What is aortic stenosis, anyway?
James Garret has always led an active, “outdoorsy” life. He’d grown up near the mountains in Utah, and whenever he wasn’t working as a flight nurse, he headed for the slopes to ski or rock climb. He and his wife—a doctor named Franziska—seem to be the picture of great health.
James was only in his 60s when he started to notice that something was different—he was consistently more fatigued than usual, even on a simple hikes. Blaming this change on “getting old,” he didn’t realize what was really wrong until one day when he snuggled up on the couch with Franziska. When she put her head on James’s chest, she became instantly alarmed. Instead of the normal “lub-dub” heart sounds, she heard whooshing and swishing—called a “murmur.” Murmurs, which also might rasp or hum, are considered to be “noisy blood flow” caused by valve abnormalities. Franziska bolted upright and told James he needed a trip to the cardiologist.
Doctors quickly confirmed that James had two problems. His aortic valve had a congenital defect, and therefore its “flaps” were thicker and less flexible than normal. On top of that, calcium deposits had collected on them. Calcium, which is a natural component in blood, is often deposited on heart valves—but when valves change due to age, plaque buildup, or inflammation, calcium deposits can become deadly. In James’s case, the valve was unable to close all the way. This explained his fatigue; his heart could not push the correct amount of blood out to his body, which reduced the amount of oxygen his cells were receiving. Plus, the heart muscle was working too hard, and getting less done. James was at a high risk of all kinds of heart emergencies—and if he didn’t get a replacement valve, he would die, probably within two or three years.
James’s diagnoses was Aortic Stenosis (AS), and his story is told in Superhuman Body. To fully understand this common disease—and how heart valves work in the first place—we need a short field trip through the heart.
The mechanics of the heart[1]
A well-functioning heart, which is only about the size of a fist, beats on average from 60 to 80 times a minute—around 100,000 times a day. Its one and only job is to pump blood, all day, every day—sending fuel to each cell in the body, from earlobe to baby toe. It does this by pumping the blood along two distinct pathways, one to the lungs, and the other to the rest of the body.
For this process to work smoothly, all four of the heart’s chambers have to work together—and all four valves must open and close, completely and in the correct rhythm. The less healthy the heart, valves, and/or arteries, the more likely this rhythm will be off—and the harder the heart has to work. If the muscle itself isn’t pumping well, or if the valves aren’t leakproof, then several things can go wrong.
Checking for heart health begins with listening to the sounds it’s making. The rhythm of the chambers’ contractions should be regular, highlighted by the “lub-dub” heartbeat sound made by the opening and closing of the valves. As the heart’s contractions push blood into the arteries, a noticeable pulse should be felt, which actually indicates a rhythmic change in blood pressure. Blood pressure is the measurement of the pressure your blood exerts against your artery walls. Normal range is less than 120/80 mm Hg (millimeters of mercury). The top number indicates pressure during the heart’s contraction; the lower number is taken during its rest phase. High blood pressure is an indication of possible heart disease—and it also provides a major clue as to why valves can suffer. When blood pressure is high (up to 180/120), the heart has to work very hard to push blood into the circulatory system.[2]
How does circulation work?
First, blood enters through veins connected to the right side of the heart, then travels along a short loop to the lungs, where it picks up oxygen and drops off carbon dioxide. This is called “pulmonary circulation.” Oxygen-rich blood is then pushed up through the left side of the heart, and back out through arteries to the entire body. That part of the process is called “systemic circulation.” The reliable heart does this again and again and again.
When oxygen-depleted blood enters the heart from the body, it arrives in the right atrium. When oxygen-rich blood enters from the lungs, it arrives in the left atrium. The atria are sort of like “holding chambers” as compared with the ventricles, which are stronger and push blood out of the heart, whether to lungs (right) or the rest of the body (left). The atria contract first—pushing blood to the ventricles. A fraction of a second later, the ventricles contract. These two sets of contractions form our pulse.
Why is the aortic valve so important?
Of the four chambers of the heart, the left ventricle does the heaviest lifting. It’s the largest, thickest, and strongest chamber, the “last stop” for blood before it heads back out to the body, and the powerhouse that keeps everything moving. In order for blood to exit the heart, it needs to be contained and then pushed through a tube, the aorta. Although the aorta is the body’s largest artery, it’s still much narrower than the ventricle, and a lot of pressure is placed on the aortic valve, which controls blood flow. This is true especially if the aorta is narrowed due to heart disease.
In fact, because of all this pressure in the left ventricle, both valves that control blood flow into and out of the that chamber are more likely to show signs of wear and tear—and disease—than their opposites on the right side of the heart. While the aortic valve regulates blood flow out of the heart, its companion, the mitral valve, is holding steady—preventing backward leakage into the left atrium.
Characteristics & diseases of the aortic valve
All heart valves are one-way gates; when formed normally, they open and close with three flaps of tissue—except the mitral valve, which has only two. The flaps, also called cusps or leaflets, are somewhat curved—each like a slice of an open umbrella. Just as rain rolls down a rounded umbrella, blood going “with the flow” is channeled along the convex side of a valve. When a chamber contracts to push the blood forward, the flaps open, and blood empties out. When a valve closes, it shuts out any blood that might remain on the other side, “against the flow”; that blood is caught in the concave curve of the leaflets.[3]
A healthy valve is able to open and close properly for a lifetime, but sometimes various conditions get in the way. For example, a person can be born with a “bicuspid” aortic valve[4], which means it has only two leaflets—which is what James had. In this case, the leaflets might be thicker and stiffer than normal, which can prevent them from opening and closing properly. It’s called “stenosis” when the valve’s opening is narrowed, and “regurgitation” when blood leaks backward because the valve doesn’t close tightly—both of which cause the heart to work harder than usual to get blood out to the body.
Even a properly formed aortic valve can change as we age, or be damaged because of high blood pressure, injury to the heart, infections that cause inflammation (“endocarditis”), and plaque-related buildup. In “All Heart,” we talk more about several conditions that can damage the blood vessels, heart, and valves—including Coronary Artery Disease (CAD) and Valvular Heart Disease (VHD). In these conditions, fat, cholesterol, and other substances, collectively known as “plaque,” not only stiffen the leaflets, but also narrow the passage created when they open.
The usual approach to many heart problems is surgery—and with surgery, valves can be repaired, or replaced with manufactured ones. Doctors usually access the heart by cutting through the breastbone and spreading the ribs. This type of major surgery requires months of recovery, and some patients are not good candidates for it because of advanced age or other health conditions.
Transcatheter Aortic Valve Replacement (TAVR)
Since James has been an ICU and flight nurse all his adult life, he was well aware of the ramifications of his diagnosis—and the surgical “gold standard” of treatment. He had helped countless patients recover from open-heart surgery—and he knew what was in store, including a very long recovery that would keep him cooped up for months. Because James was otherwise so healthy and relatively young, there was nothing contraindicating open-heart surgery.
But when James’s doctor asked when he could schedule it, James said, “Never.” He knew about an alternative.
“TAVR was absolutely considered a wild idea when it first came out,” says Jaime Wheeler, Senior Vice-President of Global Clinical Affairs at Edwards Lifesciences—a leader in medical innovations for structural heart disease. “Replacing someone’s heart valve, completely without surgery? Physicians at the time said, absolutely, this cannot be done.”
Wheeler remembers the instant impressions and early questions from colleagues. In the context of heart surgery, any alternative was considered reckless and dangerous. People asked, How will you get the valve into the heart? How can you anchor it in the heart? “It was viewed as just the wild, wild West,” she said.
The first approval for Transcatheter Aortic Valve Replacement (TAVR) was awarded in 2011—but only for patients with Aortic Stenosis, and whose overall physical conditions were too fragile for open-heart surgery. Without some kind of treatment, these patients would not have survived, and the new TAVR procedure gave them hope for, better function, a short recovery, and a normal life expectancy.
More than a decade later, James Garrett was interested in TAVR precisely because no surgery was involved. He knew that a fabricated replacement valve would be guided by a catheter through the femoral artery in his thigh, up his torso, and into the heart. It would be seated within the native valve and take over its job immediately. And interestingly, the calcium that had caused so much damage in James’s heart also would be key to TAVR’s success. The calcium would help stick the replacement valve in place.
In open-heart surgery, doctors stop the heart and put it on bypass so that they can separate fused valve leaflets, repair torn leaflets, reshape valve parts, or replace a valve entirely with a manufactured one.[5] These procedures generally have excellent outcomes—but TAVR studies are now showing similar outcomes.[6]
“With the advent of TAVR, we can intervene less invasively,” Wheeler says. “The patient can go home the next day, or a few days later, and they return back to their good quality of life.” That’s what happened for James—even during the procedure, he felt immediate relief; within a couple of weeks, he was skiing and climbing again.
Open-heart surgery is still necessary for many heart conditions—and for some patients is the only alternative. However, Aortic Stenosis patients now have a viable alternative to consider. Of course, TAVR comes with its own parameters and risks, as any medical procedure does, which patients evaluate with their doctors. “There is a process called shared decision making,” Wheeler says. “Every patient should sit down with their physician and find out what the available options are, for their particular disease stage, their particular lifestyle, their co-morbidities.” For patients who choose TAVR, Wheeler reports a “90-plus-percent success rate for a good implant, and a good outcome that’s better in 80- or 85-year-old patients than just the normal actuarial life curves.”
So far, TAVR is the most successful of the transcatheter valve replacement procedures, although non-surgical interventions are being researched for the other three valves in the heart. If someone in your life has been diagnosed with AS or another valvular disease, consult with your cardiologist for information on your options. Also, since TAVR is so celebrated, there is a lot of research data and general information available on the procedure from many clinical centers of excellence.
Resources
[1] Gaea Marelle Miranda, “Structure and Function of the Heart,” News Medical website, Life Sciences, last updated 4 September, 2022, https://www.news-medical.net/health/Structure-and-Function-of-the-Heart.aspx.
[2] American Heart Association (AHA), “Understanding Blood Pressure Readings,” AHA (website), Health Topics / High Blood Pressure, last reviewed 30 May, 2023, https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings.
[3] InformedHealth.org, “How does the heart work?”, Institute for Quality and Efficiency in Health Care (Internet), 6 December, 2011, late update 31 January, 2019, ncbi.nlm.nih.gov/books/NBK279249/#.
[4] Johns Hopkins Medicine, “Bicuspid Aortic Valve,” Johns Hopkins (website), Health / Conditions and Diseases, accessed 16 April, 2024, https://www.hopkinsmedicine.org/health/conditions-and-diseases/bicuspid-aortic-valve.
[5] Johns Hopkins Medicine, “Heart Valve Repair or Replacement Surgery,” Johns Hopkins (website), Treatments, Tests and Therapies, accessed 19 April, 2024, https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/heart-valve-repair-or-replacement-surgery.
[6] Cedars Sinai, “NEJM: Transcatheter Aortic Valve Replacement Shows Similar Safety Outcomes as Open-Heart Surgery,” Cedars Sinai (website), 29 January, 2020, https://www.cedars-sinai.org/newsroom/nejm-transcatheter-aortic-valve-replacement-shows-similar-safety-outcomes-as-open-heart-surgery/.