Hemolysis and Platelet Activation during Continuous Flow Mechanical Circulatory Support

项目概要/摘要： 心力衰竭（HF）已经达到流行病的比例，影响全世界超过540万人，其负担 预计在未来十年将呈指数级增长。持续机械循环支持（MCS） 用于患有终末期心力衰竭或急性心源性休克的患者的流量（CF）泵已经导致剧烈的 生存的改善。然而，器械操作仍然充满严重不良事件（SAE） 导致过度的发病率。CF泵血栓形成和中风的发生率很高， 需要揭示其血液学机制和治疗靶点。在慢性CF泵领域， 新设计的Heart Mate（HM）3器械，具有更好的血液相容性，如更宽的血液 流动通道，确实显示了原位泵血栓形成的减少;然而， 中风率仍然升高。尽管器械设计发生了变化，但严重血栓形成事件的持续存在， 使得充分阐明血栓形成的潜在机制至关重要。 溶血与器械血栓形成和缺血性卒中的相关性最近已被认识到， 与溶血诱导的血栓前状态一致。由于明显的临床溶血可能是一种下游反应， 考虑到器械中已形成血栓的影响，并考虑到在较新器械中可能不再发生原位血栓形成， 我们专注于评估亚临床低水平的体内影响， 溶血（LLH）对血小板活化和聚集（PA/A）的影响。在溶血性疾病，如镰状细胞 贫血时，细胞外血红蛋白可能通过清除一氧化氮（NO）和结合蛋白原而诱导PA/A。 血管性血友病因子（vWF）的血栓性超大（UL）多聚体，以防止它们被 金属蛋白酶（ADAMTS 13）。 我们的初步研究结果表明，在慢性和急性CF MCS中，LLH与7至10岁儿童的年龄相关。 随后血栓形成事件（包括缺血性卒中）的风险增加15倍。此外，我们注意到， 平均血小板体积（MPV），PA/A的替代标志物，和血栓前vWF水平高于 LLH患者与无LLH患者相比。我们的研究结果还表明， 接受血小板治疗的患者在持续CF泵支持期间发生血栓形成事件和MPV伴持续LLH NO信号增强剂，西地那非。 本提案将评估CF泵支持期间LLH与 LLH时PA/A和西地那非可降低PA/A。在目标1中，我们将招募慢性（HM 2和HM 3）患者 和急性（VA ECMO和Impella）CF MCS，以评估有和没有LLH的患者之间的PA/A。在 二次分析，我们还将检查这种关联是否可能与血小板的变化有关。 cGMP、vWF活性、vWF UL/HMW多聚体和ADAMTS 13活性。在目标2中，接受持久CF的门诊患者 在一项双盲研究中，持续LLH的泵支持患者将随机（1：1）接受西地那非或安慰剂治疗。 在指定的药物给药后测量PA/A标志物的变化 并与基线进行比较。

Project Summary / Abstract: Heart failure (HF) has reached epidemic proportions effecting over 5.4 million people worldwide and its burden is expected to grow exponentially in the next decade. Mechanical circulatory support (MCS) with continuous flow (CF) pumps for patients with end stage heart failure or acute cardiogenic shock has led to drastic improvements in survival. However, device operation remains fraught with serious adverse events (SAEs) leading to excessive morbidity. CF pump thrombosis and stroke are occurring at high rates, thereby prompting a need to uncover their hematologic mechanisms and therapeutic targets. In the chronic CF pump field, the newly designed Heart Mate (HM) 3 device, with features of greater hemocompatability such as wider blood flow passages, did show a reduction of in-situ pump thrombosis; however, the presence of disabling ischemic stroke remained elevated. Such persistence of severe thrombotic events, despite alterations in device design, makes it critically important to fully elucidate mechanisms underlying thrombus formation. The association of hemolysis with device thrombosis and ischemic stroke has recently been recognized and is consistent with a hemolysis induced pro-thrombotic state. Since overt clinical hemolysis may be a downstream effect of thrombus already formed in the device and given that in-situ thrombosis may no longer occur in newer generation of durable devices, we instead focus on assessing the in-vivo impact of sub clinical low level hemolysis (LLH) on platelet activation and aggregation (PA/A). In hemolytic disorders such as sickle cell anemia, extracellular hemoglobin may induce PA/A by scavenging nitric oxide (NO) and binding to pro- thrombotic ultra large (UL) multimers of von Willebrand factor (vWF) to prevent their proteolysis by the metalloproteinase (ADAMTS 13). Our preliminary findings indicate that during both chronic and acute CF MCS, LLH was associated with a 7 to 15 fold increased risk of subsequent thrombotic events, including ischemic stroke. Moreover, we noted that mean platelet volume (MPV), a surrogate marker of PA/A, and pro-thrombotic vWF levels were higher in patients with LLH in comparison to those with no LLH. Our findings also indicate a substantial reduction in thrombotic events and MPV with ongoing LLH during durable CF pump support in patients receiving a platelet NO signaling potentiation agent, sildenafil. This proposal will evaluate the hypotheses that LLH during CF pump support is associated with an increase in PA/A and sildenafil can lower PA/A during LLH. In Aim 1, we will recruit patients on chronic (HM 2 and HM 3) and acute (VA ECMO and Impella) CF MCS, to assess PA/A between those with and without LLH. In secondary analyses, we will also examine whether this association may be related to changes in platelet cGMP, vWF activity, vWF UL/HMW multimers and ADAMTS13 activity. In Aim 2, outpatients on durable CF pump support with ongoing LLH will be randomized (1:1) to receive sildenafil or placebo in a double-blinded manner for a 15 day period and changes in PA/A markers will be measured after assigned drug administration and compared to baseline.