darn, i just wrote out the longest answer and the cybergods vanished it! eeeek. here goes again.
regime depends on:
- patient comorbidities (a/fib, any issues leading to hypercoagulability etc)
- device being used
- bleeding status
certain devices are prone to stasis thrombosis ("red clots"). these include external devices (abiomed bvs5000, thoratec pvad, abiomed ab5000 ventricle, berlin heart excor), internal devices such as the novacor, thoratec ivad. the risk is due to potential incomplete ejection and filling of the blood sac which may lead to thrombosis.
certain patients susceptible to stasis thrombosis are those with arrhythmias (esp af) who may have incomplete ejection of their own cardiac chambers, also potentially leading to stasis thrombosis which may be ejected via the pump.
this type of thrombosis risk is mitigated by an anticoagulation regime such as postop heparin iv infusion in the acute phase until bleeding is acceptable (<30-50ml/hr) and the gut is fully functional, then coumadin is commenced to a target inr of >2.5 (usually) for the remainder of the implant duration.
devices which are based on continuous flow (heartmate ii, incor, micromed debakey, jarvik 2000, ventrassist) are more susceptible to “high shear” damage to blood cells (esp platelets). this can lead to platelet/fibrin clots (“white clot”). as such, antiplatelet therapies are key. common regimes are aspirin +/- persantine +/- plavix. these therapies should ideally be guided by tests such as thromboelastography (teg) to judge platelet response, as many people can be resistant to aspirin and/or plavix. some of these devices have bearings which generate heat and can also be a risk for red clots. given that many vad patients also suffer from arrhythmias, these patients usually also are on an anticoagulation regime to target inr >2.5.
the exception is the heartmate i device, which has a pseudointimal layer inside the blood sac which encourages incorporation of tissue so that the blood sees a “native” surface. as such, only antiplatelet therapies are required in general, although many patients also have concomitant arrhythmias and also need coumadin.
most of the vad manufacturers have recommendations for anticoagulation/antiplatelet therapies in their manuals, or on their websites.
sorry for the long answer, this is my day job and i find it fascinating!
language edited per tos