Author + information
- Received September 26, 2014
- Revision received November 22, 2014
- Accepted November 25, 2014
- Published online April 1, 2015.
- Sirtaz Adatya, MD∗∗ (, )
- Nir Uriel, MD†,
- Hirad Yarmohammadi, MD∗,
- Christopher T. Holley, MD∗,
- Amy Feng, BA∗,
- Samit S. Roy, MSPH∗,
- Mark T. Reding, MD‡,
- Ranjit John, MD∗,
- Peter Eckman, MD∗ and
- Nicole D. Zantek, MD, PhD§
- ∗Department of Medicine, Cardiology Division, University of Minnesota, Minneapolis, Minnesota
- †Department of Medicine, Cardiology Division, University of Chicago, Chicago, Illinois
- ‡Department of Medicine, Division of Hematology, Oncology and Transplantation, University of Minnesota, Minneapolis, Minnesota
- §Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota
- ↵∗Reprint requests and correspondence:
Dr. Sirtaz Adatya, Department of Medicine, Cardiology Division, 420 Delaware Street SE, MMC 508 Mayo, Minneapolis, Minnesota 55455.
Objectives This study investigated the relationship between anti–factor Xa (anti-FXa) and activated partial thromboplastin time (aPTT) for monitoring intravenous unfractionated heparin (IV-UFH) in patients with continuous-flow left ventricular assist devices (CF-LVADs).
Background CF-LVADs have become mainstream therapy for patients with advanced heart failure. Thromboembolic events, device thrombosis, and bleeding continue to be a challenge with this technology. Adequate anticoagulation is required to prevent these adverse events.
Methods A prospective study of consecutive patients implanted with a CF-LVAD was conducted. Paired samples were considered concordant if aPTT values fell into expected ranges for subtherapeutic, therapeutic, and supratherapeutic anti-FXa levels. Heparin dosing was on the basis of anti-Xa levels.
Results A total of 340 paired values from 38 patients were evaluated. Anti-FXa and aPTT were discordant in 253 samples (74.4%), with a high degree of variability in aPTT for any given anti-FXa level (r2 = 0.57). Results were discordant in 104 samples (63.8%) from patients undergoing bridging therapy with warfarin and in 149 samples (84.2%) from patients with device obstruction and/or hemolysis (p < 0.001). The most common pattern of discordance was a supratherapeutic aPTT value despite a therapeutic anti-FXa level (49.1% for bridging vs. 75.8% for device obstruction and/or hemolysis; p < 0.001).
Conclusions Levels of aPTT were disproportionately prolonged relative to the corresponding anti-FXa levels in CF-LVAD patients, particularly those with device obstruction. Hemolysis and warfarin administration may falsely elevate aPTT, resulting in overestimation of heparin concentration and under-anticoagulation. Use of aPTT and anti-FXa to guide heparin therapy may lead to different estimates of heparin concentration in the same patient.
- activated partial thromboplastin time
- anti-factor Xa
- continuous-flow left ventricular assist device
- intravenous unfractionated heparin
Dr. Zantek has a minority equity interest in Endo International PLC; and has received research funding from Sekisui Diagnostics. Drs. Uriel and Eckman are consultants for Thoratec and HeartWare Inc. Dr. John has received research grants from Thoratec and HeartWare Inc.; and is a consultant for Thoratec. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Received September 26, 2014.
- Revision received November 22, 2014.
- Accepted November 25, 2014.
- American College of Cardiology Foundation