This ECG was obtained from an elderly man with Type II diabetes and early chronic renal failure. His serum potassium level was 6.3 mmol/L, and his BUN was 52 mg/dL. We don’t know his creatinine level.
This ECG shows the beginnings of the effects of hyperkalemia. One of the early changes that increased serum K causes on the ECG is tall, peaked T waves. The bases of those T waves becomes very narrow, making the T wave look sharp and thin. In this ECG, we see the increased height of T waves in V2 and V3, with only Lead V2 having sharp peaks. It is unlikely that hyperkalemia would be diagnosed on the appearance of the T waves alone, and in fact, the hyperkalemia was not confirmed until the lab results were available. The patient’s history of known Type II diabetes and early renal failure help us know what to look for.
We also see in this ECG T wave inversion in Lead III (not an abnormality in itself) and biphasic T waves in aVF.
It is good to remember that electrolyte imbalances are not usually diagnosed only from ECG changes. It is also important to remember that the ECG changes of hyperkalemia can develop very rapidly in conditions that cause rapid increase in serum K. By the time we notice the ECG changes, the patient may very well be in a life-threatening situation.