded from the first 6-10 harmonics accurately reproduced systolic pressures. However resynthesis of the first 10-24 harmonics was necessary for accurate reproduction of waveform and first derivative of it.
Then, various left ventricular pressure waves of eight dogs obtained with eight catheter-manometer systems whose undamped natural frequencies were 19 to 64 Hz, were digitized and analyzed by Fourier analysis and the left ventricular pressure curves and their derivatives were resynthesized using the first 20 harmonics whose distortions of amplitude and phase lags were corrected according to the frequency response curve of the catheter-manometer system. Thus the pressure waves obtained from the catheter-manometer system were corrected and the comparison of the max dP/dt of the corrected pressure waves with the standard system resulted in a correlation coefficient of 0.987.