Palpitations

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What are palpitations?

Palpations are sensations by a person that they are having hard, rapid, or irregular heartbeats or a combination of these sensations. The following is a brief description of the heart's function that should help readers to better understand palpitations.

The heart is a two-stage electrical pump whose function is to circulate blood to the organs and tissues of the body. The heart's electrical system allows the heart muscle to beat in a coordinated fashion to maximize the pumping strength of the ventricles, the lower chambers of the heart, and make certain that there is an adequate amount of blood to be pumped.

The upper chambers of the heart, called the atria (single=atrium) collect blood from the body and lungs and pump it into the ventricles. There needs to be a short delay to allow the ventricles to fill and then pump the blood back to the body and lungs to complete the cycle. The heart's electrical system allows this to happen, so that each chamber of the heart beats (contracts or squeezes) when it's supposed to.

The sinoatrial node (SA node) is a collection of special cells embedded in the heart muscle of the right atrium. They act as the pacemaker for the heart by generating an electrical impulse 60 to 80 times per minute. This signal is transmitted to all the atrial muscle cells so that they can fire at the same time and pump blood from the atrium to the ventricle, the first half of a heartbeat. At the same time, an electrical impulse is sent to the atrioventricular node (AV node), located in the junction between the atrium and ventricle. The AV node acts as an electrical junction box and delays the electrical signal for a fraction of a second so that the ventricle can fill with blood from the atrium. It then sends the signal to all the muscle cells of the ventricle so that they can fire together in a coordinated fashion and generate the second half of the heartbeat that pumps blood to the body.

Every heart muscle cell has the potential to generate an electrical signal that can spread outside the normal conduction pathways that may or may not generate a heartbeat. If the SA node fails to function, other cells in the atrium attempt to generate a heartbeat. If they too should fail, the AV node can act as a pacemaker but usually generates a signal at only 40 beats per minute. If the AV node should also fail, the ventricle itself can generate its own electrical signal as a final backup, but only at about 20 beats per minute.

A palpitation describes the sensation that occurs when a patient feels an abnormality in the normal beat of the heart. Abnormalities in the electrical conducting system may cause the heart to beat too quickly, too slowly, or irregularly. Sometimes a palpitation may be a normal variant but it may also be caused by a significant problem that could be life threatening. A palpitation may be an isolated extra heartbeat or it may describe a run of many extra beats that run together for a prolonged period of time. Sometimes a missed beat or a pause can be felt.

Medically Reviewed by a Doctor on 10/23/2013

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Palpitations & Hyperthyroidism

Hyperthyroidism and Heart Palpitations

Medical Author: Ruchi Mathur, MD
Medical Editor: William C. Shiel, Jr, MD, FACP, FACR

I see a number of patients with hyperthyroidism. Very frequently, their symptoms involve the heart. The most common symptoms are a feeling of palpitations and a sensation of a racing heart beat. These symptoms are due to a physiologic effect of thyroid hormone on the heart. I thought I'd take a moment to explain more about what impact thyroid hormone can have on the heart and why these symptoms result.

Many of the signs and symptoms patients experience when they are diagnosed with hyperthyroidism result from the direct effect of thyroid hormoneson the heart. While heart effects are also seen in hypothyroidism, they are usually much more obvious in hyperthyroidism.

Excess thyroid hormone causes palpitations and some degree of exercise intolerance that is due to an increased heart rate and fatigue.