:This is the article for the heart condition generally referred to as<unk> . For<unk>  pipe, see Polyvinyl chloride. A<unk>  <unk>  is a common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node.<unk> s may cause no symptoms or may be perceived as a "skipped beat" or felt as palpitations in the chest.<unk> s do not usually pose any danger. The electrical events of the heart detected by the electrocardiogram (ECG) allow a<unk>  to be easily distinguished from a normal heart beat. However, very frequent<unk> s can be symptomatic of an underlying heart condition (such as arrhythmogenic right<unk>  cardiomyopathy). Furthermore, very frequent (over 20% of all heartbeats)<unk> s are considered a risk factor for arrhythmia-induced cardiomyopathy, in which the heart muscle becomes less effective and symptoms of heart failure may develop. Ultrasound of the heart is therefore recommended in people with frequent<unk> s. If<unk> s are frequent or troublesome, medication (beta blockers or certain calcium channel blockers) may be used. Very frequent<unk> s in people with dilated cardiomyopathy may be treated with radiofrequency ablation.
Premature ventricular contraction
Premature atrial contraction
Benign early repolarization
Pre-excitation syndrome
Ectopic beat
Ectopic pacemaker
Premature junctional contraction
Drug-induced QT prolongation