Our hearts beat on the order of 100,000 times a day, 35 million times a year. We tend to think of these pumps as tireless muscles contracting away in endless (until the end) systolic-diastolic thumps.

But there’s more to the heart than muscle. Without its four valves, the heart’s efforts would be for naught, squeezing blood in every direction at once (until it didn’t). Instead, with each beat, oxygen-sapped blood from the body enters the right ventricle. It pushes the tired fluid through the tricuspid valve into the right atrium. The blood then heads for a recharge in the lungs via the pulmonary valve (also called the pulmonic valve). Oxygenated blood from the lungs returns to the left ventricle, which pounds it through the mitral valve into the left atrium, from which it pulses out into the body through the aortic valve. This all happens with each double-thump of the ticker.

Valves can have problems, though. In particular, they can fail to seal tightly and thus allow backflow (regurgitation), and they can become narrower (stenosis, typically through calcification of a valve’s flaps), making it harder for blood to move. These problems get worse with age: 5% to 10% of those over 80 have heart-valve issues and open surgery is risky among that cohort, says Dr. John Messenger, a University of Colorado School of Medicine interventional cardiologist.

The aortic valve and TAVR

It used to be that fixing or replacing heart valves meant open-heart surgery. That changed with the U.S. Food and Drug Administration’s approval of minimally invasive transcatheter aortic valve replacement (TAVR) starting in 2011 for patients unlikely to survive open-heart surgery. The minimally invasive procedure strings a catheter through a spot near the groin up into the heart. The catheter then deploys a replacement aortic valve. Patients are back home and feeling better within a day or two. Four subsequent FDA approvals successively expanded the TAVR pool to lower and lower-risk patients.

Similar catheter-based procedures for the heart’s other valves have followed, and the field is now brimming with innovation, Messenger says.

“It’s one of the most exciting times I’ve seen in interventional cardiology,” Messenger said. “We’re really moving towards less-invasive surgical procedures and then less-invasive transcatheter replacement and repair options that really give us opportunities to tailor therapies to patient-specific needs.”

That innovation has come in a variety of forms. Medical device makers such as Edwards Lifesciences (which makes the pioneering Sapien TAVR valve, now in its third generation), Medtronic (Evolut), Abbott (Navitor), and a growing list of others have introduced new materials and valve designs. Among other innovations, newer TAVR valves are self-expandable (rather than just balloon-expandable) and have sealing skirts that stop most of the leakage around the valve’s outer edges (paravalvular leak, or PVL) that was often an issue with earlier designs. They use bovine or porcine pericardial tissue-derived materials for the leaflets through which blood flows, with nitinol or cobalt-chromium stents whose delicate shapes would trigger the envy of the most discriminating spider.

Meanwhile, other heart valves have become targets for minimally invasive replacement and repair.

The mitral valve (TEER and TMVR)

The mitral valve has been a major innovation focus, and for good reason: Mitral regurgitation is the most common form of heart-valve disease. It’s also a tricky valve: It’s big enough that replacement valves must enter the heart through either the bottom tip of the heart or the wall that separates the right and left atria. It’s D-shaped, and it’s anchored by fibers attached to the atrium that give it the look of a billowing parachute.

Two types of procedures target the valve. The first, called transcatheter edge-to-edge repair (TEER), involves using a glorified clothespin to pinch the center of the mitral valve’s flaps together. That reduces blood flow somewhat but prevents backflow. Abbott’s pioneering MitraClip was FDA-approved in 2014; Edwards Lifesciences’ Pascal device followed in 2022.

Transcatheter mitral valve replacement (TMVR) is still in its infancy. Among the devices in clinical trials include the Abbott Tendyne and Cephea valves, the Medtronic Intrepid, Edwards Lifesciences’ Sapien M3, and 4CMedical’s AltaValve.

Mitral-valve replacement trials have been going on for about a decade, Messenger says.

“It’s just a much more complex valve, and it’s taken longer to understand what the key features of these valves are,” Messenger said. “How can engineers miniaturize these valves to sit in the mitral space and provide a patient a competent mitral valve while not interfering with heart function and blood flow out of the aortic valve?”

That many patients with mitral-valve narrowing are older women with thickened ventricle walls (left-ventricle hypertrophy) compounds the problem, Messenger says.

“If you put a big, bulky valve in the mitral space, it causes obstruction of blood flow,” Messenger said. “So, they’ve had to come up with technologies to miniaturize and slenderize these devices, and even get the devices that basically sit fully within the left atrium.”

Pulmonary valve (TPVR)

Pulmonary valves can have problems also, more typically than the aforementioned valves through congenital disease such as Tetralogy of Fallot. These sorts of problems are often treated surgically when patients are young, so transcatheter pulmonary valve replacement (TPVR) is increasingly happening with follow-up surgeries, Messenger says.

“Pulmonic valve replacements for both leaky and narrow valves, as well as for patients with failed surgical valves, are now being performed routinely in that population as they get into adulthood to avoid a second, third, or fourth open heart surgery,” he said.

Edwards Lifesciences’ Sapien and Medtronic’s Harmony and Melody transcatheter pulmonary valve replacement (TPVR) valves are FDA approved for TPVR.

The Tricuspid valve (TTVR)

Messenger and other heart specialists have called the tricuspid valve “the forgotten valve” with respect to transcatheter repair. In part, Messenger says, that’s because the right ventricle doesn’t tolerate surgery well. But studies have been running for the better part of a decade now, he says, and products are coming to fruition faster than those for mitral valves.

MitraClip-style solutions that pinch the center of the valve closed have been a minimally-invasive treatment option in clinical trials. Those trials went well, and Abbott’s TriClip for the tricuspid valve won FDA approval in April.

Then in February 2024, the FDA approved Edwards Lifesciences’ Evoque tricuspid valve replacement system for transcatheter tricuspid valve replacement (TTVR).

The tricuspid valve is, in short, no longer forgotten.

Other transcatheter valve replacement innovations of note

Along with the valves themselves, the systems involved in implanting and attaching devices have also improved, Messenger says.

Companies are applying artificial intelligence to assess echocardiogram, CT, and MRI scans to help better predict which patients are best suited for a particular valve repair or replacement technology—as well as to identify patients likely to have complications, he says.

CU School of Medicine faculty James Chen, PhD, and radiologist Dr. Robert Quaife have advanced 3D imaging approaches using cardiac ultrasound and CT imaging, which enables much better catheter-based valve placement on the right side of the heart where the pulmonary and tricuspid valves are, Messenger says.

And finally, robotic approaches to mitral valve surgeries are minimizing complications for patients for whom open surgery remains the best option, he says.

Heart-valve repairs and replacements delivered via catheter have kept millions of hearts beating, and advances in the field of interventional cardiology continue. Over the next few years, Messenger says, “we’re going to markedly expand the pool of patients who are candidates for these technologies.”