Ventricular Assist Device Anti-Factor Xa (VAD ANTIX) Monitoring Study: a Prospective Randomized Feasibility Trial (VAD-ANTIX)

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The Washington University




Gastro Intestinal Bleeding
Left Sided Heart Failure
Thrombosis, LVAD
Left Ventricular Assist Device
Anti-factor Xa
Anticoagulant Therapy


Device: aPTT guided heparin management
Device: Anti-factor Xa guided heparin management

Study type


Funder types




Details and patient eligibility


This study evaluates two different methods for monitoring a patient's anti-clotting [heparin] therapy after they receive a heart pump implant [left ventricular assist device -LVAD]. One method tests for how long it takes the patient's blood to clot and uses that to determine if they are on the right dose of heparin. The other method uses a more direct measure of how much heparin is in the blood. The hypothesis is that the method that more directly measures how much heparin is in the patient's blood will provide better medical results for the patient's care after they have the heart pump implant. To that end, the investigators are conducting this feasibility trial to establish the logistics associated with the implementation of these heparin monitoring approaches.

Full description

Heart failure is a medical condition that is on the rise in the US and is associated with an enormous cost of $30 billion in healthcare expenses. People with heart failure may be treated with an LVAD that is connected to their heart and helps it pump the blood from the left side of the heart into the blood vessels that delivers blood to the body. These devices can be used to treat heart failure for the long term or they can be used while a patient waits for a heart transplant. In either case, the use of these devices is increasing. One of the primary risks associated with LVADs are those related to blood clotting. Maintenance of the LVAD depends on preventing blood clots especially right after the surgery that puts them in place. This requires putting patients with LVADs on blood thinners and then monitoring the blood thinner levels carefully so that they don't have problems with bleeding too easily or, on the other hand, forming blood clots if they aren't on the right dose of blood thinners. Excessive bleeding - called hemorrhaging - is the more common problem after surgery and half of all patients that receive an LVAD will require a blood transfusion within the first 30 days after they receive the device. A laboratory test that measures how quickly blood clots is used to determine if the patient has the right amount of blood thinners. The current standard test is called "activated partial thromboplastin time [aPTT]." There are problems with the reliability of this test because it reacts with other elements in the blood. Alternately, there is a test that more directly measures the amount of heparin blood thinner rather than coagulation time and may be more reliable than aPTT called anti-factor Xa [anti-Xa]. The investigators have developed process diagrams that show steps for making decisions [called nomograms] that tell a nurse or doctor how to manage the heparin levels using test results from the aPTT test or the anti-Xa test; however, both tests will be performed at each decision time point, but the care team will only be told the results from the testing to which their patient is assigned. The purpose of this feasibility study is to establish feasibility of using the two nomograms to determine which provides the optimal clinical information for improving patients' outcomes that have had LVADs placed. Potential subjects will be recruited prior to their surgery and may decline to participate anytime before or after the surgery takes place. Subjects will be randomized to the aPTT nomogram or the anti-Xa nomogram. If they withdraw consent, they will receive the aPTT standard of care monitoring. The study procedures are performed by the clinical care team. Clinicians will be trained to use the nomograms.


20 patients




18+ years old


No Healthy Volunteers

Inclusion criteria

  • 18 years of age and older
  • Implantation with HeartMate II® or HeartWare®, LVAD at Barnes Jewish Hospital

Exclusion criteria

  • Unable to receive heparin-based therapy
  • Hypercoagulable disorders [factor V Leiden, Antithrombin deficiency, Protein C deficiency, Antiphospholipid antibodies or other thrombophilia]
  • Incarceration
  • Pregnancy or breastfeeding

Trial design

Primary purpose




Interventional model

Parallel Assignment


Double Blind

20 participants in 2 patient groups

aPTT nomogram
Active Comparator group
aPTT guided heparin management
Device: Anti-factor Xa guided heparin management
Device: aPTT guided heparin management
Anti-factor Xa nomogram
Experimental group
Anti-factor Xa guided heparin management
Device: Anti-factor Xa guided heparin management
Device: aPTT guided heparin management

Trial documents

Trial contacts and locations



Data sourced from

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