“Surgeons can cut out everything except cause” according to one famous saying. But there’s also one other thing they struggle to cut out and that’s their patients’ fear and anxiety about the operation itself.

No one wants to hear that they need open-heart surgery. However, in the past decade there’s been a shift in Western countries towards minimally invasive procedures that don’t even require a general anaesthetic.

They’re not for everyone, but they are revolutionising the way that physicians repair or replace faulty heart valves.

The heart has four valves: mitral, tricuspid, aortic and pulmonary. So far, minimally invasive procedures have been predominantly used to treat aortic stenosis, a narrowing at the opening of the valve, which carries blood away from the heart to the rest of the body through the aorta, its largest artery.

The technique is called transcatheter aortic valve replacement (TAVR). And it has become increasingly widespread since the US Food & Drug Administration first approved its use in 2011.

Some four years later, the FDA also approved a first transcatheter pulmonary replacement valve (TPRV) product for patients with right ventricular outflow tract dysfunction following surgical repairs for congenital heart disease.

Next up will be minimally invasive procedures to treat the more anatomically complex mitral valve. There are nearly a dozen products undergoing clinical trials to deal with a narrowing of the valve that regulates the flow of blood from the lungs into the left ventricle (the heart’s main pumping chamber). Mitral valve regurgitation is the most common form of heart valve disease.

Beyond that, medical companies are also starting to design equipment for clinical trials that will use minimally invasive techniques to repair or replace the tricuspid valve. This valve separates one of the heart’s two upper and lower chambers, keeping blood flowing in the right direction.

Procedures involving TAVR have risen exponentially in recent years, overtaking open-heart surgery in the US for the first time in 2017. In Asia, however, take-up has so far been much lower: one tenth of global levels during that same year.

One reason lies in a lack of awareness about a procedure, which has two main methods of administration.

The first is called the transfemoral method. This involves inserting a collapsed or deflated valve through a catheter into a blood vessel, which is accessed via the patient’s leg. The second is called the transapical method, and involves a small incision in the chest.

The surgeon then guides the catheter through the body. Once it’s in place, he or she will expand it either with or without a balloon to replace the original valve.

The replacement valve is typically made from a metal frame incorporating cow or pig tissue. This also represents a change from the pure tissue valves that have been used for open-heart surgery since the 1960’s.

Clinical studies have consistently proven TAVR’s many benefits. For starters, the procedure only takes about an hour compared to four for open-heart surgery.

It also means that patients only need to spend a few days in hospital compared to around 10 for open-heart surgery. Physicians consequently have more time to perform additional procedures and hospitals can stretch their resources further.

More importantly, patients have less to fear from surgical complications in terms of: blood loss, post-operative infections, scars and pain, not to mention the psychological trauma that accompanies the knowledge that a surgeon will stop your heart and bypass your blood through a heart-lung machine.

TAVR success rates have also climbed as the procedure becomes more established. When the FDA first approved TAVR, it was only for patients classified as prohibitively high surgical risk – i.e had a strong likelihood of dying on the operating table due to age, or infirmities.

But such patients also faced a very high chance of dying from the disease since severe cases of aortic stenosis have a two-year 50% mortality rate.

In 2012, the FDA proceeded to allow patients to undergo TAVR if they were classified as high risk, then intermediate risk in 2016 and low risk in 2019. As a result, the profile of TAVR patients has shifted.

In 2014, some 66% of US patients fell in the high-risk category and 5% in the intermediate risk category. By 2018, 45% were in the intermediate risk category.

Post-operative mortality rates have also dropped: from 5% – 8% (over a 30-day period) in the early days to 0.5% to 1% by 2019.

However, a number of uncertainties remain. No one yet knows how long a TAVR style valve will last compared to the 10 to 20 year timeframe for a cow or pig valve.

The technique is also unsuitable for patients with excess plaque or calcification that could break off and obstruct the artery after a catheter is guided through. Sometimes the catheter can’t get through in the first place either because of the excess plaque or calcification. In these instances, surgery is recommended.

Calcification and age go hand-in-hand. So for the most elderly and infirm patients, it can also be safer to try and improve a patient’s quality of life rather than risk replacing a valve. Balloon aortic valvuloplasty (BAV) is one option: stretching the aortic valve by inflating a balloon inside it.

In Asia, Aortic stenosis is on the rise especially in countries with rapid economic growth including Japan, South Korea and Taiwan, which have a large cohort of increasingly elderly people. But TAVR procedures have not increased in tandem with the demographics, despite the fact that early adopters like Singapore allowed it in 2009 and Japan in 2013.

One reason relates to differences in Asian anatomy. Many Asians have narrower arteries and a smaller aortic annulus (a fibrous ring at the aortic root). This initially raised safety concerns about pushing catheters through.

However, a recent study in the Singapore Medical Journal highlighted that clinical research has consistently shown good results across the region. There are also now a number of Asian valve products on the market including China’s VenusA-Valve, Thailand’s Hydra valve and India’s MyVal.

Researchers from the Heart Centre at Singapore’s National University believe the main reason for lower take-up relates to a lack of reimbursement. The procedure itself can cost double open-heart surgery, although the researchers argue that this may change if it’s shown to be less costly over the long-term through improved patient outcomes.

Globally clinicians expect TAVR procedures to carry on rising. Some predict that procedure volumes will rise by 50% over the coming five years. TAVR is fast becoming the standard of care in many parts of the world. Asia may yet follow suit.