ECG Flashcards: Ectopic Beats (PAC, PJC, PVC)

What is an ectopic beat?

A premature beat originating from a site outside the SA node.

Are ectopic beats a rhythm?

No — they are isolated beats or short runs.

Where can ectopic beats originate?

Atria, Junction (AV node), Ventricles.

Why can't ectopics come from the SA node?

The SA node is the normal pacemaker, not 'ectopic'.

Where do PACs originate?

Atria.

What happens to the P wave in PACs?

Present but abnormal shape.

Possible P wave appearances in PACs?

Upright, Inverted, Flattened, Peaked.

What is the QRS in PACs?

Normal (narrow <0.12 sec).

Why is QRS normal in PACs?

Conduction still follows normal pathways (AV node → ventricles).

Where do PJCs originate?

AV junction.

What happens to the P wave in PJCs?

Often absent or inverted.

Where can the P wave appear in PJCs?

Before QRS (short PR), Hidden in QRS, After QRS.

Why are P waves inverted in PJCs?

Depolarisation travels backwards (retrograde).

What is the QRS in PJCs?

Normal (narrow).

Where do PVCs originate?

Ventricles.

What happens to the P wave in PVCs?

Usually absent.

Can a P wave appear with PVCs?

Yes, but not related to QRS; may appear after or independently.

What is the QRS in PVCs?

Wide (>0.12 sec).

Why is QRS wide in PVCs?

Impulse spreads slowly through myocardium (not conduction system).

PAC vs PJC vs PVC (P wave)?

PAC → abnormal P present; PJC → absent/inverted P; PVC → absent P.

PAC vs PJC vs PVC (QRS)?

PAC → narrow; PJC → narrow; PVC → wide.

How to quickly identify PVCs?

'Wide and weird = ventricular.'

What makes a beat 'premature'?

It occurs earlier than expected in the rhythm.

What does 'irritable focus' mean?

A part of the heart that fires before the SA node.

One-line summary of ectopics?

PAC = weird P, PJC = missing/inverted P, PVC = wide QRS.

Image 1 is multifocal

Image 2 is unifocal