What Causes an Arrhythmia?

An arrhythmia can occur if the electrical signals that control the heartbeat are delayed or blocked. This can happen if the special nerve cells that produce electrical signals don't work properly, or if electrical signals don't travel normally through the heart.

An arrhythmia also can occur if another part of the heart starts to produce electrical signals. This adds to the signals from the special nerve cells and disrupts the normal heartbeat.

Smoking, heavy alcohol use, use of certain drugs (such as cocaine or amphetamines), use of certain prescription or over-the-counter medicines, or too much caffeine or nicotine can lead to arrhythmias in some people.

Strong emotional stress or anger can make the heart work harder, raise blood pressure, and release stress hormones. In some people, these reactions can lead to arrhythmias.

A heart attack or an underlying condition that damages the heart's electrical system also can cause arrhythmias. Examples of such conditions include high blood pressure, coronary heart disease, heart failure, overactive or underactive thyroid gland (too much or too little thyroid hormone produced), and rheumatic heart disease.

In some arrhythmias, such as Wolff-Parkinson-White syndrome, the underlying heart defect that causes the arrhythmia is congenital (present at birth). Sometimes, the cause of an arrhythmia can't be found.