Biorheology Research Laboratory, Menzies Health Institute Queensland, Griffith University, Gold Coast, QLD, Australia.
School of Engineering and Built Environment, Griffith University, Southport, QLD, Australia.
Artif Organs. 2021 Jun;45(6):E146-E157. doi: 10.1111/aor.13877. Epub 2020 Dec 29.
Despite technological advances in ventricular assist devices (VADs) to treat end-stage heart failure, hemocompatibility remains a constant concern, with supraphysiological shear stresses an unavoidable reality with clinical use. Given that impeller rotational speed is related to the instantaneous shear within the pump housing, it is plausible that the modulation of pump speed may regulate peak mechanical shear stresses and thus ameliorate blood damage. The present study investigated the hemocompatibility of the HeartWare HVAD in three configurations typical of clinical applications: standard systemic support left VAD (LVAD), pediatric support LVAD, and pulmonary support right VAD (RVAD) conditions. Two ex vivo mock circulation blood loops were constructed using explanted HVADs, in which pump speed and external loop resistance were manipulated to reflect the flow rates and differential pressures reported in configurations for standard adult LVAD (at 3150 rev⸱min ), pediatric LVAD (at 2400 rev⸱min ), and adult RVAD (at 1900 rev⸱min ). Using bovine blood, the mock circulation blood loops were tested at 37°C over a period of 6 hours (consistent with ASTM F1841-97) and compared with static control. Hemocompatibility assessments were conducted for each test condition, examining hematology, hemolysis (absolute and normalized index), osmotic fragility, and blood viscosity. Regardless of configuration, continuous exposure of blood to the VAD over the 6-hour period significantly altered hematological and rheological blood parameters, and induced increased hemolysis when compared with a static control sample. Comparison of the three operational VAD configurations identified that the adult LVAD condition-associated with the highest pump speed, flow rate, and differential pressure across the pump-resulted in increased normalized hemolysis index (NIH; 0.07) when compared with the lower pump speed "off-label" counterparts (NIH of 0.04 in pediatric LVAD and 0.01 in adult RVAD configurations). After normalizing blood residence times between configurations, pump speed was identified as the primary determinant of accumulated blood damage; plausibly, blood damage could be limited by restricting pump speed to the minimum required to support matched cardiac output, but not beyond.
尽管心室辅助装置 (VAD) 在治疗终末期心力衰竭方面取得了技术进步，但血液相容性仍然是一个持续存在的问题，超生理剪切力是临床应用中不可避免的现实。由于叶轮的转速与泵壳内的瞬时剪切力有关，因此可以合理地认为调节泵速可以调节峰值机械剪切力，从而改善血液损伤。本研究调查了 HeartWare HVAD 在三种典型临床应用配置中的血液相容性：标准全身支持左 VAD (LVAD)、儿科支持 LVAD 和肺支持右 VAD (RVAD) 条件。使用已植入的 HVAD 构建了两个体外模拟循环血液回路，其中通过操纵泵速和外部回路阻力来反映标准成人 LVAD（在 3150 rev ⸱ min）、儿科 LVAD（在 2400 rev ⸱ min）和成人 RVAD（在 1900 rev ⸱ min）报告的流量和压差。使用牛血，在 37°C 下模拟循环血液回路测试持续 6 小时（与 ASTM F1841-97 一致），并与静态对照进行比较。对每个测试条件进行血液相容性评估，检查血液学、溶血（绝对和归一化指数）、渗透压脆性和血液粘度。无论配置如何，血液在 6 小时内连续暴露于 VAD 会显著改变血液学和流变学血液参数，并与静态对照样本相比导致溶血增加。三种操作 VAD 配置的比较表明，与泵速、流量和泵内压差最高的成人 LVAD 配置相关的条件导致归一化溶血指数（NIH；与较低泵速“标签外”对应物相比，成人 RVAD 配置的 NIH 为 0.01）增加（NIH 为 0.07） 儿科 LVAD 配置）。在对配置之间的血液停留时间进行归一化后，泵速被确定为累积血液损伤的主要决定因素；可以合理地通过将泵速限制在支持匹配心输出所需的最小值来限制血液损伤，但不能超过该值。
