Understanding Hypokalemia and Its ECG Manifestations

Introduction

Hypokalemia is a medical condition characterized by a low potassium level in the blood (less than 3.5 mmol/L). Potassium is essential for normal cell function, particularly in the heart, nerves, and muscles.

Causes of Hypokalemia

Hypokalemia can be caused by several factors, including: - Inadequate potassium intake (low dietary potassium from foods like bananas, oranges, and potatoes) - Increased potassium loss due to diarrhea, vomiting, or diuretic use - Shifting of potassium into cells (e.g., due to insulin administration or alkalosis)

ECG Changes in Hypokalemia

Electrocardiogram (ECG) findings in hypokalemia can vary depending on the severity of potassium depletion. Key features include:

1. Flattened or inverted T waves – Potassium plays a crucial role in repolarization; low levels lead to abnormal T waves.
2. U waves – These are positive deflections seen after the T wave, most prominent in the precordial leads (V2–V4).
3. ST-segment depression – Reflects disturbed repolarization.
4. Prolongation of the QT interval (QTc) – This increases the risk of arrhythmias.
5. Increased risk of arrhythmias – Hypokalemia can trigger dangerous ventricular arrhythmias, including Torsades de Pointes and ventricular fibrillation.

Why is Hypokalemia Dangerous?

Severe hypokalemia can cause life-threatening complications such as: - Muscle weakness and paralysis - Cardiac arrhythmias leading to sudden cardiac arrest

How is Hypokalemia Treated?

Management depends on the severity of hypokalemia: - Mild cases (3.0–3.5 mmol/L): Dietary potassium intake should be increased. - Moderate cases (2.5–3.0 mmol/L): Oral potassium supplements are recommended. - Severe cases (<2.5 mmol/L or symptomatic hypokalemia): Intravenous potassium replacement is required under close monitoring to avoid overcorrection, which can lead to dangerous hyperkalemia.

Conclusion

Hypokalemia is a serious but treatable condition. Early detection using ECG and appropriate potassium replacement can prevent serious complications such as arrhythmias and sudden cardiac events.

Source recommendations

1. American Heart Association Guidelines on Electrolyte Abnormalities

1. https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.105.166563
2. https://www.heart.org/en/news/2024/02/26/how-eating-disorders-can-damage-the-heart
3. https://pubmed.ncbi.nlm.nih.gov/10966675/
4. https://www.heart.org/en/news/2024/06/19/electrolytes-can-give-the-body-a-charge-but-try-not-to-overdo-it
5. https://pubmed.ncbi.nlm.nih.gov/26472998/

2. European Society of Cardiology Guidelines on Arrhythmias

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death
2. https://academic.oup.com/eurheartj/article/43/40/3997/6675633
3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Supraventricular-Tachycardia
4. https://pubmed.ncbi.nlm.nih.gov/36017572/
5. https://www.ahajournals.org/doi/10.1161/01.cir.0000091380.04100.84