The aorta is the main artery that carries blood out of the heart. From the left ventricle, blood flows through the aortic valve into the aorta.

In cases of aortic stenosis, the aortic valve does not open fully, decreasing blood flow from the heart. This requires the heart to pump too hard, raising blood pressure.

Ultimately, decreased blood flow weakens the heart, which can lead to heart failure.

Although fewer people suffer from aortic stenosis than mitral regurgitation, the incidence increases with age. About 1.5 million people have severe enough cases to cause symptoms that include:

• Chest pain or tightness (angina)

• Feeling faint or fainting from exertion

• Shortness of breath, especially with exertion

• Fatigue, especially during increased activity

• Heart palpitations (rapid fluttering heartbeat)

Aortic stenosis is caused by valve damage from rheumatic fever or calcification of the valve, which comes with aging.

On average, this gradual stiffening begins to occur around the age of 65, and causes symptoms within five years.

In its early stages, aortic stenosis can be managed with cardiac medications. But if it becomes serious enough to cause symptoms, surgery to repair or replace the valve may be required.

If the damage is not severe, a surgeon can remove calcification or tissue damage to restore normal function.

If the damage is severe, however, the valve may need to be replaced. In this case, the narrowed valve is removed and replaced with either a biological tissue valve or a mechanical one.

It is estimated that 20 to 30 percent of patients are too frail to undergo open-heart surgery required to repair aortic stenosis. In the past, nothing could be done for these patients.

But a few years ago, the FDA approved a procedure called transcatheter aortic valve replacement, which can replace the aortic valve without surgery.

For this procedure, physicians insert a catheter (a thin, flexible tube) through an incision in the groin or side of the chest to guide an artificial valve to the heart. Once in the proper position, the new aortic valve opens and begins to work.

Because this procedure is designed for patients who are frail either due to age or pre-existing medical conditions, it carries a higher risk of life-threatening complications.

In addition, some patients develop heartbeat irregularities with the insertion of the valve, and need a pacemaker afterward.

In a study presented at the American College of Cardiology Scientific Sessions, researchers showed that the procedure reduced all-cause mortality by 5 percent after one year.

The study was hailed as a validation for this nonsurgical procedure.