Some things that can cause a person's heart to pound at night include caffeine or nicotine intake, anxiety or panic attacks, and exercise shortly before bed, according to MedlinePlus. A pounding heartbeat is also known as heart palpitations, which can also be caused by diet pills, fever or narcotics.
Some individuals experience a pounding heart sensation when lying down after eating certain foods, explains WebMD. This is often due to heavy meals that contain high amounts of fat, sugar or carbohydrates. Other people get this sensation when eating foods with a lot of sodium or nitrates. Food sensitivity is often the cause of heart palpitations that occur after eating certain types of foods. People who frequently experience a pounding heartbeat when lying down shortly after meals should make a note of the foods that seem to cause it.
A pounding heartbeat while lying down is not usually a dangerous situation, notes MedlinePlus, but heart palpitations that are from an abnormal heart rhythm might be a sign of other medical conditions. This includes an abnormal heart valve, heart disease, an overactive thyroid or a low level of oxygen in the blood. It might also be a sign of an abnormal blood level of potassium or stem from medications taken for high blood pressure or asthma.