Background: Atrial fibrillation (AF) is estimated to affect over 33 million people worldwide
and is associated with significant co-morbidities such as embolic stroke, heart failure,
dementia. Consequently, AF poses a significant burden to the healthcare system, in both
direct and indirect costs. The management of AF is complex, especially for patients with
persistent AF, which is defined as sustained AF for > 7 days. It is preferable to terminate
the AF and restore normal sinus rhythm for relief of symptoms associated with AF or
improvement of cardiac structure and function. The maintenance of AF, especially persist AF
is associated with fibrosis of left atria. Furthermore, AF itself promotes fibrosis, which in
turn leads to increased conduction heterogeneity within the atrial substrate resulting in
further progression of AF. In animal models, alterations in myocytes after sustained AF
resemble those of myocardial hibernation. Ultimately, these structural changes would lead to
Calcium overload and metabolic stress, similar changes have been observed in humans. In
humans, atrial dilatation and degenerative changes have been observed. Interstitial fibrosis
is the prime cause of structural remodeling in left atrium. Whether reversal of sinus rhythm
can reverse fibrosis partly? The introduction of Late Gadolinium enhancement magnetic
resonance imaging (LGE-MRI) sequence now allows for non-invasive and dynamic assessment of
the location and extent of atrial fibrosis.
To date, no studies evaluating the regression of left atrial fibrosis after cardioversion
assessed by LGE-MRI have been performed. The investigators propose to use LGE-MRI to evaluate
the effects of cardioversion on atrial fibrosis. It has been shown that the extent of
fibrosis can predict the success of catheter ablation procedure. For these patients with more
"scar", control the progression of fibrosis and simultaneously provide respite from AF
recurrence would be an extremely desirable prescription.
Objectives: To determine the regression of left atrial fibrosis in patients with persist
atrial fibrillation as assessed by late gadolinium enhanced magnetic resonance imaging.
Methods: This study will be an observational trial in patients with persist AF. Candidate
inpatients or outpatients will be identified if MRI were performed after pharmacological or
electrical cardioversion at least twice. The heart rhythm will be assessed by medical records
and telephone survey.
Objective
Primary:
The primary objective of this study is to demonstrate how cardioversion may influence the
regression of left atrial fibrosis in patients with persist atrial fibrillation as assessed
by LGE-MRI, using longitudinal data from a retrospective study of patients diagnosed with
atrial fibrillation over a six month follow up period.
Secondary:
To study the effects of sinus rhythm in global parameters of myocardial remodeling such as
right and left atrial volumes and right and left ventricular volumes.
To assess whether characteristics of MRI after cardioversion can predict the rate of atrial
fibrillation sinus rhythm maintenance.
