UMEM Educational Pearls

Category: Cardiology

Title: Calcium Affect on ECG

Keywords: ECG, Calcium, hypercalcemia, hypocalcemia (PubMed Search)

Posted: 7/14/2007 by Amal Mattu, MD (Emailed: 7/8/2007) (Updated: 1/18/2022)
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Calcium's main effect on the ECG appears to be on the duration of the ST segment, such that: 1. Hypercalcemia shortens the ST segment, producing also a short QTc. 2. Hypocalcemia prolongs the ST segment, producing also a long QTc. As an aside, there are only three conditions in which a short QTc is typically noted: hypercalcemia, digitalis toxicity, and a recently described syndrome that causes sudden death--"the short QT syndrome" (in which the QTc may be < 300ms...that's REALLY short!). As another aside, there are only two conditions that prolong the QTc via prolongation of the ST segment--hypocalcemia and hypothermia.