Haemodynamic predictors of lesion progression in non-ischaemic tandem coronary stenoses

Tandem coronary stenoses pose diagnostic challenges due to complex flow interactions that can obscure lesion severity when using traditional pressure-based indices such as fractional flow reserve (FFR). Computational fluid dynamics (CFD) can offer a detailed alternative haemodynamic assessment, but its prognostic value in non-haemodynamically significant tandem lesions remains unclear.

We aimed to evaluate whether CFD-derived haemodynamic parameters could predict the 12-month progression of initially non-significant tandem lesions in the left anterior descending artery (LAD), defined by computed tomography (CT)-derived FFR (FFR-CT) >=0.80.

In a retrospective cohort of 60 1:1 propensity score-matched patients with tandem LAD stenoses, baseline and 12-month follow-up coronary CT angiography were performed. FFR-CT was computed using patient-specific CFD simulations, where FFR was defined as the ratio of the mean distal to aortic pressure under simulated hyperaemic flow conditions. CFD simulations quantified the time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT). Lesion progression was defined as diameter stenosis >70% and/or FFR-CT <0.80 at follow-up.

Baseline CT-derived FFR did not differ significantly between groups. Patients with lesion progression (n=30) exhibited significantly lower baseline TAWSS (0.32±0.10 Pa vs 0.82±0.20 Pa; p<0.001), higher OSI (0.22±0.06 vs 0.05±0.03; p<0.001), and prolonged RRT (1.9±0.6 s vs 0.7±0.3 s; p<0.001) compared with those with stable lesions. Multivariate analysis confirmed TAWSS, OSI, RRT, age, and diabetes as independent predictors of progression.

CFD-derived haemodynamic profiles strongly predict the 12-month progression of tandem LAD lesions despite a non-ischaemic baseline FFR-CT. The integration of CFD parameters with conventional physiology may improve the management of tandem coronary lesions beyond pressure-based indices alone.