How Hypertrophic Cardiomyopathy Progresses in Adults

Hypertrophic cardiomyopathy is the most common form of genetic heart disease worldwide. Researchers have estimated that up to 1 in 200 people have the condition, which is characterized by an abnormal thickening of the walls of the heart. This thickening can make it difficult for the heart to pump blood.

Hypertrophic cardiomyopathy can be a deadly disease, and there was a time when it was largely untreatable. But the last 20 years have witnessed a sea change in the condition’s management—a change that has led to an estimated 10-fold decrease in deaths.

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“Hypertrophic cardiomyopathy has this reputation that it’s difficult to live with, and that the outlook is grim,” says Dr. Barry Maron, a cardiologist and hypertrophic cardiomyopathy specialist at Beth Israel Lahey Health in Burlington, Mass. “That used to be true, but there have been huge advances in clinical care and clinical research, and hypertrophic cardiomyopathy is now characterized very differently.”

“The reality,” he adds, “is that very few people die of the disease, and fully half of patients belong in a group we consider benign and stable.”

Here, Maron and other experts describe what it’s like to live with hypertrophic cardiomyopathy. They explain the different stages or forms of the disease, how and why it progresses, and how treatment may evolve over time. They also talk about the outlook for people who are diagnosed with the condition.

An unpredictable disease

Some medical conditions—certain forms of cancer, for example—are characterized by different stages. Those stages help determine treatment, and they also reflect a patient’s prognosis.

Experts say hypertrophic cardiomyopathy is different; it doesn’t play by such tidy rules. “It’s an incredibly heterogeneous disease, and the more we learn about it, the more complex it gets,” says Dr. Christopher Kramer, distinguished professor and chief of cardiovascular medicine at the University of Virginia School of Medicine. The condition can affect the physical properties of the heart in different ways, he says, and trying to anticipate how it will behave over time is difficult. “To say to a patient, ‘You’re going to do this, and this is your likely outcome’—that’s fraught,” he adds.

Maron agrees that “there is no average” when it comes to hypertrophic cardiomyopathy. However, he says that the disease can be broken down into four general pathways. “The first pathway is the benign and stable course, and thankfully this is the most common of the four,” he says. These are patients whose disease tends to be caught incidentally sometime in midlife; for example, they undergo some type of medical imaging and their doctor notices an irregularity in their heart function—a heart murmur, for example. This leads to follow-up testing that reveals hypertrophic cardiomyopathy. In these cases, a person’s myopathy may not be obstructive, meaning it’s not limiting blood flow, and it may require little more than follow-up monitoring to ensure it’s not getting worse.

“The second pathway involves heart failure due to some kind of obstruction,” Maron says. In these obstructive cases, a person’s cardiomyopathy restricts the flow of blood out of the heart. These patients often have symptoms such as chest pain or shortness of breath. Symptoms can range from severe to very mild—so mild that a person may live with them for years without thinking much of them. “Patients will say they have no symptoms, but once you start asking questions, you find they’ve never been able to keep up with friends during exercise, or they’re often short of breath,” says Dr. Milind Desai, a cardiologist and hypertrophic cardiomyopathy specialist at the Cleveland Clinic. “A lot of people don’t realize how they’ve adapted their lifestyles to the condition over the years.”

Fortunately, this obstruction-related heart failure is often reversible with the help of either medication or some type of procedure, such as surgery to remove part of the thickened heart muscle. In rare and severe cases, a person’s myopathy may not respond to these treatments; or they may respond well initially, but then the condition eventually grows worse. “A small subset of patients develop advanced hypertrophic cardiomyopathy where the muscle of the heart is thick and stiff and non-complaint, and the only option might be a heart transplant,” Desai says. “But that, mercifully, is only the case in 3% to 5% of patients.”

The third pathway involves people whose hypertrophic cardiomyopathy leads to atrial fibrillation—a condition where the rhythms of the upper and lower chambers of the heart are misaligned. Atrial fibrillation can lead to a stroke if left untreated, and many of these patients will require anticoagulant drugs (such as blood thinners), and perhaps medication or surgery.

“The fourth pathway is someone who is at risk for sudden cardiac death,” Maron says. While identifying these cases still involves some educated guesswork, he says the latest diagnostic tools are very good at identifying at-risk patients. Treatment typically involves implanting a small defibrillator, or ICD, to correct irregular heart rhythms. “Implantable defibrillators have saved countless lives,” he adds.

While these four pathways can help sort people with hypertrophic cardiomyopathy into four rough groups, experts reiterate that the course of the disease is hard to anticipate. However, with proper care, they also say that most people diagnosed with hypertrophic cardiomyopathy will not die of the disease. “At this point, most well-managed patients can expect to live a normal lifespan,” Desai says.

Read More: What to Know About Hypertrophic Cardiomyopathy in Kids

How and why the condition progresses

Here again, experts stress the unpredictability of the disease. “Progression of hypertrophic cardiomyopathy is highly variable,” Kramer says. “It may progress and it may not, and we’re doing studies to understand who is most likely to progress and why.”

People with genetic forms of the condition—meaning those who have inherited one or more of the genetic mutations associated with hypertrophic cardiomyopathy—may have more severe and aggressive disease that often manifests earlier in life. But this isn’t always the case. “There is a portion of patients who have a genetic mutation but never develop the overt disease, and we’d never know they had it if we didn’t look for it,” says Desai. However, among patients with obstructive forms of hypertrophic cardiomyopathy—either with or without symptoms—experts say the condition is likely to get worse if left untreated. The muscle thickening will advance, symptoms will develop or become more severe, and the risk of a person developing atrial fibrillation or other life-threatening complications will increase, he says.

While predicting the course of the disease can be difficult, experts say that people who are symptomatic and diagnosed with the condition at a young age tend to face more challenges than people who are older at the time of diagnosis. “If you’re diagnosed at age 50 or 60, your prognosis is usually good—probably similar to age-matched controls,” Kramer says. “But if you have a family history of the disease and you’re diagnosed at 25, that’s less optimal.”

Other health issues can also advance the disease. Experts say obesity, high blood pressure, and diabetes can make underlying hypertrophic cardiomyopathy worse. “It’s important to stay on the ball with your health,” Desai says.

How treatment may evolve

At the time of diagnosis, most people with hypertrophic cardiomyopathy will have no symptoms and no evidence of an obstruction. Apart from follow-up monitoring, most won’t require treatment.

If the disease progresses—meaning, an obstruction or other threat to the heart arises—treatment may involve an implantable defibrillator, or medications intended to manage symptoms or reduce the risks of complications. For example, the latest anticoagulant drugs have “come close to obliterating” the risk of stroke in people who develop atrial fibrillation as a result of hypertrophic cardiomyopathy, Maron says. Meanwhile, a newer drug called mavacamten can help reduce symptoms, and possibly even reverse some heart-muscle thickening, in people with obstructive forms of the disease. Experts say this drug has helped improve quality of life for many patients, but it’s not a cure-all. “Mavacamten has made a beneficial contribution, but so far there’s nothing about this class of drug that will have a direct effect on mortality,” Maron says.

If a person responds well to the drug, they must stay on it indefinitely and undergo quarterly monitoring to ensure the heart’s functioning is stable. If their heart’s condition worsens or symptoms persist, experts say the next step in treatment is likely to be some kind of procedure. For patients who are younger or those experiencing severe obstruction, doctors may recommend a septal myectomy—an open-heart surgery to remove the thickened muscle. “This surgery is a one-time thing,” Maron says. Research has found that greater than 90% of people who undergo this surgery have significant improvement of symptoms and enjoy a long-term survival benefit. However, the procedure can be risky if not performed at a top medical institution. In patients for whom open-heart is too dangerous, such as among older seniors, experts may recommend a procedure called an alcohol septal ablation. This involves injecting a small amount of alcohol into the heart, which can shrink the thickened muscle and improve blood flow.

For “a very small number of patients”—and for reasons that are not well understood—Maron says the condition will continue to worsen despite treatment. In these cases, he says a heart transplant may ultimately be necessary.

A positive outlook

While some new medications have helped advance the treatment of hypertrophic cardiomyopathy, experts say improvements in their knowledge of the disease and its clinical management deserve most of the credit for reducing mortality. “When I started 40 years ago, mortality was 6% per year, and treatment was inadequate at best,” Maron says. Nowadays, the annual risk of death for a patient is below 1% percent, his research has estimated.

Experts are also looking ahead to further advancements—and maybe even early interventions that could neutralize the disease before it takes hold. Desai mentions gene editing as, perhaps, the “next frontier” in hypertrophic cardiomyopathy care. “This would involve removing the abnormal piece of genetic material that causes hypertrophic cardiomyopathy,” he says. Gene therapies that aim to replenish certain protein deficiencies are also an area of active research. “If the concept works, in the future patients could walk into the clinic, get an infusion, take immunosuppressants for a few weeks, and potentially be cured or significantly improved,” he says. In the near term, experts are also exploring how the newest medications, if taken early, might be able to reduce or arrest the condition’s progression. “A lot of exciting things are happening in this space,” Desai says.

Hypertrophic cardiomyopathy remains a shifty and unpredictable foe. But experts say they’ve learned to roll with its punches. “Things have moved in the direction we hoped,” Maron says. “This is now a very treatable disease.”