ECG RHYTHM LAB

Second-Degree AV Block · 2:1

Alternate atrial impulses do not conduct. This strip alone cannot classify the block as Mobitz I or II.

Generated six-second Lead II example · 80 bpm target rate · not a patient recording.

Typical rate

Ventricular rate is half the atrial rate

Regularity

Regular ventricular response

P waves

Two P waves for each QRS

PR interval

Constant on conducted beats

QRS

Narrow in this example

What to look for

Count two P waves for each QRS; avoid inferring a Mobitz subtype from a 2:1 strip alone.

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Sources and limitations