A study on complication and monitoring of warfarin in post-valve surgery

This study was carried out to determine the incidence of complication related to warfarin in patients with valve surgery and identify potential risk factors for complication and study its monitoring aspects.

A combined retrospective and prospective observational study including a total of 185 patients who underwent mechanical valve replacement in Shahid Gangalal National Heart Centre. The study was conducted from 4 November 2006 till 1 February 2007.

There were a total of 141 episodes of bleeding. Among them significant bleeding occurred in 15.7% patients, major bleeding was 3.2 per 100 patient-years (3.8%) and minor bleeding was 11.8 per 100 patient-years (11.9%). Epistaxis (16.8%) was the most common bleeding complication. Menorrhagia was the most common bleeding complication in females with 20.5 per 100 patient-years (27.4%). Thromboembolic complications occurred at the rate of 2.3 per 100 patient-years. Patients on warfarin were outside the INR target range 67.8% of the time, with 21% INR values above range and 46.8% INR values below range. However, dose adjustment was done only 31.8% of times when INR was outside range.

There is high incidence of bleeding complication in patients on warfarin and hypertension is significantly associated with bleeding. Difficulty in tightly controlling INR probably is related to high incidence of bleeding. Better patient education, stricter adjustment of INR, frequent monitoring of INR at peripheral hospitals and standardization of the test at different hospitals are suggested to reduce the warfarin related complications.