Hideichi Kamada

Onset of pulsatile waves in the heart walls at end-systole

We have previously developed a novel ultrasonic method, namely, the phased tracking method, for accurately tracking the movement of the heart wall based on both the phase and magnitude of the demodulated signals to determine the instantaneous position of an object. With this method, it is possible to accurately detect small-amplitude velocity signals of less than a few micrometers of the heart wall that are superimposed on the motion of the heart wall due to the heart beat. There are several remarkable pulsatile waves during one cardiac cycle in the resultant velocity signals, some of them being commonly obtained for both healthy subjects and patients. These pulsatile waves cannot be recognized in standard echocardiography M-mode images. In this paper, by focusing on one pulsatile wave that occurs around the end-systole, the physiological meaning of these is considered based on various in-vivo experiments. The pulsatile wave measured by this novel ultrasonic method will offer potential for a quantitative assessment of myocardial viability.

Non-invasive estimation of human left ventricular end-diastolic pressure

Sato et al. (Electronic Letters 32, 949-950, 1996) reported that one can obtain a non-invasive estimate of left ventricular (LV) pressure at around end-diastole in an isolated canine preparation. In this study we examined whether this method can be applied to humans. Using the method proposed by Kanai et al. (IEEE. Trans. UFFC, 43, 791-810,1996), we detected small amplitude LV vibration from an ultrasonic pulse Doppler signal reflected from the interventricular septum in five patients (44-63 y.o., male;4, female;1). We measured the oscillation frequency of the LV wall through the wavelet transform of small amplitude LV vibration, and calculated LV pressure at around end-diastole from the values of oscillation frequency, internal radius and wall thickness using Mirskys equation. The estimated LV pressures at around end-diastole were similar to end-diastolic pressure measured directly by cardiac catheterization. These results show the possibility that this method allows for the non-invasive estimate of LV pressure at around end-diastole, and furthermore provides the basis for future clinical applicability of this technique.

Regional myocardial layer function in Doxorubicin cardiomyopathy; clinical evaluation using novel ultrasonic Doppler method

We examined whether the novel Doppler technique could be a sensitive diagnostic method for the histological deterioration of Doxorubicin cardiomyopathy (DoxCM). 25 patients with acute lymphoblastic leukaemia were examined for six years. Moreover, in Doxorubicin injected rabbits, histological damage was compared to the myocardial layer function by the Doppler technique. In normal subjects, myocardial layer thickening occurred in a synchronized fashion during the cardiac cycle. However, in patients, it was characterized by the appearance of a non-functioning layer in the septum. The conventional echocardiography could not be sensitive enough to demonstrate the change in DoxCM. In contrast, the myocardial layer function by this novel method obviates subclinical change in the myocardium. The histological examination in rabbits verified the linear relationship between the myocardial damage and the myocardial layer function. We concluded that the novel Doppler technique could be a useful modality for the histological change in DoxCM.