Heart valve replacement without surgery

Since 2000, nearly 1000 patients in Europe have had a catheter procedure instead of open heart surgery for replacement of their dysfunctional pulmonary valve. How is this technique possible?

(Source: German Heart Institute Berlin, Germany)

Medtronic Inc, in Minnesota was the first company to offer patients with congenital heart disease a pulmonary heart-valve replacement that does not involve open heart surgery. However, several other medical suppliers are now able to offer this technology. Some doctors call the new procedure a revolution, believing that it will permanently change the way in which we treat people with heart diseases. Others are more sceptical, believing that not enough evidence has yet been gathered, and that the procedure only postpones open heart surgery. Nevertheless, the procedure has received a lot of attention from both patients and health personnel.

Who started the procedure?

Philipp Bonhoeffer, professor and chief of cardiology and director of the Catheterisation Laboratory, Great Ormond Street Hospital for Children in London, implanted the world’s first transcatheter valve in September, 2000, in Paris. The valve manufactured by Medtronic obtained a CE mark (the last step for acceptance in Europe) on September 29, 2006. Less than 3 months later it was approved for commercial release by the Canadian authorities. In February, 2007, the first patient in the USA had this Melody implant, and a feasibility study was started for the procedure in the USA. However, this valve is yet not available commercially in the USA.

At the same time, another US medical supplier is undertaking a similar study. Edwards Lifesciences Corporation of Irvine in California has developed the Sapien transcatheter heart valve. The first three patients were enrolled in this clinical trial on April 17, 2008, and 30 patients in total from three hospitals in the USA will participate. The company has experience with similar aortic valves.

What is the problem with surgery?

The great thing about this innovation is that surgery is not needed. Of course, surgery is fantastic and has many advantages, but all patients have a risk of morbidity. The patient needs 1–2 weeks at hospital for surgery, and then it takes at least 4–6 weeks before the patient is back to normal. The recovery time is normally longer the more procedures that you need and the more complicated they are. After a catheter procedure, the patient can normally leave the hospital the next day and return to their normal lives.

Another fact is that adolescents and adults are reluctant to undergo reoperation when there is no guarantee that future operations will be successful.

How does the valve work?

A tube containing the compressed valve is inserted into a blood vessel and threaded up to the heart (Source: German Heart Institute Berlin, Germany)

A transcatheter pulmonary valve consists of a segment of bovine jugular vein (the Melody valve is from a cow) with a thinned venous wall having a central, competent venous valve. The valve is sewn into a stent—a frame made of platinum wire—and then compressed onto a balloon that is the approximate diameter of a pencil. A tube (catheter) containing the compressed balloon with the stent mounted valve is inserted into a venous blood vessel at the groin and threaded up to the heart. The balloon is inflated to implant the stent with the new valve over the dysfunctional one. The catheter is then removed, leaving the new, functioning valve in place. The whole procedure normally takes about 2 hours and is done under X-ray control. Most centres perform the implantation under general anaesthesia, whereas others let the patient sleep with the help of a potent hypnotic drug.

Who is this procedure relevant for?

Patients with congenital heart defects involving the right ventricular outflow tract—such as Fallot’s tetrade, pulmonary atresia and ventricular septal defect, truncus arteriosus and transposition of the great arteries, and patients with a replaced pulmonary valve after the so called Ross-procedure—might benefit from this medical breakthrough. Many of these patients have a surgically implanted heart valve between the right ventricle and the main artery to the lung. However, the functional life span of these channels is fairly short, and thus most patients with this type of defect need several open heart surgeries over their lifetime. The transcatheter valve provides a non-surgical means to restore effective valve function, and thus can reduce the number of surgical procedures for these patients. However, because of the size of the catheters used to implant the valve, the procedure can be offered to patients with a body weight of no less than 20 kg.

Will the valve last?

Tissue valves (implanted surgically or by catheters) are seldom permanent because of three main factors. First, a valve that is implanted in a child does not adapt to the growth of the patient. The size of the valve that is needed for a 1-month-old baby will not be sufficient for a 4-year-old child. Furthermore, adults need much larger valves; thus tissue valves do need to be changed. Second, these valves are attacked from the immune system as foreign bodies, especially in. As a consequence, their bodies start to deposit a lot of calcium, leading to stenosis (narrowing of the area). Third, the valve might be “eaten up”, making it very leaky. Any of these problems causes extra workload for the right ventricle. Nevertheless, there are people walking around with the same transcatheter pulmonal valve, in good function, 5 years after implantation. Thus these transcatheter valves might eliminate or postpone the need for surgery. There is also an option to insert a new transcatheter valve if the old one degenerates.

However, it is too early to tell what the situation will be after 10, 15 or even 20 years.

Other valve options

Adult non-congenital heart patients with aorta stenosis can have a transcatheter aortic heart valve by a similar procedure. The first of this kind was done in Rouen, France, in 2002. There is also a self expanding aortic valve undergoing clinical testing. These aortic valves are only suitable for elderly adults.

Assessment of this non-surgical procedure

The first study to investigate the long-term effects of the Melody transcatheter pulmonary valve-procedure has started in Germany.

Little is known of the long-term effects of this procedure since the published clinical experience is limited to less than 5 years (as at September, 2008).

The study started in October, 2007, and will last 7 years. It is sponsored by the Medtronic Bakken Research Center in the Netherlands.

This post-marked surveillance study is designed to assess the clinical performance of this specific transcatheter pulmonary valve for 5 years after implantation. The secondary objective is to assess the quality of life of enrolled patients who are aged 15 years and older. In this clinical study, 60 patients from seven participating centres in Europe and Canada will be involved. However, most of the patients enrolled so far are treated at the German Heart Centers in Berlin and Munich.

Pictures from the inside

Pulmonary regurgitation before valve replacement (Source: German Heart Institute Berlin, Germany)

Valve-carrying stent in place before implantation (Source: German Heart Institute Berlin, Germany)

Deployment of valve by balloon dilatation (Source: German Heart Institute Berlin, Germany)

Valve after placement without regurgitation (Source: German Heart Institute Berlin, Germany)