Mitral Valve Replacement: Indications and Surgical Risks

The mitral valve is the heart valve which is present on the left side of the heart separating and regulating the blood flow between the left atrium and ventricle. Blood which gets oxygenated in the lungs enters the left atrium and flows to the ventricle through the mitral valve. After this, the valve closes when the left ventricle contracts to prevent backflow into the atrium, allowing blood to enter the aorta (the large artery leaving the left ventricle) and supply the rest of the body.

Mitral valve replacement is a surgical procedure where a new prosthetic valve is placed over or in lieu of the damaged mitral valve. This is done when the damage is too severe to be treated by mitral valve repair alone.

Indications for Mitral Valve Replacement

Structural changes in the mitral valve can result in mitral stenosis or narrowing with inadequate blood flow across the valve, or to mitral regurgitation with loose valves that do not close properly, allowing backflow of blood from the ventricle to the atrium. Both conditions require correction depending on the severity of the problem.

Types of Prosthetic valves

• Biological valves: these valves are made from tissues obtained from animals like pigs and cows. Human heart valve tissue is also frequently being used. These are effective at restoring function, but are however prone to degeneration with time, and may require a second replacement after 10 to 15 years.
• Mechanical Valves: these valves are made from metal or other synthetic material. They are robust and do not degrade with time. However, they have the risk for serving as a surface for clot formation. Hence, the individual receiving a mechanical valve will need to take blood thinning medication for the remainder of their life.

Surgical Approach

The procedure can be done through multiple surgical approaches:

• Open heart surgery: This involves the traditional surgery where the individual is placed under anaesthesia and the chest is opened by a sternotomy, an incision through the sternum (breastbone). The patient is places on a heart lung machine while the beating of the heart is stopped to facilitate handling the heart for the procedure. Recovery takes longer and a large scar is visible on the front of the chest.
• Minimally invasive heart surgery: In this, the heart is accessed by making several incisions on the side of the chest to allow entry of surgical instruments. The patient is then placed on a heart lung machine for the duration of the procedure. Recovery takes a shorter time, there is less pain and better cosmesis is achieved.
• Catheter based procedure: This involves inserting a thin wire (catheter) through a peripheral artery to reach the heart valve. Another wire is inserted carrying the new heart valve which has been folded to occupy little space. At the site of the mitral valve, the new valve is released and it expands to take the place of the old one. The advantage of catheter procedures lies in its shorter recovery time and lesser pain.

The choice of surgical approach is made based on the type of procedure planned and the surgeon’s expertise with it. It is definitely better to undergo open heart surgery from an experienced surgeon than to demand minimally invasive surgery from someone inexperienced.

Risks and Side Effects of Surgery

• Bleeding
• Blood clot formation and risk of dislocation to rest of the body
• Stroke arising from a dislodged blood clot or from poor blood supply to the brain during surgery
• Arrythmias or abnormal heart rhythm
• Heart attack from reduced blood supply to the heart tissue during surgery
• Inadequate correction or further damage to the heart valves
• Infection of the valves and blood stream (Infective Endocarditis)
• Death

Prognosis and Post-Surgical Care

Generally, patients recover well and are able to resume normal daily activities. Depending on the nature of the new valve being inserted, the individual may need to take additional medications.

In the first few months, all patients will be required to take a blood thinner such as warfarin to prevent the formation of blood clots. For those with mechanical valves, blood thinners need to be continued lifelong. This will also involve regular monitoring of effectiveness of warfarin though measurement of INR (International Normalised Ratio). The desired value is 2 – 2.5 for individuals with a mechanical heart valve.

Periodic follow up with the cardiologist and primary care physician is required to maintain health. Lifestyle modification, incorporating a balanced diet, moderate exercise and smoking cessation is also beneficial.

References:

1. What is heart valve disease? National Heart, Lung, and Blood Institute
2. What is heart surgery? National Heart, Lung, and Blood Institute