A descriptive evaluation of warfarin use in patients with pulmonary arterial hypertension

Although warfarin is often recommended for pulmonary arterial hypertension (PAH) management to mitigate thrombotic risk and improve survival, limited information exists to guide anticoagulation therapy. The purpose of this study was to compare and contrast warfarin therapy monitoring requirements and outcomes in patients with PAH and atrial fibrillation (AF) receiving long-term anticoagulation.

Patients initiated on warfarin for PAH between January 1, 2000 and December 31, 2008 were matched by warfarin initiation date (±90 days), age (±5 years), chronic disease score (±1 points), and sex to patients initiated for AF. The primary study endpoint was frequency of INR monitoring per 30 days of observation. Secondary endpoints included indicators of INR control and warfarin-related adverse events.

A total of 84 patients were included - 18 and 66 in the PAH and AF groups, respectively. Patients with PAH had a higher median rate of INR measurements per 30 days compared to patients with AF (median=2.0, interquartile range [IQR]=1.5 - 2.3 vs. median=1.6, IQR=1.3 - 2.0, p=0.046). There were no differences between groups with respect to percent of INR measurements in range, overall time in therapeutic range (TTR), or warfarin-related adverse events (all p>0.05). Study results suggest that patients with PAH may be more difficult to manage as seen through more frequent INR monitoring. Potential management difficulties did not translate to a lower performance on indicators of INR control or increased risk of warfarin-related adverse events.