Aortic Valve Stenosis
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Aortic Valve Stenosis
Aortic Valve Stenosis is the narrowing or obstruction of the hearts aortic valve. The aorta is a large artery that originates in the left ventricle (lower chamber) of the heart. The narrowing and obstruction of the aortic valve prevents it from opening properly and blocks the flow of blood from the left ventricle to the aorta and onward towards the rest of the body. Aortic valve stenosis occurs in approximately 5 out of every 10,000 people.1 It occurs more commonly in males than females. Symptoms do not often appear until middle age or older.
Aortic valve stenosis is characterized by the left ventricular pressure being much greater that the aortic pressure during left ventricular ejection. The pressure gradient across the stenotic lesion results from both increased resistance (related to narrowing of the valve) and turbulence distal to the valve. The magnitude of the pressure changes is determined by the severity of the stenosis and the flow rate across the valve. Severe aortic stenosis results in reduced ventricular stroke volume due to increased afterload, increased end-systolic volume, and a compensatory increase in end-diastolic volume and pressure. Aortic valve stenosis is associated with a mid-systolic murmur because of turbulence that occurs as blood moves across the stenotic valve.5
Aortic valve stenosis of any cause can be a serious condition because it can weaken the heart. If the aortic valve is narrowed, the left ventricle has to work harder to pump a sufficient amount of blood into the aorta and onward to the rest of the body. In response, the left ventricle may thicken and enlarge. At first, these adaptations help the left ventricle pump blood with more force, but eventually these changes weaken the left ventricle and ultimately the heart overall.
The most common cause of aortic valve stenosis in patients 65 or older is called “senile calcific aortic stenosis”, or otherwise known as calcification, which is calcium build up on the valve.2 With aging, protein collagen of the valve leaflets is destroyed, and calcium is deposited on the leaflets. This calcification reduces valve leaflet mobility causing turbulence across the valve, scarring, thickening, and ultimately stenosis of the valve.
Bicuspid aortic valve, also known as congenital heart defect, is the most common cause of aortic valve stenosis in patients under the age of 65.2 Normal aortic valves have three thin leaflets called cusps. About 2% of people are born with aortic valves that have only two cusps (bicuspid valves).2 Although bicuspid valves usually do not impede blood flow when the patients are young, they do not open as widely as normal valves with three cusps. Therefore, blood flow across the bicuspid valve is more turbulent, causing increased wear and tear on the valve leaflets. Over time, excessive wear and tear leads to calcification, scarring, and reduced mobility of the valve leaflets. About 10% of bicuspid valves become significantly narrowed resulting in the symptoms and heart problems of aortic valve stenosis.2
Another cause of aortic valve stenosis is rheumatic fever. Rheumatic fever is a complication of strep throat and a once common childhood illness in the United States resulting in damaged heart valves. Rheumatic fever may result in scar tissue forming on the aortic valve which alone can narrow the aortic valve and lead to aortic valve stenosis. Scar tissue can also create a rough surface on which calcium deposits can collect contributing to aortic valve stenosis later in life. Rheumatic fever may damage more than one heart valve, and in more than one way, so the valve may not open or close properly. While rheumatic fever is no longer prevalent in the United States, some older adults had rheumatic fever as children.
The symptoms of aortic valve stenosis range from mild to severe. Signs and symptoms typically develop when narrowing of the valve is severe and can include chest pain, dizziness, fatigue (especially during times of increased activity), shortness of breath, and heart murmurs. Most children with aortic valve stenosis have no symptoms, so its quite difficult to detect. A small number of children may be prone to dizziness and fainting within the first ten years of life. If the obstruction is great, infants may suffer from severe heart failure, although death is uncommon. Adolescents with hypertrophic cardiomyopathy, a type of aortic stenosis where the left ventricle is noticeably enlarged, have the greatest risk of sudden heart failure.4
Aortic valve stenosis may not produce any warning signs right away, making it difficult to detect at first. It is often discovered during a routine physical when a doctor hears a heart murmur. This murmur may occur long before other signs and symptoms develop. A doctor can also detect pulse abnormalities and will see irregularities on an electrocardiogram (ECG). A chest x-ray may also show an enlarged left ventricle. An echocardiogram is another technique that uses ultrasound waves to create an image of the heart and its function. In cases where severe blockage is suspected and surgery most likely, doctors