A premature, broad QRS complex without a preceding P wave. What is this?

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Multiple Choice

A premature, broad QRS complex without a preceding P wave. What is this?

This describes a premature ventricular contraction, a beat that starts in the ventricles rather than through the normal atrial–AV node pathway. Because the impulse originates in ventricular tissue, the QRS complex is broad and wide (usually over 120 ms) and there is no preceding P wave just before that beat. The ventricles depolarize via cell-to-cell conduction, which is slower and produces that bizarre, widened shape. The beat arrives early, ahead of the expected rhythm, often followed by a compensatory pause as the normal conduction system resets. Premature atrial contractions would show an early P wave with a relatively narrow QRS, since the impulse still travels through the normal pathway. Ventricular pacing would show pacing spikes and a paced-looking QRS. Supraventricular tachycardia is a rapid rhythm typically with a narrow QRS unless there’s aberrant conduction, not a single premature wide beat.

This describes a premature ventricular contraction, a beat that starts in the ventricles rather than through the normal atrial–AV node pathway. Because the impulse originates in ventricular tissue, the QRS complex is broad and wide (usually over 120 ms) and there is no preceding P wave just before that beat. The ventricles depolarize via cell-to-cell conduction, which is slower and produces that bizarre, widened shape. The beat arrives early, ahead of the expected rhythm, often followed by a compensatory pause as the normal conduction system resets.

Premature atrial contractions would show an early P wave with a relatively narrow QRS, since the impulse still travels through the normal pathway. Ventricular pacing would show pacing spikes and a paced-looking QRS. Supraventricular tachycardia is a rapid rhythm typically with a narrow QRS unless there’s aberrant conduction, not a single premature wide beat.

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