Which of the following calcium channel blockers is known to decrease heart rate at rest and during exercise?

Diltiazem is classified as a non-dihydropyridine calcium channel blocker, which means that it acts on both the heart and blood vessels. It decreases heart rate by inhibiting the influx of calcium ions into cardiac myocytes and conducting tissues, particularly in the sinoatrial and atrioventricular nodes. This action leads to a reduction in the force of contraction (negative inotropic effect) and a decrease in heart rate (negative chronotropic effect), both at rest and during exercise.

Diltiazem is particularly effective in treating conditions like hypertension and certain types of angina because of its ability to reduce heart workload while simultaneously dilating blood vessels. This makes it a valuable medication for managing cardiovascular conditions where lower heart rates are desirable for better outcomes during physical activity or rest.

In contrast, amlodipine primarily targets peripheral blood vessels, leading to vasodilation without significantly affecting heart rate. Lisinopril is an ACE inhibitor, primarily affecting blood pressure but not heart rate. Metoprolol is a beta-blocker that does decrease heart rate as well, but it is not a calcium channel blocker, distinguishing it from diltiazem.