Microcirculation of the Bulbar Conjunctiva in the Goat Implanted with a Total Artificial Heart: Effects of Pulsatile and Nonpulsatile Flow

Abstract

A new system toI observe the microcirculation on the bulbar conjunctiva was developed using a digital high definition microscope to investigate the influence of the flow patterns on the microcirculation in a goat with a total artificial heart (TAH). The undulation pump TAH was implanted into the goat. When the whole body condition became stable, the flow pattern was modulated between the pulsatile and the nonpulsatile mode, and the changes in the microcirculation were observed. When the flow pattern was changed from pulsatile to nonpulsatile mode, the erythrocyte velocity in capillaries dropped from 526 Ϯ 83 to 132 Ϯ 41 m/s and remained at a low level. The number of perfused capillaries decreased as well. Then the nonpulsatile flow mode was maintained for 20 minutes. After the flow pattern was returned to the pulsatile mode again, the erythrocyte velocity recovered to the initial level (433 Ϯ 71 m/s). In many cases, the flow of the nonperfused capillaries in the nonpulsatile mode recovered to the initial level after the flow pattern was changed to the pulsatile mode again. The perfused capillary density in the nonpulsatile mode (19.7 Ϯ 4.1 number of capillaries/mm) was significantly lower than that in the pulsatile mode (34.7 Ϯ 6.3 number of capillaries/mm).It is thought that the basal and flow stimulated endothelium derived nitric oxide release in the microvessels decreased because of the disappearance of pulsatility and that the nitric oxide induced the constriction of arterioles after the flow pattern was changed to the nonpulsatile mode. At the same time, the baroceptors might sense the decrease in the arterial peak pressure or dp/dt, and the sympathetic nerve increases activities and induce the constriction of arterioles. Then, the erythrocyte velocity in capillaries would decrease. Because of the flow pattern further in the chronic phase, it is important to follow the change in the microcirculation. ASAIO Journal 2004; 50:321-327. mplantation of the total artificial heart (TAH) triggers complex responses in the recipient's organism. Therefore, an important question is whether the microcirculation (MC) of the animal with a TAH is kept normal . The physiologic relations of the cardiovascular system can be changed and can lead to significant alterations because of a TAH. 1-2 Artificial perfusion is a complex process, and, at this point, the interactions taking place on the level of central and peripheral regulations are not fully understood. There is also another long standing question of whether arterial pulsation is essential to maintain adequate blood flow and aerobic metabolism in key organs. Nonpulsatile circulation has been widely used in the clinical setting of cardiopulmonary bypass or circulation support. 3-5 Many studies have been performed in cardiopulmonary bypass or in left ventricular support. 6 -13 In some studies, the organ to which attention was directed was the brain. 14 -20 The undulation pump total artificial heart (UPTAH) is an implantable TAH that has been in development at the Univers...

Influence of Flow Design on Microcirculation in Conditions of Undulation Pump‐Left Ventricle Assist Device Testing

“…reported a significant increase of catecholamine level in nonpulsatile systemic circulation accompanied by altered oxygen meta‐bolism (25). Recently, a very important finding was described by Baba et al (2003), who observed the drop of the velocity of erythrocytes in the capillaries of the bulbar conjunctiva and the decreased number of perfused vessels in the conditions of nonpulsatile flow—after the flow was returned to pulsatile, the velocity of erythrocytes and the flow in nonperfused vascular segments recovered to the initial level as well (26,27). This effect of the pulsatile flow is probably related to the enhanced stimulation of the endothelium‐derived nitric oxide release in the terminal microvascular bed (28).…”

Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller

“…The peak activity of these stretch‐sensitive mechanoreceptors located in the viscoelastic walls of the aortic arch and the carotid sinuses has been reported to coincide with the maximum slope of the aortic pressure ( , Eq. ) , leading to an increased use of to evaluate pulsatile hemodynamic effects : …”

Comparison of Hemolytic Properties of Different Shapes of Occlusion of Blood Sac in Occlusive‐type Pulsatile Blood Pump

“…Because our blood pump is both a pulsatile type and an occlusive type, we have to consider both aspects during hemolytic testing. From the pulsatile point of view, although there has long been a controversy regarding the clinical benefits of pulsatile and nonpulsatile devices (11)(12)(13)(14)(15), pulsatile flow is important for blood circulation because flow pulsatility can reduce the resistance of peripheral vessels, while blood passes through highresistance areas (16).Therefore, the parameter affecting hemolysis, dP/dt, is crucial in the assessments needed for the development of the pulsatile cardiac device. It is suggested that a high maximum dP/dt results in a high level of hemolysis; the maximum dP/dt of 5000 mm Hg/s is damaging to the blood, while that of 2500 mm Hg/s yields good results in clinical studies (17).…”