Which statement is true regarding a pacemaker vs an ICD?

• A. An ICD defibrillates but does not pace
• B. Pacemaker primarily controls rhythm; ICD can defibrillate
• C. Both devices require MRI compatibility
• D. Neither device affects conduction

Answer: (B)

The main idea is that pacemakers and ICDs have different primary jobs in managing the heart. A pacemaker’s primary role is to provide electrical impulses to keep the heart beating at an adequate rate when the native conduction is slow or blocked. An ICD, on the other hand, is designed to recognize life-threatening fast rhythms and deliver a high-energy shock to terminate them, which is its key function. Many ICDs also include pacing capabilities for backup or bradycardia situations, but their defining purpose is defibrillation. That's why the statement that a pacemaker primarily controls rhythm and an ICD can defibrillate is the most accurate description.

Other choices aren’t as correct because they oversimplify or mischaracterize the devices. An ICD can pace in some situations, so saying it does not pace is incomplete. MRI compatibility varies by device type and model, so claiming both are universally MRI-compatible isn’t guaranteed. And both devices can influence conduction by delivering pacing stimuli or by responding to conduction problems, so saying neither affects conduction isn’t accurate.