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Atrial fibrillation
Cardiac MRI assessment of atrial fibrosis in atrial fibrillation: implications for diagnosis and therapy
  1. Koji Higuchi,
  2. Mehmet Akkaya,
  3. Nazem Akoum,
  4. Nassir F Marrouche
  1. Comprehensive Arrhythmia Research & Management Center, University of Utah, Salt Lake City, Utah, USA
  1. Correspondence to Professor Nassir Marrouche, Comprehensive Arrhythmia Research & Management Center, University of Utah Health Sciences Center, 30 North 1900 East, Room 4A100, Salt Lake City, UT 84132-2400, USA; nassir.marrouche{at}carma.utah.edu

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Atrial fibrillation (AF) is the most commonly encountered cardiac arrhythmia in clinical practice, with a prevalence of 0.4–1% in the US population.w1 AF is a potent risk factor, increasing the risk of stroke fivefold and accounting for approximately 15% of all strokes in the USA.w2 AF also significantly increases the risk of mortality from heart failure.w3–7 Many therapies, including pharmacological approaches and direct current cardioversion, have been tried to treat this malignant arrhythmia, but were not found to be that effective.1 w8–w11

Catheter ablation of AF has provided better outcomes compared with other treatments, especially by applying pulmonary vein (PV) isolation in patients with paroxysmal AF.2 w12

However, other procedures modifying the substrate of AF, such as complex fractionated atrial electrogram ablation3 or posterior wall debulking,4 are required to obtain satisfying results for persistent AF patients with massive left atrial structural remodelling (LASRM) caused by massive atrial fibrosis.w13

Since atrial fibrosis is one of the main factors determining AF relapse after catheter ablation, evaluating atrial fibrosis in AF subjects is now of increasing importance for AF ablation strategies. Nowadays echocardiography is the mainstream technique for detecting LASRM which may cause left atrial (LA) volume expansion and atrial conduction slowing and heterogeneity.w14–16 Late gadolinium enhancement (LGE) MRI has recently been proved to be a powerful tool for detecting atrial fibrosis. This article discusses the efficacy and implications of LGE-MRI assessment of atrial fibrosis in AF.

Development of atrial fibrosis

Electrical remodelling: ‘AF begets AF’

Recognising that AF alters atrial electrophysiological properties and promotes AF induction and maintenance—that is, ‘AF begets AF’—is a breakthrough in AF pathophysiology.5 AF induces electrical remodelling primarily due to a very rapid atrial rate and associated tachycardia induced atrial remodelling. Action potential duration (APD) decreases during AF due to disruption of ion channel functions such as …

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