AF Pathophysiology 2

Question 1

Which ion channel dysfunction is most directly responsible for the perpetuation of atrial fibrillation through remodeling?

Accepted Answer

Downregulation of L-type calcium channels (ICaL)

Answer

Downregulation of ICaL shortens the atrial action potential duration, promoting shorter refractory periods that sustain re-entrant wavelets in AF.

Question 2

What structural change at the cellular level most contributes to conduction slowing in chronically fibrillating atria?

Accepted Answer

Connexin 43 lateralization and reduced gap junction coupling

Answer

Lateralization and remodeling of gap junction proteins (connexins) disrupts cell-to-cell coupling, causing heterogeneous and slowed conduction.

Question 3

In AF, the loss of organized atrial contraction leads to blood stasis primarily in which structure?

Accepted Answer

Left atrial appendage

Answer

The left atrial appendage has a narrow neck and trabeculated interior that promotes stagnant flow when coordinated atrial contraction is absent.

Question 4

Which of the following best describes the concept of 'rotors' in the context of AF maintenance?

Accepted Answer

Localized high-frequency spiral re-entrant circuits that drive fibrillatory conduction

Answer

Rotors are stable spiral wave re-entrant circuits that act as AF drivers, sending fibrillatory waves into the surrounding atrial tissue.

Question 5

Atrial fibrosis in AF is primarily mediated by activation of which signaling pathway?

Accepted Answer

TGF-β / angiotensin II pathway

Answer

TGF-β1 and angiotensin II activate fibroblast proliferation and differentiation into myofibroblasts, driving interstitial fibrosis that sustains AF.

(AF) Atrial Fibrillation Certification Practice Test