A premature ventricular contraction (PVC) is a common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node. PVCs may cause no symptoms or may be perceived as a "skipped beat" or felt as palpitations in the chest. PVCs do not usually pose any danger.The electrical events of the heart detected by the electrocardiogram (ECG) allow a PVC to be easily distinguished from a normal heart beat. However, very frequent PVCs can be symptomatic of an underlying heart condition (such as arrhythmogenic right ventricular cardiomyopathy). Furthermore, very frequent (over 20% of all heartbeats) PVCs 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 PVCs. If PVCs are frequent or troublesome, medication (beta blockers or certain calcium channel blockers) may be used. Very frequent PVCs in people with dilated cardiomyopathy may be treated with radiofrequency ablation. Signs and symptoms
Although there are many possible symptoms associated with PVCs, PVCs may also have no symptoms at all. PVCs may be perceived as a skipped heart beat, a strong beat, palpitations, or lightheadedness. They may also cause chest pain, a faint feeling, fatigue, or hyperventilation after exercise. Symptoms may be more pronounced at times of stress.
If symptoms are infrequent, other forms of continuous heart beat recording may be used, such as a 24 or 48-hour Holter monitor  or even 14- to 30-day recorders if the symptoms are very occasional. The advantage of these monitors is that they allow a quantification of the amount of abnormal beats ("burden") and ensure that there are no heart arrhythmias present that might require attention, such as ventricular tachycardia. If symptoms are associated with exercise, a supervised cardiac stress test may be required to reproduce the abnormality. Specifically, if this shows exercise-induced ventricular tachycardia this would require specific treatment. If PVCs are suppressed by exercise, this is an encouraging finding.On electrocardiography (ECG or Holter) premature ventricular contractions have a specific appearance of the QRS complexes and T waves, which are different from normal readings. By definition, a PVC occurs earlier than the regular normally conducted beat. Subsequently, the time between the PVC and the next normal beat is longer as the result of a compensatory pause. PVCs can be distinguished from premature atrial contractions because the compensatory pause is longer following premature ventricular contractions, in addition to a difference in QRS appearance.In some people, PVCs occur in a predictable pattern. Two PVCs in a row are called doublets and three PVCs in a rows are triplets. Depending whether there are one, two, or three normal (sinus) beats between each PVC, the rhythm is called bigeminy, trigeminy, or quadrigeminy. If 3 or more consecutive PVCs occur in a row it may be called ventricular tachycardia.