Which statement about Calcium Channel Blockers is true?

• A. They prolong the QT interval
• B. They block calcium entry into cardiac cells, decreasing contraction and causing vasodilation
• C. They primarily increase AV node conduction
• D. They increase peripheral vasoconstriction

Answer: (B)

Calcium channel blockers work by blocking L-type calcium channels, which reduces calcium entry into both cardiac myocytes and vascular smooth muscle. In the heart, less calcium means weaker contractions (negative inotropy) and, with non-dihydropyridines, slower conduction through the AV node. In the vessels, reduced calcium causes smooth muscle relaxation, leading to vasodilation. This combination lowers blood pressure and myocardial oxygen demand.

So the statement describing them as blocking calcium entry into cardiac cells, decreasing contraction and causing vasodilation is correct. They don’t primarily increase AV nodal conduction, and they don’t cause peripheral vasoconstriction; those would be opposite effects. While they can affect AV conduction (especially some agents), the core effect described here accurately matches their mechanism and clinical action.