Feeling like you’re going to pass out can be scary, especially if you’re alone. Fainting, which doctors call syncope, happens when your brain gets less blood flow than it needs. Many causes of fainting are temporary and no reason for alarm. But, sometimes, serious conditions like transthyretin amyloid cardiomyopathy (ATTR-CM) can be to blame for fainting spells.

In ATTR-CM, amyloid buildup in the heart makes it harder for the heart muscle to pump blood to parts of the body, including the brain. Although the most common symptoms of ATTR-CM are shortness of breath and edema (swelling), some people may experience fainting spells before other symptoms begin.

Here’s what you need to know about ATTR-CM and fainting.

Why Does Fainting Occur in ATTR-CM?

Transthyretin amyloidosis (ATTR) is a rare condition in which abnormal proteins clump together within certain parts of the body and lead to tissue damage. ATTR-CM happens when amyloid proteins build up within the heart muscle. These amyloid deposits then take the place of normal, healthy cells within the heart.

Amyloid deposits cause the heart muscle to become stiffer over time. This makes it more difficult for the heart to send blood where it needs to go. When not enough blood reaches the brain, a person may pass out or feel dizzy.

The protein clumps also cause structural changes by thickening the walls of the heart. These thicker walls make it harder for the heart to relax between beats and refill with blood. When buildup affects the heart’s electrical system, it can change the heart rhythm. This can lead to arrhythmias — abnormal heartbeats that are too slow, too fast, or otherwise irregular.

Having an arrhythmia can cause you to pass out or feel lightheaded if it prevents the brain from getting the blood it needs.

Fainting can also happen if your blood pressure falls abruptly. Often, ATTR amyloidosis also affects other parts of the body, such as the nerves. Nerve involvement can cause orthostatic hypotension, which is a sudden drop in blood pressure when you change positions.

Can Fainting Help With Diagnosis?

ATTR-CM is a rare condition. Because healthcare providers do not see ATTR-CM often, it can sometimes be hard to diagnose. The two types of ATTR-CM, hereditary and wild-type, also come with their own challenges when it comes to diagnosis.

Hereditary ATTR-CM (hATTR-CM) can be mistaken for heart disease related to high blood pressure or hypertrophic cardiomyopathy (a disease that causes an enlarged, stiffened heart). Meanwhile, wild-type ATTR-CM may not cause symptoms until it becomes severe.

Unexplained fainting episodes can be one of the first signs of ATTR-CM. Fainting, along with dizziness, trouble breathing, and heart palpitations, is a common symptom of arrhythmias and can prompt doctors to investigate the heart.

In fact, between 40 percent and 60 percent of people with ATTR-CM were reported to have atrial fibrillation (a type of arrhythmia) when they were diagnosed.

How the Cause of Fainting Is Diagnosed

To figure out the cause of your fainting spells, your provider may perform tests such as:

• Tests that record the electrical activity of your heart, such as an electrocardiogram (ECG) or an electrophysiology study
• Imaging tests that provide detailed views of the heart or brain, such as an echocardiogram or computed tomography (CT) scan
• Stress tests to see how your heart responds to exercise or other types of stress
• Wearable heart monitoring that records heart rhythm and rate for a specific amount of time
• Autonomic reflex testing to see how your heart rate, blood flow, and blood pressure respond to stimuli

Fainting, with other signs of ATTR-CM, such as carpal tunnel syndrome or imaging that shows thickened heart walls, may lead doctors to do more specific testing for ATTR-CM.

Does Fainting Mean ATTR-CM Is Getting Worse?

ATTR-CM gets worse over time, and fainting can be a sign that ATTR-CM is progressing. Unexplained fainting can point to:

• The heart having more trouble pumping blood to the brain
• Changes to the heart’s structure and its ability to relax between heartbeats
• New electrical issues causing irregular heartbeats

As ATTR-CM becomes more severe, it can lead to serious conditions like arrhythmias, heart failure, and disorders of the heart’s electrical system. These are complications that arise as the disease worsens, all of which can cause fainting. These complications can be life-threatening, resulting in stroke or sudden cardiac death.

What Should You Do if You Have a Fainting Episode?

People living with ATTR-CM need to be regularly monitored by their cardiologist. Tell your doctor about any new symptoms, such as fainting episodes, as soon as possible, so that they can assess how your heart is working. Depending on your test results, your provider will recommend treatment options, such as medications or a pacemaker, to address arrhythmias.

In some cases, fainting can be a sign of an emergency that requires immediate medical care. Call 911 if you feel like you’re going to pass out and have other symptoms, including:

• Chest pain
• Fast, slow, or irregular heart rhythm, along with trouble breathing or chest pain
• Intense shortness of breath that occurs abruptly, especially along with coughing that produces foamy, white or pink mucus
• Severe weakness

How Can You Stay Safe if You Have a History of Fainting?

If you’ve passed out before, you may have noticed certain symptoms popping up right before you fainted. You might have felt dizzy, lightheaded, or sick to your stomach. Or you may have felt that your heart wasn’t beating in its regular rhythm — feeling a fluttering or otherwise irregular sensation in your chest. People with a history of fainting often experience warning signs like these before they pass out.

In some situations, you may be able to avoid fainting by taking action when you first notice these warning signs. You can help reduce your risk of fainting by:

• Sitting or lying down quickly and elevating your legs
• Tensing or activating your arm muscles
• Forming your hands into fists
• Squeezing your thighs together or crossing one leg over the other

You can also take proactive steps to help prevent fainting spells. For example, drinking enough water to stay hydrated can be helpful for some people. Your cardiologist may recommend you take medications or use a pacemaker or other device to manage fainting caused by arrhythmias.

What Are Other Reasons for Fainting?

Although ATTR-CM can cause you to pass out, there are also many other reasons you might faint. Fainting can happen for any reason that causes a drop in your heart rate, blood pressure, or the amount of blood that reaches your brain.

Some other possible causes of fainting include:

• Staying in a hot environment too long
• Changing positions too fast, especially when standing up
• Not having enough water or salt in your body
• Standing for long periods of time
• Drinking too much caffeine or alcohol or eating too much food
• Using certain blood pressure medications or decongestants

Often, fainting due to other causes isn’t a cause for alarm and can be prevented by managing your triggers. For example, if you tend to feel faint when you stand up, try getting up more slowly.

Even if you think you know the cause of your fainting, it’s still important to talk to your healthcare team about any fainting spells. Talking to your doctor about any new fainting is essential so that they can make sure your ATTR-CM is well managed.

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