Palpitations are unpleasant sensations of irregular and/or forceful beating of the heart. In some patients with palpitations, no heart disease or abnormal heart rhythms can be found. Reasons for their palpitations are unknown. In others, palpitations result from abnormal heart rhythms (arrhythmias). Arrhythmias refer to heartbeats that are too slow, too rapid, irregular, or too early. Rapid arrhythmias (greater than 100 beats per minute) are called tachycardias. Slow arrhythmias (slower than 60 beats per minute) are called bradycardias. Irregular heart rhythms are called fibrillations (as in atrial fibrillation). When a single heartbeat occurs earlier than normal, it is called a premature contraction. Abnormalities in the atria, the ventricles, the SA node, and the AV node of the heart can lead to arrhythmias.

Premature contractions are isolated heartbeats that occur earlier than expected. The premature contraction is followed by a pause, as the heart electrical system "resets" itself. The contraction following the pause is usually more forceful than normal contractions. The patients frequently perceive these more forceful contractions as palpitations.

Normal Heartbeat

The normal resting adult heart beats regularly at an average rate of 60 times per minute. How fast the heart beats (heart rate) is governed by the speed of electrical signals originating from the pacemaker of the heart, the SA node. The electrical signals from the SA node travel across the atria and cause these two upper heart chambers to contract, delivering blood into the lower heart chambers, the ventricles. These electrical signals then pass through the AV node to reach the ventricles. Electrical signals reaching the ventricles cause these chambers to contract, pumping blood to the rest of the body, generating the pulse. During rest, the speed of electrical signals originating from the SA node is slow, thus the heart beats slowly. During exercise or excitement, the speed of signals from the SA node increases, and heartbeat quickens.

Symptoms

Arrhythmias are pattern and/or speed changes from the normal heart rhythm. Some patients are totally unaware of their arrhythmias. Others may report symptoms, such as palpitations, skipping or fluttering sensations, dizziness, fainting, shortness of breath, or chest pain.