A stepwise strategy integrating dynamic stress CT myocardial perfusion and deep learning-based FFR${}_{CT}$ in the work-up of stable coronary artery disease

To validate a novel stepwise strategy in which computed tomography-derived fractional flow reserve (FFR${}_{CT}$) is restricted to intermediate stenosis on coronary computed tomography angiography (CCTA) and computed tomography myocardial perfusion imaging (CT-MPI) was reserved for vessels with gray zone FFR${}_{CT}$ values. This retrospective study included 87 consecutive patients (age, 58 ± 10 years; 70% male) who underwent CCTA, dynamic CT-MPI, interventional coronary angiography (ICA), and fractional flow reserve (FFR) for suspected or known coronary artery disease. FFR${}_{CT}$ was computed using a deep learning-based platform. Three stepwise strategies (CCTA + FFR${}_{CT}$ + CT-MPI, CCTA + FFR${}_{CT}$, CCTA + CT-MPI) were constructed and their diagnostic performance was evaluated using ICA/FFR as the reference standard. The proportions of vessels requiring further ICA/FFR measurement based on different strategies were noted. Furthermore, the net reclassification index (NRI) was calculated to ascertain the superior model. The CCTA + FFR${}_{CT}$ + CT-MPI strategy yielded the lowest proportion of vessels requiring additional ICA/FFR measurement when compared to the CCTA + FFR${}_{CT}$ and CCTA + CT-MPI strategies (12%, 22%, and 24%). The CCTA + FFR${}_{CT}$ + CT-MPI strategy exhibited the highest accuracy for ruling-out (91%, 84%, and 85%) and ruling-in (90%, 85%, and 85%) functionally significant lesions. All strategies exhibited comparable sensitivity for ruling-out functionally significant lesions and specificity for ruling-in functionally significant lesions (p > 0.05). The NRI indicated that the CCTA + FFR${}_{CT}$ + CT-MPI strategy outperformed the CCTA + FFR${}_{CT}$ strategy (NRI = 0.238, p < 0.001) and the CCTA + CT-MPI strategy (NRI = 0.233%, p < 0.001). The CCTA + FFR${}_{CT}$ + CT-MPI stepwise strategy was superior to the CCTA + FFR${}_{CT}$ strategy and CCTA+ CT-MPI strategy by minimizing unnecessary invasive diagnostic catheterization without compromising the agreement rate with ICA/FFR. Our novel stepwise strategy facilitates greater confidence and accuracy when clinicians need to decide on interventional coronary angiography referral or deferral, reducing the burden of invasive investigations on patients.