Transcatheter Aortic Valve Implantation (TAVI)

Overview
Surgical aortic valve replacement is still the standard form of treatment for most patients with severe symptomatic aortic valve stenosis. However, not all patients qualify for surgery. These patients are left with suboptimal approaches such as medical management or balloon valvuloplasty.

There is an important breakthrough for replacing the aortic valve called Transcatheter Aortic Valve Implantation (TAVI) also previously known as Percutaneous Aortic Valve Replacement (PAVR).

Aortic Stenosis
A normal heart valve allows blood to flow in one direction only without obstruction. A valve that is narrowed is said to have "stenosis". Aortic stenosis (narrowing of the aortic valve that lies between left ventricle and aorta) is the most common valve problem.


FIGURE 1: Heart with aortic valve stenosis

Aortic stenosis occurs due to formation of calcium deposits on the leaflets of aortic valve in the heart causing it to become rigid. In most people such calcium deposits cause no problems. Sometimes they can progress to cause narrowing of aortic valve (aortic valve stenosis), restricting the blood flow across the valve. Aortic stenosis has a long asymptomatic phase, but when symptoms do finally occur, the condition can deteriorate swiftly.

Aortic stenosis may lead to shortness of breath due to heart failure with build up of fluids in the lungs. It can also cause angina because of insufficient blood reaching heart muscles. Blackouts can occur due to insufficient blood reaching the head. It can also cause sudden death.

The standard form of treatment has long been replacement of the aortic valve via open heart surgery, however, there are many patients who are not suitable or are very high risk for surgical replacement due to advanced age, or conditions such as kidney problems, chest problems, problems with blood supply to brain, weak heart muscles or previous heart surgery. Percutaneous approach to implant the aortic valve could become a viable option for patients with severe symptoms due to its less invasive approach.

TAVI techniques
There are two techniques currently used to implant aortic valve percutaneously. These are retrograde and transapical techniques. In the retrograde, access is gained via the femoral artery and the delivery catheter with aortic valve prosthesis is advanced to the stenosed valve. This technique is faster and technically easier, however injury to aortofemoral vessels can be sustained and with failure of the aortic valve prosthesis to cross the aortic arch. Transapical technique requires a small incision to be made between the ribs. The apex of the left ventricle is then punctured with a needle, and the prosthetic valve is then advanced via the puncture site to the stenosed valve. CoreValve Revalving System uses the retrograde implantation technique.

CoreValve Revalving System

 
FIGURE 2: CoreValve Prosthesis

CoreValve Prosthesis is composed of three bovine pericardial leaflets, made from porcine pericardium (pericardium is a thin sack in which the heart lies) mounted and sutured within a self expanding metal (Nitinol) frame. This prosthesis has three distinctive structural segments. The top portion flares to fixate and stabilise the deployed aortic valve prosthesis in the ascending aorta. The mid portion carries the valve leaflets and it tapers to avoid coronary artery ostia, whereas the bottom portion exerts a high radial force that extends and pushes aside the calcified native aortic leaflets and avoids recoil.




Procedure
The diseased valve is pushed aside by inflation of a Balloon (Aortic Balloon Valvuloplasty). The CoreValve Prosthesis, loaded in a specialised delivery catheter is then advanced to the stenosed aortic valve via a small whole in the femoral artery in the groin (Retrograde technique) or a small incision in the chest (Transapical technique). Once correctly positioned, the external sheath of the delivery system is progressively retracted deploying the CoreValve Prosthesis. The delivery catheter is then closed and retrieved.

After the Procedure
After the procedure the patients will be transferred to Intensive Care Unit (ICU). Patients will have a urinary catheter until mobile, an intravenous (IV) line, a temporary pacemaker in the neck vein and may need an oxygen mask. The patients are on their feet the same day or the next day at the latest. After intensive care, the patients will go to a less intensive monitoring environment. They will chest electrocardiogram (ECG) leads and two small boxes to carry around (one to transmit ECG signals to a central station and another to pace the heart if neccessary). There maybe bruising on the groin. There will be a consultation on rehabilitation. Hospital stay may be 5-6 days.

Outcomes withTAVI 
CoreValve prosthesis delivery abolishes the aortic valve narrowing. Important leakage is rare. There is 90% chance of achieving this without death or stroke and almost all patient have improvement in symptoms. Tissue heart valves deteriorates with time, but so far this has not been observed, as only a few patients has had the valve for more than three years.

VIDEO DEMONSTRATIONS

 View TAVI procedural animation
 View CoreValve Prosthesis deployment: Radiographic illustration
 View TV3 Close Up: PAVR Video

Associated Documents

  CoreValve successfully treats the first Pacific Rim patients with its ReVal vingĀ® System for percutaneous aortic valve replacement - Ronald Trahan, APR, Ronald Trahan Associates Inc., 508-359-4005, x108
 CoreValve announces successful completion of initial series of proctored cases in Australia and New Zealand using its ReValvingĀ® System for percutaneous aortic valve replacement - Ronald Trahan, APR, Ronald Trahan Associates Inc., 508-359-4005, x108
  'Good as new' a day after heart op: New Herald News Article 
 TAVI: Patient Information Brochure