From the Guidelines
Hypocalcemia is associated with characteristic ECG changes, primarily prolongation of the QT interval due to lengthening of the ST segment, as noted in the most recent study 1. This occurs because low calcium levels delay ventricular repolarization. The most specific finding is a prolonged QTc interval (corrected for heart rate), which increases risk of dangerous arrhythmias like torsades de pointes. Other ECG changes include:
- T wave flattening or inversion
- In severe cases, ventricular arrhythmias may develop The ST segment prolongation differs from the QT prolongation seen in hypokalemia, which primarily affects the T wave. Clinically significant ECG changes typically appear when ionized calcium falls below 0.7-0.8 mmol/L (normal range 1.1-1.3 mmol/L) 1. These changes are reversible with calcium replacement therapy. Patients with hypocalcemia may also present with symptoms like:
- Paresthesias
- Muscle cramps
- Tetany
- Seizures Prompt recognition of these ECG patterns is essential as they may precede life-threatening arrhythmias, especially in patients with underlying heart disease or those taking QT-prolonging medications, as highlighted in 1. It is crucial to monitor and manage hypocalcemia to prevent such complications, particularly in patients with 22q11.2 deletion syndrome, where hypocalcemia is a common issue 1.
From the Research
ECG Changes in Hypocalcemia
- Hypocalcemia can lead to various ECG changes, including QT interval prolongation 2
- The QT interval prolongation is thought to be caused by a calcium-dependent inactivation mechanism on the L-type calcium channel (LTCC) 2
- Lower extracellular calcium levels can lead to a decreased ICaL, causing intracellular calcium to take longer to reach the critical threshold to induce CDI of the LTCC, resulting in prolonged repolarization of the ventricular myocyte 2
- This prolonged repolarization can lead to early after-depolarizations and ensuing life-threatening ventricular arrhythmias 2
Clinical Manifestations of Hypocalcemia
- Hypocalcemia can cause a range of clinical manifestations, from asymptomatic to life-threatening conditions 3
- Symptoms of acute hypocalcemia include neuromuscular irritability, tetany, and seizures, which can be rapidly resolved with intravenous administration of calcium gluconate 4
- Chronic hypocalcemia can have more subtle manifestations, and treatment options vary depending on the underlying disorder 4
Treatment and Management of Hypocalcemia
- Intravenous calcium infusion is essential to raise calcium levels and resolve or minimize symptoms in the setting of acute hypocalcemia 3
- Oral calcium and/or vitamin D supplementation is the most frequently used treatment for chronic hypocalcemia 3
- In hypoparathyroidism, providing the missing hormone with the use of recombinant human PTH(1-84) has been recently approved for treatment 3