Coagulation factor abnormalities related to discordance between anti-factor Xa and activated partial thromboplastin time in patients supported with continuous-flow left ventricular assist devices.
High levels of discordance between activated partial thromboplastin time (aPTT) and anti-factor Xa (anti-FXa) have been reported in patients with continuous-flow left ventricular assist devices (CF-LVADs). We sought to determine the biochemical basis for discordance by simultaneous measurement of coagulation factors with aPTT and anti-FXa.



Consecutive CF-LVAD patients admitted for intravenous unfractionated heparin (IV-UFH) therapy were studied. IV-UFH was monitored based on an anti-FXa. International normalized ratio (INR), aPTT, lactate dehydrogenase, and coagulation factors II, V, VII, VIII, IX, X, XI, and XII were measured simultaneously with anti-FXa.



The discordance rate between anti-FXa and aPTT was 74.7% overall (568 of 760 samples from 62 patients). In samples in which coagulation factors were simultaneously measured, the discordance rate was 66% (49 of 74 samples from 52 patients). In patients with INR ≤ 1.0 the discordance level was 31.8% vs 82.7% with INR > 1.8. No difference was observed in the rate of discordance between samples with low vs normal vitamin K-dependent factors (65.9% vs 64.7%, p = 0.99). Low factor XII was found in 15%; of these, 90.9% exhibited anti-FXa/aPTT discordance. Low factor V was found in 8.2%, and all were discordant. Factor VIII was elevated in 97% of samples, and 65.7% were discordant.



In addition to the effects of warfarin administration on aPTT, the influence of other factors, such as low factor XII or V, may contribute to the discordance between aPTT values and anti-FXa. Coagulation factor levels may assist in individualization of anti-coagulation targets while patients implanted with CF-LVADs are on IV-UFH.
Department of Medicine, Cardiology Division, University of Chicago, Chicago, Illinois. Electronic address: sadatya@medicine.bsd.uchicago.edu.
Sirtaz
S
Adatya
Cardiovascular Division, Department of Medicine, University of Minnesota, Minneapolis, Minnesota.
Roy
R
Sunny
University of Minnesota Medical School, Minneapolis, Minnesota.
Megan J
MJ
Fitzpatrick
Cardiology Division, Minneapolis, Minnesota.
Monica
M
Colvin
Cardiovascular Division, Department of Medicine, University of Minnesota, Minneapolis, Minnesota.
Thennapan
T
Thennapan
Division of Cardiothoracic Surgery, Department of Surgery, Minneapolis, Minnesota.
Ranjit
R
John
Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota.
Nicole
N
Dodge Zantek
Cardiovascular Division, Department of Medicine, University of Minnesota, Minneapolis, Minnesota.
Marc
M
Pritzker
Cardiology Division, Department of Medicine, Minneapolis Heart Institute, Minneapolis, Minnesota.
Peter
P
Eckman
Department of Medicine, Cardiology Division, University of Chicago, Chicago, Illinois.
Nir
N
Uriel
D000925:Anticoagulants / Q000008:administration & dosage; D001779:Blood Coagulation Factors / Q000378:metabolism*; D001780:Blood Coagulation Tests; D065427:Factor Xa Inhibitors / Q000494:pharmacology*; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000097:blood / Q000601:surgery*; D006353:Heart-Assist Devices; D006493:Heparin / Q000008:administration & dosage*; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D011446:Prospective Studies; D013927:Thrombosis / Q000097:blood / Q000517:prevention & control*
D000925:Anticoagulants; D001779:Blood Coagulation Factors; D065427:Factor Xa Inhibitors; D006493:Heparin
PTT; activated partial thromboplastic time; anti-coagulation; anti-factor Xa; bleeding; coagulation factors; device thrombosis; hemolysis; heparin; ventricular assist device; warfarin