For some people, a sudden rapid heartbeat while lying down can be alarming. But the good news is that in most cases, this condition is usually harmless, according to the health website Healthline (USA).

A rapid heartbeat can be triggered by many factors, the most common of which are anxiety, stress, caffeine intake, and lying down. Orthostatic tachycardia often occurs at night, as this is when we begin to rest and lie down.

During rest, the body adjusts to reduce physical activity. The heart also adjusts its activity to better distribute blood throughout the body. As a result, the heart works harder and beats faster, resulting in the feeling of palpitations.

Sleeping in certain positions can also compress blood vessels and interfere with nerve pathways, causing irregular heartbeats. For example, sleeping on your left side can irritate the vagus nerve, which runs from the brain to the abdomen and regulates heart rate. This interferes with the electrical impulses to the heart, causing it to beat abnormally fast.

In addition, sleeping on the left side can sometimes increase internal pressure and cause the heart to beat faster. Because lying on the left side will cause the body weight to press on the left chest, affecting breathing, thereby affecting the heart. Sleeping on the right side will have less risk of this happening.

Additionally, stress, medication side effects, and lifestyle choices can also cause a rapid heartbeat while lying down. For example, when you are about to sleep, stressful thoughts can trigger a reaction in your body that causes your heart to beat faster. Certain medications, such as those for asthma, high blood pressure, and thyroid disorders, can also cause a rapid heartbeat as a side effect. Using stimulants like caffeine and nicotine close to bedtime can also cause this symptom.

If the condition of rapid heartbeat persists for a long time without a clear cause, the patient should see a doctor. The doctor will screen for arrhythmia, heart muscle problems or some other heart diseases, according to Healthline.