Assessment of the structural remodeling of the left atrium by 64-multislice cardiac CT: comparative studies in controls and patients with atrial fibrillation.

BACKGROUND: To assess the functional differences among the three anatomic compartments of the left atrium (LA) using 64-multislice cardiac CT in controls and patients with atrial fibrillation (AF).
METHODS: We examined 144 individuals (105 males, mean age 56.42 ± 12.04 years) undergoing 64-multislice cardiac CT and divided them into 48 control, 53 paroxysmal AF (PAF), and 43 persistent AF (PeAF) patients. The LA was divided into three anatomic compartments according to their embryologic origins: venous LA (VLA), anterior LA (ALA), and LA appendage (LAA). Each volume was calculated using a threshold-based, three-dimensional segmentation. The LA parameters were defined as maximum and minimum LA volume indices, emptying volume, and ejection fraction. We compared the LA parameters of each compartment in controls, PAF patients, and PeAF patients.
RESULTS: In each of the three LA compartments, the maximum LA volume index was lowest in controls (LAA, 4.8 ml/m(2); VLA, 18.3 ml/m(2); ALA, 37.1 ml/m(2)) and highest in PeAF patients (LAA, 9.8 ml/m(2); VLA, 30.0 ml/m(2); ALA, 67.3 ml/m(2)). Regarding the three LA compartments, the ejection fraction was highest in the LAA and lowest in the VLA in controls (LAA, 58.3%; VLA, 29.0%; ALA, 47.4%) and in PAF patients (LAA, 47.3%; VLA, 18.3%; ALA, 39.2%). In PeAF patients, the emptying volumes and ejection fractions of the VLA were approximately zero.
CONCLUSIONS: The anatomic compartments of the LA play different roles in AF patients. The LAA has both highest contractility and independent function, and the VLA is the most severely affected by LA dysfunction. Our results may be helpful in understanding the pathophysiology of AF and predicting treatment responses to radiofrequency ablation in the future.