Cálculo de la reserva fraccional de flujo coronario por TC cardíaco en arterias coronarias epicárdicas humanas

Abstract

The objective of this doctoral thesis was to compare the diagnostic performance of Coronary Fractional Flow Reserve measured by Computed Tomography (CT-FFR) "on-site" with the invasive measurement of FFR obtained by invasive coronary angiography (ICA) as the reference method. In this study, the patients referred to ICA for clinical indication were previously subjected to a Cardiac CT (CTC) and CT-FFR study. The calculation of CT-FFR was performed without knowing the results of ICA and its values were compared with those obtained with invasive FFR. A porcine model was also developed to generate progressive and quantifiable coronary stenoses both anatomically and functionally. The study recruited 47 patients with a total of 131 analyzable vessels. The mean age was 66 ± 10 years with 88% men. The average time elapsed between the CTC and ICA was 31 ± 20 days. Forty percent of patients (19/47) had previous ischemic heart disease and 38% of vessels had an invasive FFR ≤ 0. 80. The average radiation dose in the CTC studies was 4. 1 ± 1. 4 mSv and the average segmentation and computing time of FFR-TC was 26. 4 ± 9. 2 minutes. A paired data comparison was made for CT-FFR and FFR in 123 vessels analyzed. The mean FFR-TC measured 4 cm from the interrogated lesion was 0. 93 ± 0. 04 in lesions with minimal stenosis, 0. 88 ± 0. 07 in mild stenosis, 0. 81 ± 0. 11 in moderate stenosis and 0. 60 ± 0. 18 in significant stenosis. A good agreement between CT-FFR values and invasive FFR was observed with an average difference between values of -0. 025 (95% CI - 0. 27 - 0. 21). The diagnostic performance of CT-FFR at the vessel level was adequate and superior to isolated CTC for detecting lesions with invasive FFR ≤ 0. 80 (AUC of 0. 95 vs 0. 91; p = 0. 11). The sensitivity, specificity, positive predictive value and negative predictive value to identify vessels with pathological invasive FFR was 88%, 82%, 70% and 93% for vessels with a QCA ≥70% for CTC while for an CT-FFR ≤ 0. 80 it was 85%, 88%, 81% and 90%, respectively. Severely calcified vessels had lower concordance between CT-FFR and invasive FFR values. Nevertheless, the diagnostic accuracy of CT-FFR to predict functionally significant stenoses was higher than isolated CTC thanks to a higher specificity and positive predictive value. The inter-observer variability of repeated CT-FFR measurements in the same CTC studies was acceptable with a kappa index of 0. 72 (95% CI 0. 58 - 0. 86; p <0. 01). This was only slightly reduced in patients with significant atherosclerotic burden and/or very stenotic lesions. The creation of a porcine model with which to generate progressive and quantifiable coronary stenoses both anatomically and functionally was feasible but complex. It was concluded that CT-FFR calculated with "on-site" software has a good correlation with invasive FFR in the diagnosis of functionally significant coronary stenoses. In addition, the diagnostic performance of CT-FFR was superior to that of isolated CTC and the inter-observer variability of repeated CT-FFR measurements in the same CTC studies was low.

Date of Award	16 May 2023
Original language	Spanish
Supervisor	Francisco de Asís Carreras Costa (Director)