What is Aortic Valve Stenosis (AS)?

Aortic valve

The heart has four chambers. There are two chambers at the top of the heart (atria) and two pumping chambers at the bottom (ventricles). Each ventricle has two valves. One valve controls the blood flowing into the ventricle. The other valve controls the blood flowing out of the ventricle
Each valve is made up of flaps, which are also known as leaflets or cusps. These flaps open and close, acting as one-way gates for the blood to flow through.

The aortic valve controls the flow of blood out of the heart’s left ventricle to the body’s main artery (the aorta). From here, the blood travels to the rest of the body.

Aortic stenosis (AS)

AS is a disease that the aortic valve does not open fully. There is a restriction of blood flow from the left ventricle into the aorta. Basically, the more narrowed the valve, the less blood that can get through, the more severe the problem is likely to be. Your heart (the left ventricle) needs to work harder to pump blood to your body. Eventually, symptoms will develop and the left ventricular may become weaken.

 
What is the aortic stenosis symptoms and the prognosis?

Causes of aortic stenosis

1. Progressive wear and tear of a bicuspid valve present since birth (congenital).
2. Wear and tear of the aortic valve in the elderly.
3. Scarring of the aortic valve due to rheumatic fever as a child or young adult.

Over years, these valves develop fibrotic thickening, fusion and calcification that limit valve motion.

 
Treatment of symptomatic severe aortic stenosis

 If you have symptomatic severe aortic stenosis, up to recently, you’ll usually need open heart surgery to replace the valve. Currently, however, aortic valve replacement can be done without open heart surgery. The criteria for choosing appropriate case for TAVI/TAVR has rapidly evolved in short period of time.

What is TAVI or TAVR?

Transcatheter Aortic Valve Implantation or Replacement (TAVI or TAVR) is a new treatment. It was developed in France in 2002. First use in UK in 2007. FDA approved for use in high risk patient in US in 2012. It is an alternative treatment to the conventional standard surgical aortic valve replacement. The standard surgery is a major open heart surgery requires chest open (sternotomy) and the need of cardiopulmonary bypass equipment. During this open heart surgery, the old stenotic valve will be removed and replaced with either mechanical or bioprosthetic valve. This standard aortic valve replacement for severe symptomatic aortic valve stenosis is considered to be one of the most successful open heart surgery. It also has an excellent long term result. However some patient is too high risk and may not be a candidate for this major open heart surgery.
 
TAVI/TAVR is much less invasive, the risk of the procedure is less. The early and complete recovery time is much shorter. The long term result is not available due to short follow up time. Once TAVI/TAVR has proved to be as reliable and has good long term result, this technique may replace the conventional open heart surgery valve replacement in many patients.  
 
TAVI (or TAVR) utilizes catheter-based technique similar to balloon and stent treatment for coronary artery disease and others. It requires only a small incision at the point of catheter insertion. The new valve is collapsed and mounted onto the distal end of the catheter that can be advanced to the position of the calcific stenotic aortic valve. Then the new valve will be deployed by balloon expansion or self-expanded depends on type of valve for this technique.

Who can have TAVI/TAVR

Indication for TAVI/TAVR is expanding rapidly because of the positive early result. Early on, it was recommended for either inoperable or high risk unsuitable for open heart surgery for isolated severe symptomatic aortic stenosis. The current indication include patient with moderate risk and the indication is less rigid in term of valve characteristic due to more experience and advancement in technology. There is a multi-disciplinary approach team of intervention cardiologist, heart surgeon, anesthesiologist, Imaging and others, called “heart team”. The heart team will provide the final recommendation for individual patient along with discussion of advantages/disadvantages for each treatment.
 
 Route of (catheter) entry

• Transfemoral. Entering femoral artery (Legs artery). The most commonly used.
• Transapical. Entering through a small left lower chest incision.
• Transaortic. Entering from a small right upper chest incision.
• Transaxillary. Entering axilla/brachial artery

Type of valve used in TAVI/TAVR (2014)

• Sapien valve from Edward (A). Requires balloon inflation to expand the collapsed valve for deployment.
• Core valve from Medtronic (B). Self-expanded valve

(A) Sapien valve. Prosthetic valve collapsed and mounted onto the deflated balloon at the distal end of the catheter. Balloon inflation will expand the valve
 
(B) Core valve. With the sheath retract, the valve will expand by itself. 
 
Patient preparation

Proper patient selection and preparation for this technique will require additional tests of

• Detailed transthoracic echocardiogram for severity of aortic stenosis and other cardiac function.
• CT of main arteries for suitable catheter entry site.
• CT and esophageal echocardiogram for aortic valve ring evaluation
• Status of coronary artery which may include noninvasive test, CT scan or coronary angiogram.
• Complete evaluation of the patient comorbid conditions.

Since this is an elective procedure, there should be enough time to complete the necessary investigation and properly patient preparation.

Potential risks of the procedure
 
Successful implantation: 92%. Risk of heart attack: 1%. Risk of stroke: 2-3%. In hospital mortality 2%. Risk of requiring a permanent pacemaker: 4-20% (Sapien valve), 10-40% (Core valve). Risk of dialysis 2.5%. Risk of major vascular injury at the catheter entry site: 6.5%. Require emergency open heart surgery 0.5%
 
Recovery in the hospital and at home
 
This will depend on individual pre procedure comorbid, general condition, motivation and complication that may occur. In general recovering from this procedure is faster than the conventional standard aortic valve open heart surgery. Post op hospital stay is about 5 days. Home recovery is usually much faster than the standard surgery particular with appropriate cardiac rehabilitation medical follow up system.
 
TAVI/TAVR at Bangkok Heart Hospital
 
The procedure is done in our new state of the art full function hybrid operating room.