Early recurrence of atrial fibrillation after catheter ablation with left atrial fibrosis identified at cardiac magnetic resonance by late gadolinium enhancement

In patients with atrial fibrillation (AF), the atria may undergo structural remodelling characterized mainly by atrial fibrosis [Burstein and Nattel, 2008]. The presence of extensive atrial fibrosis identified by late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (cMRI) has been associated with early recurrence after catheter ablation of atrial fibrillation [McGann et al. 2014].

A 53-year-old woman, without cardiovascular risk factors and valvular disease, with a history of symptomatic, drug-resistant, persistent AF (for 2 years), was referred for AF catheter ablation. Blood test revealed normal values of galectin 3 (12.2 ng/ml), a reported marker of fibrosis [Ho et al. 2014], however with an altered neutrophil/lymphocyte ratio (3.2) [Trivedi et al. 2013]. The electrophysiological study showed low voltage or electrical silent area in the left atrium.

Catheter ablation of AF was performed through pulmonary vein isolation and complex fractionated atrial electrograms present at the basal area of the posterior wall. After a 3-month blanking period, however, the patient experienced AF recurrence. Before any further attempt at catheter ablation, the patient was reassessed on the basis of a cMRI performed just before the prior intervention of catheter ablation; cMRI had been performed with a 1.5 T magnet (Achieva, Philips Healthcare, Best, The Netherlands) with a cardiac phased-array multicoil. The study of the left atrium by cine magnetic resonance imaging (MRI) sequences had shown a slight dilatation (anteroposterior diameter: 4.1 cm; area: 24 cm²), while the study of LGE had revealed extensive left atrial fibrosis (stage 4 according to the Delayed-Enhancement MRI Determinant of Successful Radiofrequency Catheter Ablation of Atrial Fibrillation (DECAAF) study) (Figure 1). No evidence of LGE was present in the right atrium. Therefore, no further attempt at ablation was done and the patient was discharged in treatment with rivaroxaban and without antiarrhythmics.

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Figure 1.

Cardiac magnetic resonance imaging showing left atrial fibrosis at late gadolinium enhancement: (a) left atrium short-axis view; (b) four-chamber view; (c) two-chamber view; (d) late enhancement, short-axis view; (e) late enhancement, four-chamber view; (f) 12-lead rest electrocardiogram recorded just before catheter ablation.

Extensive atrial fibrosis identified by LGE on cMRI has been associated with early recurrence after AF catheter ablation [McGann et al. 2014] and a more aggressive ablation approach including left atrial roof or box lesions or mitral isthmus could be considered in such cases [Di Biase et al. 2010]. Marrouche and colleagues categorized atrial fibrosis as stage 1 (<10% of the atrial wall), 2 (⩾10% to <20%), 3 (⩾20% to <30%) and 4 (⩾30%) and showed how larger areas of LA fibrosis are associated with a higher risk of AF recurrence after catheter ablation [Marrouche et al. 2014].

In our case, extensive atrial fibrosis occurred in a middle-aged woman with lone paroxysmal AF and without cardiovascular risk factors and valvular disease [Mahnkopf et al. 2010]; we classified left atrial fibrosis, identified through LGE MRI, as stage 4. This finding was also confirmed during the electrophysiological study with a left atrial voltage map. However, no defined cutoff values for the definition of left atrial fibrosis using voltage mapping exist [Tops and Schalij, 2014].

Galectin 3 is a potential mediator of cardiac fibrosis and may be involved in the development of atrial fibrosis and AF. Higher circulating galectin 3 concentrations have recently been associated with increased risk of incident AF [Ho et al. 2014]. Despite that, galectin 3 levels were normal and there was a discrepancy with the neutrophil/lymphocyte ratio.

Careful consideration of a cMRI study performed just before catheter ablation would probably have discouraged any intervention in the presence of such severe and diffuse atrial fibrosis.

In conclusion, the study of LGE with cMRI in patients with persistent drug-resistant AF could be a valuable noninvasive tool for the selection of patients suitable for successful catheter ablation.