What effect do calcium channel blockers like Verapamil and Diltiazem have on the cardiovascular system?

Calcium channel blockers, such as Verapamil and Diltiazem, primarily work by inhibiting the influx of calcium ions through L-type calcium channels, particularly affecting the cardiac and smooth muscle cells. One of the notable effects of these medications is their ability to decrease conductivity through the AV node.

By reducing calcium entry into cardiac cells, these blockers slow down the conduction speed of electrical impulses through the AV node, which is crucial for regulating heart rhythm. This property makes them particularly useful in treating conditions like atrial fibrillation or atrial flutter, where control of the ventricular response rate is necessary.

The reduction in conductivity through the AV node leads to a more controlled heart rate and can prevent rapid or irregular heartbeats from propagating through the ventricles. This mechanism distinguishes calcium channel blockers from medications that may enhance automaticity or increase heart rate, as their primary function is to decrease conduction velocity, thus stabilizing the rhythm rather than accelerating it.