Which mechanism best explains how calcium channel blockers help in angina?

Which mechanism best explains how calcium channel blockers help in angina?

• A. They block voltage-gated L-type calcium channels, relaxing blood vessels and reducing myocardial oxygen demand.
• B. They increase myocardial oxygen demand.
• C. They block beta-adrenergic receptors to reduce heart workload.
• D. They inhibit HMG-CoA reductase to lower cholesterol.

Answer: (A)

Calcium channel blockers help in angina by blocking L-type calcium channels, which reduces calcium entry into vascular smooth muscle and cardiac cells. In vessels, this causes relaxation of arteriolar smooth muscle, dilating arteries (including coronary arteries) and lowering systemic vascular resistance (afterload). That vasodilation improves coronary blood flow and reduces the heart’s workload, lowering myocardial oxygen demand. In the heart, fewer calcium ions enter cardiac muscle cells can decrease contractility and, with certain agents, heart rate as well, further reducing oxygen consumption. Angina results from an imbalance between oxygen supply and demand, so this combination of increased supply (via coronary dilation) and decreased demand (via lower afterload and contractility) helps relieve symptoms. Options that suggest increased oxygen demand, or point to other drug classes like beta-blockers (which reduce workload through beta-adrenergic blockade) or statins (which lower cholesterol), don’t explain the calcium channel blocker’s mechanism in angina.

Calcium channel blockers help in angina by blocking L-type calcium channels, which reduces calcium entry into vascular smooth muscle and cardiac cells. In vessels, this causes relaxation of arteriolar smooth muscle, dilating arteries (including coronary arteries) and lowering systemic vascular resistance (afterload). That vasodilation improves coronary blood flow and reduces the heart’s workload, lowering myocardial oxygen demand. In the heart, fewer calcium ions enter cardiac muscle cells can decrease contractility and, with certain agents, heart rate as well, further reducing oxygen consumption. Angina results from an imbalance between oxygen supply and demand, so this combination of increased supply (via coronary dilation) and decreased demand (via lower afterload and contractility) helps relieve symptoms. Options that suggest increased oxygen demand, or point to other drug classes like beta-blockers (which reduce workload through beta-adrenergic blockade) or statins (which lower cholesterol), don’t explain the calcium channel blocker’s mechanism in angina.