Anatomical remodeling of left atria in subjects with chronic and paroxysmal atrial fibrillation evaluated by multislice computed tomography.

PURPOSE: We used ECG-gated enhance multislice computed tomography (MSCT) to evaluate and compare anatomical change to left atria (LA) including left atrial appendage (LAA) in subjects with chronic and paroxysmal atrial fibrillation (CAF and PAF, respectively).
MATERIALS AND METHODS: Retrospective ECG-gated MSCT (Light Speed Ultra 16, General Electric) was performed in 16 subjects with CAF (10 male, median age 68/period of CAF 6 years, 3 severe or moderate mitral stenosis (MS), 3 mitral regurgitation (MR)) and 17 with PAF (11 male, median age 62/period of PAF 3 years, one MS, one MR) 30 s and 8 min after injection of contrast. We evaluated: qualified observed morphology of pectinate muscles (PM) in LAA (well/poorly/non-developed); absolute thickness of LA anterior wall; presence of abnormal late enhancement (LE) of LA wall suggesting fibrotic changes; defect of contrast in LAA only in early phase and LAA enlargement; comparison of LA diameter evaluated by 4-chamber view obtained by transthoracic echocardiogram.
RESULTS: CAF group: well-developed PM (19% subjects), poor PM (43%), no PM (38%). PAF group: well-developed PM (41%), poor PM (47%), no PM (12%). Incidences of well- and non-developed PM were significantly less and more in CAF group, respectively. CAF subjects with no PM had longer periods of CAF and larger LA diameter than those with developed PM (p<0.01). By contrast, there was no relation between PM morphology and PAF periods or LA diameter. Incidence and mean thickness of abnormal LE of LA wall were similar in both groups (2.6 mm): 25% (CAF); 24% (PAF). There was a negative correlation in the CAF group between thickness of LA wall and LA diameter (R2=0.19), but not in the PAF group. Contrast defect in LAA only in early phase and enlargement of LAA were observed in 56%, 88% (CAF) and 24%, 41% (PAF); ratios were significantly higher in CAF group (p<0.01).
CONCLUSIONS: There were anatomical differences between CAF and PAF groups in MSCT. In CAF group, depending on the period of CAF or degree of LA diameter enlargement, anatomical remodeling (e.g. recession of PM, thinning of LA wall, enlargement of LAA) may appear, which may cause blood flow stagnation, seen as contrast defect in LAA in early phase.