Fujio Miyawaki

Influence of static pressure and shear rate on hemolysis of red blood cells.

The purpose of this study was to investigate the effect of multiple mechanical forces in hemolysis. Specific attention is focused on the effects of shear and pressure. An experimental apparatus consisting of a rotational viscometer, compression chamber, and heat exchanger was prepared to apply multiple mechanical forces to a blood sample. The rotational viscometer, in which bovine blood was subjected to shear rates of 0, 500, 1,000, and 1,500 s-1, was set in the compression chamber and pressurized with an air compressor at 0, 200, 400, and 600 mm Hg. The blood temperature was maintained at 21°C and 28°C. Free hemoglobin at 600 mm Hg was observed to be approximately four times higher than at 0 mm Hg for a shear rate of 1,500 s-1 (p < 0.05). The results suggest that the increase in hemolysis is strongly related to pressure when high shear rates are applied to the erythrocytes. The data acquired in this study will be helpful in the development of artificial organs, where it will facilitate the prediction of hemolysis in flow dynamics analysis, flow visualization, and computational fluid dynamics.

Recovery directed left ventricular assist device: a new concept.

To promote cardiac recovery, we developed a recovery directed left ventricular assist device (RDLVAD) that consists of a valved apical conduit, an afterload controlling chamber (ACC), and a pump. We evaluated its efficacy by comparison with an ordinary LVAD. In each of six pigs with ischemia-induced heart failure, flow and pressure measurements were made while maintaining the total blood flow and arterial pressure equal in the two groups. RDLVAD was able to direct all the blood ejected from the LV into the ACC (0-15 mm Hg) but not into the aorta (73 mm Hg). In the ordinary LVAD, however, some ejection occurred into the aorta despite vigorous suction of the LV. Thus, RDLVAD increased DPTI/SPTI 2.3 times (p < 0.005) and decreased left ventricular end-diastolic pressure by 40% and maximum dP/dt by 20% (p < 0.05). Even the apical valve, at approximately half the diameter of the aortic valve, was able to allow all the blood ejected from the LV to enter the ACC. In one control group pig that achieved almost no ejection into the aorta, left ventricular relaxation and dilatation was extremely limited. RDLVAD may promote cardiac recovery by ensuring less LV work, a greater blood supply/demand ratio in the coronary circulation, and full ventricular relaxation.

Removal of trypsin complexed alpha-2 macroglobulin by plasma fractionation.

Ischemia-reperfusion injury in open heart surgery can cause atherosclerotic changes in both bypass grafts and native coronary arteries by increasing endothelial permeability and allowing excessive influx of LDL into the subendothelium. The authors used LDL apheresis during cardiopulmonary bypass (CPB) to actively remove serum LDL before reperfusion, minimizing LDL influx. They evaluated the efficacy and safety of this new procedure in eight hypercholesterolemic patients. The control group consisted of 41 patients. Mean LDL cholesterol (LDL-C) level on admission was 180 +/- 41 (SD) in the LA group and 139 +/- 32 mg/dl in the control group (p = 0.02). After 105 +/- 27 min of apheresis, the LDL-C level in the LA group decreased to 62 +/- 25 mg/dl (reduction rate: 59 +/- 18%). In contrast, in the control group, the LDL-C level was reduced to 117 +/- 41 mg/dl (reduction rate: 16 +/- 9.5% [P = 0.0001]) after CPB. No significant difference was observed in intraoperative blood loss, postoperative blood loss, platelet count, prothrombin time, activated partial thromboplastin time, incidence of wound complications, or early patency rate of bypass graft between groups. Low density lipoprotein apheresis during CPB is a safe and effective method for lowering serum LDL level sufficiently before reperfusion, and can adequately reduce LDL influx into the vessel wall.Ischemia-reperfusion injury in open heart surgery can cause atherosclerotic changes in both bypass grafts and native coronary arteries by increasing endothelial permeability and allowing excessive influx of LDL into the subendothelium. The authors used LDL apheresis during cardiopulmonary bypass (CPB) to actively remove serum LDL before reperfusion, minimizing LDL influx. They evaluated the efficacy and safety of this new procedure in eight hypercholesterolemic patients. The control group consisted of 41 patients. Mean LDL cholesterol (LDL-C) level on admission was 180 +/- 41 (SD) in the LA group and 139 +/- 32 mg/dl in the control group (p = 0.02). After 105 +/- 27 min of apheresis, the LDL-C level in the LA group decreased to 62 +/- 25 mg/dl (reduction rate: 59 +/- 18%). In contrast, in the control group, the LDL-C level was reduced to 117 +/- 41 mg/dl (reduction rate: 16 +/- 9.5% [P = 0.0001]) after CPB. No significant difference was observed in intraoperative blood loss, postoperative blood loss, platelet count, prothrombin time, activated partial thromboplastin time, incidence of wound complications, or early patency rate of bypass graft between groups. Low density lipoprotein apheresis during CPB is a safe and effective method for lowering serum LDL level sufficiently before reperfusion, and can adequately reduce LDL influx into the vessel wall.

Evaluation of recovery directed left ventricular assist device using isolated perfused rabbit hearts.

We have developed a recovery directed left ventricular assist device (RDLVAD) that can promote cardiac recovery by achieving very low ventricular work and ensuring full ventricular relaxation and filling. It consists of a valved apical conduit, an afterload controlling chamber, and a centrifugal pump. To test the previously described effects of RDLVAD on the left ventricle, we made an RDLVAD suitable for isolated perfused rabbit hearts. The control LVAD was of a continuous flow type (CLVAD). Thirty-two rabbits were used. The working left heart model proved inappropriate for evaluation of LVAD. In the isolated heart-lung preparation (n = 4), the CLVAD showed a substantial backward flow and a severe negative pressure during diastole. This negative pressure may have resulted in severe restriction of ventricular relaxation and filling. In contrast, in the RDLVAD with the afterload controlling chamber pressure kept as low as possible, the pump flow was stable and increased by 86% (NS), and the peak left ventricular pressure, max dP/dt, and systolic pressure time index decreased by 22.3% (p = 0.022), 29.4% (p = 0.017), and 42% (p = 0.022), respectively. In conclusion, these results indicate that the RDLVAD does not restrict ventricular relaxation or filling and greatly reduces ventricular workload. The RDLVAD, therefore, can promote cardiac recovery.

Development of cardiac massage vest system

Summary form only given. We developed a new CPR system and evaluated it on a dummy for CPR training. This main feature is a cardiac massage vest that consists of front and rear boards and their connecting belts. A bellows-type air bag placed between the front board and the sternum is inflated and deflated by a controller connected to a high-pressure air or oxygen supply from an air compressor. (for hospital use) or gas cylinder (for ambulance use). Results 1) Set-up for use on a patient took only less than 20 sec. 2) Stable and effective chest compression meeting AHA standards was obtained without crawling of the air bag even in the prone, lateral or sitting, position. 3) Patch-type electrodes developed for defibrillation and ECG monitoring allowed defibrillation while the vest was in place. 4) Cardiac catheterization can be performed during automatic cardiac massage because cardiac massage in a thin and fragile fluoroscopy table was possible with this system. 5) A pressure-limited ventilator gave an adequate minute volume without any pause in cardiac massage.