Premature atrial and ventricular contractions !

Extra heartbeats that come too early, felt as a skip or a thump. Very common and usually harmless, but sometimes a sign of heart disease.

Updated 2026-11-01

Structures involved

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Why it happens

What it is

Premature contractions (extrasystoles) are beats that arise earlier than the next expected sinus beat from an ectopic focus outside the sinoatrial node. Premature atrial contractions (PACs) start in the atria and premature ventricular contractions (PVCs) in the ventricles. They are the most common arrhythmias. Isolated beats in a normal heart are usually benign, but a high burden can cause symptoms or cardiomyopathy, and they may reflect structural heart disease or a metabolic problem.

Who gets it

Very common: some PACs and PVCs appear on 24-hour monitoring in most adults, and their frequency rises with age. They are seen more often in people with hypertension, heart failure, ischaemic or Chagas heart disease. In Colombia and Latin America, frequent or complex PVCs in someone from a rural endemic area should prompt testing for Chagas disease.

Causes

Idiopathic in a normal heart (for example from the right ventricular outflow tract)
Stimulants: caffeine, nicotine, alcohol, cocaine and amphetamines, some decongestants
Electrolyte disorders: low potassium or magnesium
Structural heart disease: ischaemic heart disease, cardiomyopathies (including Chagas), valve disease, heart failure
Hyperthyroidism, hypoxia, sleep apnoea, stress and anxiety, digoxin toxicity

Risk factors

Older age
Hypertension and structural heart disease
Caffeine, alcohol, tobacco and stimulant use
Sleep deprivation and emotional stress
Electrolyte disturbances, often from diuretics

Pathophysiology

Three mechanisms produce premature beats: enhanced automaticity of an ectopic focus, triggered activity from afterdepolarisations (as in digoxin toxicity or hypokalaemia), and micro re-entry around scar. A PAC is conducted through the AV node, giving a narrow QRS preceded by an abnormal P wave, and often resets the sinus node (non-compensatory pause). A PVC spreads slowly through ventricular muscle rather than the conduction system, giving a wide, bizarre QRS without a preceding P wave, usually followed by a full compensatory pause. The beat after the pause is stronger, which patients feel as a thump. A PVC burden above roughly 10 to 15 % of beats can cause dyssynchrony and a reversible PVC-induced cardiomyopathy.

Classification

By origin: atrial (PAC), junctional, ventricular (PVC)
PVC morphology: unifocal (monomorphic) versus multifocal (polymorphic)
Patterns: bigeminy (every other beat), trigeminy, couplets; three or more in a row is non-sustained ventricular tachycardia
R-on-T PVCs (falling on the T wave), which can trigger ventricular fibrillation in an ischaemic heart

Symptoms and signs

Many people have no symptoms
Sensation of a skipped beat, a pause or a strong thump in the chest
Fluttering or palpitations, often noticed at rest or lying down
Light-headedness with frequent beats
Fatigue or dyspnoea when the burden is high or heart function is reduced

Diagnosis

Clinical: History of palpitations, triggers (caffeine, alcohol, stimulants, sleep), drugs and family history; examination for murmurs and heart failure. An irregular pulse with occasional pauses suggests premature beats. The aim is to separate benign isolated ectopy from beats that signal heart disease.
Tests: 12-lead ECG identifies the type and morphology. Holter or longer ambulatory monitoring measures the burden and detects runs. Potassium, magnesium, thyroid function and, where relevant, digoxin level; Chagas serology in people from endemic areas. Exercise testing: PVCs that disappear with exercise are usually benign, while those that increase deserve further study.
Imaging: Echocardiography to look for structural heart disease and PVC-induced cardiomyopathy when PVCs are frequent, complex or symptomatic. Cardiac magnetic resonance when echocardiography suggests cardiomyopathy.

Differential diagnosis

Atrial fibrillation (irregularly irregular rhythm)
Sinus arrhythmia
Second-degree AV block (dropped beats)
Supraventricular tachycardia
Non-sustained ventricular tachycardia
Anxiety or panic disorder with sinus tachycardia

Goal of treatment

Reassure when benign, remove triggers, correct the cause and treat symptoms or a high burden that threatens ventricular function.

Treatment

Conservative: Reassurance and explanation for isolated beats in a normal heart; no treatment needed when asymptomatic.
Lifestyle: Reduce or avoid caffeine, alcohol, tobacco, stimulants and decongestants; improve sleep and manage stress.
Medical: Correct low potassium or magnesium, treat hyperthyroidism, review drugs such as digoxin, and treat underlying heart disease.
Medical: Symptomatic or frequent beats: beta-blockers or non-dihydropyridine calcium channel blockers first; antiarrhythmic drugs in selected cases.
Procedure: Catheter ablation of the ectopic focus for frequent symptomatic PVCs, failure of drugs or PVC-induced cardiomyopathy.
Follow-up: Nursing: assess the patient, not just the monitor; report new, frequent, multifocal or R-on-T PVCs and runs, check potassium and magnesium, and monitor closely after myocardial infarction.

Complications

Usually none in a normal heart
PVC-induced cardiomyopathy with a high burden
Triggering of atrial fibrillation (frequent PACs, especially from the pulmonary veins)
Ventricular tachycardia or fibrillation in an ischaemic or diseased heart
Anxiety and reduced quality of life from palpitations

Prognosis

Isolated PACs and PVCs in a structurally normal heart carry an excellent prognosis. Frequent PACs predict later atrial fibrillation, and frequent or complex PVCs with structural heart disease are linked to higher risk of arrhythmic death. PVC-induced cardiomyopathy often improves after the burden is reduced.

Prevention

Moderating caffeine and alcohol and avoiding tobacco and stimulants
Adequate sleep and stress management
Control of hypertension and monitoring of electrolytes in patients on diuretics

Test yourself

Think of the answer, then tap the question to see it.

How does a PVC look on the ECG?

A wide, bizarre QRS without a preceding P wave, usually followed by a full compensatory pause.

How does a PAC look on the ECG?

An early, abnormal P wave followed by a narrow QRS, usually with a non-compensatory pause.

What is ventricular bigeminy?

A PVC after every normal sinus beat.

Which electrolytes should be checked in a patient with frequent PVCs?

Potassium and magnesium.

What can a very high PVC burden cause?

A reversible PVC-induced cardiomyopathy.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Arrhythmias - Types | NHLBI, NIH (National Heart, Lung, and Blood Institute (NHLBI), NIH, 2026); Arrhythmias: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

Right atrium highlighted on the Durgical 3D model