Premature ventricular contraction overview

# Overview
Premature ventricular contraction is a form of irregular heart beat in which the ventricle contracts prematurely.   This results in a skipped beat followed by a stronger beat.   Individuals may report a feeling that their heart stops after a premature ventricular contraction.

# Classification
Premature ventricular contractions can be classified based upon the number of normal beats between them and defined accordingly into bigeminy, trigeminy, or quadrigeminy.

# Pathophysiology
Premature ventricular contraction is a relatively common event where the heartbeat is initiated by Purkinje fibres in the ventricles rather than by the sinoatrial node, the normal heartbeat initiator.  Re-entrant signalling and enhanced automaticity in some ectopic focus are the main pathophysiological explanations.

# Causes
Premature ventricular contractions can occur in a healthy person of any age, however they are more common in patients with underlying heart disease such as ischemic heart disease and structural heart disease.  Patients on tricyclic antidepressant are at risk of having PVCs.

# Differentiating Premature Ventricular Contraction from other Diseases
A premature ventricular contraction originates in the ventricle, and this must be differentiated from an impulse that originates above the ventricle (i.e. it is supraventricular in origin) and conducts with a delay (i.e. a wide complex, it is aberrantly conducted).

# Epidemiology and Demographics
The prevalence of premature ventricular contractions (PVCs) varies between 100 to 400 per 100,000 individuals worldwide on standard 12-lead electrocardiography and 4000 to 7500 per 100,000 individuals on  24- to 48-hour Holter monitoring. Patients of all age groups may develop PVC and the incidence increases with age. African- American individuals are more likely to develop PVCs. Men are more commonly developed the disease than women.

# Risk Factors
Premature ventricular contraction can occur due to activation of the sympathetic nervous system and the common risk factors are anxiety, physiological stress etc.  Patient with copper deficiency are also prone to PVCs.

# Natural History, Complications and Prognosis
Premature ventricular contraction caries no risk of mortality in the absence of any underlying heart disease.  Heart rate turbulence is a phenomenon representing the return to equilibrium of the heart rate after a PVC.  These parameters correlate significantly with mortality after myocardial infarction.

# Diagnosis

## History and Symptoms
Premature ventricular contraction patients may have no symptom at all or may present with exercise intolerance and chest pain.  Sometimes patients may present with a non specific feeling of forceful beat which might need the use of Holter monitor to pick up PVCs.

## Physical Examination
Complete physical examination help determine any heart defects as a cause for premature ventricular contractions.

## Laboratory Findings
Many cases of premature ventricular contraction have no definite cause, it may be the result of various other problems.  If PVC patients present with symptoms, a generalized approach is done to find the precipitating factors.

## Electrocardiogram
When looking at an electrocardiograph, premature ventricular contractions are easily spotted and therefore a definitive diagnosis can be made.  The QRS and T waves look very different to normal readings.  The spacing between the PVC and the preceding QRS wave is a lot shorter than usual and the time between the PVC and the proceeding QRS is a lot longer.  However, the time between the preceding and proceeding QRS waves stays the same as normal due to the compensatory pause.

# Treatment

## Medical Therapy
Isolated premature ventricular contractions with benign characteristics require no treatment.  In healthy individuals, PVCs can often be resolved by restoring the balance of magnesium, calcium and potassium within the body.

## Ablation
Radiofrequency ablation is useful for treating patients with high frequency of premature ventricular contraction episodes.

## Primary Prevention
The most effective treatment of premature ventricular contraction is the elimination of triggers particularly the cessation of the use of substances such as caffeine, and certain drugs.