What are the electrocardiogram (ECG) changes associated with hypokalemia (low potassium levels)?

From the Guidelines

Hypokalemia on an EKG is characterized by broadening of the T waves, ST-segment depression, and prominent U waves, with potential progression to life-threatening arrhythmias, as noted in the 2017 update to practice standards for electrocardiographic monitoring in hospital settings by Sandau et al 1.

Key EKG Changes

• Broadening of the T waves
• ST-segment depression
• Prominent U waves
• Potential for various arrhythmias, including first or second-degree atrioventricular block, atrial fibrillation, and ventricular arrhythmias such as premature ventricular contractions, ventricular tachycardia, torsades de pointes, ventricular fibrillation, and cardiac arrest

Severity Classification

Hypokalemia is typically classified as mild (3.0–3.5 mEq/L), moderate (2.5–2.9 mEq/L), or severe (<2.5 mEq/L), with more severe deficiencies associated with a higher risk of significant cardiac complications, as suggested by recent studies 1.

Clinical Implications

It is crucial to monitor serum potassium levels closely, especially in patients with heart failure, who may require maintaining a level of at least 4 mEq/L to prevent cardiac complications, and to address the underlying cause of hypokalemia while providing appropriate potassium replacement therapy based on the severity of the deficiency and the patient's clinical status, as emphasized in the update by Sandau et al 1.

From the Research

Hypokalemia Changes on EKG

• Hypokalemia, or potassium levels less than 3.5 mEq/L, can cause various changes on an electrocardiogram (EKG) 2, 3.
• Common EKG changes associated with hypokalemia include:
  • Dynamic changes in T-wave morphology
  • ST-segment depression
  • U waves, often best seen in the mid-precordial leads (V2–V4)
  • Prolonged PR interval
  • Increased amplitude of the P wave 3, 4
• These changes can increase the risk of life-threatening arrhythmias and are often seen in patients with severe hypokalemia (potassium levels less than 3.0 mEq/L) 2, 3.

Clinical Significance

• Hypokalemia is a common electrolyte disturbance that can have significant clinical implications, particularly in patients with cardiovascular disease 2, 5.
• The management of hypokalemia involves replacing potassium intravenously or orally, and preventing further potassium loss 2, 6.
• EKG changes are an important diagnostic clue for recognizing hypokalemia, and can guide immediate diagnosis and treatment 3, 4.