Impact of Initial Warfarin Dosing on Time in Therapeutic Range for Postoperative Left Ventricular Assist Device Patients.

Abstract

Initial warfarin dosing and time in therapeutic range (TTR) are poorly characterized for early post-operative left ventricular assist device (LVAD) patients. This study evaluated TTR after LVAD implantation compared between patients receiving low-dose (<3 mg) and high-dose (≥3 mg) warfarin. This single-center, retrospective analysis included 234 LVAD patients who received warfarin within 5 days of implantation. The primary outcome was TTR during the 5 days following first international normalized ratio (INR) ≥2 compared between low-dose and high-dose groups. Secondary outcomes were hospital and intensive care unit length of stay, time to first INR ≥2, TTR after first INR ≥2, and reinitiation of parenteral anticoagulation. No difference in TTR was detected between warfarin groups (57.2% vs. 62.7%, P = 0.13). Multivariable analysis did not detect any factors predictive of TTR during the primary outcome timeframe, but age and body mass index were associated with the warfarin dose. The low-dose group received a mean warfarin dose of 1.9 mg (±0.64 mg), and the high dose group received 4.34 mg (±1.38 mg). Cohort TTR during the primary outcome timeframe was 60.5% and 56.5% for hospitalization. The low-dose group had longer intensive care unit length of stay, shorter time to therapeutic INR, and more frequently reinitiated parenteral anticoagulation. Patients with recent LVAD implantation are complex and have diverse warfarin sensitivity factors, which did not allow for optimal warfarin dose detection, although half of all patients received doses between 2.04 mg and 4.33 mg. Individualized dosing should be used, adjusting for patient-specific factors such as age, body mass index, and drug interactions.