By Dr Paul Chiam
Published on Medical Grapevine on May 2015
The aortic valve allows blood to be pumped out of the heart to the rest of the body. With aging, the aortic valve may become narrowed (aortic valve stenosis [AS]).
When the valve narrowing becomes severe, patients develop breathlessness, fainting spells and chest discomfort. Left untreated, the death rate is high, with up to 50% of patients dying from the condition within 2 years.
Open heart surgery to replace the aortic valve is the conventional method of treating this disease, relieving patients of their symptoms and prolonging their life span. For many elderly patients and for patients with other debilitating diseases (for example those with very poor heart function, severe lung disease, end stage renal failure on dialysis etc), the surgical risk for open heart surgery is high, and some patients are even considered inoperable.
A relatively novel method of “replacing” this aortic valve was first performed in a human in 2002, as an alternative to open heart aortic valve replacement (AVR) in a “no surgical option” patient. A small incision was made in the patient’s groin and a new valve was delivered via a catheter (tube) into the heart and implanted within the patient’s native aortic valve. This technique has been termed “Transcatheter Aortic Valve Replacement or Implantation” (TAVR/ TAVI).
Currently, this minimally invasive method is mostly performed via a small puncture in the groin, although in a small number of patients, other access sites are required (via the subclavian artery in the chest, via the aorta directly or through a 5-6 cm incision in the left chest wall). The groin approach is the least invasive and thus preferred.
Unlike open heart surgery to replace the aortic valve, with TAVR, the patient does not need the chest cracked open, the heart is not stopped and the transcatheter heart valve is implanted on a beating heart, the native aortic valve is not removed and the newly implanted transcatheter heart valve is not sutured in place. The procedure can also be done under local anesthesia for the groin approach.
There are 2 transcatheter heart valves commonly used: The Sapien XT transcatheter heart valve made by Edwards Lifesciences and the CoreValve made by Medtronic. There are now over 130,000 implants worldwide using these 2 valves.
Several large randomized studies have shown the promise of this technology. The PARTNER trial (using the Sapien valve) showed that TAVR was superior to (better than) medical therapy in patients with severe aortic valve stenosis (AS) who were inoperable and was non-inferior (equal) to open heart AVR in patients at high surgical risk. Very recently, the CoreValve trial demonstrated that TAVR using the CoreValve was superior to (better than) open heart AVR in high risk patients. Thus TAVR is now the treatment of choice for inoperable patients and may be a safer treatment option in patients at high surgical risk.
Up till recently however, the transcatheter heart valves though safe and effective, could not be repositioned or recaptured if they were implanted in a suboptimal position. In effect, the team had “one chance” to optimally deploy the valve. In January 2015, two repositionable and recapturable valves became available in Asia – the Medtronic CoreValve Evolut R and the Boston Lotus valves.
These new generation transcatheter heart valves can be recaptured and repositioned if the initial implant position is deemed suboptimal, and can even be removed from the body if a smaller or larger sized valve is required. These features increase the accuracy and safety of the procedure. Mount Elizabeth Hospital became the 1st hospital in Asia to perform TAVR/TAVI with these 2 valves. The cases were successfully performed under local anesthesia and sedation, via an access in the groin.
These new generation valves are indeed a “game changer” and will offer many patients with severe aortic valve stenosis not only an alternative treatment with TAVR/TAVI, but also a more accurate and safer TAVR/TAVI procedure.