Hello, I'm Jeremy Thaden. I'm a cardiologist at Mayo Clinic and I'd like to talk to you today about aortic valve disease. The normal aortic valve is a three leaflets structure that separates the ascending aorta from the left ventricle, which is the main pumping chamber of the heart.
During the contraction of the heart, the aortic valve typically opens three to five square centimeters. As the heart relaxes, this valve then closes and prevents leakage of blood from the ascending aorta backwards into the heart. Over the course of one's life span, the aortic valve typically opens and closes and average of several billion times.
There are two main disease categories that can affect the aortic valve during one's lifetime. The first is aortic stenosis. This is uncommon in young patients, but becomes exponentially more common as we age.
The prevalence is felt to be 6% or greater in each grade, age 75 or older here in the United States. It's felt a result from an active inflammatory process. It has microscopic features which are in some ways similar to atherosclerosis.
Risk factors for the development of aortic stenosis include high blood pressure, abnormal lipids, diabetes, and chronic kidney disease. Some individuals are felt to be genetically predisposed aortic stenosis. Aortic stenosis is in general a progressive disease. Progressive calcification of the valve results in progressive narrowing and a pressure overload phenomenon in the heart. This can cause thickening of the heart muscle and stiffening.
In early phases, this can cause shortness of breath and chest discomfort. In more advanced phases, this can cause congestive heart failure, sudden loss of consciousness, and in some cases, sudden death.
Individuals with a normal trileaflet valve typically don't experience significant narrowing until their seventies or eighties. By contrast, individuals with a congenitally abnormal valve, meaning a unicuspid or single cusp valve, or a bicuspid, a two cusp valve. These patients frequently will suffer significant narrowing of the valve earlier in life. For instance, those with bicuspid valve may suffer from significant narrowing in their fifties or sixties.
Diagnosis is often suspected based on physical examination and can be confirmed by transthoracic echocardiography. By echocardiography, we are able to determine the heart size and function, were also able to quantitate the degree of stenosis. We're able to calculate a valve area, and a mean transfer valvular gradient. A valve area less than one centimeter squared and a mean gradient greater than 40 millimeters of mercury is generally considered severe.
In select cases, we also use cardiac CT or cardiac catheterization, to better understand the severity of narrowing. Indications for operation in aortic valve stenosis include a severe degree of narrowing in conjunction with symptoms, cardiac dysfunction, or in some cases, rapid progression of the degree of narrowing.
By contrast, aortic regurgitation is a condition where there's significant leakage at the valve from the ascending aorta backwards into the heart. Instead of a pressure overload phenomenon, this results in a volume overload phenomenon. This can cause dilatation of the heart muscle as well as thickening of the heart muscle.
There are a variety of reasons why the aortic valve can leak. Most commonly, this results from a structural abnormality of the valve itself. This can be a congenitally abnormal valve like a unicuspid valve or a bicuspid valve. Alternatively, this can be an acquired condition where there's previous infection of the valve or endocarditis.
In some cases there can be significant leakage even in the setting of a structurally normal aortic valve. This is most common if there's significant dilatation of the aortic root or an ascending aneurism. Diagnosis again, is predominantly suspected based on physical examination and is confirmed by transthoracic echocardiography. Just like aortic stenosis, we're able to quantify the severity of leakage. But sometimes transesophageal echocardiography or a cardiac MRI is required to better understand the degree of leakage.
Indications for an operation and aortic valve regurgitation include severe degree of leakage in combination with symptoms: Cardiac dysfunction or significant cardiac enlargement. Aortic valve disease is in general a surgically treated disease. There are no medical options that are effective in treating either aortic stenosis or aortic regurgitation.
In most cases this requires aortic valve replacement. However, there are minority of cases where these valves can be repaired. However, in recent years, there have been increasing options available for patients with these two diseases. Recently we've developed techniques in addition to a traditional open operation. We have minimally invasive techniques such as thoracotomies that can be used to treat these diseases without an open sternotomy.
More recently, there has been development of transcatheter techniques or TAVR. This technique involves small catheters inserted typically through the groin arteries that result in replacement of the valve without midline sternotomy and without requiring the need for cardiopulmonary bypass.