A 65 year old male with a history of heart failure sees his physician for a routine checkup. He has been on a stable regimen of metoprolol and furosemide to manage his blood pressure and heart failure. A routine ECG in the office shows flattening of the T wave, appearance of a U wave, and ST segment depression. What is the most likely explanation for the ECG findings?
High serum magnesium
High serum potassium
Low serum magnesium
Low serum potassium
Recent myocardial infarction
Explanation
The ECG findings are characteristic of hypokalemia. This man is at risk of hypokalemia because he is on long-term furosemide.
Isolated magnesium abnormalities (A,C) do not typically cause these ECG abnormalities.
(B) High serum potassium typically manifests as peaked T waves, shortened QT interval, disappearance of p waves, and eventually a widened QRS and a sine wave pattern.
Flattening of the T wave and U waves are not typical of MI.