Heart Disease - Heart Rhythm Disorders (Arrhythmias)
Heart rhythm disorders (arrhythmias) occur either independently or as a result of other cardiac conditions, such as coronary artery disease and myocardial infarction (heart attack). In any case, rhythm disorders signal abnormalities in the conduction system of the heart.
Heart rhythm disorders are categorized as either bradycardia (slow heartbeat) or tachycardia (rapid heartbeat). Tachycardia may further sub-divided into ventricular tachycardias (involving only the ventricles) and supraventricular tachycardias (involving both the atria and the ventricles).
|Symptoms of bradycardia
|Symptoms of tachycardia|
Examples of specific arrhythmias include:
- Atrial fibrillation: Rapid and irregular heartbeat due to signals in the atria that cause the ventricles to contract abnormally. This condition prevents blood from flowing through the heart's chambers, often causing it to accumulate in the atria. A blood clot may form as a result of atrial fibrillation, leading to stroke or myocardial infarction (heart attack).
- Ventricular fibrillation: Rapid contractions of the heart caused by irregular electrical signals in the ventricles. The condition is common after myocardial infarction (heart attack) or from electrocution or drowning. The condition is life-threatening and should be treated immediately with electric shock (defibrillation) to the heart followed by anti-arrhythmic drugs.
- Premature ventricular contraction: An abnormal signal from the ventricles causes the heart to beat prematurely (early). Premature ventricular contraction is common in children and teenagers and may not require treatment. However, in some cases when the condition is caused by disease or injury, it could lead to ventricular tachycardia and also fibrillation.
- Heart block: Interruption of electrical communication between the atria and ventricles. This results in the ventricles contracting less often than the atria. The condition leads to episodes of dizziness, fainting spells or stroke. Heart block is categorized by its severity. More severe cases are commonly treated with an artificial pacemaker, or less commonly, with drugs (such as isoproterenol).