Daiki Kikugawa

Analysis of the relationship between left ventricular pressure and motor current for evaluation of native cardiac function during left ventricular support with a centrifugal blood pump

Control of the ventricular assist device (VAD) for native heart preservation should be attempted, and the VAD could be one strategy for dealing with the shortage of donors in the future. In the application of nonpulsatile blood pumps for ventricular assistance from the ventricular apex to the aorta, bypass flow and hence the motor current of the pumps change in response to the ventricular pressure change. Utilizing these intrinsic characteristics of the continuous-flow pumps, in this study we investigated whether motor current could be used as an index for continuous monitoring of native cardiac function. In study 1, a centrifugal blood pump (CFP) VAD was installed between the apex and descending aorta of a mock circulatory loop. In this model, a baseline with a preload of 10 mmHg, afterload of 40 mmHg, and LV systolic pressure of 40 mmHg was used. The pump speed was fixed at 1300, 1500, and 1700 rpm, and LV systolic pressure was increased up to 140 mmHg by steps of 20 mmHg while the changes in LV pressure, motor current, pump flow, and aortic pressure were observed. In study 2, an in vivo experiment was performed using three sheep. A left heart bypass model was created using a centrifugal pump from the ventricular apex to the descending aorta. The LVP was varied through administration of dopamine while the changes in LV pressure, pump flow, and motor current at 1500 and 1700 rpm were observed. An excellent correlation was observed in both in vitro and in vivo studies in the relationship between motor current and LV pressure. In study 1, the correlation coefficients were 0.77, 0.92, and 0.99 for 1300, 1500, and 1700 rpm, respectively. In study 2, they were 0.88 (animal no. 1), 0.83 (animal no. 2), and 0.88 (animal no. 3) for 1500 rpm, and 0.95 (animal no. 2) and 0.93 (animal no. 3) for 1700 rpm. These results suggest that motor current amplitude monitoring could be useful as an index for the control of VAD for native heart preservation.

A Case Report of Juxtarenal Aortic Occlusion due to Takayasu's Arteritis.

われわれは非常に珍しい高安大動脈炎が成因と考えられる高位腹部大動脈閉塞症の1例を経験したので報告する. 症例は46歳男性, 主訴は間歇性跛行の増悪, 下腹部痛, 発熱. 入院時, 血液検査で炎症所見著明で, 腹部CT上も大動脈壁の著明な肥厚を伴う腹部大動脈閉塞を認めた. ステロイド内服を開始し, 炎症所見が正常化した後手術を施行した. 手術は大動脈-両側大腿動脈バイパス術で, 中枢側吻合は端々吻合で行い, グラフトの残りで吻合部のラッピングを追加した. また大動脈周囲の癒着は著明で, 炎症性病変を示唆した. 血管壁の病理診断は高安大動脈炎であったが, 術前の抗リン脂質抗体陽性より, 抗リン脂質抗体症候群も本症例の成因の可能性を示唆した. 今後, 炎症の再燃に十分気をつけながら経過観察していくつもりである.

Implantation of a Ventricular Assist Device in Animals: Progress and Regress

Two types of ventricular assist device (VAD) were tested in vitro and in vivo. A biventricular bypass type total artificial heart utilizing two pusher-plate pumps was implanted in 11 sheep. Following the implantation, the animal’s heart was fibrillated. They survived for 2–48 days, with an average of 11.3 days. The pump flow ranged from 90 to 100ml/min per kg. Other hemodynamic data and the hematological data were normal, except for a low hemoglobin level. We have been developing an implantable motor-driven VAD in collaboration with the Baylor College of Medicine. This pump provided 81/min output against a mean afterload of 120 mmHg with a filling pressure of 20 mmHg. Nine in vivo studies have been conducted. Three sheep survived for 10–12 h. The pump flow ranged from 0.8 to 2.51/min. From these data, left atrial cannulation may not be sufficient to drain adequate blood flow into the pump.