The group of cardiac arrhythmias includes all conditions characterized by an alteration in the rhythm of contraction of the heart, either in excess or in defect or associated with irregularities that make the action of pumping blood through the arteries less efficient.
When the arrhythmia causes an acceleration of the heart rhythm it is called a tachyarrhythmia (which can be in the atria or ventricles of the heart), while when it is associated with a slowed rhythm it is called a brachiarrhythmia.
A very common atrial tachyarrhythmia in the Western population is atrial fibrillation; other arrhythmias in the same group are atrial flutter, supraventricular tachyarrhythmia, and Wolff-Parkinson-White syndrome.
Major ventricular tachyarrhythmias include ventricular tachycardia, ventricular fibrillation, and long QT syndrome.
The most common brachiarrhythmias are sinus node disease and atrioventricular conduction block.
An additional type of arrhythmia is represented by extra-systoles, which are generally perceived as a “missing beat” or a “stumble” in the heart rhythm, but which actually correspond to occasional “extra” beats (i.e., more than the normal contraction sequence).
Some arrhythmias are extemporaneous and completely harmless (e.g., tachyarrhythmia associated with strenuous physical activity in a healthy person); others, which are persistent, may damage the heart muscle or increase the risk of developing other cardiovascular diseases or going on to severe acute events (e.g., stroke or pulmonary embolism in the case of atrial fibrillation).
