Accuracy of vascular tortuosity measures using computational modelling

Vishesh Kashyap,Lucy Mcgrath-Cadell,Susann Beier,Mark Webster,Robert M Graham,Ramtin Gharleghi,Chris Ellis,Darson D Li

doi:10.1038/s41598-022-04796-w

Abstract

Severe coronary tortuosity has previously been linked to low shear stresses at the luminal surface, yet this relationship is not fully understood. Several previous studies considered different tortuosity metrics when exploring its impact of on the wall shear stress (WSS), which has likely contributed to the ambiguous findings in the literature. Here, we aim to analyze different tortuosity metrics to determine a benchmark for the highest correlating metric with low time-averaged WSS (TAWSS). Using Computed Tomography Coronary Angiogram (CTCA) data from 127 patients without coronary artery disease, we applied all previously used tortuosity metrics to the left main coronary artery bifurcation, and to its left anterior descending and left circumflex branches, before modelling their TAWSS using computational fluid dynamics (CFD). The tortuosity measures included tortuosity index, average absolute-curvature, root-mean-squared (RMS) curvature, and average squared-derivative-curvature. Each tortuosity measure was then correlated with the percentage of vessel area that showed a < 0.4 Pa TAWSS, a threshold associated with altered endothelial cell cytoarchitecture and potentially higher disease risk. Our results showed a stronger correlation between curvature-based versus non-curvature-based tortuosity measures and low TAWSS, with the average-absolute-curvature showing the highest coefficient of determination across all left main branches (p < 0.001), followed by the average-squared-derivative-curvature (p = 0.001), and RMS-curvature (p = 0.002). The tortuosity index, the most widely used measure in literature, showed no significant correlation to low TAWSS (p = 0.86). We thus recommend the use of average-absolute-curvature as a tortuosity measure for future studies.

Highlights

Mild coronary tortuosity, marked by larger vascular bending angles, is common and can even be found in people lacking coronary artery d isease[1,2]
Increased coronary tortuosity has been reported in patients suffering from spontaneous coronary artery dissection (SCAD)[4], a condition with a high prevalence in females, and a global scoring system based on the number and angle of curves in the coronary arteries has been proposed for the use in evaluating tortuosity in these p atients[4]
The current work utilized a statistical analysis of CFD results from the evaluation of 127 patient-specific left main coronary bifurcations, to determine which among four tortuosity metrics—tortuosity index, average absolutecurvature, RMS-curvature, or average squared-derivative-curvature—would better explain variations in Time Averaged WSS (TAWSS)

Summary

Introduction

Mild coronary tortuosity, marked by larger vascular bending angles, is common and can even be found in people lacking coronary artery d isease[1,2]. For tortuosity in the left circumflex (LCx) artery, one study showed a weak correlation[2] with low Time Averaged WSS (TAWSS) whereas another showed a strong negative c orrelation[16] Contrary to both these findings, another study found that the wall shear stress in LMCA decreased overall with tortuosity[3]. The tortuosity index has been deemed a useful metric in clinical practice and research due to its ease of calculation and clinical applicability with 2D medical imaging, given that many important coronary imaging modalities (invasive CA and CTCA) utilize 2D representations of 3D structures As a result, it is commonly considered as a clinically relevant measure and has been widely published as a measure for arterial tortuosity

Objectives

Methods

Results

Conclusion