Understanding 4 of the Most Common Complications of Hypertrophic Cardiomyopathy

You could argue that the complications of a disease, rather than the disease itself, create most of the problems associated with that condition. Take hypertrophic cardiomyopathy, or HCM, a primarily genetic condition that results in a thickening of the walls of the heart—specifically its left ventricle, which is the chamber that pumps blood out of the heart and into the aorta. According to the Hypertrophic Cardiomyopathy Association, HCM is the most common genetic heart condition, affecting at least 1 in every 500 adults—possibly more, given that as many as half of all people with the disorder have no symptoms or ones that are so mild, they go unnoticed.

The American Heart Association (AHA) reports that about two-thirds of those who have been diagnosed with HCM have so much thickening in their heart muscle that it obstructs blood flow out of the left ventricle and into the aorta. This is called, aptly, obstructive hypertrophic cardiomyopathy. This kind of obstruction is behind many of the more troublesome and life-threatening complications of HCM.

In nonobstructive HCM, the thicker muscles may mean the ventricle is less able to pump the normal volume of blood, but the blood is able to move in and out of the ventricle unimpeded. Most people who have the nonobstructive version of the disease will have milder symptoms and lower risk of death than those with its obstructive relative. In other words, they’re likely to have fewer, though by no means zero, complications of their disease.

With that in mind, here’s a look at what to know about four of the most common HCM complications—including how they manifest and how they’re treated.

Atrial fibrillation (AFib)

There are two main types of heart arrhythmias, and you’re probably already familiar with one of them: atrial fibrillation, or AFib. It describes a rapid and irregular heartbeat that can lead to blood clots within the heart, which, in turn, can increase the risk of stroke. “The longer a patient has the condition, the more likely atrial fibrillation is to occur,” says Dr. Steve Ommen, director of the Hypertrophic Cardiomyopathy Clinic at the Mayo Clinic in Rochester, Minn.

AFib shows up in about a quarter of people with HCM. However, Dr. Milind Desai, director of the Hypertrophic Cardiomyopathy Center and vice chair of the Heart, Vascular and Thoracic Institute at the Cleveland Clinic, says that estimate may be too low. “I don’t believe we have accurate data,” he notes, “as many patients have short bursts of AFib that are asymptomatic.” In these instances, the heart beats irregularly, but the person feels none of the usual symptoms to warn them of the arrhythmia.

Those who do experience symptoms might report heart palpitations or a sense of a rapidly pounding heart, shortness of breath, dizziness, or fainting. Treatment often focuses on the use of anticoagulant drugs, which prevent the formation of the blood clots that can lead to stroke. Cardiologists may also recommend drugs to restore a more normal heartbeat, including beta blockers or calcium channel blockers, which work by lowering the heart’s pumping rate and giving the cardiac muscles a bit of a biological break.

When AFib recurs or doesn’t respond to medications, a minimally invasive procedure known as cardiac ablation may be considered. It involves using heat or cold to create very small scars in the heart tissue to interrupt the abnormal electrical signals that lead to the rapid or irregular heartbeat.

Read More: What to Know About Hypertrophic Cardiomyopathy in Kids

Ventricular tachycardia (VT)

Ventricular tachycardia is another type of abnormal heart rhythm, in which an extremely fast heartbeat begins in the lower chambers of the heart. The rapidity of the beat prevents the ventricles from filling with enough blood before they contract again.

The symptoms of ventricular tachycardia are similar to those of AFib and include palpitations, dizziness, shortness of breath, and fainting, but may also include neck tightness, chest pain, and even cardiac arrest. As with AFib, a cardiologist might prescribe beta blockers or calcium channel blockers to treat the symptoms and control the heart’s rhythm. When people don’t respond to medication, or if they have particularly advanced VT, they may need an implantable defibrillator. That’s “a special pacemaker-like device to monitor the heart for dangerous arrhythmias and deliver an electric shock to reset the heart to a normal rhythmif they occur,” says Dr. Michelle Kittleson, director of Education in heart failure and transplantation and professor of medicine at the Smidt Heart Institute at Cedars-Sinai in Los Angeles.

Compared to atrial fibrillation, VT packs a much bigger cardiac punch. “In terms of risk, ventricular tachycardia is the one we screen for annually in HCM,” Ommen says. “Ventricular tachycardia itself can make the squeezing function of the left ventricle ineffective; it can also degenerate into ventricular fibrillation.” While VT is about a rapid heartbeat, the problem in ventricular fibrillation, or VF, is that the ventricles contract in a sort of quivering and random beat. The AHA calls VF the “most serious abnormal heart rhythm,” and notes that, without treatment, it can lead to sudden cardiac death within minutes.

Kittleson agrees. “Ventricular arrhythmias are more dangerous,” she says, “because they can cause sudden cardiac death, as the heart cannot pump efficiently and no blood gets to the body.” In fact, VT that becomes ventricular fibrillation is the most common cause of sudden cardiac death.

Heart failure

Another common HCM complication is heart failure, a broad term that means your heart isn’t able to pump enough blood out into your circulation to properly oxygenate the rest of your body. The heart fails, in other words, to effectively do its most essential job. Heart failure is not, however, the same thing as cardiac arrest, which is when the heart stops—arrests—its beating altogether.

In HCM, heart failure is generally a result of the thickening and stiffening of the heart’s ventricles. In that sense, according to the Hypertrophic Cardiomyopathy Association, HCM is simply a form of heart failure. Specifically, people with HCM tend to develop a type of heart failure in which the left ventricle can’t fill with enough blood—because of its overly muscular walls—to then pump sufficient blood throughout the body. With less blood in the ventricle in the first place, even a perfectly pumping heart won’t be able to force as much blood out into the circulation as it’s meant to. And a heart with walls thickened by HCM is unlikely to be a perfectly pumping heart.

Still, Desai notes, not all HCM patients experience heart failure. “Many HCM patients can be asymptomatic,” he says. “But if you have shortness of breath due to a cardiac problem, technically you have some element of heart failure.”

In addition to an inadequate supply of oxygenated blood in the body, heart failure tends to lead to an accumulation of fluid in the body’s tissues, which is called congestive heart failure. In addition to the obvious physical signs of fluid accumulation, like swollen ankles, there are the more subtle and potentially dangerous ones. Fluid from the processes of heart failure is especially prone, for instance, to build up in the lungs; this can lead to coughing and shortness of breath, generalized symptoms that aren’t always as benign as they may initially seem.

The treatment of heart failure itself—rather than the disease that causes heart failure, like HCM—tends to focus on the treatment of congestive heart failure, specifically. Cardiologists will likely prescribe diuretics, drugs meant to help the body’s kidneys process the extra fluid. Patients might be asked to limit both time on feet and fluid intake. The same beta blockers and calcium channel blockers used to treat arrhythmias can also be used to slow the heart enough to allow the left ventricle to fill to the best of its ability. For those with the most severe forms of heart failure, heart transplantation may be the best option.

Read More: 9 Weird Symptoms Cardiologists Say You Should Never Ignore

Sudden cardiac death

Sometimes the first—and, sadly, last—sign of HCM is also its most feared complication. Sudden cardiac death, which is also known as sudden cardiac arrest, occurs when the heart stops beating or beats so irregularly or weakly that it can no longer provide enough oxygen to the body to sustain life. A death falls under the sudden cardiac death label if it occurs within an hour of the onset of symptoms such as feeling faint, dizzy, or noticing the feeling of an irregular heartbeat—in other words, the signs of ventricular fibrillation. If the heart actually stops beating, however, death will occur within minutes, unless emergency measures are taken.

Experts stress that sudden cardiac death—which, in HCM, occurs when the heart’s electrical system misfires, resulting in ventricular tachycardia or ventricular fibrillation—is not the same as a heart attack, in which a blocked artery prevents blood from getting to the heart, killing off the heart’s muscles.

HCM is one of the most common identifiable causes of sudden cardiac death in athletes under 35. And although it is by no means a common outcome for those with HCM, sudden cardiac death occurs in approximately 0.8% of affected individuals each year, says Ommen. “Assessing each individual’s risk is thus an important part of regular checkups,” he notes.

The cascade to sudden cardiac death can be treated, if caught immediately after its onset, using CPR to keep blood flowing through the body, an external defibrillator to reset the heart rhythm, and medications to restore the heart’s normal rhythms.

Read More: How to Talk to Your Family About Their Heart Health History

Better still, cardiologists say, is to treat the arrhythmias and other electrical-impulse issues that can arise in an individual with HCM—or to treat the HCM itself—sand thereby stave off sudden cardiac death altogether.

Overall, says Kittleson, it’s important to remember that “HCM is not a death sentence. With current methods of diagnosis, evaluation, and treatment, survival is comparable to that of the general population. With proper management, patients can live full and Healthy lives.”