Aortic Valve Thrombus in a Patient With an Extracorporeal Left Ventricular Assist Device: The Dilemma of Management.

PATIENTS with severely compromised left ventricular output undergo left ventricular assist device (LVAD) placement for a variety of reasons. Intracorporeal (totally implantable) devices are placed either as bridge therapy to cardiac transplantation or as destination therapy in patients ineligible to undergo transplantation. Most modern devices are small and rely on impellers to produce axial, nonpulsatile flow in series with the left ventricle (LV). An example of such a device is the HeartMate II (Thoratec Corporation), which is approved by the FDA for both bridge-to-transplantation and destination therapy. In the setting of cardiogenic shock such as acute myocardial infarction (AMI) or significant insult to the LV during cardiopulmonary bypass (CPB), temporary extracorporeal devices may be used for circulatory support. In a patient with a sternotomy, typical cannulation sites are the left atrium and ascending aorta, resulting in flow that is in parallel to native LV flow. These devices are meant to be used as a bridge to recovery of myocardial function or as a bridge to a more definitive decision (such as intracorporeal LVAD or termination of care). An example of a device used in this setting is the Centrimags (Thoratecs Corporation) VAD, which also can be used for biventricular support if indicated. High flow through both types of devices can overpower and completely bypass the flow through the native left ventricular outflow tract. As a result, stasis of flow in the ascending aorta can occur, with reduced AV cusp excursion. This can contribute to perivalvular thrombus formation. Possible sequelae may include compromised coronary blood flow, heart failure, and embolic events such as AMI or cerebrovascular accident (CVA). The guidelines released in 2013 for mechanical circulatory support recommend warfarin with the optional addition of aspirin to prevent thrombotic complications in LVAD patients. On the flip side, mechanical shear stress from ventricular assist devices leads to an acquired von Willebrand factor deficiency and platelet dysfunction. This, along with pharmacologic anticoagulation, can place these patients at an increased risk for bleeding complications. Karimi et al have suggested that antiplatelet therapy titration with the utilization of thromboelastography may reduce bleeding risk in this population.