What mechanism of action do calcium channel blockers have on the heart?

Calcium channel blockers primarily function by inhibiting the influx of calcium ions through voltage-gated calcium channels in the vascular smooth muscle and cardiac muscle. The blockage of these channels results in the relaxation of smooth muscle, leading to vasodilation, which reduces systemic vascular resistance and lowers blood pressure. This mechanism not only facilitates improved blood flow but also decreases the workload of the heart.

By causing peripheral vasodilation, calcium channel blockers can also lead to a decrease in heart rate and contractility, although their main action is related to vascular smooth muscle. This makes option B the correct answer, as it accurately captures the core function of calcium channel blockers in the cardiovascular system.