Closed-loop geometric multi-scale heart-coronary artery model for the numerical calculation of fractional flow...

Fractional flow reserve (FFR) is considered to be the "gold standard" for the clinical diagnosis of functional myocardial ischemia. With the development of medical imaging and computational fluid dynamics (CFD), noninvasive computation of FFR has been developed. The most representative calculation method is the noninvasive FFR derived from coronary CT angiography (FFR_CT), but it cannot thoroughly simulate the real physiological structure of the cardiovascular system. In this study, we propose a noninvasive closed-loop FFR derived from coronary CT angiography (FFR_CCT).

The closed-loop multi-scale model includes three parts: the heart module, the coronary artery module with microcirculation structure and the systemic circulation module. The proposed structure was formed by coupling a lumped parameter model (0D) with a 3D model, such that the 0D model provides the boundary conditions for the 3D model. We enrolled 100 patients through a prospective multi-center clinical trial and calculated their FFR_CCT. Then, we extracted the pressure and flow waveforms of the coronary stenosis vessels through closed-loop geometric multi-scale CFD calculations. We evaluated the accuracy of FFR_CCT in diagnosing myocardial ischemia using the clinical measurement of FFR as the standard.

The results of FFR_CCT calculation in all patients showed a good correlation between FFR_CCT and FFR (r = 0.64, p < 0.05). The AUC (95% CI) of FFR_CCT was 0.819 [0.72, 0.91]. The accuracy, specificity, sensitivity, positive predictive value and negative predictive value of FFR_CCT were 86%, 95%, 62%, 86% and 83%, respectively.

The closed-loop multi-scale model proposed in this study can simulate the physiological cycle in a more realistic way. FFR_CCT is a reliable diagnostic index for myocardial ischemia.