Serum Potassium and the Electrocardiogram in Hypokalemia

Abstract

A definite correlation can be established between the electrocardiogram and the serum potassium level at hypokalemic levels. A study was made at the Mayo Clinic of 130 hypokalemic patients with relatively stable clinical states. Variations in Q-T intervals, P-R intervals, atrial rhythm, P waves, T/R values, and T-wave and U-wave contour in hypokalemia were noted as were the relationships between the T-U complex, electrical repolarization phenomena and potassium metabolism. Since modifying factors such as drugs, certain electrolyte disturbances, variations in cardiac rate, conduction defects, and myocardial ischemia were eliminated by careful selection of patients, only the influence of acid-base imbalance, sodium-potassium ratio, and hypertension on the electrocardiogram was studied. Acid-base imbalance and hypertension often simulated or obscured electrocardiographic evidence of hypokalemia. Electrocardiographic criteria of hypokalemia include various combinations of the following signs: (1) T/U value of 1 or less in lead II or V 3 , (2) U-wave amplitudes of greater than 0.5 mm. in lead II or greater than 1 mm. in V 3 , and (3) S-T depression of 0.5 mm. or more in lead II or leads V 1 , V 2 , and V 3 . It must be remembered that a normal electrocardiogram does not exclude hypokalemia and that an electrocardiogram which fulfills the established criteria does not necessarily indicate hypokalemia unless the factors discussed have been eliminated or minimized.

Systemic beta‐adrenoceptor responses to salbutamol given by metered‐ dose inhaler alone and with pear shaped spacer attachment: comparison of electrocardiographic, hypokalaemic and haemodynamic effects.

“…We found that doses lower than those used for 1-: F'T-l .1 I I., V nebuliser therapy (2.5-5.0 mg) produced marked hypokalaemic and ECG effects in normal subjects. The ECG effects of salbutamol were consistent with changes due to either hypokalaemia or hypomagnesaemia (Weaver & Burchel, 1960;Eisenberg, 1986). High dose inhaled salbutamol may produce small falls in plasma magnesium (Lipworth et al, 1988a) although levels were not measured here.…”

Heterogeneous ventricular chamber response to hypokalemia and inward rectifier potassium channel blockade underlies bifurcated T wave in guinea pig

“…The T wave, representing final repolarization, has been linked to dispersion of repolarization across the ventricular wall (40). However, the preferential appearance of bifurcated T waves in leads II and V 3 during hypokalemia (39) suggests that the predominant heterogeneity during hypokalemia may be regional rather than transmural.…”

Ectopic Ventricular Tachycardia, Hypokalemia and Convulsions in Alcoholics

“…Arrhythmias, including ventricular extrasystoles and ventricular bigeminy, have been consistently observed by Surawicz and Lepeschkin [16] when the potassium values are below 2.6 meq./l, and disappear after administration of potassium. Weaver and liurcheU found extrasystoles with a potassium below 3.6 meq./l in 24% of normotensive and in 30% of hypertensive pa tients [18]. Ventricular tachycardias have been encountered in pa tients with potassium depletion following infusion of glucose with a relatively small amount of potassium [4,12].…”