Hypercalcemia in the myocardium results in which of the following effects?

Hypercalcemia in the myocardium results in which of the following effects?

• A. Increased contractility
• B. Increased irritability
• C. Decreased contractility
• D. Decreased irritability

Answer: (A)

Calcium drives how strongly the heart muscle contracts. When calcium levels are high outside the cells, more calcium enters during the action potential and triggers even more calcium release from the sarcoplasmic reticulum. This increases the amount of calcium available to bind to troponin C, promoting more cross-bridge cycling between actin and myosin. The result is a stronger, more forceful contraction—positive inotropy. That is why increased contractility is the best answer. Notes: calcium also affects electrical properties (it shortens the plateau and QT interval), but the most direct and consistent effect of hypercalcemia on myocardium is the stronger contraction.

Calcium drives how strongly the heart muscle contracts. When calcium levels are high outside the cells, more calcium enters during the action potential and triggers even more calcium release from the sarcoplasmic reticulum. This increases the amount of calcium available to bind to troponin C, promoting more cross-bridge cycling between actin and myosin. The result is a stronger, more forceful contraction—positive inotropy. That is why increased contractility is the best answer.

Notes: calcium also affects electrical properties (it shortens the plateau and QT interval), but the most direct and consistent effect of hypercalcemia on myocardium is the stronger contraction.