All Sample Questions

Atrial Fibrillation Mechanism 1

Question

Vignette: A 55-year-old man presents to his primary care physician for a follow-up appointment. He has a history of Type 2 diabetes mellitus and hypertension, both of which are well-controlled with medication. He reports feeling generally well, but notes some new difficulty with breathing during mild exertion. His vital signs are within normal limits. A chest x-ray reveals a dilated left atrium. An EKG shows atrial fibrillation.

Question: Which of the following is the most likely mechanism for this patient's atrial fibrillation?

Choices

A) Increased sympathetic stimulation

B) Atrial ischemia due to coronary artery disease

C) Oxidative stress from hyperglycemia

D) Stretching of the atrial myocardium

E) Overstimulation of the Beta-1 adrenergic receptors

Answer

D) Stretching of the atrial myocardium

Explanation

Atrial fibrillation (AF) is the most common sustained cardiac rhythm disturbance, and can lead to a variety of complications including stroke and heart failure. Chronic conditions such as hypertension and diabetes can lead to structural changes in the heart, including left atrial enlargement. This enlargement can cause stretching of the atrial myocardium, which can promote the development of AF. Stretching of the atrial myocardium alters the normal electrical properties of the heart, disrupting the normal pattern of electrical conduction and leading to the irregular rhythm seen in AF. Increased sympathetic stimulation (Choice A), atrial ischemia (Choice B), oxidative stress from hyperglycemia (Choice C), and overstimulation of the Beta-1 adrenergic receptors (Choice E) can contribute to the development of AF, but are not the primary mechanism in this patient's case.