Cardiovascular · PANCE / PANRE

Premature Atrial and Ventricular Contractions

Common ectopic beats — usually benign in structurally normal hearts; high burden may herald cardiomyopathy and warrant evaluation.

Also known as: PAC, premature atrial contraction, premature atrial complex, PVC, premature ventricular contraction, ectopic beats

Overview

Premature atrial contractions (PACs) are early beats originating from ectopic foci within the atria, producing an early P wave (often with altered morphology) followed by a narrow QRS. Premature ventricular contractions (PVCs) originate below the AV node, generating a wide QRS (>120 ms) without a preceding P wave, often followed by a fully or partially compensatory pause. Both are common and often benign in structurally normal hearts.

Epidemiology

PACs and PVCs are extraordinarily common; >50% of healthy adults will have at least one PVC on ambulatory monitoring. Frequency rises with age and underlying cardiovascular disease. A PVC burden >10-15% of total beats on 24-hour Holter is associated with risk of PVC-induced cardiomyopathy.

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Risk factors

Caffeine, nicotine, alcohol, stimulants (cocaine, methamphetamine, decongestants), recreational drugs
Electrolyte disturbances: hypokalemia, hypomagnesemia
Hyperthyroidism
Anemia, fever
Anxiety, sympathetic activation, sleep deprivation
Structural heart disease: prior MI, cardiomyopathy, valvular disease, heart failure
Ischemia
Sleep apnea
Mitral valve prolapse
Medications: digoxin (especially toxicity), bronchodilators (β-agonists, theophylline), QT-prolonging drugs

Pathophysiology

PACs arise from enhanced automaticity, triggered activity, or microreentry within atrial myocardium or pulmonary vein sleeves — the latter are a key substrate for atrial fibrillation. PVCs arise from similar mechanisms within ventricular tissue, most commonly the outflow tracts (especially the right ventricular outflow tract, producing a characteristic LBBB pattern with inferior axis) or fascicular Purkinje system. Frequent PVCs (>10-15% burden) can produce dyssynchronous ventricular contraction, ventricular remodeling, and a reversible cardiomyopathy.

Clinical presentation

Symptoms

Often asymptomatic and found incidentally
Palpitations described as 'skipped beats,' 'flip-flop,' or 'thump' (the strong post-extrasystolic beat is what patients often perceive)
Lightheadedness, fatigue, or rarely syncope with very high burden
Symptoms of heart failure if PVC-induced cardiomyopathy has developed
Anxiety triggered by perceived irregular heartbeat

Signs / physical exam

Irregular pulse with intermittent skipped or strong beats
Variable intensity of S1 (with PVCs interrupting normal AV synchrony)
Cannon A waves on JVP examination if AV dissociation
Heart murmurs may vary in intensity beat-to-beat
Otherwise normal exam unless underlying structural disease

Classic findings

PAC: early, narrow QRS preceded by an abnormal P wave, often followed by a non-compensatory pause. PVC: early, wide QRS without preceding P wave, often followed by a fully compensatory pause; the next sinus beat returns at the expected time.

Differential diagnosis

Atrial fibrillation / atrial flutter (when frequent PACs in bigeminy) — Irregular rhythm without identifiable P waves vs PAC bigeminy with discrete early P; longer monitoring may clarify
Sinus arrhythmia — Phasic variation in sinus rate with respiration; normal P wave morphology
Ventricular tachycardia (when frequent PVCs/runs) — ≥3 consecutive PVCs at >100 bpm constitutes NSVT; sustained >30 sec is VT
Aberrantly conducted PAC vs PVC — Preceding P wave (often abnormal) suggests PAC with aberrancy; AV dissociation/fusion beats favor PVC
Pacemaker spikes — Distinguished by pacing artifact preceding QRS
Catecholaminergic polymorphic VT (CPVT) — Exercise- or emotion-triggered bidirectional VT in young patients with normal resting ECG; RYR2 mutations
Arrhythmogenic right ventricular cardiomyopathy (ARVC) — LBBB-pattern PVCs with epsilon waves, T-wave inversion V1-V3; RV structural abnormalities on MRI

Diagnostic workup

Labs

BMP including potassium, magnesium
TSH
CBC for anemia
Troponin if ischemia suspected

Imaging

12-lead ECG to characterize morphology and define PVC origin (RVOT, LVOT, fascicular, etc.)
Ambulatory 24-48 hour Holter monitor to quantify burden — key for risk stratification and need for further workup; PVC burden >10-15% suggests need for further evaluation
Echocardiography in symptomatic patients, those with frequent PVCs (>5-10%), or any suspicion of structural heart disease
Stress testing if symptoms are exertional or to assess suppression vs provocation with exercise
Cardiac MRI for unusual morphology, suspected ARVC, sarcoid, or unexplained cardiomyopathy
Electrophysiology study selectively in patients considered for catheter ablation

Diagnostic algorithm

Feature	PAC	PVC
P wave before QRS	Yes (early, often abnormal morphology)	No
QRS width	Narrow (<120 ms) unless aberrancy	Wide (≥120 ms)
Post-extrasystolic pause	Non-compensatory (resets sinus node)	Fully compensatory (sinus node not reset)
Common origin	Atrial myocardium, pulmonary veins	RVOT, fascicular system, LVOT, scar
Risk if high burden	Initiation of AFib	PVC-induced cardiomyopathy
First-line therapy if symptomatic	Beta-blocker, trigger modification	Beta-blocker, trigger modification
Definitive therapy (refractory)	Pulmonary vein ablation (if triggering AFib)	Catheter ablation (especially RVOT)

Comparison of premature atrial and ventricular contractions.

Treatment

First-line

Asymptomatic PACs/PVCs with structurally normal heart and low burden: reassurance and observation — these are typically benign
Address modifiable triggers: reduce caffeine, alcohol, stimulant use, nicotine; correct electrolyte abnormalities; treat hyperthyroidism, anemia, sleep apnea; minimize stress; ensure adequate sleep
Beta-blockers (metoprolol, propranolol, atenolol) — first-line pharmacologic therapy for symptomatic PACs or PVCs; nondihydropyridine CCBs (diltiazem, verapamil) are alternatives, particularly for idiopathic RVOT or fascicular PVCs

Second-line / adjunct

Class IC antiarrhythmics (flecainide, propafenone) for symptomatic PVCs in structurally normal hearts (avoid in CAD, LV dysfunction)
Amiodarone for symptomatic PVCs in patients with structural heart disease or HF, though chronic toxicity profile limits enthusiasm
Catheter ablation for: symptomatic PVCs refractory to medical therapy, PVC-induced cardiomyopathy (high burden + reduced EF), or specific high-yield morphologies (RVOT PVCs have ~90% ablation success)
Treat underlying structural heart disease, ischemia, or HF aggressively
ICD is NOT indicated for PVCs alone in the absence of high-risk markers (sustained VT, low EF meeting primary prevention criteria, etc.)

Complications

PVC-induced cardiomyopathy (typically with >10-15% burden, often reversible with PVC suppression or ablation)
Triggering of sustained ventricular tachyarrhythmias in patients with structural heart disease
Initiation of atrial fibrillation by frequent PACs (especially those originating in pulmonary veins)
Anxiety, depression, reduced quality of life from symptom burden
Inappropriate or unnecessary cardiac testing

PANCE pearls

PVC-induced cardiomyopathy: typically requires burden >10-15% of total beats on 24-hour monitoring. EF often improves substantially after suppression with medication or ablation — the cardiomyopathy is reversible.
Right ventricular outflow tract (RVOT) PVCs (LBBB morphology, inferior axis, transition V3-V4) are the most common idiopathic PVCs in structurally normal hearts and respond well to catheter ablation.
PACs originating in pulmonary veins are the dominant trigger for AFib initiation — frequent PACs can be a harbinger.
Compensatory pause: PVCs typically have a FULLY compensatory pause (the next sinus beat returns at expected time because the PVC does not reset the sinus node); PACs typically have an INCOMPLETE compensatory pause (resetting the sinus node).
Cardiac MRI is useful when PVC morphology suggests ARVC, sarcoidosis, or other structural substrate not seen on echo.

Images

Premature atrial contraction — early P wave with abnormal morphology, narrow QRS

Premature ventricular contraction — wide, bizarre QRS without preceding P wave, often followed by compensatory pause

References

AHA/ACC/HRS 2017 — 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death (Al-Khatib et al., JACC 2018)
EHRA/HRS/APHRS 2019 — EHRA/HRS/APHRS/LAHRS Expert Consensus Statement on Catheter Ablation of Ventricular Arrhythmias (Cronin et al., Heart Rhythm 2020)
AHA Statement 2020 — Premature Ventricular Contractions and Their Role in the Development of Cardiomyopathy: AHA Scientific Statement (Marcus, Circulation 2020)

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