Diffuse ventricular fibrosis in atrial fibrillation: Noninvasive evaluation and relationships with aging and systolic dysfunction

Objectives: The purpose of this study was to evaluate diffuse myocardial fibrosis of the left ventricle (LV) in patients with atrial fibrillation (AF). Background: Diffuse myocardial fibrosis is a hallmark of cardiomyopathy. Unlike replacement fibrosis, it is not visualized on delayed-enhancement cardiac magnetic resonance (CMR) imaging, but may be quantified with contrast-enhanced T₁ mapping methods. In atrial fibrillation (AF), it may be induced by arrhythmia or reflect pre-existing cardiomyopathy. Methods: Ninety subjects underwent CMR using a clinical 1.5-T scanner: 23 controls, 40 paroxysmal AF patients, and 27 persistent AF patients. Cardiac morphology and function was evaluated from CMR cine imaging. A histologically validated T₁ mapping sequence was used to calculate post-contrast T₁ relaxation time (T₁ time) of the LV myocardium as an index of diffuse myocardial fibrosis. Results: Age was similar across controls, paroxysmal AF patients, and persistent AF patients (54 ± 12 years, 58 ± 9 years, and 56 ± 10 years, p = NS). Persistent AF patients had larger indexed left atrium volume (55 ± 18 ml vs. 41 ± 12 ml and 47 ± 14 ml) and lower ejection fraction (54 ± 10% vs. 65 ± 6% and 61 ± 8%) than controls and paroxysmal AF patients (p < 0.05). Post-contrast ventricular T₁ time differed across all groups (controls, 535 ± 86 ms; paroxysmal AF, 427 ± 95 ms; persistent AF, 360 ± 84 ms; p < 0.001). Univariate predictors of post-contrast ventricular T ₁ time included age, sex, AF category, ejection fraction, LV mass, congestive heart failure, and body mass index. After multivariate analysis, age, AF category, and ejection fraction remained independent predictors. Conclusions: Post-contrast ventricular T₁ mapping identifies diffuse LV fibrosis in patients with AF and provides new insights into the association between AF and adverse ventricular remodeling.