Final answer:
A pacemaker is primarily used to treat complete heart block, a type of bradyarrhythmia, by delivering electrical impulses to the heart to ensure it contracts and pumps blood effectively.
Step-by-step explanation:
A pacemaker is the treatment of choice for several types of heart arrhythmias when the heart maintains a junctional rhythm, which originates in the AV node. Of the options provided, complete heart block, which is a type of bradyarrhythmia (slow heart rate), is the condition where a pacemaker is most commonly indicated. In complete heart block, the electrical signals that control the heart's timing are interrupted, and the pacemaker can take over this role, delivering electrical impulses to ensure the heart contracts and pumps blood effectively. Pacemakers are also programmable and can provide stimulation either temporarily upon demand or on a continuous basis. For other options like supraventricular tachycardia and atrial flutter, medications such as beta blockers and antiarrhythmic agents are commonly used first. Ventricular fibrillation, a type of ventricular arrhythmia, is a medical emergency that often requires immediate defibrillation rather than a pacemaker.