A recording shows P waves before QRS complexes in a patient with pacing wires. What is the rhythm?

The presence of P waves before QRS complexes indicates that atrial depolarization is occurring before ventricular depolarization, which is a hallmark of normal sinus rhythm. In a normal physiological sequence, the electrical impulse originates in the sinoatrial (SA) node, travels through the atria, and leads to the sequential contraction of the atria and then the ventricles. This orderly process is manifested in the ECG as the P wave preceding the QRS complex.

This rhythmic pattern is typical of normal sinus rhythm, suggesting that the heart's electrical system is functioning as it should. In patients with pacing wires, seeing P waves indicating atrial activity supports a scenario where the sinus node is still firing effectively alongside the pacing mechanism.

Other rhythms listed may exhibit variations in the relationship between P waves and QRS complexes, such as atrial flutter, where P waves may appear in a sawtooth pattern without a stable relationship to QRS complexes. Junctional rhythms can lack P waves altogether or have them occur after QRS complexes, while accelerated ventricular rhythms are characterized by wide QRS complexes and typically reflect a lack of P wave activity or an independent focus in the ventricles. This clear distinction confirms that the consistent presence of P waves preceding QRS complexes is