Left Atrial Late Gadolinium Enhancement is Associated With Incident Atrial Fibrillation as Detected by Continuous Monitoring With Implantable Loop Recorders

OBJECTIVES: We hypothesized that left atrial (LA) fibrosis was associated with incident atrial fibrillation (AF) as detected by continuous long-term monitoring in an at-risk population. BACKGROUND: LA late gadolinium enhancement (LGE) measured with cardiac magnetic resonance is emerging as a marker of atrial fibrosis and has been associated with worse outcomes in AF ablation procedures; however, the prognostic value of LA LGE for incident AF remains unknown. METHODS: Cardiac magnetic resonance, including measurement of left ventricular and LA volumes and function, as well as left ventricular extracellular volume fraction and LA LGE, was acquired in 68 patients aged at least 70 years with risk factors for stroke. All included patients received an implantable loop recorder and were continuously monitored for previously unknown AF. Incident AF was adjudicated by senior cardiologists. RESULTS: Patients were monitored for AF with an implantable loop recorder during a median of 41 (interquartile range: 7) months. AF episodes lasting ≥6 min were detected in 32 patients (47%), and 16 patients (24%) experienced AF episodes lasting ≥5.5 h. In Cox regression analyses adjusted for sex, age, and comorbidities, we found that LA volumes and function and LA LGE were independently associated with incident AF. For LA LGE, the hazard ratios for time to AF episodes lasting ≥6 min and ≥5.5 h were 1.40 (95% CI: 1.03 to 1.89) per 10 cm2 increase (p = 0.03) and 1.63 (95% CI: 1.11 to 2.40) per 10 cm2 increase (p = 0.01), respectively. LA LGE was significantly associated with high burden of AF. The addition of LA LGE to a multivariable risk prediction model for incident AF significantly increased the predictive value. CONCLUSIONS: Extent of LA fibrosis measured by LA LGE was significantly associated with incident AF detected by implantable loop recorder. (Atrial Fibrillation Detected by Continuous ECG Monitoring [LOOP]; NCT02036450).