An 89-year-old man is followed in the geriatrics clinic because of dementia. He lives in a nursing home, and is able to walk regularly without discomfort. He has no known cardiac problems, and no history of syncope:

• Sinus rhythm with Mobitz II Sinoatrial exit block (3:2 SA conduction)
• Left axis deviation, compatible with left anterior fascicular block

Note the alternating short and long P-P intervals; the long interval is slightly less than twice the short interval. In type II sinoatrial block, the long cycle is frequently slightly shorter than an exact multiple of the basic P-P interval.