Valvular Heart Disease

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Heart Valve Defect

There are 4 valves in the heart- Tricuspid Valve, Mitral Valve, Pulmonary Valve, Aortic Valve. We have discussed in detail about the role of each valve. But sometimes a defect may arise in the valve of a person and that cause serious complications. First let us understand what are the defects that may arise with the valves.

1. Regurgitation: We learnt that the basic function of a valve is to maintain an uni-directional flow of blood so that blood does not flow back. For example, if the Left Ventricle pumps blood into the Aorta, but the Aortic Valve does not close tightly, then some amount of blood will flow back into the left ventricle which is not at all desirable. This condition will be called as Aortic Regurgitation. The same phenomenon can occur with any other Valve. Lets, take the Mitral Valve. When the Right Ventricle pumps blood into the Aorta, the Mitral valve is closed so that blood does not enter the Right Atrium, but if the Mitral Valve does not close properly, some blood will leak into the Right Atrium. So Regurgitation is the process when the Valve does not close completely
2. Stenosis: We learnt that stenosis means narrowing of the opening. So basically what happens in Stenosis, the flaps become thicker and therefore, when the Valve opens, the diameter of the opening is reduced. That means that lesser volume of blood will pass through that valve. This is the opposite of Regurgitation, when the Valve does not open completely. Lets understand this by an example. The same example of Aortic Valve. If there is a stenosis, complete blood will not pass from the Left Ventricle. Therefore the Left Ventricle has to pump harder to pump out the blood. This eventually leads to thickening of the walls of Left Ventricle called Left Ventricular Hypertrophy.
3. Atresia: In this condition, the valve isn't formed, and a solid sheet of tissue blocks the blood flow between the heart chambers. This is generally a congenital problem

Causes of Heart Valve Defects

Valve Defects can be Congenital which is basically present by birth. If the defect is small, it may cause very little or no symptom at all. But in some cases as the age progresses, the valves may degenerate over time causing the symptoms to develop and that how the problem gets detected. In acquired valve disorders, the reason can be a Streptococcus infection which releases a toxin which damages the valve of the heart.

Valve Repair and Replacement

If the valve is suffering from a Stenosis or Regurgitation, then there are two approaches to correct this. The surgeon will check if the valve can be repaired or not, otherwise the valve needs to be replaced. There are two types of Valves available for replacement- Mechanical Valve and Tissue Valve. Mechanical heart valves are made from materials such as titanium and carbon. They usually consist of two leaflets and a metal ring surrounded by a ring of knitted fabric, which is sewn onto the heart in place of the original valve. There are several different models available for aortic and mitral replacement surgeries.

Tissue valves, also known as biological or bioprosthetic valves, are composed of animal or human tissue. The valves are derived from animal tissue such as porcine (pig), bovine (cow) and equine (horse) models, and then fixed with a preserving solution that may be mounted on a flexible frame to assist in deployment during surgery. As with mechanical valves, the bottom of a tissue valve is often surrounded by a ring of knitted fabric that is sewn onto the heart.

What are the Advantages and Disadvantages of Mechanical v/s Tissue Valve?

The main advantage of Mechanical valves is that they are very durable. However, these valves provide a surface on which blood clots can form easily. As a result, anyone who has been implanted with a mechanical valve needs to be on lifelong blood-thinning medication, such as warfarin, to prevent the development of blood clots that can cause heart attack or stroke.  Advantages of Tissue valves compared to mechanical valves include the avoidance of lifelong warfarin therapy to prevent the development of blood clots. A disadvantage is their relatively poor durability compared to mechanical valves, with many requiring a re-operation in 10 to 20 years.

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