Answer:

Indefinite anticoagulant use after mechanical heart valve replacement is mandatory. Mechanical heart valves are made from artificial materials (metal, carbon, etc.). When these materials come into contact with blood, the body identifies them as "foreign objects" and tends to activate the natural blood clotting process. Regular anticoagulant use helps avoid this risk.

In addition, after valve replacement surgery, small blood clots can form and adhere to the surface of the artificial heart valve, leading to two dangerous complications. The first is heart valve obstruction, which occurs when the blood clot grows larger, preventing the valve from opening and closing normally, causing acute valve obstruction. This is a medical emergency and can cause acute heart failure, stroke, and death if not treated promptly. The second is systemic embolism, where the blood clot can break off and travel through the bloodstream to other organs, causing blockages such as cerebral embolism (causing stroke), limb embolism, and kidney embolism.

To prevent these complications, you need to take anticoagulants, specifically vitamin K antagonists. The treatment goal is to maintain the International Normalized Ratio (INR) within a certain limit, called the "target therapeutic range." Your doctor will determine the appropriate INR range for your valve type and location. Adhere to the prescribed dosage and attend follow-up appointments to monitor your INR to ensure your heart valve is functioning properly and safely.

Regarding the relationship between anticoagulants and heart attack prevention, anticoagulants do not prevent heart attacks. The main cause of a heart attack (also known as a myocardial infarction or acute angina) is atherosclerotic plaques within the coronary arteries (the main blood vessels that supply the heart). Over time, these plaques can rupture. When this happens, the body reacts by forming a blood clot at the rupture site to "patch" it. This blood clot grows rapidly, suddenly blocking blood flow to a part of the heart muscle, causing necrosis in that area. This process primarily involves platelets and the local coagulation system against a background of atherosclerosis.

Meanwhile, vitamin K antagonists mainly inhibit vitamin K-dependent clotting factors in the liver, thereby thinning the blood and preventing blood clot formation in the heart chambers and on the surface of the artificial valve. Theoretically, thinner blood may slow down the formation of a blood clot when a plaque ruptures, but this is not the primary or effective mechanism for preventing heart attacks.

Heart attack prevention mainly focuses on controlling risk factors (high blood pressure, diabetes, dyslipidemia, smoking, stress, obesity, etc.). Use medications (if prescribed by a doctor) such as antiplatelet drugs (the primary drug class that prevents platelets from sticking together and to ruptured plaques, usually prescribed for patients at high risk or who have had a heart attack) and statins (cholesterol-lowering medications that help stabilize plaques, reduce inflammation, and prevent rupture).

Regular anticoagulant (vitamin K antagonist) use after mechanical heart valve replacement surgery is necessary to prevent complications like valve obstruction or stroke, but it's not the primary measure to prevent heart attacks. You need to strictly adhere to the prescribed anticoagulant regimen and monitor your INR. Discuss other cardiovascular risk factors with your doctor to develop a comprehensive plan for preventing coronary artery disease and heart attacks.

MSc. Dr. Pham Hoang Trong Hieu

Interventional Cardiology Center

Tam Anh General Hospital, TP HCM