A 72-year-old man comes to the office due to palpitations, fatigue, and dyspnea for the past 2 weeks. The patient experienced an episode of atrial fibrillation 4 years ago during hospitalization for pneumonia; the episode spontaneously resolved 2 days later. Since then, he has had 3 episodes of symptomatic atrial fibrillation that self-terminated within a week. Other medical history includes hypertension, type 2 diabetes mellitus, and chronic heart failure. Blood pressure is 130/84 mm Hg and pulse is 110/min. The lungs are clear to auscultation. Cardiac examination demonstrates tachycardia with irregularly irregular heartbeats. ECG confirms atrial fibrillation. The patient's ventricular rate is controlled with beta blocker therapy, but the arrhythmia fails to resolve as in previous episodes. Which of the following factors is most likely involved in the progression of this patient's arrhythmia?

Question

A 72-year-old man comes to the office due to palpitations, fatigue, and dyspnea for the past 2 weeks.  The patient experienced an episode of atrial fibrillation 4 years ago during hospitalization for pneumonia; the episode spontaneously resolved 2 days later.  Since then, he has had 3 episodes of symptomatic atrial fibrillation that self-terminated within a week.  Other medical history includes hypertension, type 2 diabetes mellitus, and chronic heart failure.  Blood pressure is 130/84 mm Hg and pulse is 110/min.  The lungs are clear to auscultation.  Cardiac examination demonstrates tachycardia with irregularly irregular heartbeats.  ECG confirms atrial fibrillation.  The patient's ventricular rate is controlled with beta blocker therapy, but the arrhythmia fails to resolve as in previous episodes.  Which of the following factors is most likely involved in the progression of this patient's arrhythmia?

Quizplus · Accepted Answer

11ec160b_3a7f_3857_9249_91a8b09df592_MD0001_00 This patient's progression from paroxysmal atrial fibrillation (resolving spontaneously within 7 days) to persistent atrial fibrillation (lasting >7 days) is most attributable to atrial remodeling. The development of atrial fibrillation is primarily driven by both structural and electrical conduction changes in the atrial myocardium that predispose to the initiation and maintenance of electrical reentrant circuits and/or ectopic foci: The structural component of atrial remodeling likely involves comorbidities that lead to chronic atrial stretching and dilation. These include hypertension, heart failure, and mitral valve disease. Physiologic age-related atrial dilation also contributes. The electrical conduction component likely involves age-related changes as well as previous exposure to atrial fibrillation. During atrial fibrillation, the conduction system undergoes changes that facilitate propagation of the arrhythmia; over time it becomes more difficult to reverse (ie, atrial fibrillation begets atrial fibrillation). As atrial remodeling progresses, the atria become increasingly susceptible to electrical triggers (eg, ectopic foci in pulmonary veins) that initiate fibrillation and more likely to maintain persistently disorganized electrical activity. (Choice A) An abnormal pathway in the atrioventricular node is the typical cause of atrioventricular nodal reentrant tachycardia. This arrhythmia most commonly affects young patients with an otherwise normal heart. (Choice C) Cardiac autonomic neuropathy, which can develop in patients with Parkinson disease or poorly controlled diabetes mellitus, typically leads to an impaired sympathetic cardiac response. This often results in exercise intolerance and orthostasis but does not significantly contribute to cardiac arrhythmia. (Choice D) Conduction system fibrosis (often age-related) is a primary contributor to bradyarrhythmias, including sinus bradycardia (eg, sick sinus syndrome) and atrioventricular block. (Choice E) Enhanced sinoatrial node automaticity causes sinus tachycardia (eg, physiologic with exercise). During atrial fibrillation, electrical signals in the sinoatrial node are suppressed by widespread disorganized electrical activity throughout the atria. Educational objective: Atrial remodeling is the major pathogenic contributor to atrial fibrillation. Age and comorbidities that cause atrial dilation (eg, hypertension, heart failure, mitral valve disease) cause atrial structural changes that predispose to atrial fibrillation development. In addition, age and previous atrial fibrillation cause atrial conduction system changes that further propagate atrial fibrillation. __________ References: Atrial remodeling and atrial fibrillation: recent advances and translational perspectives. (http://www.ncbi.nlm.nih.gov/pubmed/24613319)

A 72-Year-Old Man Comes to the Office Due to Palpitations