American Board of Internal Medicine (ABIM) Certification Practice Exam

For patients with significant pauses greater than 3 seconds in sinus rhythm, which is a potential indication for pacemaker placement?

1. Asymptomatic complete heart block

2. Symptoms with mild bradycardia

3. Short-term atrial flutter

4. Persistent heart rate above 50/min

The correct answer is: Asymptomatic complete heart block

The rationale for identifying asymptomatic complete heart block as a potential indication for pacemaker placement lies in the nature of the heart block itself. Complete heart block, or third-degree AV block, is characterized by a disconnection between the atrial and ventricular pacing, leading to a complete dissociation in the electrical activity of the heart. This condition poses a risk for significant pauses in the heart's rhythm, which can lead to bradycardia or even asystole. In cases where there is complete heart block, even in an asymptomatic patient, there is an inherent risk for the development of symptoms due to reduced cardiac output, especially during exertion or in situations where physiological demand increases. The possibility of symptoms arising from episodes of complete heart block justifies the need for intervention through pacing, even if the patient currently exhibits no symptoms. In contrast, the other options describe conditions where the indication for pacing may not be as clear-cut. Symptoms associated with mild bradycardia may indicate a need for further evaluation, but do not automatically necessitate a pacemaker. Short-term atrial flutter may not cause significant pauses, and a persistent heart rate above 50/min typically does not warrant a pacemaker unless accompanied by other concerning symptoms or underlying conditions. Thus