Appropriate sizing of the frozen elephant trunk: How to predict proximal descending aortic diameter prior to dissection?

OBJECTIVE:The predissection aortic diameter is the best reference for determining the size of the frozen elephant trunk in aortic dissection. We aimed to develop a new prediction method to estimate the predissection diameter of proximal descending aorta. Furthermore, we evaluated the accuracy of the estimated predissection proximal descending aortic diameters calculated using three prediction methods. METHODS:A total of 39 patients with acute type A aortic dissection who underwent predissection computed tomography were included in derivation sets. We measured the aortic dimensions at three levels of the proximal descending aorta: 5, 10, and 15 cm from zone 2. We developed a new prediction method-postdissection aortic diameter divided by 1.13 (AoDNew factor) - and estimated the predissection aortic diameter using the new and previously proposed methods by Rylski (AoDRylski) and Yamauchi (EquationYamauchi). Furthermore, we validated the new prediction method using a validation dataset with 24 patients. RESULTS:The rate of bias ≤ 2 mm was significantly higher with EquationYamauchi and AoDNew factor than with AoDRylski in the derivation group at each level of the proximal descending aorta (P < 0.001). In the validation group, the rate of bias ≤ 2 mm was significantly higher with EquationYamauchi and AoDNew factor than with AoDRylski at 10 cm and 15 cm from zone 2 (10 cm: P = 0.014, 15 cm: P < 0.001). CONCLUSIONS:These results suggest that the new prediction method can be used as a simple and accurate estimation method for the predissection aortic diameter at the proximal descending aorta.