Scenario: The following ECG waveform was obtained in an 85-year-old male patient admitted to the telemetry unit for evaluation of syncope. His pertinent medical history includes hypertension, coronary artery disease, and prior inferior/lateral myocardial infarction (MI).

Interpretation: Normal sinus rhythm with a first-degree and second-degree atrioventricular (AV) block type II (Mobitz II).

Atrioventricular block occurs when there is intermittent or sudden loss of conduction from the atria to the ventricles. Degree is a term used to describe the severity of the AV block, with the least severe being a delay in atrial conduction (first degree), moderate severity occurs when some atrial impulses are blocked (second degree), and the most severe form when no atrial impulses are conducted (third degree). This patient has both a first-degree AV block (PR interval >0.30 seconds) with every sinus beat, and a second-degree type II AV block, occurring after the second, third, fourth, and fifth...

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