A common mistake is to call this pattern Mobitz II block

An elderly c/o of dizziness. What is the rhythm?

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As you can see, the P to P rate is about 100. Some of the P's are hiding in the T waves and distorting it. So this is 3:1 AV block. This is high-degree AV (or advanced) AV block.

According to Dr. Goldberger, a subset of second degree heart block occurs when there are multiple consecutive non-conducted P waves present (P-QRS ratios of 3:1 or 4:1). This is referred to as high-degree (or advanced) AV block. It can occur at any level of the conduction system.A common misnomer is to call this pattern Mobitz II block. 

This case went to complete heart block and a pacemaker was eventually inserted.

Reference: 

Goldberger A. 2013. Goldberger’s Clinical Electrocardiography : A Simplified Approach. 8Ed Ph Elsevier

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