What is the mechanism of action for calcium channel blockers in treating angina?

Calcium channel blockers work primarily by allowing blood vessels to relax and open, which is essential in the treatment of angina. They achieve this by inhibiting the influx of calcium ions through voltage-gated calcium channels in the smooth muscle of the arterial walls. When calcium entry is blocked, the smooth muscle cells relax, leading to vasodilation. This dilation of blood vessels reduces the resistance the heart has to work against, effectively lowering myocardial oxygen demand while simultaneously enhancing blood flow to the heart muscle, which is crucial during episodes of angina.

In addition to their vasodilatory effects, calcium channel blockers can help reduce heart workload by decreasing the force of contraction and heart rate indirectly, as the heart benefits from less resistance. This is particularly useful in patients who experience angina due to coronary artery disease, where oxygen supply is limited by narrowed vessels.

The other options do not accurately reflect the primary action of calcium channel blockers. For example, increasing heart rate is contrary to the therapeutic effects aimed for in angina treatment, where a lower heart rate may reduce oxygen demand. Stabilizing the myocardial membrane pertains more to anti-arrhythmic medications or specific cardiac electrolyte modifiers, and reducing blood pressure is a result of the blood vessels relaxing but not the main mechanism