ECG-CHANGES DURING FUROSEMIDE-INDUCED HYPOKALEMIA IN THE RAT

Electrolyte abnormalities have become an increasingly important cause of arrhythmias owing to the widespread use of high-potency diuretics. Hypokalemia is one of the common complications of diuretic use. Althou gh some studies of hypokalemia induced by furosemide as well as of pot assium-deficient diets in the rat have been reported, the electrocardi ographic (ECG) changes during hypokalemia in the rat are poorly unders tood. This study was designed to examine such changes. For this purpos e, hypokalemia was induced by furosemide administration, and the diagn ostic criteria for ECG manifestations of hypokalemia were determined. During hypokalemia, conduction in most parts of the heart was suppress ed to an extent depending on plasma potassium concentration. Prolongat ion of the QT interval was also observed, which agrees with findings i n humans and dogs. Furthermore, prolonged durations of the P wave and QRS complex were observed during hypokalemia in the rat. The extent of alteration of the PR interval induced by hypokalemia was less signifi cant than that of P wave and QRS complex durations. These results sugg est that the excitabilities of the myocardium in the atria and ventric les may be affected by extracellular potassium level rather than by th e atrioventricular conduction system in the rat. Wave amplitude, excep t that of the P wave, was decreased by severe hypokalemia. These chang es were not dependent on the plasma potassium concentration. Typical T wave changes observed with hypokalemia in humans and dogs did not occ ur in the rat. The ECG manifestations of acute hypokalemia in the rat did not include the typical T wave changes seen in species with ST-seg ment type ECGs; however, other ECG parameter changes occurring with hy pokalemia were qualitatively similar to those in other species. These results may be useful for testing the toxicity of potassium-depleting drugs in the rat.