ECG RHYTHM LAB

Sinus Rhythm with PACs

An early atrial beat interrupts sinus rhythm and resets its timing.

Generated six-second Lead II example · 72 bpm target rate · not a patient recording.

Typical rate

Underlying sinus rate varies

Regularity

Interrupted by early atrial beats

P waves

Premature P with a different shape

PR interval

May differ on the premature beat

QRS

Usually narrow

What to look for

Find the early, different P wave before a narrow QRS. The pause is not fully compensatory.

Show this rhythm

Sources and limitations