[A cardiodynamic study on cardio-assistive effect of the assist device: evaluation on left ventricular dehematizing...

Of late years, assist artificial heart device has been more and more investigated with subsequent reports being made of its clinical application. Dehematization of left ventricular assist device (LVAD) is divided into two systems, i.e., left atrial dehematization and left ventricular dehematization according to the location of the canula's tip. At present in our country, the former system is being adopted for the majority of LVADs and is generally regarded as preferably acceptable. However, because of low survival rate of LVAD in spite of its comparatively good rate of break-away, not a few cases appear to exist beyond the limit of the former system's effects. Then, compared with the left atrial dehematizing system, LVAD according to the left ventricular dehematizing system was examined for its cardio-assistive effect both blood circulatorily and cardiodynamically. A pneumatically-driven diaphragm type pump was implanted between the left ventricular apex and the descending aorta of a dog and was driven by ECG-synchronous counterpulsation method with heart rate versus pump beating number ratios of 1:1, 2:1 and 4:1 and fixed beating number method with beating number of 60 and 80 beats/min (bpm). In order to measure the left ventricular diameter and myocardial length, 7 pairs of ultrasonic sonomicrometers were embedded intra-left ventriculomurally. Ischemia was prepared by ligating the left anterior descending coronary artery (LAD). Bulk mechanical work and regional mechanical work were calculated from these dimensions and the left ventricular pressure. The following results were obtained: 1) In all driving modes but that of 4:1, compared with non-driven pumping, heart rate, peak left ventricular pressure, mean left atrial pressure and total peripheral resistance showed low values, and mean aortic pressure and total blood flow showed high values. Moreover, in the above driving modes, total bypass was obtained. 2) In the above driving modes, bulk and regional mechanical works were practically null with a de-loading effect of 100% or so being obtained. 3) Compared with the left atrial dehematizing system, peak left ventricular pressure showed remarkably low value with increases in mean aortic pressure and total blood flow, and with remarkable decreases in bulk and regional mechanical works. 4) In driving modes of 2:1, 1:1, I60 and I80, little difference in the effect according to the driving mode was noted.(ABSTRACT TRUNCATED AT 400 WORDS)