As previously noted, AF is associated with structural remodeling of the left atrium. Motivated by the success of LGE-MRI in identifying structural heart disease and, in particular, fibrosis, Oakes et al82 analyzed LGE-MRI scans from a cohort of 81 AF patients and six normal volunteers to explore the relationship between contrast enhancement and AF structural remodeling. This study revealed a positive correlation between low-voltage tissue regions in EAMs (bipolar voltage amplitude ≤0.5 mV) and left atrial wall enhancement (r2 = 0.61, P < .05). Furthermore, patients with mild (<15%, n = 43), moderate (15%-35%, n = 30), and extensive (>35%, n = 8) amounts of left atrial wall enhancement were found to have significantly different rates of AF recurrence at a mean follow-up of 9.6 months (14%, 43%, and 75%, respectively). These findings suggest that the degree of left atrial wall enhancement, which is assumed to reflect extent of fibrosis in the atrial tissue, is a predictor of failure for ablation. Based in part on these results, a staging system for determining the amount of enhancement has been proposed. Figure 25–3 shows the Utah staging system, with examples of LGE-MRI scans from each of the four stages. Under this system, patients with Utah stage III or IV enhancement are not considered to be ideal candidates for ablation therapy.
The utility of the Utah AF stages is currently under extensive evaluation, both at our institution and through a multicenter clinical study involving major AF centers from around the world.