Novel Aortic Root Measurement Technique More Effectively Identifies Patients At Risk for Type A Dissection

A. Kalyanasundaram¹, M. Zafar², H. Ellauzi³, B. Ziganshin⁴, J. Elefteriades^4
1Yale Aortic Insititute, New Haven, Connecticut ²Yale School of Medicine, New Haven, Connecticut ³Aortic Institute, Yale New Haven Hospital, New Haven, Connecticut ⁴Yale University School of Medicine, New Haven, Connecticut

Purpose: Per Laplace’s law, aortic wall stress is directly proportional to luminal diameter. However, determining the aortic root “diameter” is challenging due to its cloverleaf shape. Commonly used measurements (sinus-to-commissure) underestimate wall tension and dissection risk. We investigate the utility of a new, biomechanically-optimised measuring technique in potentially preventing aortic dissections.

Methods: The electronic health records of a large hospital were reviewed to identify patients with a type A aortic dissection (2003-2020) who had at least one pre-dissection chest CT scan. From these scans, the “Laplace root diameter” was measured with our new technique: (1) the viewing plane is rotated in the axial, sagittal, and coronal axes to make it exactly perpendicular to the long axis of the aorta at the level of the aortic root. (2) Lines are then drawn connecting the midpoint of each sinus to the directly opposite commissure. (3) A measurement is taken from the intersection point of these 3 lines (“center”) to the midpoint of the furthest sinus (“Laplace radius”--Fig.1). (4) This is doubled to get the Laplace diameter. Among 212 ascending aortic dissections, 33 patients had pre-dissection CT scans. 14 scans were of sufficient quality to take this measurement.

Results: The mean root diameter using standard techniques (sinus-to-commissure) was 42.8mm, while the mean Laplace root diameter was 49.7mm (16.1% increase).

Under the old surgical guideline for ascending aortic aneurysms of 55mm (applicable at the time of the patients’ pre-dissection scans), none of the patients would have qualified for surgery if standard measurements were used. However, 3 patients would have qualified for surgery based on a Laplace root diameter >55mm, meaning 3/14 dissections (21.4%) could have been prevented by an operation.

Under the new surgical guideline of 50mm, 2 patients would have qualified for surgery using standard measurements on the aortic root, and likewise for the ascending aorta only. 4 would have qualified if the largest diameter in either the root or ascending portions were considered. However, 9 patients would have qualified if Laplace root measurements were taken, representing an increase of 125% (5 more dissections prevented; Fig. 1).

Conclusion: Our recently-published root measurement technique is here validated clinically, utilizing pre-dissection CT scans of a retrospective patient cohort. More patients qualify for surgery using Laplace measurements. Thus, their dissections could have been prevented. We encourage consideration of this novel technique (based on bioengineering analysis) to enhance surgical decision making.

Identify the source of the funding for this research project: None.