Scenario: A relatively healthy 82-year-old man presents with complaints of weakness, occasional confusion, and diarrhea. The only medication he reports taking is a “water pill” (spironolactone) for high blood pressure. However, he admits that although instructed to not eat bananas while taking his “water pill,” he has recently returned from a Caribbean cruise where he could not resist eating a banana every day.

Interpretation: Normal sinus rhythm (65 beats per minute), first-degree atrioventricular (AV) block, prior anterior wall infarction, and ST-T contours suggesting hyperkalemia.

The criteria for first-degree AV block has been met with a lengthened PR interval greater than .20 seconds (atrial depolarization delays are often seen in early phases of hyperkalemia). In addition, prior anterior wall infarction is evident in leads V2 and V3 because there are no R waves. The peaked T waves on...

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