Validation of a physics-based computational model of epicardial and microvascular coronary physiology against continuous infusion thermodilution

Introduction

Coronary microvascular dysfunction is associated with myocardial ischaemia and an adverse prognosis, but accurate invasive assessment is technically challenging, requires dedicated hardware and increases procedure time and cost. Assessment can be performed with three-dimensional (3D) computational fluid dynamics (CFD) modelling, but this technique lacks robust in-vivo validation. In this study, we compared the accuracy of a 3D CFD method against continuous thermodilution.

Methods

Patients with acute and chronic coronary syndromes, undergoing continuous thermodilution and angiography-derived assessment, were recruited from two tertiary cardiac centres. Microvascular resistance reserve (MRR) and absolute flow were computed using 3D CFD in reconstructed coronary arteries. Invasive pressure measurements informed the CFD boundary conditions.

Results

Paired flow results were available for 131 arteries from 89 patients. Median computed MRR was 2.31 [1.83 – 3.00], which was significantly lower than continuous thermodilution assessed MRR (2.79 [2.21 – 3.52], z = 3.57, p = 0.0004). There was evidence of a moderate relationship between computed and measured MRR (ρ = 0.58, p<0.0001) and area under the receiver operator characteristic curve was 0.77 (95% CI 0.68–0.86), indicating fair classification. There was a modest relationship between computed and measured hyperaemic vessel inlet flow (ρ=0.44, p<0.0001). For both MRR and flow, agreement improved at lower, more clinically relevant, values.

Discussion

In this clinical validation study, when compared with continuous thermodilution, the novel CFD method demonstrated a moderate correlation, and fair diagnostic accuracy. This CFD method may be a useful, low-cost and less-invasive tool in the assessment of microvascular physiology that could complement current invasive techniques.

Graphical Abstract