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  •    Delayed Enhancement MRI in Predicting Response to Atrial Fibrillation Ablation Procedure and is Lone AF really Benign?
    Siva Soma, MD, Allegheny General Hospital, Pittsburgh, PA.

    Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice. Current guidelines (ACC/AHA/ESC 2006 guidelines) for treatment of atrial fibrillation recommend that ablation is a second line therapy in all categories. Lone AF generally applies to younger individuals with out clinical or echocardiography evidence of cardio pulmonary disease. They generally have a better prognosis.


    Atrial structural remodeling (SRM) is a well known phenomenon and over time creates a favorable substrate for AF progression. Delayed enhancement MRI (DE-MRI) is very effective method to non-invasively assess and quantify the extent of LA structural remodeling. Oakes et al. previously showed that the extent of LA fibrosis was an independent predictor of response to AF ablation procedure.


    In the study by Mahnkopf et al., researchers from University of Utah compared the SRM (using DE-MRI) of LA in patients with Lone AF versus those with co-morbidities. The authors found that degree of structural remodeling and fibrosis as detected by DE-MRI is independent of AF type and associated comorbidities.


    333 patients undergoing AF ablation between 2006 and 2009 were analyzed for the study. Of these 40 patients were classified as having Lone AF. Persistent AF was significantly higher in non-lone AF and paroxysmal AF was higher in lone AF. Delayed enhancement MRI was performed to assess the extent of LA fibrosis. Patients were assigned to 4 groups (Utah I, II, III and IV) based on the percentage of LA wall enhancement.  Most patients (both lone AF and non-lone AF) were in Utah group II and III.   But when the groups were compared based on the amount of fibrosis (as measured by DE-MRI), there was a statistically significant difference. The group with the highest fibrosis (Utah IV ;> 35% enhancement) had the highest recurrence rates: Utah IV = 95.5%, Utah III = 36.62%, Utah II = 27.51% and Utah I = 0%. Interestingly, the recurrence rates (22.86% for lone AF and 35% for no lone AF) were not statistically significant between lone AF and non-lone AF. ACE inhibitors which have been previously shown to decrease the amount of fibrosis in LA did not have any effect on the degree of LA fibrosis in this study.


    The authors conclude that DE-MRI might be an important tool in the future for non invasive measurement of fibrosis and predicting response to AF ablation. The small number of patients in lone AF is a drawback in this study. Nevertheless, it provides interesting data that needs to be validated by larger randomized control trials in the future.


    References:


    1. Oakes RS, Badger TJ, Kholmovski EG, et al. Detection and quantification of left atrial structural remodeling with delayed-enhancement magnetic resonance imaging in patients with atrial fibrillation. Circulation 2009; 119:1758–1767.


    2. Mahnkopf C, Badger TJ, Burgon NS, Daccarett M, Haslam TS, Badger CT, McGann CJ, Akoum N, Kholmovski E, Macleod RS, Marrouche NF. Evaluation of the left atrial substrate in patients with lone atrial fibrillation using delayed-enhanced MRI: implications for disease progression and response to catheter ablation. Heart Rhythm. 2010 Oct;7(10):1475-81.


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