Sometimes a pattern develops between PVCs and normal beats. This is known as group beating. Bigeminy is a term used when every other beat is a PVC (see Figure 6.3). The underlying rhythm must still be reported.

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Figure 6.3. Bigeminy of Premature Ventricular Complexes

Bigeminy of Premature Ventricular Complexes ECG

When the ECG shows PVCs in a bigeminy pattern with an underlying sinus rhythm, the rhythm is referred to as a sinus rhythm with bigeminy. A pattern where every third beat is a PVC is known as trigeminy. A pattern where every fourth beat is a PVC is known as quadrigeminy (see Figure 6.4). 

The same descriptions are used to describe grouped PACs and premature junctional complexes.

Figure 6.4. Quadrigeminy of Premature Ventricular Complexes

The premature ventricular complex precedes three sinus rhythm complexes.

Characteristics of Premature Ventricular Complexes 

1. Ectopic beats disrupt the regularity of the underlying rhythm
2. Rate depends on the underlying rhythm and the number of ectopic beats
3. P waves are preceded by a P wave; dissociated P waves may be seen near the abnormal complex
4. There is no PR interval since the ectopic beat is generated by a lower focus
5. The QRS complex is wide and irregular: > 120 milliseconds
6. The T wave usually appears in the opposite direction to the R wave