Volumetric measurements predict aortic complications after ATAAD surgery

Monitoring the progress of and predicting postsurgical complications in patients who underwent acute type A aortic dissection (ATAAD) repair is possible with the use of postoperative CT volumetric measurements, suggests a Singapore study.

Specifically, patients with disproportionately expanded false lumen (FL) presenting with true lumen (TL):FL ratio <1 are at greater risk of aortic complications.

“Hence the TL:FL ratio may be a reliable and useful parameter to monitor postoperative disease progression and to assess the risk of late complications in ATAAD patients,” said the researchers, who conducted a single-institution retrospective aortic volumetric analysis of patients after ascending aorta replacement performed during 2001–2005.

The researchers then obtained the volumetric measurements of total lumen (L), TL, FL, and TL:FL ratio from the first and second postoperative computer angiograms. They also analysed the predictive utility of TL:FL ratio using a generalized structural equation model.

OF the 125 patients who underwent surgical intervention, 97 were eventually discharged and assessed for postoperative complications. Nineteen patients were included in the final analysis. [Singapore Med J 2025;66:469-475]

The FL and total L volumes in patients with late postoperative aortic complications were significantly higher on the first (LF volume: p=0.041; total L volume: p=0.05) and second (FL volume: p=0.01; total L volume: p=0.007) postoperative scans.

The likelihood of developing aortic complications rose by 1 percent for every 1-cm³ increase in total L volume and by 2 percent for every 1-cm³ increase in FL volume. Notably, the TL:FL ratio was significantly lower in those with complications.

"The higher rate of enlargement with expansion of FL volume suggests undesirable aortic remodelling leading to a drop in the TL:FL ratio to less than 1,” the researchers said. “This group of patients is associated with aortic disease progression and needs to be considered for closer follow-up and early intervention to prevent life-threatening complications.”

Aortic diameter

In the management of aortic pathology, the current guidelines are based on the aortic diameter, and CT contrast-enhanced aortogram is the gold standard in follow-up of ATAAD patients. Moreover, the most common method of assessing disease progression is the use of maximal diameter.  [Mayo Clin Proc 1994;69:763-768]

"However, data published from the International Registry of Aortic Dissection reports that 60 percent and 40 percent of aortic complications could occur with diameters under 5.5 cm and under 5.0 cm, respectively,” the researchers said. [Circulation 2007;116:1120-1127]

“Hence, aortic diameter might not accurately predict potential complications, and finding new methods to evaluate aortic remodelling is an important area of research,” they added.

Another approach in monitoring aortic remodelling after ATAAD surgery is the maximal aortic area management. However, using the aortic area management may not accurately reflect the remodelling of aortic aneurysm as a three-dimensional structure, according to the researchers. [Circulation 2005;112(suppl 9):249-252]

In another study, the use of volumetric aortic measurements for spiral CT images has been proposed, demonstrating good reproducibility coefficient of intra- (5 percent) and inter-observer (10 percent) testing. [Eur J Vasc Endovasc Surg 1998;16:472-476; J Vasc Surg 2000;31:490-500]

"It is reported as a relevant and consistent method to assess aortic remodelling after type B dissection,” the researchers said. [J Comput Assist Tomogr 1997;21:481-486]

“However, based on literature analysis, for type A dissection, volumetric measurement is neither studied nor validated and is considered a relatively new method. Hence, our project aims to fill this knowledge gap in the literature,” they added.