Quantitative Analysis of the Electrocardiographic Pattern of Hypopotassemia

Abstract

Electrocardiographic patterns typical of hypopotassemia and compatible with hypopotassemia were defined on the basis of the number of electrocardiographic signs of hypopotassemia present in 2 leads (generally leads II and V3). In 50 hypopotassemic patients a good correlation was found between the electrocardiographic pattern and plasma potassium concentration. Appearance of the electrocardiographic signs of hypopotassemia was not prevented by disturbance of other plasma electrolytes or by blood pH. LLECTROCARDIOGRAMS of patientswith low concentrations of extracellular potassium frequently show characteristic abnormalities that disappear after administration of potassium salts.1' 2 Regression of the electrocardiographic pattern of hypopotassemia during administration of potassium is characterized by a gradual increase of T-wave amplitude, decrease of U-wave amplitude, and diminution of S-T segment depression in the standard limb and precordial leads without any change in Q-T or other components of the Q-U interval.' This sequence of regression suggests that the converse, the evolution of the hypopotassemia pattern, consists of a progressive decrease of T-wave amplitude, increase of U-wave amplitude, and S-T segment depression in the standard limb and precordial leads. Accordingly, a schematic construction of 5 patterns, representing 5 stages in the evolution of the electrocardiogram in hypopotassemia, has been made.' At that time no During the past fewl years we have gained an impression that in a majority of patients with hypopotassemia, electrocardiograms can be correlated with the concentration of extracellular potassium. However, since others3-7 have failed to find a correlation between the electrocardiogram and serum potassium level, it was thought that a new investigation might be helpful. We made an attempt to develop quantitative criteria for objective evaluation of the electrocardiographic changes ill these patients. We also considered certain factors other than the potassium concentration that, may influence the electrocardiogram of patients with hypopotassemia.This paper presents the results of the correlation between the electrocardiogram and plasma potassium level in 50 patients with hypopotassemia. METHODS ANXI) MATERIALFifty adult patients with plasma potassium levels below 3.5 mEq./L. were selected for the study.

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