What is the primary effect of calcium channel blockers on the cardiovascular system?

Calcium channel blockers primarily cause a decrease in oxygen consumption by the heart. They exert this effect mainly by reducing the influx of calcium ions into cardiac and smooth muscle cells, which leads to vasodilation of arteries and a decrease in peripheral vascular resistance. This reduction in workload on the heart translates to decreased oxygen demand, making calcium channel blockers particularly effective in conditions like angina, where reducing myocardial oxygen consumption is crucial.

In this context, the other choices do not accurately reflect the primary effect of calcium channel blockers on the cardiovascular system. For instance, increasing heart contractility is contrary to the effect of calcium channel blockers, which typically reduce contractility in cardiac muscle. Likewise, causing arterial spasms and increasing heart rate are also not effects associated with calcium channel blockers; rather, these medications promote relaxation of vascular smooth muscle and may have a neutral or even negative effect on heart rate, depending on the specific drug and individual patient responses.