Figure 1: Light microscopy of post-mortem myocardial specimens
without a history of AF (A), paroxysmal AF (B) and persistent AF (C)
(Masson’s trichrome stain, magnification x 200) (adapted with permission
from (58)). Burden of fibrotic tissue, stained in blue, correlates with
duration of AF. D) Diagram detailing normal atrial myocyte bundles and
different patterns of fibrotic deposition. In replacement (reparative)
fibrosis, degenerating myocytes are replaced by fibrotic tissue within
myocyte bundles. Reactive (interstitial) fibrosis involves expansion of
the fibrotic tissue in between myocyte bundles. Both forms may coexist
within a single atrium.