Effect of Exercise on Electrocardiograms of Patients with Low Serum Potassium

Twelve adult patients (10 hypertensive and two normotensive) with low serum potassium levels but without electrocardiographic signs diagnostic of hypokalemia were subjected to nonstrenuous exercise. Electrocardiographic signs of hypokalemia appeared following exercise in all but the two hypertensive patients receiving digitalis. The severity of the changes and the duration correlated with the degree of hypokalemia present prior to exercise. The results were similar in the normotensive and hypertensive patients and in those made chronically or acutely hypokalemic. Following potassium repletion, exercise did not produce electrocardiographic changes of hypokalemia. The frequency with which S-T segment and T-wave changes occurred following exercise during potassium depletion suggested that hypokalemia can introduce an error in interpreting results of exercise tolerance tests in patients receiving thiazide compounds, when serum potassium is at the low normal or borderline level. These results may reflect intra...