AF Pathophysiology 3 — Questions and Answers
Question 1: Which of the following best explains why patients with hypertrophic cardiomyopathy (HCM) have a high prevalence of AF?
- Left atrial dilation and fibrosis secondary to diastolic dysfunction and outflow obstruction (Correct answer)
- Increased systolic function causing left atrial underfilling
- Bundle branch block promoting re-entry in atrial tissue
- Right ventricular pressure overload compressing the left atrium
Correct answer: Left atrial dilation and fibrosis secondary to diastolic dysfunction and outflow obstruction
In HCM, diastolic dysfunction and elevated filling pressures cause left atrial enlargement and fibrosis, providing ideal substrate for AF initiation and maintenance.
Question 2: In AF with rapid ventricular response, tachycardia-induced cardiomyopathy can develop. What is the primary mechanism?
- Calcium overload and impaired energy metabolism from sustained rapid ventricular rates (Correct answer)
- Ischemia from coronary artery spasm triggered by tachycardia
- Immune-mediated myocarditis activated by rapid conduction
- Valvular regurgitation caused by mitral annulus dilation
Correct answer: Calcium overload and impaired energy metabolism from sustained rapid ventricular rates
Chronic rapid ventricular rates cause intracellular calcium overload, mitochondrial dysfunction, and energy depletion, leading to reversible ventricular systolic dysfunction.
Question 3: Which electrophysiological feature distinguishes 'long-standing persistent' AF from 'persistent' AF in terms of underlying pathophysiology?
- Greater degree of structural remodeling, fibrosis, and loss of electrical organization (Correct answer)
- Higher density of pulmonary vein triggers
- More prominent vagal modulation of AERP
- Increased number of accessory pathways
Correct answer: Greater degree of structural remodeling, fibrosis, and loss of electrical organization
Long-standing persistent AF involves advanced atrial structural remodeling with extensive fibrosis that makes spontaneous or induced termination increasingly unlikely.
Question 4: How does mitral stenosis predispose to AF development?
- Chronically elevated left atrial pressure causes atrial dilation, fibrosis, and conduction heterogeneity (Correct answer)
- Turbulent flow through the mitral valve directly irritates atrial tissue
- Mitral stenosis reduces left ventricular preload, leading to compensatory tachycardia
- The stenotic valve generates emboli that lodge in atrial conduction tissue
Correct answer: Chronically elevated left atrial pressure causes atrial dilation, fibrosis, and conduction heterogeneity
Mitral stenosis impedes left atrial outflow, raising atrial pressure and causing progressive atrial enlargement and fibrosis that sustains AF.
Question 5: What is the Coumel triangle triad for AF initiation?
- Trigger, vulnerable substrate, and modulating factors (autonomic nervous system) (Correct answer)
- Trigger, aberrant pathway, and shortened QT interval
- Ectopic focus, accessory pathway, and catecholamine surge
- Re-entry circuit, conduction block, and dispersion of repolarization
Correct answer: Trigger, vulnerable substrate, and modulating factors (autonomic nervous system)
Coumel's triangle describes AF as requiring a trigger (usually ectopic PV activity), a susceptible substrate (fibrosed/remodeled atrium), and modulating factors (autonomic tone).
Question 6: In AF, atrial contractile dysfunction persists for days to weeks after cardioversion due to which phenomenon?
- Atrial stunning — prolonged mechanical dysfunction despite return of sinus rhythm (Correct answer)
- Persistent atrial ischemia from coronary artery disease
- Residual atrial fibrosis preventing coordinated contraction
- Complete sinus node dysfunction requiring recovery time
Correct answer: Atrial stunning — prolonged mechanical dysfunction despite return of sinus rhythm
Atrial stunning refers to the reversible mechanical dysfunction after cardioversion, related to intracellular calcium overload and energy depletion from sustained AF.
Question 7: Which of the following best describes the role of oxidative stress in AF pathophysiology?
- ROS production from NADPH oxidase causes ion channel dysfunction, fibrosis, and electrical remodeling (Correct answer)
- Oxidative stress selectively destroys AV nodal cells, accelerating ventricular rate
- Free radical damage impairs sinus node automaticity, promoting ectopic atrial rhythms
- Mitochondrial ROS exclusively triggers pulmonary vein ectopy
Correct answer: ROS production from NADPH oxidase causes ion channel dysfunction, fibrosis, and electrical remodeling
Reactive oxygen species generated by NADPH oxidase (particularly Nox2/Nox4) impair calcium handling, alter ion channel expression, and activate fibroblasts, perpetuating AF substrate.
AF Pathophysiology 3
Which of the following best explains why patients with hypertrophic cardiomyopathy (HCM) have a high prevalence of AF?