Pump thrombosis (PT) is considered a specific case of a major device malfunction, and is classified as either suspected or confirmed pump thrombus. Typically, the device is an implanted blood pump such as a left ventricular assist device. The malfunction is a blockage in the flow of blood anywhere along a vessel (upstream or downstream) and it is mainly due to the bio-incompatible presence of a fairly complex mechanical apparatus. Pump thrombus is dreaded complication of CF LVAD technology[1] that can require repeat surgery to replace the pump or lead to death.[2]
In suspected pump thrombus, the clinical patient condition or pump parameters suggest thrombus on any of the blood-contacting surfaces of the pump (inflow cannula, pump itself, or outflow graft). Confirmed pump thrombus is done by visual inspection (during device exchange, transplantation, autopsy), irrefutable radiographic evidence, or absence of Doppler inflow or outflow signals.Not all ventricular assist devices (VADs) are fully biocompatible, thus device thrombosis has always been a significant complication. Older generation pulsatile VADs were relatively large and it was practically impossible to thrombose the entire pump and cause hemodynamic consequences.Instead, any thrombus created in the pump could be dislodged, possibly resulting in an embolic stroke. In contrast, the newer continuous flow left ventricular assist devices (CF LVAD) are much smaller and have smaller gaps between the various components of the pump. These characteristics predispose CF LVAD to thrombosis of the entire pump where the clot stays in the device, leading to increased hemolysis and device dysfunction.[citation needed]
Thrombosis of CF LVADSs can occur as a result of various factors,[3] which can be divided into three categories: the pump, the patient, and the clinician. Management protocols for VADs are usually institution-dependent and there is a large variability in clinician-related factors. A decrease in anticoagulation thresholds[4][5][6] has been postulated to have resulted in an increase in CF LVAD thrombosis.[7][8]
A complex balance exists between over-anticoagulation and under-anticoagulation, in a patient population where the coagulation system response to the CF LVAD device varies greatly between individuals. Common adverse events precipitated by over-anticoagulation include bleeding problems such as gastrointestinal bleeding and intracranial hemorrhage, while common complications due to under-anticoagulation include hemolysis, pump thrombosis and ischemic/embolic strokes.[citation needed]
Unfortunately, robust and individually-tailored anticoagulation therapy protocols do not exist in most institutions, which usually utilize a "one size fits all" approach. One anticoagulation protocol example targets the therapeutic window of coumadin of an international normalized ratio (INR) goal of 2–3 and full-dose aspirin for antiplatelet activity. In the complex dynamics of the interaction of patients' systems, there is no completely safe zone between thrombosis or bleeding, or both.
^"Archived copy" (PDF). Archived from the original (PDF) on 2016-02-22. Retrieved 2016-02-05.{{cite web}}: CS1 maint: archived copy as title (link)
^"Serious Adverse Events with Implantable Left Ventricular Assist Devices (LVADs): FDA Safety Communication". Food and Drug Administration. Archived from the original on 2017-07-22. Retrieved 2019-12-16.
^Uriel, N; Han, J; Morrison, KA; et al. (2014). "Device thrombosis in HeartMate II continuous-flow left ventricular assist devices: a multifactorial phenomenon". J Heart Lung Transplant. 33 (1): 51–9. doi:10.1016/j.healun.2013.10.005. PMID 24290832.
^Slaughter, MS; Naka, Y; John, R; et al. (2010). "Post-operative heparin may not be required for transitioning patients with a HeartMate II left ventricular assist system to long-term warfarin therapy". J Heart Lung Transplant. 29 (6): 616–24. doi:10.1016/j.healun.2010.02.003. PMID 20400335.
^Slater JP, Rose EA, Levin HR, et al. Low thromboembolic risk without anticoagulation using advanced-design left ventricular assist devices. Ann Thorac Surg 1996;62:1321-7; discussion 1328.
^Netuka, I; Litzler, PY; Berchtold-Herz, M; et al. (2014). "Minimal adverse events in HeartMate II patients with no antiplatelet therapy: preliminary results from the European TRACE study". J Heart Lung Transpl. 33 (4): S11. doi:10.1016/j.healun.2014.01.055.
^Kirklin, JK; Naftel, DC; Kormos, RL; et al. (2014). "Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) analysis of pump thrombosis in the HeartMate II left ventricular assist device". J Heart Lung Transplant. 33 (1): 12–22. doi:10.1016/j.healun.2013.11.001. PMID 24418730.
^Starling, RC; Moazami, N; Silvestry, SC; et al. (2014). "Unexpected abrupt increase in left ventricular assist device thrombosis". N Engl J Med. 370 (1): 33–40. doi:10.1056/nejmoa1313385. PMID 24283197. S2CID 54522781.
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