Authors:
P. Bernhardt¹, G. Pilz¹, M. Klos¹, G. Braeuner¹, B. Hoefling¹, ¹Hausham - Germany,

Background: Left atrial appendage (LAA) emptying velocities (LAAv) are an important predictor for cerebral embolism in patients with atrial fibrillation (AF). Transesophageal echocardiography (TEE) is able to determine this risk factor accurately. Aims of our study were to assess LAA volumes and ejection fraction with cardiac magnetic resonance imaging (CMR) and to correlate with LAAv as quantified by TEE.

Methods: Consecutive patients with AF scheduled for TEE prior to cardioversion were included to the study. Patients with sinus rhythm and other TEE indication served as controls. All patients were scanned in a 1.5-T whole body scanner. Contiguous functional images covering the entire LAA in long axis orientations were performed (figure). LAA minimal and maximal volumes were calculated and LAA ejection fraction quantified and correlated to LAAv as determined by TEE.

Results: 32 patients (21 with AF and 11 with sinus rhythm) were included to the study. Patients with AF had a significantly larger LAA (12.8 ± 4.6 ml vs. 5.9 ± 2.5 ml, p<0.0001) and lower LAAv (0.3 ± 0.2 m/s vs. 0.7 ± 0.1 m/s, p<0.0001) compared to patients with sinus rhythm. LAAv highly correlated with LAA ejection fraction as determined by CMR in all patients (r=0.95, CI 0.90-0.98, p<0.0001). Mean LAA ejection fraction in patients with reduced LAAv (=0.2 m/s) was 8.4 ± 1.7%.

Conclusion: CMR is able to determine LAA ejection fraction with a high correlation to LAAv. Reduced LAA ejection fraction (=10%) as seen by CMR matches with reduced LAAv (=0.2 m/s) indicating an increased embolic risk in patients with AF. Thus, CMR can possibly act as a non-invasive tool to detect patients with increased embolic risk.