Atrial fibrosis quantified using late gadolinium enhancement MRI is associated with sinus node dysfunction requiring pacemaker implant

Abstract

Introduction: Sinus node dysfunction (SND) commonly manifests with atrial arrhythmias alternating with sinus pauses and sinus bradycardia. The underlying process is thought to be because of atrial fibrosis. We assessed the value of atrial fibrosis, quantified using late gadolinium enhanced-MRI (LGE-MRI), in predicting significant SND requiring pacemaker implant.

Methods: Three hundred forty-four patients with atrial fibrillation (AF) presenting for catheter ablation underwent LGE-MRI. Left atrial (LA) fibrosis was quantified in all patients and right atrial (RA) fibrosis in 134 patients. All patients underwent catheter ablation with pulmonary vein isolation with posterior wall and septal debulking. Patients were followed prospectively for 329 ± 245 days. Ambulatory monitoring was instituted every 3 months. Symptomatic pauses and bradycardia were treated with pacemaker implantation per published guidelines.

Results: The average patient age was 65 ± 12 years. The average wall fibrosis was 16.7 ± 11.1% in the LA, and 5.3 ± 6.4% in the RA. RA fibrosis was correlated with LA fibrosis (R(2) = 0.26; P < 0.01). Patients were divided into 4 stages of LA fibrosis (Utah I: <5%, Utah II: 5-20%, Utah III: 20-35%, Utah IV: >35%). Twenty-two patients (mean atrial fibrosis, 23.9%) required pacemaker implantation during follow-up. Univariate and multivariate analysis identified LA fibrosis stage (OR, 2.2) as a significant predictor for pacemaker implantation with an area under the curve of 0.704.

Conclusions: In patients with AF presenting for catheter ablation, LGE-MRI quantification of atrial fibrosis demonstrates preferential LA involvement. Significant atrial fibrosis is associated with clinically significant SND requiring pacemaker implantation.

Figure 1

MRI acquisition and quantification of atrial fibrosis—2-dimensional MRI illustrating the right and left atrial chambers and 3-dimensional color reconstructions of the left and right atria of 4 sample patients from the 4 Utah stages of fibrosis. The green color overlaid on a blue background corresponds to areas of atrial fibrosis.

Figure 2

Correlation between left and right atrial fibrosis—plot of left atrial fibrosis (x-axis) against right atrial fibrosis (y-axis), with a linear regression fit, illustrating that increased left atrial fibrosis is associated with a higher degree of right atrial fibrosis.

Figure 3

Right atrial fibrosis—right atrial 3-dimensional reconstruction for 3 patients with various degrees of fibrosis. The septal region appears commonly affected at the early stage with more diffuse involvement of the right atrium at more advanced stages.

Figure 4

ROC analysis: Received operating characteristic (ROC) curve obtained following multivariate logistic regression analysis for predictors of pacemaker implantation. The area under the curve is calculated at 0.7040 indicating that advanced atrial fibrosis is significantly associated with pacemaker implantation.