P waves in Idioventricular Rhythm?

• A. No P waves
• B. P waves present before QRS
• C. P waves present after QRS
• D. Variable P waves

Answer: (A)

Idioventricular rhythm is a ventricular escape rhythm where the ventricles pace themselves due to a failure of the higher pacing systems. Because the impulse comes from the ventricular tissue, atrial depolarizations don’t coordinate with ventricular depolarizations. This leads to AV dissociation and a lack of a consistent atrial (P) wave relationship to the QRS. On the ECG, you typically see wide, slow ventricular beats with little or no visible P waves that are tied to the QRS; therefore, no P waves is the best description. In some tracings you might detect P waves that occur independently, but they are not preceding or consistently linked to the QRS complexes.