Which type of dysrhythmia indicates that the pacemaker is located in the ventricles?

The indication that the pacemaker is located in the ventricles is best represented by ventricular rhythms. In the context of heart function, the ventricles can generate their own electrical impulses if the higher pacemaker sites (like the sinoatrial node or atrioventricular node) fail to do so.

When ventricle cells create these impulses, the resulting rhythm is categorized as a ventricular rhythm, which is characterized by wide QRS complexes on an electrocardiogram (ECG). These rhythms can arise from various conditions, including heart block or severe bradycardia, where the sinoatrial or atrioventricular node is unable to maintain proper heart rhythm and thus the ventricles take over to ensure some level of cardiac output.

In contrast, other types of rhythms listed do not originate in the ventricles. Arrest rhythms would not produce a pacing action, sinus rhythms originate from the sinoatrial node indicating normal heart function, and atrial rhythms stem from the atria, meaning the pacemakers in these cases reside above the ventricles. Thus, recognizing that ventricular rhythms originate specifically from the ventricles clarifies why this answer is the one illustrating pacemaker location.