Yutaka Senda

Estimation of the Hydromotive Source Pressure from Ejecting Beats of the Left Ventricle

The relationship between peak isovolumic developed pressure (Pmax) and end-diastolic volume can indicate ventricular contractility. Therefore, we propose a practical method to estimate Pmax from the pressure curve of an ejecting contraction of left ventricle. For the estimation, we first considered the left ventricle a linear time varying hydromotive pressure source (HMP(t)) coupled in series with an internal impedance. To formulate the HMP(t) we Fourier analyzed isovolumic pressure curves obtained under various conditions in six dogs. Since the higher order harmonics were found to be very small, HMP(t) could be described simply as where Pd = end-diastolic pressure and w = 2/T in which T is duration of contraction. Finally, HMP(t) for ejecting contraction was estimated by fitting the equation to the isovolumic portions of the pressure curve of ejecting contractions. The estimated Pmax values correlated well with actually observed Pmax values (r = 0.951, N = 24). We conclude that the proposed technique can be used to estimate Pmax from a single ejecting beat.

Real-time measurement of the spatial magnitude of the ST segment with the automated vectorcardiographic ST segment analyzer.

ST segment deviation has been used as an indicator of the degree of myocardial ischemic injury. An automated vectorcardiograph, i.e., an ST segment analyzing system developed in our laboratory, was applied to experimental coronary artery occlusion in dogs, and continuous real-time measurements of ST segment deviation were undertaken. ST segment deviations of the X, Y and Z leads of the Frank lead system were measured and averaged during eight-second periods (STX, STY and STZ). From the ST segment deviation in three dimensions, the spatial ST magnitude and the direction of ST segment deviation (azimuth and elevation) were computed with the use of a microcomputer. The spatial changes of the ST segment after the occlusion of the coronary arteries in the experimental animals were quite compatible with the site of the occlusion. In addition, various interventions influenced the spatial magnitude of the ST segment resulting from coronary artery occlusion.