Which medication is typically administered for bradycardia associated with severe heart block?

Atropine is commonly administered for bradycardia associated with severe heart block because it acts as an anticholinergic agent, blocking the vagal tone and increasing heart rate. In cases of severe bradycardia or complete heart block, the body's inherent pacemaker may be too slow to maintain an adequate heart rate, leading to potential hemodynamic instability. By inhibiting the action of the vagus nerve on the heart, atropine increases the heart rate, thereby providing symptomatic relief and improving cardiac output.

This medication is particularly beneficial in acute situations where prompt intervention is necessary to restore an appropriate heart rhythm. In a clinical setting, it is often the first line of treatment for symptomatic bradycardia resulting from heart block.

Other medications listed, such as lidocaine and amiodarone, are primarily used for arrhythmias and ventricular tachycardia, respectively, rather than addressing bradycardia. Epinephrine is used in cases of severe bradycardia but is typically reserved for more critical situations such as cardiac arrest or severe anaphylaxis where immediate cardio-stimulation is required. Therefore, atropine is the preferred choice for managing bradycardia due to its direct effect on increasing heart rate rapidly.