Premature Ventricular Contractions (PVCs)
Premature Ventricular Contractions (PVCs)
An early, wide-complex beat from the ventricles, with no P wave of its own, a discordant T wave and a fully compensatory pause.
On the trace
Read the strip in this order.
- Find the early beat.
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It arrives before the next sinus beat is due, and its QRS is wide (120 ms or more) and bizarre. - Look in front of it.
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No P wave belongs to it. The sinus P that was due is still firing on time, usually buried inside the PVC. - Look at its T wave.
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It points the opposite way to the QRS. That discordance is expected in a PVC, not a sign of ischaemia. - Measure the pause.
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The R-R from the sinus beat before the PVC to the sinus beat after it is exactly two normal cycles: a fully compensatory pause. - Compare PVCs.
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Each one arrives the same distance after its sinus beat (a fixed coupling interval) and has the same shape: one focus.
How to recognise it
| Feature | Value | Notes |
|---|---|---|
| Timing | Premature | Earlier than the next expected sinus beat. |
| QRS width | ≥ 120 ms | Wider the further the focus is from the His-Purkinje system. |
| P wave | None of its own | The sinus P is usually hidden in the PVC; occasionally a retrograde P follows it. |
| T wave | Discordant | Opposite to the main QRS deflection. |
| Pause | Fully compensatory | The R-R spanning the PVC equals two sinus R-R intervals. |
| Coupling interval | Fixed | The same sinus-to-PVC interval each time points to one focus. |
The strip
Mechanism
An irritable focus in the ventricular muscle fires before the sinus impulse arrives. Its impulse travels cell to cell through ordinary muscle rather than down the fast His-Purkinje system, so the ventricles are activated one after the other instead of together, which makes the QRS wide and lopsided.
The sinus node is not disturbed. It fires on schedule, but its next impulse reaches a ventricle still refractory from the PVC and does not conduct. The one after that does, exactly two cycles after the last sinus beat: that is why the pause is fully compensatory.
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Background
Occasional PVCs are found in most healthy people; clinical significance scales with frequency, symptoms, and whether there is structural heart disease underneath.
What the morphology reveals
- Left ventricular origin: right bundle branch block pattern (broad R in V1).
- Right ventricular origin: left bundle branch block pattern (broad negative complex in V1).
- Septal origin: narrower, because both ventricles are reached almost together.
The outflow tracts are the commonest source of benign PVCs in a normal heart. Right ventricular outflow tract PVCs show a left bundle branch block pattern with an inferior axis (tall R in II, III and aVF), and they respond well to catheter ablation.
The R-on-T phenomenon
A PVC landing on the preceding T wave falls in the vulnerable period of repolarisation and can, rarely, trigger VF. The risk matters with a long QT, acute ischaemia or an otherwise unstable heart; in a normal heart R-on-T PVCs are usually benign.
When PVCs become a run
Two in a row is a couplet. Three or more at 100 bpm or faster is non-sustained VT. The boundary is a counting convention for risk stratification, not a change in mechanism.
Clinical impact
Two things decide what PVCs mean: burden and substrate. In a structurally normal heart they are almost always benign. With reduced ejection fraction, prior infarction or a cardiomyopathy, frequent PVCs can depress function further and mark a higher arrhythmic risk.
Management
Measure the burden
A 24- to 48-hour Holter gives the PVC percentage and flags couplets and runs. A burden of about 10% or more warrants echocardiography; below that, with a normal heart, reassurance is usually enough.
Remove reversible triggers
Low potassium or magnesium, caffeine, stimulants, sympathomimetics and digoxin toxicity. Exclude ischaemia in new, frequent PVCs with cardiac risk factors.
Symptoms: beta-blocker first
A beta-blocker reduces PVC frequency and the palpitations they cause. A non-dihydropyridine calcium-channel blocker (verapamil or diltiazem) is the alternative.
Catheter ablation
For PVC-induced cardiomyopathy, for symptoms despite medication, and as a first-line option for symptomatic outflow tract PVCs. LV function often recovers over the following months.
Differential
Also premature, but usually narrow, with an abnormal P wave in front of it and a pause that is not fully compensatory. Even a PAC conducted with aberrancy keeps its preceding P.
Three or more PVCs in a row at 100 bpm or faster: the same mechanism, now counted as a run.
References
- 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death — European Heart Journal, 2022
- 2017 AHA/ACC/HRS Guideline for Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death — Circulation, 2018
- Premature Ventricular Complex-Induced Cardiomyopathy, a Review: Current Insights, Diagnostic Challenges, and Therapeutic Strategies — Journal of Clinical Medicine, 2026