Heart palpitations represent a sudden, conscious awareness of the heartbeat. Patients generally describe the heartbeat as having an odd quality, such as irregularity, unusual rapidity or exceptional forcefulness. Heart palpitations are often categorized based on the underlying cause, including abnormal heart rhythms, heart problems unrelated to the cardiac rhythm and problems outside of the heart.
Arrhythmias
The heart contains a natural pacemaker and a network of conduction fibers that carry electrical signals from the pacemaker to the rest of the heart, resulting in regular, coordinated cardiac contractions. Transient or permanent problems with the cardiac pacemaker or conduction system can cause heartbeat abnormalities, or arrhythmias. Heart palpitations may accompany a cardiac arrhythmia.
Many different types of cardiac arrhythmias occur. Some are potentially life threatening, although most are medically harmless, according to the National Heart, Lung and Blood Institute. For example, sudden fear may trigger a release of adrenalin, the "fight or flight" hormone, and an episode of palpitations. Other strong emotions can similarly provoke a temporary awareness of a racing heartbeat. The National Heart Lung and Blood Institute emphasizes that certain signs and symptoms may indicate a serious medical problem if they occur with heart palpitations, including dizziness, fainting, confusion, shortness of breath, chest pain or pressure, pain in the arm or jaw and unexplained sweating.
Non-Arrhythmic Cardiac Disorders
Certain types of heart problems unrelated to the cardiac conduction system can also cause palpitations. Problems with the heart valves remain a frequent cause of non-arrhythmia cardiac palpitations. In a 2005 article published in "American Family Physician," Dr. Allan Abbott notes that abnormalities of the aortic valve, through which oxygenated blood passes as it enters the bloodstream, can cause palpitations. Similarly, holes in the wall that separates the right and left sides of the heart may precipitate episodes of palpitations. Other heart disorders that may provoke palpitations include cardiomyopathy, an abnormal thinning or thickening of the heart muscle; heart failure; inflammation of the heart sac, or pericarditis, and congenital malformations of the heart.
Non-Cardiac Disorders
A variety of substances and conditions that provoke increases in heart rate or the forcefulness of heart contractions can cause palpitations. Stimulants such as cocaine, methamphetamine, diet pills, caffeine and nicotine are frequent causes of transient palpitations. Prescription and over-the-counter medications that may cause palpitations include bronchodilators for asthma, decongestants and certain types of heart or blood pressure medicine.
Diseases and conditions that may affect the heart and provoke palpitations include high fever, decreased blood oxygen content, overactive thyroid disease and severe anemia, notes the National Library of Medicine's online medical encyclopedia MedlinePlus.
