The nurse recognizes third-degree AV block on a patient's EKG strip. What does the nurse expect the treatment to be?

Choice B rationale Third-degree or complete heart block occurs when there is a total dissociation between the atria and the ventricles. No atrial impulses reach the ventricles, resulting in independent pacing of both chambers. Because the ventricular escape rhythm is typically slow (20 to 40 beats per minute) and unreliable, it cannot maintain adequate cardiac output. A permanent pacemaker is the definitive treatment to provide a reliable heart rate and restore synchronized electrical activity, preventing syncope or cardiac arrest. Choice A rationale This medication is a calcium channel blocker used primarily to slow the ventricular rate in rhythms like atrial fibrillation or supraventricular tachycardia by delaying conduction through the AV node. In third-degree heart block, the AV node is already non-functional or completely blocked. Administering a drug that further slows AV conduction or suppresses escape rhythms would be dangerous and could lead to ventricular asystole. It is contraindicated in this setting where the heart rate is already critically low. Choice C rationale Third-degree heart block is the highest degree of block and represents a medical emergency due to the risk of profound bradycardia and low cardiac output. Monitoring or observation is inappropriate because the patient is at high risk for sudden cardiac death. Immediate intervention with transcutaneous pacing is required as a bridge until a permanent pacemaker can be placed. Waiting for further progression is not a clinical option as there is no higher degree of block to observe. Choice D rationale This is a Class 1A antiarrhythmic used to treat ventricular arrhythmias and certain supraventricular tachycardias by slowing conduction velocity. Like other antiarrhythmics, it can further suppress the heart's natural escape rhythms. In the presence of a complete heart block, where the patient relies on a slow ventricular escape rhythm to survive, this medication could eliminate that remaining heartbeat entirely. It is not indicated for the treatment of bradycardias or AV blocks and would be harmful.