Vignette: 70yo with h/o HTN, s/p valve replacement c/o one-sided facial numbness and dizziness. Work-up for stroke was negative. CBC - N, chemistry and troponin - N, CXR negative for acute disease.
What is the rhythm?
Image 1 - Long lead II
Long lead II can be interpreted as atrial fibrillation (AF). However, it is very odd for AF to be regular unless there is a complete heart block, AF with a pacemaker and AF with entrance block and junctional rhythm with an exit block. The machine read this rhythm as AF.
Image 2 - Long lead II and V1
Adding long lead V1 revealed a different story. Organized atrial activity can be seen in V1. The PP rate is about 88 bpm. Some of the P waves are distorting the initial and terminal portion of the QRS.
Image 3 - Ladder diagram
Image 3 marked in red arrows some hidden P waves. The complexes with red arrows highlight the typical morphology of a QRS with no P wave distortion.
The laddergram also illustrates an interesting pattern. The P waves depolarizing the the QRS is "skipping" the nearest QRS. The initial QRS complexes are conducted with 1:1 pattern and the latter part is conducted with a 2:1 pattern (rate ~ 40 bpm). There is a very long PRI of about 0.56 sec and a left bundle branch block.
Interpretation: Sinus rhythm, first degree AV block, second degree AV block type I (Wenckebach/Mobitz I), LBBB.
This patient eventually got a pacemaker.