Perception of an occasional skipped heartbeat

Atrial premature beats or ventricular premature beats

Sudden episodes of rapid heartbeats that abruptly slow to the normal rate; often in people who have had previous episodes of rapid heartbeats

PSVT or Wolff-Parkinson-White syndrome

Less often ventricular tachycardia or congenital long QT syndrome

A constant sensation of rapid, irregular heartbeats

Atrial fibrillation

Fainting during palpitations

Ventricular tachycardia, congenital long QT syndrome, inherited hypertrophic cardiomyopathy, atrial fibrillation, or Brugada syndrome

Palpitations during exercise or an emotional situation

Sinus tachycardia (the heart's normal response to stress), particularly common in healthy people

Abnormal heart rhythm caused by a decrease in blood flow triggered by exercise, more common in people who have coronary artery disease or congenital heart diseases

In people with a family history of fainting or sudden death

Brugada syndrome, congenital long QT syndrome, or inherited dilated or hypertrophic cardiomyopathy

In people who are bleeding, have a fever, are in pain, or have lost fluids (as may result from vomiting or diarrhea)

Sinus tachycardia

Intolerance of heat, weight loss, bulging eyeballs, and tenderness and/or swelling in the front of the neck

Sinus tachycardia or atrial fibrillation due to hyperthyroidism