Florida State Paramedic Practice Exam

What effect does a calcium channel blocker have on heart rate?

1. Increases heart rate

2. Decreases heart rate

3. No effect on heart rate

4. Regulates heart rate to normal

The correct answer is: Decreases heart rate

A calcium channel blocker primarily works by inhibiting the calcium ions from entering the cells of the heart and blood vessels. Calcium plays a crucial role in the contraction of heart muscle and in the conduction of electrical impulses in the heart. By blocking these calcium channels, the heart's contractility decreases, leading to a reduction in heart rate. Calcium channel blockers can specifically slow down the conduction through the sinoatrial (SA) node and the atrioventricular (AV) node, which are critical points in the heart's electrical conduction system. This slowing of conduction associated with decreased contractility results in a notable decrease in heart rate. Therefore, the effect of a calcium channel blocker on heart rate is primarily a decrease, making the correct response accurate in the context of how these medications influence cardiac function. It is important to note that while some medications may stabilize heart rate or affect heart rates under certain conditions, the fundamental action of calcium channel blockers is to decrease the rate, particularly in scenarios often treated with these agents, such as hypertension and certain arrhythmias.