Objectives: There is currently no agreement on the best method of assessing active left atrial (LA) emptying. This study evaluated the relative merits of cine- and velocity encoded (VENC) magnetic resonance imaging (MRI) for the assessment of active LA emptying.
Methods: Total LA emptying volume (TLAEV) and active LA stroke volume (ALASV) were assessed in 107 consecutive patients using cine-MRI and transmitral flow measurements by VENC-MRI. The fraction of active LA emptying (ALAEF) was calculated as the ratio of ALASV to TLAEV. LA and left ventricular (LV) output were calculated by multiplying TLAEV and LV stroke volume by heart rate, respectively.
Results: Intra- and inter-observer variances were significantly larger for cine-MRI than for VENC-MRI measurements of ALASV (24.7 mL(2) vs. 3.7 mL(2) and 57.7 mL(2) vs. 4.2 mL(2); P < 0.0001). Biplane cine-MRI underestimated TLAEV (mean difference -57 ± 32 %; P < 0.0001) and ALASV (mean difference -24 ± 51 %; P < 0.0001) but overestimated ALAEF (mean difference 31 ± 54 %, P < 0.0001) compared with VENC-MRI. There was significantly better agreement between LV output and LA output measured by VENC-MRI compared with LA output measured by cine-MRI (mean difference 0.30 ± 1.12 L/min vs. -2.05 ± 1.44 L/min; P < 0.0001).
Conclusion: VENC-MRI is the more appropriate method of assessing active LA emptying and its use should be favoured.