Hypokalemia electrocardiogram

; Associate Editor-In-Chief: ; Assistant Editor(s)-In-Chief: Jack Khouri

Overview

 * Caused mainly by delayed ventricular repolarization
 * Seen at potassium levels <3 meq/L (90% of patients with potassium levels <2.7 meq/L have abnormal ECG findings)
 * Rapidly reversible with potassium repletion

ECG changes

 * 1) ST segment depression, decreased T wave amplitude, prominent U waves
 * 2) * seen in 78% of patients with a K < 2.7 meq
 * 3) * seen in 35% of patients with a K > 2.7 and < 3.0
 * 4) * seen in 10% of patients with a K > 3.0 and < 3.5
 * 5) * U waves are also prominent in bradycardia and LVH
 * 6) Prolongation of the QRS duration
 * 7) * uncommon except in severe hyperkalemia
 * 8) Increase in the amplitude and duration of the P-wave
 * 9) Cardiac arrhythmias and AV block
 * 10) Contrary to popular belief there is not prolongation of the QTc, this is artifactually prolonged due to the U wave. In some cases there is fusion of the T and the U wave making interpretation impossible.