Why Does My Heart Race or Pound When I Lie Down?

Why Does My Heart Race When I Lie Down but Not Just When I Stand?

Lying down is its own trigger, and our team treats it as a separate problem with its own causes. The standing side has its own page on why your heart races when you stand. When the speed-up starts once you're flat and the heart checks out, the clinic looks at 3 things lying flat changes: the gut and vagus nerve, the inner ear's balance system and the neck's pressure sensors.

On your back Left side

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The video above also names autonomic dysreflexia, a reflex after a spinal cord injury where something irritating below the injury, such as a full bladder, sends blood pressure up. Our team leaves it off this page because the animal studies we found describe the heart slowing with it.

Can a Big Meal Make Your Heart Race When You Lie Down?

The first group of causes our team looks at is mechanical. In our team's view, a full stomach can press against the heart, and an inflamed gut, whether from an infection or a condition like Crohn's disease, can irritate it. In the clinic's view, both can irritate the vagus nerve, which carries that signal up to the brain.

The vagus nerve is the main nerve of the parasympathetic system. It sends information about the state of the inner organs to the brain, and it helps control digestion and heart rate (Breit, 2018). The vagus nerve normally acts as a brake on the heart, so in the clinic's view, gut irritation that changes its signal can ease that brake and let the heart speed up.

Eating itself shifts how the nervous system steers the heart. In 9 healthy volunteers, a 500-calorie meal raised a heart rate variability measure called the LF-to-HF ratio within the first 30 minutes, from 1.78 while fasting to 2.50, and the authors put that mainly down to less vagal activity (Lu, 1999). The study was small, the volunteers were healthy, and it measured heart rate variability only, so it didn't report heart rate or test lying down.

Timing matters too. In our team's experience, one of the most common patterns is a big meal late in the evening followed by lying flat. With a full stomach, the clinic's view is that blood flow out of the chest gets crowded, and you can feel that as a palpitation. Some people find that rolling over or moving stops it.

Why Are Palpitations Worse When I Lie on My Left Side?

Many people notice their palpitations most on their left side. In our team's view, the simplest reason is position. On your left side, the heart sits a little closer to the chest wall, so you feel each beat more and it can seem to echo through your body.

In many of the autonomic cases our team sees, there's a second reason. When a position kinks or presses on an artery, whether in the arteries in the neck and shoulder or in the arteries to the gut, the change in blood flow can reverberate back to the heart, and you feel it as a palpitation. In the clinic's view, if moving clears it, it's worth checking whether that position was changing the flow.

Inflammation can add to it. In our team's view, if the lining around the heart, the pericardium, is inflamed, lying close to the chest wall can irritate the heart, and each beat can feel stronger. No study cited on this page tests that. An inflamed pericardium, called pericarditis, is a medical diagnosis, and chest pain with palpitations is a reason for urgent care, as in the box below.

If you're wondering how to sleep with this, our page on POTS and the best sleeping position covers it, including how a position can press on the vessels in your neck.

Can the Balance System or the Neck's Pressure Sensors Speed Up the Heart Lying Down?

The other group our team looks at is the body's sensors. Besides sensing movement, the inner ear's balance organs feed into blood pressure control. A review of these reflexes describes how signals from the otolith organs in the inner ear help control blood pressure during movement and changes in posture, and notes that they can act before blood actually shifts in the body (Yates, 2014).

Inner ear input can change heart rate in people too. In healthy adults, electrical stimulation of the balance system briefly slowed the heart (Pliego, 2021), so this input can move heart rate, though that study didn't show a speed-up. In a study of 29 patients with balance problems and 16 healthy controls, head movements that brought on dizziness raised breathing rate more in patients with more physical symptoms (Yardley, 1998).

Lying down is often when people with a vestibular problem first feel dizzy. In our team's experience, some of them don't feel dizzy and notice a faster heartbeat instead, coming from the same problem in the vestibular system.

Pressure sensors called baroreceptors, including ones in your neck, help set heart rate, and they keep working while you lie flat. A study of heart rate variability recorded while people lay flat concluded that one part of the signal may reflect this baroreflex control of the heart (Moak, 2007). In the clinic's view, if those sensors read the shift in blood volume inaccurately when you lie down, the heart can speed up. That's our team's position, and the study doesn't show it.

Is It Adrenaline When My Heart Pounds at Night?

If a pounding heart and a rush of adrenaline jolt you awake, our page on adrenaline dumps at night in hyperadrenergic POTS covers it, and a night episode with chest pain, fainting or an irregular beat needs a heart check first.

When Is a Racing Heart Lying Down an Emergency?

Palpitations deserve a proper workup even without those signs. In a study of 190 patients with palpitations, researchers assigned a cause in 84%: the heart in 43% and anxiety or another psychiatric cause in 31%. Within the first year, 75% had palpitations again, though serious outcomes were rare (Weber, 1996). A fast or irregular beat that starts when you lie down can come from the heart's own rhythm, and that's what an ECG and a Holter monitor look for (Govender, 2022).

Palpitations in pregnancy or after giving birth belong with your obstetric team, who can check them against the normal changes of pregnancy.

What Should Be Checked If This Keeps Happening?

The standard first test is a 12-lead ECG taken while the symptoms are happening. If that moment is missed, a Holter monitor worn for 24 to 48 hours can catch it (Govender, 2022).

• It comes with chest pain, breathlessness, fainting or nearly fainting, or a fast heart rate that won't settle at rest. Get urgent care.
• It settles when you roll over or move, and the heart tests are clear. Look at position and blood flow, in the left side section.
• It starts after a big or late meal, and the heart tests are clear. Look at the gut and the vagus nerve, in the meal section.
• It comes with dizziness but no faintness, and the heart tests are clear. Look at the balance system, in the sensor section.

This sorting is our team's clinical view, and the urgent care line follows Govender, 2022.

When the heart tests come back clear and the pattern keeps going, our team looks at the gut and vagus nerve, the inner ear's balance system and the neck's pressure sensors. If changing position settles it, the clinic measures blood flow with your head and arms in different positions to see whether any of them restricts it.

Heart Racing When Lying Down: FAQ