Hypokalaemia and Its ECG Manifestations

Introduction

Hypokalaemia refers to a decreased level of potassium in the blood, typically below 3.5 mmol/L. Since potassium is essential for normal heart function, its deficiency can cause significant changes in the electrical activity of the heart, which can be detected on an ECG (electrocardiogram).

Causes of Hypokalaemia

Hypokalaemia can result from various conditions, including: - Increased potassium loss through the gastrointestinal tract (vomiting, diarrhea) or kidneys (diuretics, hyperaldosteronism) - Insufficient potassium intake due to poor diet or starvation - Intracellular shift of potassium in conditions such as alkalosis or excessive insulin administration

ECG Changes in Hypokalaemia

When potassium levels drop, characteristic ECG changes begin to occur: 1. Flattening of T waves – The normally upright, rounded T waves become flatter. 2. Prominent U waves – A distinguishing feature of hypokalaemia, U waves appear after the T wave. 3. ST segment depression – The ST segment may appear lower than normal. 4. Prolonged QT interval (due to lengthened QU interval) – This can increase the risk of ventricular arrhythmias. 5. Increased risk of arrhythmias, such as premature ventricular contractions, atrial fibrillation, and, in severe cases, ventricular tachycardia or torsades de pointes.

Clinical Implications and Treatment

• Mild hypokalaemia (3.0–3.5 mmol/L): Often asymptomatic but requires monitoring.
• Moderate hypokalaemia (2.5–3.0 mmol/L): May cause muscle weakness and ECG changes.
• Severe hypokalaemia (<2.5 mmol/L): Increases the risk of life-threatening arrhythmias.

Treatment

• Potassium supplementation (oral or intravenous, depending on severity)
• Address the underlying cause (e.g., stopping potassium-wasting diuretics, correcting acid-base imbalances)
• Monitoring ECG and potassium levels closely in hospitalized patients, especially those at risk of cardiac complications

Conclusion

Hypokalaemia affects cardiac function significantly, and recognizing its ECG manifestations is crucial for early treatment. If you experience symptoms like palpitations, weakness, or muscle cramps, consult your doctor immediately.

Source recommendations

1. American Heart Association Guidelines for the Management of Electrolyte Imbalances

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://www.ejinme.com/article/S0953-6205(24)00444-8/fulltext
4. https://www.heart.org/en/health-topics/arrhythmia/prevention--treatment-of-arrhythmia/implantable-cardioverter-defibrillator-icd
5. https://link.springer.com/article/10.1007/s44231-023-00054-3

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