Sahand Sohrabi MD, Abstract Co-Author: Nothing to Disclose

Zlatko Devcic, Abstract Co-Author: Nothing to Disclose

Maria Clara Neves Lorca MD, Abstract Co-Author: Nothing to Disclose

Alexander W. Keedy MD, Abstract Co-Author: Nothing to Disclose

Michael D. Hope MD, Abstract Co-Author: Nothing to Disclose

David A. Saloner PhD, Abstract Co-Author: Nothing to Disclose

Karen Gomes Ordovas MD, Presenter: Nothing to Disclose

Left atrial (LA) enlargement is associated with increased risk of adverse cardiovascular events. LA volume is a reliable measure of the LA size that can be obtained from contrast-enhanced CT images. However, volumetric quantification methods are very time consuming and thus not routinely used in clinical practice. We aimed to assess the accuracy of LA transverse and antero-posterior (AP) diameters obtained from non-gated chest CT angiography for detection of LA enlargement.

Contrast-enhanced 64-slice MDCT scans were used to measure the volume and the maximum transverse and AP diameters of the LA in 222 subjects with known atrial fibrillation. CT scans were performed without cardiac gating, with a slice thickness of 0.625-1.25 mm. LA volume was measured using the modified Simpson’s method. Volumes were indexed to the body surface area. LA enlargement was defined as a LA volume index higher than 41.8mm/m2. Receiver Operating Characteristic (ROC) curves were fitted to assess the accuracy of the AP and transverse LA diameters for detection of LA enlargement. A Wald test was used to compare area under the curves (AUC). Threshold values with high sensitivity were determined for both AP and transverse LA diameters.

Patients had a mean (±SD) age of 60±11 years, and 71% (158) were male. Median LA indexed volume was 55.9 ±24.4 ml/m2. LA enlargement was present in 83% (184) of the patients. The median (±IQR) AP and transverse diameters were 4.95cm ± 1.05 and 7.8 cm± 1.2, respectively. Both AP and transverse LA diameters were accurate estimators of the presence of LA enlargement. However, the transverse diameter demonstrated higher accuracy than the AP diameter (AUC of 0.89 {CI=0.84-0.94} and 0.81 {CI=0.73-0.89}, respectively; p<0.05). A transverse LA diameter of 7.3cm had a sensitivity of 84% and a specificity of 84% for detection of LA enlargement. At the same sensitivity level, an AP diameter of 4.3 cm had a specificity of 60.5%.  

The transverse diameter of the LA is superior to the AP diameter in diagnosing LA enlargement. With very high sensitivity and specificity (84%), a transverse diameter higher than 7.3 cm can be used to detect LA enlargement on non-gated chest CT.

Transverse diameter of LA can be used as a screening tool to diagnose LA enlargement on non-gated contrast-enhanced chest CT and detect patients who should be further evaluated by echocardiography.

Sohrabi, S, Devcic, Z, Lorca, M, Keedy, A, Hope, M, Saloner, D, Ordovas, K, Left Atrial Transverse Diameter on Chest CT Scan Can Accurately Diagnose Left Atrial Enlargement.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12023082.html