Grant: Project Grant

Heart valves control blood flow through the heart. If they are damaged, patients may need heart surgery to replace the diseased valve with a mechanical valve. Mechanical heart valves require life-long blood thinners to prevent blood clots from forming. These clots can cause strokes or valve failure. The only approved blood thinner for mechanical valves is called warfarin (Coumadin). The amount of warfarin that a patient takes is adjusted to achieve a degree of blood thinness called the International Normalized Ratio (INR). If the INR is too high, there is higher risk of bleeding, while an INR that is too low increases the risk of blood clots. The recommended INR targets for patients with mechanical heart valves aim to prevent blood clots while keeping the risk of bleeding low, but these recommended targets are based on low quality evidence. Newer designs of mechanical valves are thought to be a lower risk of clot formation and may not require the INR targets to be as high as once believed. A recent summary of studies on higher versus lower INR targets suggests that lower INR targets may prevent blood clots just as well as higher INR target with less risk of bleeding. A large study comparing a lower INR target to the standard INR target in patients with a mechanical heart valve is needed to determine the optimal target. In the Low INR to Minimize bleeding with mechanical valves Trial (LIMIT trial), patients will be randomized (like the flip of a coin) to either a low INR target or to the current recommended INR target. Adult patients who have had their aortic heart valve replaced with a mechanical valve for at least 3 months will be eligible. In this early study phase, we will enroll 400 patients from 5 centres in Canada to assess if a large, international study is feasible with the current study design. The LIMIT trial has the potential to increase the safety of using blood thinners in patients with mechanical heart valves.