Ventricular premature complexes (VPCs)
Early beats that start in the ventricular muscle itself rather than arriving from above, so they miss the fast conduction system and have to spread the slow way.
Key ECG features
- ✓Beat arrives early
- •Wide, bizarre QRS
- ✓No premature P wave before it
- •T wave deflected opposite the QRS
- ±Full compensatory pause
✓ required · • typical · ± may be present
ECG characteristics
A wide, bizarre QRS with no preceding P wave, arriving before the next sinus beat was due, with the T wave usually deflected opposite to the QRS. A full compensatory pause typically follows. A left- versus right-ventricular origin can often be inferred from the dominant QRS deflection.
This illustration is schematic. Dashed line is a normal rhythm. The grid is not drawn to scale.
Common causes
Underlying myocardial disease, but equally often extra-cardiac: gastric dilatation-volvulus, splenic disease, trauma, sepsis, hypoxia, and electrolyte disturbance.
Why it matters
They may be entirely incidental. Burden and complexity guide the level of concern - isolated uniform complexes matter far less than couplets, triplets, runs or multiform complexes. R-on-T carries weight mainly in patients with underlying myocardial disease, as the guide explains.
Differentiate from
- Ventricular escape rhythmIdentical in shape. The premature complex comes early; the escape beat comes late, after a pause, and must never be suppressed - it is the rhythm keeping the patient alive.
- Atrial premature complexesBoth are premature. The atrial one has a P wave in front and a normal-looking QRS.
- Bundle branch blockAlso wide, but on time and preceded by a P wave, because it is still a supraventricular beat.
- Pathological Q waveAn ectopic beat can open with a broad negative deflection, but it is early and occasional; a pathological Q sits on every beat in the same lead.