Why AFib Happens While You Sleep

It’s 3 a.m., and you’re wide awake, wishing the fluttering in your chest would stop. When you’re living with atrial fibrillation (AFib), these nights might happen more often than you’d like.

So, why does AFib happen when you sleep, and what can you do about it? We asked cardiovascular researcher David Van Wagoner, PhD, to break things down.

Why does AFib happen at night?

There are many possible causes of nighttime AFib episodes, including:

• A drop in heart rate while you sleep
• Sleep apnea
• Changes in sleep position
• Disrupted sleep patterns or poor-quality sleep

Let’s take a closer look at each one.

Drop in heart rate

Your heart rate is supposed to drop a bit while you sleep. This typically occurs in everyone. But when you have AFib, a lowered heart rate opens the door for abnormal electrical activity that can cause wonky rhythms. Dr. Van Wagoner explains why.

“Under normal conditions, a cluster of cells called the sinoatrial node — or SA node, for short — sends out electrical impulses that control heart rate. The SA node is your heart’s natural pacemaker,” he says. “It tells your heart to beat faster or slower based on what you’re doing at the moment. When you’re sleeping, the SA node slows your heart.”

If you have AFib, things get a bit more complicated. Other “pacemakers” (clusters of cells in your heart) start to send out impulses, too. These pacemakers are located in your heart’s upper left chamber (left atrium) inside your pulmonary veins, which bring oxygenated blood back to your heart from your lungs.

“When your spontaneous beating rate slows during sleep, the electrical activity originating from the pulmonary veins can collide with the normal signals coming from the SA node,” Dr. Van Wagoner explains. That means now, instead of just one set of impulses telling your heart what to do, you have two or more sets — and that can make a steady rhythm turn chaotic.

It’s like if you drop several pebbles into a pond at the same time, instead of just one. Each pebble creates ripples, and those ripples collide with each other. This “interference” from the other pacemakers (the other pebbles) can lead to a fast, unruly rhythm that can feel bad and slow down blood flow to your lower heart chambers (ventricles).

Sleep apnea

Sleep apnea halts your breathing while you sleep. “These pauses in breathing raise the pressure in your chest,” Dr. Van Wagoner says. “This puts pressure on your heart and can disrupt normal electrical signaling, leading to AFib episodes.”

AFib and sleep apnea are both common conditions — meaning plenty of folks have both, often without even realizing it. Sleep apnea can go unrecognized for months or even years. If you often feel tired upon waking or need naps to get through the day, tell a healthcare provider so they can get to the bottom of the issue.

Changes in sleep position

Before you curl up into a cozy ball, check which side you’re lying on if you’re looking to avoid AFib at night. Research shows that sleeping on your left side can sometimes trigger AFib episodes.

The reason? Sleeping on your left side puts pressure on your heart’s left atrium. This increase in left atrial pressure can trigger the pulmonary vein “pacemakers” to send out electrical impulses when they shouldn’t.

“Those impulses can interact with the SA node signals, sometimes initiating AFib episodes,” Dr. Van Wagoner explains.

Poor-quality sleep

You probably already know that choppy or restless sleep isn’t good for you. But it’s especially concerning when you have AFib or even risk factors for developing it. That’s because poor sleep can:

• Increase levels of cortisol and catecholamines in your blood (these are stress-related compounds that can increase your blood pressure and heart rate)
• Lead to inflammation and changes to your metabolism that reduce muscle mass and increase central body fat

“All of these changes are associated with an increased risk of AFib,” he adds.

While everyone has a rough night’s sleep every now and then, it shouldn’t happen all the time. If you regularly have trouble falling asleep or staying asleep, talk to a healthcare provider to find the cause.

Common nighttime symptoms

How can you know if you’re going into AFib overnight? The exact symptoms vary from person to person. It may feel like your heart is:

• Beating out of sync
• Racing
• Pounding
• Fluttering
• Skipping a beat
• Adding a beat

These sensations may wake you from sleep.

On the flipside, some people have no symptoms. Your only clue might be an alert on your watch or monitoring device.

What you can do about it

If you suspect you’re in AFib at night (or any time), it’s important to track episodes. The information you collect can help your healthcare provider notice trends and plan next steps.

Dr. Van Wagoner offers this advice for your detective work:

• Check your pulse if you think you’re in AFib. “Use your thumb and index finger to feel the pulse at your wrist,” he recommends. “When in normal sinus rhythm, your pulse should be stable, typically at a rate of 50 to 80 beats per minute. In AFib, the rate is often fast and quite irregular.” Make a note of what you feel.
• Use a monitoring device. Many wearables, like watches and exercise monitors, can detect AFib. Ask your provider for advice on which to choose. They may decide it’s best to prescribe you a monitor — like a Holter monitor or skin patch — to capture abnormal rhythms.
• Keep a log. Consider keeping a diary of AFib episodes when you feel them or your device detects them. Some devices can produce reports about the frequency and duration of abnormal heart rates or rhythms.

Above all, take comfort in knowing that healthcare providers diagnose and manage AFib all the time.

From age 40, you have a 1 in 4 chance of developing AFib. But this common condition doesn’t have to keep you tossing and turning or fearful of bedtime.

“Having AFib episodes at night can be anxiety-producing,” Dr. Van Wagoner recognizes. “But there are solutions. Talk to your doctor about the treatment plan that’s right for you.”