BY STEPHANIE STEMMLER

Study the anatomy of a human heart, and you’ll notice that there are four chambers and four valves that work sequentially to move blood into the heart and then out into the body. As the heart contracts and relaxes, its valves work in a set order, opening and closing to ensure that blood flows in one direction. One valve opens to allow blood to flow in and then closes to prevent backward flow.

When one or more valves are not working properly, resulting blood-flow problems may affect the heart and the rest of the body. While symptoms may be nonexistent or minor for years, malfunctioning valves can cause chest pain, shortness of breath, dizziness, fainting and swelling in the abdomen, ankles and feet. Upon examination, a physician may hear a “whoosh” sound or heart murmur and may detect abnormally low or high blood pressure, depending upon the valve affected. Some people with heart-valve problems notice an irregular heartbeat.

Valve disorders and diseases

The four valves in the heart are called the aortic, mitral, pulmonary and tricuspid valves. The mitral valve has two flaps, called leaflets, that open and close; the others have three flaps. In broad categories, valve problems can be caused by:

ALAN ZAJARIAS, MD, (LEFT) AND COLLEAGUE IN SURGERY.

• Stenosis: valve flaps become stiff or thick, preventing the valve from opening fully
• Regurgitation: valve flaps don’t close properly, causing blood to leak backwards
• Congenital abnormalities (present at birth)

The risk of developing heart-valve problems increases with age. Other risk factors include high blood pressure, high cholesterol, diabetes, obesity and a history of coronary artery disease and heart failure. Infections, particularly rheumatic fever, also can damage heart valves.

Left untreated, heart-valve disorders can lead to strokes, blood clots, heart rhythm problems, even heart failure. Advances made in cardiology and heart surgery now allow specialists to repair or replace any of the four heart valves using a variety of techniques, including minimally invasive surgery.

Valve repair: a short history

The first successful mitral valve repair was documented in 1923 at Brigham and Women’s Hospital in Boston. It wasn’t until the development of the heart-lung bypass machine in 1953, however, that open heart surgery made it possible to treat valve disease effectively.

The first artificial mechanical heart valve was developed in 1952 by Charles Hufnagel, MD, a surgeon at Georgetown University. Called a ball and cage valve, it functioned like a marble in a tube. When the heart contracted, the resulting pressure caused the ball to rise to a wider section of the tube, enabling blood to flow through. Once the muscle relaxed, the ball dropped, and the opening closed. The first mechanical mitral valve replacement took place in 1960; replacement with a mechanical aortic valve occurred just a year later. Within the same decade, donor grafts became an option, with valve tissue harvested from a deceased human donor (called an allograft) or from a pig or cow (called a xenograft).

In the late 1960s, a new procedure came to the forefront to treat aortic valve disease. Called the Ross procedure, it was developed by London heart surgeon Donald Ross, MD. During this treatment, the surgeon removes the non-functioning aortic valve from the patient, replacing it with the patient’s own pulmonary valve. A donor pulmonary valve is then implanted to replace the one that has been moved.

Tsuyoshi Kaneko, MD, Washington University cardiothoracic surgeon at Barnes-Jewish Hospital and chief of the university’s section of cardiac surgery, explains that a pulmonary valve is like an aortic valve in size and shape. The Ross procedure is effective because it substitutes the failing aortic valve with the patient’s own pulmonary valve, which can manage the job of an aortic valve with less risk of failure than other replacement options. Because the donor valve implanted into the pulmonary position is under less stress than it would be in the aortic position, it is more likely to function long-term.

TSUYOSHI KANEKO, MD, (RIGHT) AND MEMBERS OF HIS SURGICAL TEAM.

“This procedure can be effective in treating severe aortic valve disease in both children and adults,” Kaneko says. “And, unlike standard surgical aortic valve replacement or even less invasive procedures, the Ross procedure remains the only treatment option that restores normal life expectancy to young and middle-aged patients with aortic stenosis.” For patients in this age group who are treated with the Ross procedure, Kaneko says, “fewer than a third require further intervention up to 25 years after the initial surgery.”

Advancing the field

While open-heart surgery is often used to treat valve disease in people under 60, less invasive, transcatheter procedures are becoming more common. Offering excellent outcomes and faster recovery times for patients, this treatment uses a small catheter that is threaded into an artery through a small incision in the groin or chest. The surgeon moves the catheter through the artery to the diseased valve, where it is used to remove the valve and replace it with a new one.

Specialists at the Washington University and Barnes-Jewish Heart & Vascular Center have pioneered several types of minimally invasive valve surgeries. Alan Zajarias, MD, interventional cardiologist at the center, performed St. Louis’ first transcatheter aortic valve replacement, also known as TAVR, in 2008, working with cardiothoracic surgeon Ralph Damiano, MD, and interventional cardiologist John Lasala, MD, PhD. The U.S. Food & Drug Administration (FDA) formally approved the TAVR procedure for aortic valve replacement in 2010. Two years later, specialists in Denmark performed the first human transcatheter mitral valve replacement procedure.

In 2021, the Heart & Vascular Center’s valve team was among the first in the world to use a transfemoral approach, through an artery in the leg, in a procedure to treat severe regurgitation in a tricuspid valve. “It was during the COVID-19 pandemic, and we received special, ‘compassionate care’ approval from the FDA to use a mitral valve device to treat tricuspid regurgitation in a patient who had failed three previous bypass surgeries,” says Zajarias, who performed the procedure with cardiovascular surgeon Puja Kachroo, MD, and other colleagues. “It worked beautifully.”

Transcatheter tricuspid valve replacement is now an evolving advancement in valve replacement techniques.

Valve replacement options

The two types of replacement valves available— mechanical and natural tissue—present two different sets of factors to consider. Mechanical devices require that patients take blood-thinning medications for the rest of their lives. Biologic tissue valves do not require blood thinners; however, they wear out and often need replacement within 10 to 20 years. Both Kaneko and Zajarias note that newer TAVR devices are smaller and more sophisticated, and their delivery systems—the way these devices are deployed in the body—are improving. As a result, specialists can now access the valve through smaller femoral blood vessels and more accurately position replacement valves for optimal outcomes.

“TAVR is a good, safe procedure for patients with aortic stenosis,” Zajarias says. “In older patients, it is often the procedure of choice. For younger patients, we have a thoughtful conversation concerning the risks and benefits of each valve type, taking into consideration their own anatomy and other health concerns, in addition to age.”

“The concept of lifetime management has become a new conversation in our field,” Kaneko says. “As we perform heart-valve procedures on younger people—those in their 50s or 60s—we know that there is a strong predictability they will need another procedure in their 80s because many replacement heart valves wear out over time.” Both Zajarias and Kaneko note that ongoing research and clinical trials are working to identify better valve designs and materials that will offer more options to patients.

Artificial intelligence and heart-valve treatment

Artificial intelligence (AI) and computer simulation tools have opened up new possibilities in the treatment of valve disease. These technologies are being used to aid in planning before surgery and in optimizing long-term use of replacement valves.

In planning valve surgery, Zajarias says, “there’s a lot of consideration given to which replacement valve should be used and how it should be placed. New technology allows us to simulate placement to determine the best option. AI tools also provide a computer simulation of what might happen if or when we must do another procedure farther down the line to replace that valve again.”

As more data becomes available that can inform artificial intelligence tools, Kaneko and Zajarias point out, the technology has the potential to produce even more accurate predictive modeling. And they anticipate it will become a critical element in treating heart-valve disease in younger patients, an important consideration given that valvular disease is on the rise around the globe.

“What we do today for patients will affect their overall health and health-care decisions years down the road,” Zajarias says. “AI and computer simulations help us make better decisions about the first interventions we undertake for patients, and they can help us better predict how they will do long-term. In effect, we now have better, more accurate ways to care for people with valvular heart disease.”