We created a thread for this ECG with all the follow-up questions and tested a group of frontier AI models to see how they responded. Here’s how they did: Most models agreed the ECG shows **sinus rhythm with second-degree AV block type I (Mobitz I/Wenckebach)**, based on progressive PR prolongation with grouped beating and a dropped QRS. The main differences were that one model called it **sinus tachycardia + Mobitz I**, while another interpreted it as **PACs in bigeminy** rather than AV block; a rate estimate of about **78 bpm** also appeared, supporting non-tachycardic sinus rhythm. 🔗 Full thread: medicalsphere.ai/cases/28b1c…

Sinus tachycardia AV Wenckebach block, RBBB + LAFB. This Wenckebach block is infranodal with change in the 2nd RBBB configuration. Moreover bilateral BBB or masquerading BBB with slow RWPT in DI where there's a narrow S (not from LAFB) compared to broad R in aVR. For PM implant.

I think LAFB, RBBB, grouped beating with Mobitz 1. In aVL I think the third blocked P is clearly visible

PR Interval Alternans. Alternating conduction pathway.

Why is PW biphasic in III?