Premature Ventricular Contractions (PVCs): ECG, Causes & When to Worry

A premature ventricular contraction is an early, extra heartbeat from the ventricles — usually harmless and felt as a skipped beat, but sometimes a clue to something more.

What is a PVC?

A premature ventricular contraction (PVC) is an early heartbeat that starts in the ventricles rather than the SA node, producing a wide, bizarre QRS with no preceding P wave. Because it fires early and out of sequence, it is followed by a compensatory pause, which many people feel as a "skipped beat" or a flutter.

PVCs on the ECG

• A wide, early QRS (≥ 0.12 s) with no preceding P wave
• An abnormal, bizarre QRS shape
• Usually a compensatory pause before the next normal beat

Patterns have names: bigeminy (every other beat is a PVC), trigeminy (every third), couplets (two in a row), and runs of three or more — which become ventricular tachycardia.

Causes

• Common triggers — caffeine, stress, nicotine, alcohol, fatigue
• Electrolyte disturbance (low potassium or magnesium)
• Ischaemia or structural heart disease
• Stimulant drugs and some medications

When are PVCs a concern?

Occasional PVCs in a structurally normal heart are usually benign. They warrant closer attention when they are very frequent, occur in runs, happen alongside structural heart disease or symptoms (syncope, chest pain), or fall on the preceding T wave ("R-on-T"), which can trigger dangerous arrhythmias. A very high PVC burden can, over time, weaken the heart.

Key takeaways

• A PVC is a wide, early ventricular beat with no preceding P wave.
• Bigeminy, couplets, and runs describe their patterns.
• Occasional PVCs in a normal heart are usually benign.
• Frequent PVCs, runs, or symptoms with heart disease need evaluation.

Frequently asked questions

What is a premature ventricular contraction?

An early, extra heartbeat that starts in the ventricles, producing a wide, bizarre QRS with no preceding P wave, often felt as a skipped beat.

What do PVCs look like on an ECG?

A wide, early QRS (≥0.12 s) with an abnormal shape and no preceding P wave, usually followed by a compensatory pause.

What is bigeminy?

A pattern in which every other beat is a premature ventricular contraction.

What causes PVCs?

Caffeine, stress, nicotine, alcohol, and fatigue, as well as electrolyte disturbances, ischaemia, structural heart disease, and stimulant drugs.

When are PVCs dangerous?

When they are very frequent, occur in runs, happen with structural heart disease or symptoms, or fall on the T wave (R-on-T), which can trigger ventricular tachycardia.