Premature Ectopic Beats

Presentation

Premature ectopic beats or contractions usually present as an incidental finding during medical consultation when the heart rate is noticed to be irregular. This typically occurs in the fetus during routine antenatal care and in the hospital situation where the heart rate is monitored eg intensive care unit. They may be increased by myocardial stimulants eg. caffeine, β sympathomimetics and by electrolyte disturbance.

Occasionally they are noticed by an older child who interprets them as a "missed" beat or as a thumping beat. They do not cause haemodynamic compromise in those with otherwise normal hearts.

Mechanism

A focal area of myocardium (atrial or ventricular) stimulates myocardial contraction ahead of the normal sinus node. There is usually a slight compensatory pause after this beat, followed by a stronger beat due to the increased filling time. This accounts for the person's symptoms.

ECG

Below is a typical isolated premature atrial contraction (PAC). Note the shorter RR interval, different p wave shape (not always present) and the longer RR after the PAC. The QRS complex is narrow as the ventricles are activated in the normal way through the AV node and the His-Purkinje system.

The premature ventricular contractions (PVCs) below also have a shorter RR interval preceding the PVC with a longer RR interval after the PVC but in contrast to the PAC the ectopic beat is a broad complex confirming its ventricular origin. If the PVC complexes have the same morphology they are referred to as "unifocal", if of different morphologies "multifocal". When they are frequent, as shown in this strip, they may alternate with a sinus beat and the rhythm is then called bigemminy.

Multiple Premature Ventricular Contractions

Management

In the majority of people both PACs and VEs are a normal phenomenon and not a disease process. If frequent their benign nature can be established by exercising the person (either formally or by jumping on the spot) and observing whether the increased sinus rate overrides the ectopic focus. Reassurance is all that is necessary.

In those with structural cardiac disease or multifocal PVCs their presence may not be so benign and a full assessment and follow up are necessary.

This page was last edited 14/2/2004

Acknowledgements