Effectiveness of aortic valve replacement surgery
The effectiveness of valve replacement surgery in treating aortic valve stenosis depends on how much your symptoms have improved and on a number of other factors, including:
- Whether you have heart failure.
- The cause of heart failure.
- Whether your heart has been permanently damaged.
- Whether you have other serious medical conditions.
The following sections explain how each of these factors affects the success of your valve replacement surgery.
A narrowed aortic valve causes a buildup of pressure (pressure overload) inside the left ventricle. To compensate for the pressure overload, your heart muscle thickens (hypertrophies) in an attempt to squeeze harder and force enough blood through the valve to meet the body's needs. Eventually the pressure overwhelms the left ventricle and begins to impair the ventricle's ability to pump blood, a condition called heart failure. By replacing the narrowed aortic valve with one that allows the blood to flow freely when the left ventricle contracts, you will effectively relieve the pressure overload in your ventricle.
If you do not have heart failure, valve replacement surgery can prevent permanent damage to your heart muscle from pressure overload and in time will relieve the hypertrophy that developed as your heart tried to compensate for the pressure overload.
If you do have heart failure, the effectiveness of valve replacement depends on the cause and the severity of your heart failure.
The cause of heart failure
If your heart failure is caused by pressure overload from aortic valve stenosis only, valve replacement surgery will almost always provide some degree of relief for your symptoms and your heart failure. The degree of improvement depends on whether the prolonged pressure overload in the left ventricle has permanently damaged your heart.
If your heart failure is caused partially or completely by coronary artery disease (CAD) or other heart conditions, valve replacement surgery still may relieve the pressure overload in the left ventricle, but it may not completely restore the ventricle's ability to pump blood. In most cases you will need to treat the other condition to see significant improvement in your heart's function. For example, if you have CAD and undergo coronary bypass surgery in addition to valve replacement surgery, the improvement in your heart function may be significantly increased. As with heart failure caused by aortic valve stenosis, the overall degree of improvement after treatment will depend on whether your heart has been permanently damaged.
Permanent heart damage
Damage to your heart refers primarily to damage that affects the heart's ability to contract and pump blood. Heart damage from aortic valve stenosis results mainly from the pressure overload in the left ventricle. Although the left ventricle can compensate for this pressure overload for a long time by thickening (hypertrophy), eventually the intense pressure will begin to stretch the ventricle out of shape, a process called dilation. If your ventricle dilates beyond a certain point, the heart will begin to lose its ability to contract. This is a principal mechanism of heart failure. Even when valve replacement surgery relieves the pressure in the left ventricle, your heart may not return to normal functioning if the muscle has been stretched too far.
A number of other heart conditions can permanently damage your heart and limit the effectiveness of valve replacement surgery. In particular, a heart attack (myocardial infarction, or MI) can kill a portion of the heart if one of the coronary arteries that supply oxygen-rich blood to your heart becomes blocked. If a previous heart attack has damaged the muscle in your left ventricle, valve replacement surgery will not fully restore the function of that muscle.
Other serious medical conditions
Serious medical conditions that can affect the results of valve replacement surgery include CAD and a previous heart attack, which are discussed above. It is not uncommon for people who have aortic valve stenosis to have other valve problems, such as aortic or mitral regurgitation (a leaky aortic or mitral valve), which can also affect the success of valve replacement surgery, particularly if more than one valve needs to be replaced.
Measuring the effectiveness of valve replacement surgery
Your doctor will measure your improvement after valve replacement surgery using the following key measurements:
- Size of left ventricle. When the new aortic valve relieves the pressure inside the left ventricle, the ventricle will no longer have to compensate for high pressure by thickening. As a result, the degree of thickening will decrease over time. If the pressure had already begun to stretch (dilate) the ventricle, the space inside the ventricle should also get smaller.
- Function of left ventricle. The most important measure of how well your left ventricle is functioning is your ejection fraction, which is the percentage of the blood inside the filled ventricle that pumps each time the ventricle contracts. When your new valve relieves the pressure overload and allows blood to flow freely, the ventricle should regain some or all of its ability to pump blood effectively.
Does valve replacement surgery "cure" aortic stenosis?
Even if valve replacement surgery succeeds in restoring your heart to original function, replacing your aortic valve does not "cure" the condition for the following reasons:
- You may have to take medication after valve surgery, particularly if you receive a mechanical valve, in which case you will have to take medication for as long as you have the valve.
- Current replacement valves do not last forever—you may need to replace the valve in the future.
- Artificial valves do not have openings as wide as a normal valve and may not effectively relieve pressure overload.
- There is also a small chance that the valve will malfunction, so you will need to periodically monitor how well the valve is working.