In acute disseminated Lyme disease, what cardiac problem is most common?

• A. Atrial fibrillation
• B. Myocardial infarction
• C. Heart failure
• D. AV block

Answer: (D)

The key concept here is that acute disseminated Lyme disease most often involves the heart’s electrical system, not the muscle itself. Borrelia burgdorferi can inflame the conduction pathways, especially the AV node, leading to atrioventricular block. That block can range from a mild delay in conduction to higher-grade blocks and even intermittent complete block, and it’s this disturbance in the heart’s pace-making system that is most commonly seen in early disseminated Lyme disease. Clinically, you might notice bradycardia or dizziness from the slowed conduction, and the problem can fluctuate as inflammation waxes and wanes. Importantly, this conduction disturbance typically improves with appropriate antibiotic therapy, though severe blocks may require temporary pacing while treatment takes effect. Other cardiac problems like atrial fibrillation, myocardial infarction, or heart failure aren’t the hallmark findings of disseminated Lyme carditis, even though myocarditis and related issues can occur less commonly.