Biofunction Study Of FW-Ⅱ Axial Blood Pump For Short-Term Assistance

Objective:FW-Ⅱaxial blood pump is rotary impeller continuous blood ventricular assist device with design optimization of computational fluid dynamics. In this study, we observed assistance effect of FW-II axial blood pump, and evaluated its impact on hemodynamics, liver and renal function by large animal survival experiment.Methods:9 small tail sheep were divided into axial blood pump group(n=6) and sham group(n=3):for pump group, left ventricular-axial blood pump-descending aorta model was established by the left lateral thorocotomy; for sham group, incise and suture cardiac apex and descending aorta without implanting pump. All sheep were used heparin to maintain 150-200 seconds of ACT, and then received oral aspirin(100mg/day) and warfarin(3mg/day). We used Swan-Ganz to monitor indices of hemodynamics perioperatively:left ventricular stroke work index(LVSWI), cardiac index(CI), acceleration index(ACI), rate-pressure-product(RPP), pulmonary Capillary wedge pressure(PCWP); Aortic valve opening and closing was observed by transesophageal echocardiography under different rotational speed, the relation between different pump speed and mean arterial pressure, pulse pressure, and aortic valve opening was analyzed. Serum creatine kinase (CPK), lactate dehydrogenase (LDH), total protein, total bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN) and creatinine (Cr) level were detected in the preoperative,1,3,5,7,10 and 14 days to assess the function of liver and kidney.Results:All sheep were extubated 6-8 hours postoperatively. For pump group,5 sheep were assisted for 14-16 days without pump dysfunction, one sheep died of hemorrhage at 7 days. Within 14 days, the pump was maintained 7500-8500 rounds per minute(RPM), and produce stable blood flow(3.0±0.7L/min). Compared with the preoperative value, LVSWI, CI, ACI, and RPP were significantly lower (P<0.01). within the range of pump speed setting, compared with aortic valve opening, pump speed, diastolic pressure, mean arterial pressure significantly increased (P<0.05), pulse pressure significantly reduced (P<0.05), systolic blood pressure insignificantly changed (P> 0.05) when aortic valve closed. compared to high speed (9000rpm), the number of aortic valve opening reduced significantly with low-speed (7000rpm) (22% vs 97%, P<0.001). Compared with low pulse pressure (<15mmHg), the number of aortic valve opening with high pulse pressure(>15mmHg) increased significantly (65% vs 24%, P<0.001). CPK and LDH levels of two groups peaked in day 3(673±26 vs 642±22 IU/L,357±13IU/L vs 302±14IU/L, P>0.05), gradually recovered to preoperative level at day 10. Total protein levels in two groups were the lowest at day 3(5.9±0.09g/dL vs 6.1±0.12g/dL, P> 0.05), returned to normal level at day10; total bilirubin of two groups peaked at day 3 (0.5±0.04mg/dL vs 0.31±0.03mg/dL, P <0.05), decreased to preoperative level at day 5. AST level of two groups increased significantly, peaked at day 3 (229.4±31.9 vs 203.4±31.9 IU/L, P> 0.05), declined to preoperative level at day 10; there was no significant difference between pre and post operative ALT level of two groups (12.9±3.1 vs 15.6±6.1, P> 0.05). within 14 days, BUN and Cr levels in both groups remained stable, peaked at day 5 (14.5±2.5 vs13.2±2.1mmol/L; 1.6±0.03 vs 1.5±0.03μmol/L).Conclusions:FW-Ⅱaxial blood pump can safely assist animals, unload left ventricular obviously, present stable hemodynamics, and has little effect on liver and kidney function. Blood Compatibility Study of FW-II Axial Blood Pump for Short-Term AssistanceObjective:To provide anticoagulation evidence and monitoring methods for future clinical use, we observed blood compatibility of FW-II axial blood pump and the relation between leukocyte-platelet aggregation and thrombosis for short-term assistance.Methods:At preoperative and postoperative day 1,3,5,7,10,14, venous samples of pump and sham group were collected to detect hematologic indices:red blood cells, white blood cells, platelets count, plasma free hemoglobin and coagulation parameters. serum interleukin-6(IL-6), tumor necrosis factor (TNF-α), C3a and C5a content were also detected by enzyme-linked immunosorbent assay(ELISA). Platelet activation and leukocyte-platelet aggregation were detected by flow cytometry. At day 10, venous samples of different speed(7000-9000 round per minute) were collected to detect leukocyte-platelet aggregation. At the day of preoperative, postoperative, platelet count normalization, aspirin, and warfarin, venous samples were collected, platelet aggregation induced by arachidonic acid (AA) and adenosine diphosphate (ADP) was detected through PFA-100 analyzer. Thrombelastography(TEG) was used to monitor coagulation status:R time (R value), K time (K), maximum amplitude(Ma), (a), coagulation index (CI). FW-II axial blood pumps were explanted and each part was inspected to find any thrombus formation. Macroscopic and histological examination were checked on heart, brain, kidney and spleen respectively for thrombosis.Results:Postoperative red blood cell count of two groups decreased, reached the lowest level at day 3 (2.4×1012/Lvs3.2×1012/L), and returned to preoperative level respectively at day 10 and 14. Plasma free hemoglobin of pump group peaked at day 3(170mg±20mg/L), maintained 50mg/L within 7 days, and gradually decreased from day 10. White blood cell count of two groups peaked at day 5(13.28±0.24×109/L vs 11.74±0.96×109/L), and then gradually decreased. Compared to sham group, WBC count of pump group had been a high level. Platelet count of two groups decreased within 3 days, and gradually returned to preoperative level. Compared with preoperative baseline, the number of platelet activation and leukocyte-platelet aggregates reached the peak at postoperative day 2(42±6%,40±5%,P<0.01), retained a high level within 7 days, then gradually decreased, but were still higher than preoperative level at day 14 (17±4%,20±6%, P>0.05). According to rotating speed, the number of platelet activation and platelet-leukocyte aggregates were lowest at the speed of 8000 round per minute (15±3%,16±4%). Platelet-leukocyte aggregates of the third sheep were significantly higher than other four sheep. Compared with preoperative baseline, platelet aggregates significantly increased after platelet count recover to normal level. Compared with preoperative baseline, there was no significant change for R and K value, aangle and MA significantly increased after platelet count recovered to normal level, coagulation index increased after postoperatively platelet count normalization, reduce significantly after oral aspirin. Minus thrombus were found in front and rear hub of pump rotor(0.008±0.004g). except round thrombus of inflow housing in the third pump, no thrombus at other components (flow straighter, impeller, pump housing) was found. There was not any ischemia and infarction evidence in macroscopic and histological examination of heart, brain, kidney and spleen.Conclusion:FW-Ⅱaxial blood pump can be used to assist left ventricular circulation for 2 weeks with a satisfactory antithrombosis ability. The level of platelet activation and leukocyte-platelet aggregation can be reduced to bottom at a optimized pump speed.