Quadrigeminy on the ECG
Quadrigeminy is a repeating pattern in which every fourth beat is a premature ectopic, so that three normal sinus beats are followed by one ectopic beat in a sustained sequence.
ECG criteria
| Feature | What you see in Quadrigeminy |
|---|---|
| Pattern | Sinus, sinus, sinus, ectopic, repeating. |
| Ectopic type | Usually ventricular — wide QRS, no preceding P wave. Atrial quadrigeminy occurs but is less common. |
| Rate | Three beats in four generate a pulse, so any pulse deficit is small. |
| Rhythm | Regularly irregular on a four-beat cycle. |
| Coupling interval | Constant. |
| Morphology | Ectopics identical in the usual unifocal form. |
How to spot it
- Establish that the irregularity repeats rather than being random.
- Count the sinus beats between ectopics — three normal beats to one ectopic is quadrigeminy.
- Check the ratio holds over several cycles rather than appearing once.
- Classify the ectopic as ventricular or atrial.
- Report the burden as well as the pattern, since that is what determines whether it matters.
What it gets confused with
| Looks like | How to tell them apart |
|---|---|
| Trigeminy | Every third beat is ectopic rather than every fourth. |
| Bigeminy | Every second beat is ectopic. |
| Occasional PVCs | Ectopics not arranged in a sustained repeating ratio. |
| Atrial fibrillation with ectopy | Underlying rhythm irregular and without P waves, so no pattern can be established. |
Traps
- The only thing separating quadrigeminy from trigeminy or bigeminy is the count, so count rather than estimate.
- A pattern seen once is not quadrigeminy. It should be sustained across the strip.
- A low ectopic burden makes quadrigeminy the least significant of the patterned ectopics, but the pattern still needs naming correctly.
- As always, say whether the ectopic is ventricular or atrial.
Why it happens
An ectopic focus fires once for every three sinus beats, in the same self-sustaining coupling relationship that produces bigeminy and trigeminy at higher ratios. Nothing about the mechanism differs; only the frequency with which the ectopic focus reaches threshold.
Why it matters
Quadrigeminy has the lowest ectopic burden of the patterned ectopic rhythms and is usually of little consequence in a structurally normal heart. It is worth naming precisely because the name conveys the burden, and burden is what determines follow-up.
Questions
What is quadrigeminy?
A repeating pattern in which every fourth beat is a premature ectopic — three sinus beats followed by one ectopic, sustained across the tracing.
Is quadrigeminy serious?
It is the least significant of the patterned ectopic rhythms because the ectopic burden is lowest. In a structurally normal heart it usually needs no treatment.
How is quadrigeminy different from bigeminy and trigeminy?
Only the ratio of normal beats to ectopics: one-to-one in bigeminy, two-to-one in trigeminy, three-to-one in quadrigeminy.
Reading about quadrigeminy is not the same as calling it on a tracing you have never seen.
Practise on real cases in ECG Pro