ECG RHYTHM LAB

First-Degree AV Block

Every atrial impulse conducts, with a prolonged PR interval.

Generated six-second Lead II example · 65 bpm target rate · not a patient recording.

Typical rate

Underlying rate varies

Regularity

Regular

P waves

One P for each QRS

PR interval

>200 ms; constant

QRS

Usually narrow

What to look for

Measure the PR: it stays long and every P is followed by a QRS.

Show this rhythm

Sources and limitations