Aortic Stenosis and the Role of Catheter Based Therapies

When Less Invasive TAVR is Preferable in the Treatment of this Serious Heart Condition

Aortic valve disease is one of the most encountered structural abnormalities of the heart.  The aortic valve is a trileaflet structure that separates the left ventricle from the aorta. In systole, during left ventricular contraction, the aortic valve opens between 3 -5 cm2 to allow blood flow.

Aortic valve disease is one of the most encountered structural abnormalities of the heart.  The aortic valve is a trileaflet structure that separates the left ventricle from the aorta. In systole, during left ventricular contraction, the aortic valve opens between 3 -5 cm2 to allow blood flow through the aorta and to the rest of the body.

The most common disease of the aortic valve is aortic stenosis. Aortic stenosis is the result of calcification and narrowing of the aortic valve. As a result, the valve does not open adequately in systole, causing strain and pressure overload on the left ventricle. Aortic stenosis is the result of active inflammation of the valve, which in many ways is similar to atherosclerosis.

Risk factors for developing aortic sclerosis include hypertension, high cholesterol, diabetes and chronic kidney disease. There is perhaps also a genetic predisposition to developing aortic stenosis. Aortic stenosis is more prevalent in the older population. It is mostly diagnosed and treated in patients in their 70’s and 80’s. It is estimated that over six percent of the population in the United States over the age of 70 suffer from aortic stenosis. However, aortic stenosis can present earlier if the patient is born with an abnormal valve such as an unicuspid or bicuspid valve. In these instances, symptoms develop earlier in the fifth and sixth decade of life.Healthy Aortic Valve

Symptoms of aortic stenosis include chest pain, shortness of breath and palpitation. If left untreated, it can ultimately cause congestive heart failure and loss of consciousness – and ultimately sudden cardiac death. The three-year prognosis in aortic stenosis is extremely poor once the patient has developed symptoms.

Diagnosis of aortic stenosis hinges on a physical examination and noninvasive diagnostic cardiac testing such as echocardiography.  Severe aortic stenosis results in a harsh systolic murmur heard best on the left sternal border. The second heart sound is also blunted or absent in this area. Echocardiography shows thickening and calcification of the valve with significantly reduced mobility in systole. The ultimate diagnosis is made by measuring pressure gradient across the aortic valve, utilizing Doppler Wave Echocardiography. A mean gradient of over 40 mmhg, or a valve area of less than 1 cm square, strongly predicts severe aortic stenosis.Aortic Valve Assessment

Treatment of aortic stenosis requires active intervention. Medical therapy alone does not resolve the severe narrowing of the valve. Traditionally, patients have required open heart surgery to replace the narrowed valve with either a bioprosthesis or a mechanical valve. This would require a sternotomy and 4-6 weeks of recovery post operation.

Over the past decade, though, a new technique utilizing transcatheter methods has been shown to be either equivalent or superior to surgical replacement in most patients regardless of their surgical risks. During this procedure commonly known as Transcatheter Aortic Valve Replacement (TAVR), a new valve is advanced from the femoral artery in the groin (in most instances) and placed inside the narrowed valve. There is no surgical incision during TAVR, therefore recovery is much faster.Transcatheter Aortic Valve Replacement

 

Patients undergoing TAVR need elaborate work up prior to their procedure. Aortic valve size needs to be determined prior to the procedure, unlike the traditional procedure when the surgeon decides on valve size during the surgery. While most valves are delivered through the femoral arteries, there are instances where femoral arteries are either too small or diseased to accommodate delivery of the valve. In these instances, alternative access should be utilized to deliver the valve.

A gated CT angiography is essential to address sizing and access before the procedure. Cardiac catheterization is also needed to define patency of the coronary arteries before the procedure. Significant coronary artery disease usually needs to be addressed prior to TAVR. There are currently three commercially available TAVR valves. Which valve to use depends on the anatomical and clinical characteristics of each individual patient for optimal outcome.

Finally, TAVR in lieu of surgical aortic valve replacement (SAVR) is determined on a case by case basis. For example, a patient with extensive multivessel coronary artery disease (CAD), who will need coronary bypass surgery, should also have SAVR at the same time. Some patients with bicuspid aortic valve also have ascending aortic dilatation and will need surgical repair of their aorta, which can be done at the time of SAVR.

Lastly, there are patients who can go either route depending on their circumstances. For example, a younger patient with a small aortic valve might undergo TAVR now. But it is conceivable that their TAVR valve will deteriorate over the next decade or two and they will need another procedure. The small size of the aortic valve might prohibit another TAVR procedure down the line. So, this patient might decide to have a TAVR now and reserve SAVR for a later time, or, alternatively, do the reverse depending on the circumstances. That is why it is important that the treatment recommendation is made after input from every member of the valve team, including an interventional cardiologist as well as a cardiac surgeon.