New classification of aortic dissection during the cardiac cycle as pulsating type and static type evaluated by electrocardiogram-gated multislice CT.

Purpose: In some four-dimensional images acquired by electrocardiogram (ECG)-gated multislice computed tomography (MSCT) of thoracic aortic dissection (AD), true lumen (TL) gets larger (pulsating-type), whereas in others, TL and false lumen (FL) do not change (static-type) in a cardiac cycle. We have characterized these types.

Materials And Methods: Twenty subjects (10 with a double-barrel type thoracic descending AD and 10-controls) were enrolled. MSCT covered the thorax, and reconstructed every 10% from 0-90% of the R-R interval. Two physicians measured the TL and FL areas of descending thoracic aorta for each phase at 1) left-pulmonary-artery, 2) left-main-coronary-artery, and 3) right-coronary-artery levels.

Results: By designating the pulsating-range acquired from the control data as normal, AD subjects were classified as pulsating or static type when the maximum area of TL was >125% of the minimum TL area at any of the 3 levels. Five subjects were classified as pulsating and 5 as static-type AD. Excluding those with entry at the distal portion of the descending-thoracic-aorta with retrograde flow in FL, the mean-period from onset was 4.3+/-5.9 in the pulsating-type and 42.0+/-13.0 months in the static-type (P<0.05). Percentages with entry at the distal-portion of the descending-thoracic-aorta with retrograde flow in FL in the pulsating-type and static-type were 0% and 40%, respectively.

Conclusion: In AD, pulsating-type is more common if in the acute-phase from onset or the entry is not located at the distal-portion of descending-thoracic-aorta with retrograde flow in FL. This new classification of AD may usefully differentiate unstable-AD affected by cardiac pulsation from stable-AD.