A nurse is caring for a client admitted to the intensive care unit for a cardiac dysrhythmia. The nurse understands the prescribed calcium channel blocker has which of the following mechanisms of action?

A. Calcium channel blockers primarily decrease heart rate and contractility, not increase them. B. While they can indirectly improve oxygen supply by reducing myocardial oxygen demand, they do not directly increase systemic oxygen. C. This option accurately describes the mechanism of action of calcium channel blockers, which decrease heart contractility and conduction through the AV node, helping to manage dysrhythmias. D. Calcium channel blockers do not act on beta cells; they specifically inhibit calcium influx into cardiac and vascular smooth muscle cells.