Pilot Study of St George’s Vascular Institute Protocol for Comprehensive Assessment of Type B Aortic Dissection Morphology: A Reproducible Protocol for Clinical and Research Applications

Abstract

Introduction:

Aortic morphology plays a critical role in determining treatment pathways and predicting outcomes in patients presenting with acute type B aortic dissection (TBAD). However, there is no consensus on the optimal methodology for the morphological assessment of TBAD. This study aims to demonstrate the reproducibility of a comprehensive imaging protocol for the analysis of aortic morphology of TBAD for clinical and research purposes.

Materials and Methods:

Protocol for comprehensive assessment of TBAD morphology was designed based on systematic review and expert opinion. A total of 56 morphological parameters were assessed across 6 morphological domains: aortic arch, aortic measurement, dissection morphology, false lumen morphology, endovascular intervention, and aortic remodeling. To validate the protocol, 4 observers measured these variables on 20 computed tomographic angiograms (CTAs) on a total of 10 patients using 3-dimensional imaging reconstruction software. One observer performed repeated measurements. The intraobserver and interobserver variabilities were calculated for all continuous variables. Cohen’s kappa was used to assess agreement between observers for categorical variables. Measurement time for all 56 features was recorded.

Results:

Aortic arch, false lumen morphology, endovascular intervention, and aortic remodeling showed strong levels of agreement. Aortic measurements, including aortic diameter and false lumen diameter, showed satisfactory intraobserver and interobserver variabilities with maximum repeatability coefficient (RC) for interobserver variability of 5.02 mm and intraobserver variability of 2.42 mm across all measurements. False lumen thrombosis assessment revealed moderate to almost perfect agreement (κ range=.58–1) and almost perfect intraobserver agreement (κ range=1–1). Entry tear morphology, including primary entry tear (PET) size and distance from left subclavian artery (LSCA), showed small mean differences but was associated with high RCs. Location of PET lesser curve location was found to have moderate to almost perfect interobserver agreement (κ range=.58–1) and strong intraobserver agreement (κ=.73). The measurement protocol was completed in a median time of 28 (24, 35) minutes.

Conclusion:

Accurate 3-dimensional analysis of TBAD morphology can be reliably performed within a reasonable timeframe. Measurements based on consistent anatomical landmarks demonstrated the highest reproducibility. It is suggested that this protocol is adopted for clinical studies and trials on acute TBAD.

Clinical Impact

The morphological characteristics of the aorta play a pivotal role in guiding treatment strategies and prognosticating outcomes in patients with acute type B aortic dissection (TBAD). Despite its critical importance, there remains a lack of consensus regarding the optimal approach to the morphological assessment of TBAD. This study presents a standardized and internally validated protocol for the evaluation of aortic morphology. The proposed methodology is intended to facilitate both clinical decision-making and research endeavors in the context of acute TBAD.