Class IV: Calcium Channel Blockers
- Treat supraventricular arrhythmias and to reduce ventricular rate in atrial flutter and atrial fibrillation.
They block calcium channels, so they are most effective at the sinoatrial and atrioventricular nodes, which rely on calcium ions for rate control.*
We draw the curve of a normal nodal action potential, and show that calcium channel blockers prolong nodal conduction and the effective refractory period.*
They prolong the PR interval on ECG (like the Class II drugs).*
- We use non-dihydropyridine calcium channel blockers
- Examples
–
Verapamil and Diltiazem; both target myocardial cells, and diltiazem has some vasodilator effects.
Both drugs are associated with
constipation, and, due to their
negative inotropic effects, can cause bradycardia and lower cardiac output.
Thus, use caution when combining these drugs with beta blockers, which have similar effects, and,
avoid using in patients with heart failure with reduced ejection fraction.
For References, please see our full tutorial on Class IV Anti-arrhythmic drugs.
