Role of the Cardiac-Synchronized Computed Tomography Angiography in Diagnosis and Follow-Up of the Dissection of Descending Thoracic Aorta

Objectives: Computed tomography (CT) is crucial for the diagnosis of descending thoracic aortic (DTA) dissection, especially in emergency setting, due to its accuracy and ready availability. An appropriate and accurate imaging protocol permits not only to perform the diagnosis but to improve the clinical outcomes in these cases. Our aim is to identify a possible role of the cardio-synchronized CT angiography (CCTA) in the DTA. Methods: Twenty-three CCTAs (retrospective gating) in suspected acute aortic syndromes or in chronic thoracic dissections were retrospectively analyzed measuring total vessel areas (ToTA) and areas of the true lumen (TLA) and false lumen (FLA) (at two levels: 2 cm below the isthmus and 3 cm above the diaphragm), with measurements in two arterial phases (40% and 75% of the cardiac cycle) and in the venous one (no cardio-synchronized acquisition). Results: TLA average in the 40% and 75% phases was, respectively, 462 (SD=283) and 419 (SD=276) in the proximal site and 436 (SD=269) and 388 (SD=267) in the distal site, significantly larger in the 40% versus 75% phase at both sites (P < 0.0001). The data were inverted with FLA: It was smaller in the arterial phase at 40% than at 75% in both sites (proximal and distal). No significant differences emerged for the ToTA. In the venous phase, no statistically significant differences were seen between TLA, FLA, and ToTA. Conclusion: Intimal flap dynamic and lumen variations are significantly affected by the various phases of the cardiac cycle. CCTA in DTA dissection can represent a reliable imaging technique to accurately compare the patient examinations during the follow-up. Furthermore, in the presence of symptoms, CCTA can help promptly identify patients who could require treatment because of transient blood flow reduction, due to intimal flap motion along the cardiac cycle.