The mitral valve is one of the heart’s four valves, acting as a one-way door between the upper left chamber (left atrium) and the lower left chamber (left ventricle). Its function is to open and allow oxygen-rich blood into the ventricle and then snap shut to prevent blood from leaking backward when the ventricle contracts to pump blood to the body. Mitral Valve Replacement (MVR) is a surgical procedure that involves removing a damaged or diseased native mitral valve and replacing it with a manufactured, prosthetic valve to restore proper blood flow.
Conditions Requiring Mitral Valve Replacement
The need for MVR typically arises when the mitral valve is damaged to the point where it severely impedes the heart’s ability to move blood efficiently. The two main types of dysfunction are a restricted opening (mitral stenosis) and a failure to close properly (mitral regurgitation).
Mitral stenosis occurs when the valve leaflets become stiff, often due to calcification or a history of rheumatic fever, narrowing the passageway. This narrowing causes blood to back up into the lungs and forces the heart to work harder to push blood through the smaller opening.
Mitral regurgitation, or a “leaky valve,” happens when the valve leaflets do not close tightly, allowing blood to flow backward into the left atrium with each heartbeat. This inefficiency leads to strain and enlargement of the heart chambers. Both conditions cause symptoms such as fatigue and shortness of breath, particularly during physical activity. If the damage is too extensive for a surgical repair, replacement is necessary to prevent heart failure.
Choosing the Replacement Valve Type
When a replacement is necessary, patients and surgeons must choose between two primary prosthetic types: mechanical valves and bioprosthetic or tissue valves. Mechanical valves are highly durable, typically constructed from materials like pyrolytic carbon, and are designed to last for the patient’s lifetime. However, their synthetic surfaces pose a high risk of blood clot formation, necessitating a strict regimen of lifelong anticoagulant medication, such as Warfarin.
Bioprosthetic valves are created from animal tissue, usually from pigs or cows, and are mounted on a frame for implantation. The main advantage of these tissue valves is a much lower risk of clotting, meaning patients often do not require lifelong daily anticoagulants. However, bioprosthetic valves are less durable and typically begin to degenerate and fail after 10 to 15 years, often requiring a second surgery.
The patient’s age is a primary factor in this decision, as mechanical valves are generally preferred for younger patients who are likely to outlive a tissue valve. Patients under 60 may be advised to select a mechanical valve due to its durability. Conversely, patients over 70 are often candidates for a bioprosthetic valve to avoid the risks associated with lifelong anticoagulation therapy. The ability to manage the required medication and monitoring is also a serious consideration.
Surgical Approaches for Replacement
The traditional method for performing MVR is through a median sternotomy, which involves a large incision down the center of the chest and dividing the breastbone to gain full access to the heart. Once access is established, the patient is connected to a heart-lung machine, which takes over the function of circulating and oxygenating the blood while the heart is temporarily stopped. The surgeon then removes the diseased mitral valve and sews the new prosthetic valve into the valve ring (annulus).
An alternative approach is minimally invasive mitral valve surgery, performed through a much smaller incision, often on the right side of the chest (minithoracotomy). This technique avoids a full division of the sternum, leading to reduced post-operative pain and a more favorable cosmetic outcome. Minimally invasive procedures may also use robotic technology, allowing the surgeon to operate with enhanced precision through small ports.
While the minimally invasive approach is becoming common, it may require a slightly longer time on the heart-lung bypass machine compared to the traditional sternotomy. However, the benefits often include a shorter hospital stay, fewer blood transfusions, and a faster return to normal daily activities. The choice of surgical technique depends on the patient’s overall health, the complexity of the valve disease, and the surgeon’s specific expertise.
Recovery and Long-Term Management
The initial recovery period involves a hospital stay of approximately four to seven days, beginning in the intensive care unit for close monitoring. Pain management is a focus, and the medical team monitors for immediate complications, such as irregular heart rhythms or excessive bleeding. Patients are encouraged to begin walking and engaging in light activity within the first few days.
Full physical recovery, including the ability to lift heavy objects and return to strenuous activity, generally takes between four to twelve weeks, depending on the surgical approach. Long-term management requires anticoagulation for mechanical valve recipients, who must take blood-thinning medication daily. This medication, typically Warfarin, requires regular blood tests to ensure the dose prevents both clotting and excessive bleeding.
Patients with bioprosthetic valves may only need antiplatelet therapy, such as daily aspirin, but they require consistent monitoring for valve deterioration. Annual or bi-annual follow-up appointments, including echocardiograms, are necessary to check the function of the new valve. Vigilance is required to recognize signs of potential prosthetic valve failure, such as new or worsening shortness of breath, which may indicate the need for a reoperation.