Dilated vs. Hypertrophic Cardiomyopathy: What’s the Difference?

While they share many signs and symptoms, dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM) are distinct conditions that impact the structure and function of your heart very differently. But they’re easy to confuse, because they affect the same part of your heart.

Cardiologist Wilson Tang, MD, breaks down the differences and explains what they mean for you.

Key differences between DCM and HCM

Both DCM and HCM affect the wall of your left ventricle, which is your heart’s main pumping chamber. DCM makes the left ventricular wall weaker and relatively thinner, which causes your heart to grow larger. HCM, on the other hand, makes this one part big and thick, without proportionally enlarging the rest of your heart.

“With dilated cardiomyopathy, your heart grows bigger to compensate for that thin, weak left ventricular wall,” Dr. Tang explains. “By changing its shape, your heart can fill with more blood.”

That becomes a problem over time because the stretched-out muscle can’t pump blood as well as it should. Dr. Tang compares it to a rubber band that gets over-stretched.

With HCM, the wall of your heart’s main chamber becomes unusually thick. There are many reasons why this can happen, but the effect is the same.

“The heart is never able to completely relax,” he continues. “So, segments of the heart start to grow bigger and bigger from overuse.” This affects your heart’s ability to pump blood.

In some people, the thickening also narrows the path that blood takes as it exits the heart. That’s called obstructive hypertrophic cardiomyopathy.

Common signs and symptoms

Dilated and hypertrophic cardiomyopathy cause similar symptoms — and both tend to get worse when you’re physically active. Both DCM and HCM can cause:

• Shortness of breath (dyspnea)
• Fatigue
• Chest pain
• Swelling and weight gain from fluid retention
• Dizziness or lightheadedness
• Palpitations

“These two conditions may present the same way, but the mechanism — the thing causing your symptoms — is different,” Dr. Tang clarifies.

Untreated, both conditions can lead to signs and symptoms of heart failure or life-threatening arrhythmias. But with the right combination of medications and lifestyle changes, they both have the potential to become manageable chronic conditions.

Causes and risk factors

You may have read that hypertrophic cardiomyopathy is an inherited condition (something you’re born with), while dilated cardiomyopathy is something you develop as you get older because of your lifestyle. Dr. Tang says both statements are oversimplifications.

“DCM can be both inherited and acquired,” he explains. “About 1 in 6 people with DCM have a known disease-causing genetic variant.”

A perfect storm of genetic and environmental factors can also cause DCM. Dr. Tang calls them “seed-and-soil cases,” where DCM develops from a combination of genes and a trigger, like:

• A viral infection
• Heavy alcohol use
• Chemotherapy
• Unmanaged high blood pressure
• Pregnancy
• Autoimmune or metabolic diseases

Like DCM, HCM can be acquired or inherited — but it’s much more common to inherit HCM than it is to inherit DCM. It’s also possible to be the first one in your biological family born with a genetic variant.

“The cause of hypertrophic cardiomyopathy is more predictable,” Dr. Tang reports. “Around 50% or more of cases are the result of a known disease-causing genetic variant.”

But not everyone with a genetic variant that can cause HCM actually develops it. Something has to push the condition into action — whether it’s environmental factors, multiple genetic variants or a specific inheritance pattern.

The most important reason to narrow down the cause of your DCM or HCM is to find out if you have a family history of heart muscle disease. If you do, your provider may recommend that your family members get genetic testing to determine their risk.

Treatment and outlook

Whether you’ve been diagnosed with DCM or HCM, the goal of treatment is the same: to help you preserve your lifestyle and manage heart failure symptoms, if you have them.

Dilated cardiomyopathy treatment

Dr. Tang says the following classes of medication may be prescribed to address DCM, especially if your heart isn’t functioning as it should:

• ACE inhibitors
• Angiotensin II Receptor Blockers (ARBs)
• Angiotensin receptor/neprilysin inhibitors (ARNIs)
• Beta-blockers
• Mineralocorticoid receptor antagonists
• SGLT2 inhibitors

Dr. Tang says these medications can help you feel better and live longer.

“People who take these drugs are less likely to die or come into the hospital with heart failure,” he reports. “It’s actually quite remarkable how much they can help.” In fact, some people’s heart function actually improves with these therapies.

But sometimes, medication isn’t enough. You may need a device like a pacemaker, an implanted cardioverter defibrillator (ICD) or a left ventricular assist device. If other therapies don’t work, your provider may consider a heart transplant.

Hypertrophic cardiomyopathy treatment

The goal of HCM treatments is to:

• Address the thickened heart muscle
• Reduce the obstruction (if needed)
• Relieve symptoms

Traditionally, doctors turned to beta-blockers and calcium channel blockers to slow your heart rate and improve blood flow. But Dr. Tang says newer cardiac myosin inhibitors work differently. They target the heart muscle directly to keep it from overworking.

“These drugs can reduce the blockage and make people feel better quickly,” he notes. “They can even increase the time before someone needs surgery to remove or reduce thickened tissue.”

A small percentage of people living with HCM need an ICD to prevent dangerous rhythms and lower the risk of sudden cardiac death.

Reason for hope

There’s no sugarcoating it: Whether you’ve got DCM or HCM, you’re facing a serious heart condition.

But thanks to medical advances, cardiomyopathy doesn’t have to define you. Talk to your cardiologist about how treatments can help you keep your symptoms in check, slow disease progression and improve your well-being.