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 thinners for mechanical valves are vitamin K antagonists (VKA). The amount of VKA 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, the risk of bleeding is higher, while an INR that is too low increases the risk of blood clots. 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 mechanical valves are thought to be at lower risk of clot formation and may not require the INR targets to be as high as once believed. A summary of studies on higher versus lower INR targets suggests that lower INR targets may prevent blood clots just as well as higher INR targets with less risk of bleeding. A large study comparing a lower INR target to standard INR targets in patients with a mechanical heart valve is needed to determine the optimal target. We have demonstrated conducting such a study is feasible. In the Low INR to Minimize bleeding with mechanical valves Trial (LIMIT trial), patients are randomized (like the flip of a coin) to either a low INR target or to the current recommended INR target. Patients who have had their aortic heart valve replaced with a mechanical valve for at least 3 months are eligible. We will enroll 2625 patients from 30 centres internationally to evaluate the safety and efficacy of a common, lower INR range in patients with bileaflet aortic mechanical valves. The LIMIT trial will increase the safety of using blood thinners in patients with mechanical heart valves.