What is the main action of calcium channel blockers in the context of treating PSVT?

Calcium channel blockers play a significant role in managing paroxysmal supraventricular tachycardia (PSVT) by reducing both the atrial and ventricular rates. They work by blocking calcium channels, which decreases the influx of calcium ions into cardiac and smooth muscle cells. This mechanism leads to a reduction in myocardial contractility and an overall depressant effect on cardiac electrical activity.

In the context of PSVT, these medications primarily target the atrioventricular (AV) node, where they help to slow down conduction and consequently control the rapid heart rate associated with PSVT. By reducing the conduction velocity through the AV node, calcium channel blockers effectively decrease the number of impulses that are transmitted from the atria to the ventricles during episodes of tachycardia. This results in a more controlled heart rate and amelioration of symptoms experienced by the patient.

Additionally, calcium channel blockers may not directly increase cardiac output, enhance electrical conduction, or improve heart rate variability, which distinguishes their primary therapeutic effects in treating PSVT. Instead, their benefits arise from the stabilization of the heart rhythm and the mitigation of excessive tachycardia.