Higher-Than-Usual Target International Normalized Ratio (INR) Range Required With On-X Aortic Valve Secondary to Recurrent Thromboembolic Strokes: A Case Report.

Although the On-X aortic valve (AO) is considered less thrombogenic compared to its counterparts, we present a case where recurrent thromboembolic ischemic stroke occurred, first with a sub-therapeutic, then even with an elevated International Normalized Ratio (INR).  A 36-year-old male, the background of On-X AO replacement but no other risk factors, developed thromboembolic stroke twice while on Warfarin, first with INR 1.4, second with INR 2.