The Electrocardiographic Pattern of Hypopotassemia with and without Hypocalcemia

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Abstract
The components of the Q-U interval were measured in synchronous leads in relation to heart rate and sex. In 25 cases of pure hypopotassemia the duration of these components was normal. In 8 cases of hypopotassemia with hypocalcemia, Q-T and its components are prolonged as in pure hypocalcemia but Q - U is normal; this leads to increased merging of T and U, Admn. of either K or Ca corrected only the ecg. changes due to deficiency of the particular electrolyte. The synchronously registered phonocardiogram showed that the mechanical systole in in hypopotassemia is either of normal duration or shortened; in hypocalcemia it is prolonged, but not as much as Q-T. The typical ecg. pattern of hypopotassemia consists of a "sagging" depression of the S-T segment, lowering and later inversion of the T wave and elevation of the U wave, in left precordial leads. Ectopic rhythms usually appeared in the more severe cases. Complete merging of the T and U waves without a distinct kink in the merged wave occurs in hypopotassemia. Differentiation between such a T + U wave and a T wave with prolonged Q-T can be made by a supplementary lead which shows a kink between T and U. If in a synchronous phonocardiogram the 2d heart sound begins earlier than 0.03 sec. before the apex of the wave, it is probably a merged T + U. Intraven. Ca injn. will shorten Q-T and usually separate T from U. The degree of development of the hypopotassemia pattern is in general parallel to the decrease in serum K, but a closer relation to the ratio [image] K is Probable.