Quantitative coronary computed tomography angiography for the detection of cardiac allograft vasculopathy

Abstract

Objectives: To associate coronary wall volume and composition, derived from coronary computed tomography angiography (CTA), with cardiac allograft vasculopathy (CAV) detected on invasive coronary angiography (ICA) in heart-transplanted (HTX) patients.

Methods: We included consecutive adults who received ICA and coronary CTA for evaluation of CAV ≥ 10 months after HTX. In all coronary segments, we assessed lumen and wall volumes and segmental length, calculated volume-length ratio (VLR) (volumes indexed by segmental length; mm³/mm), wall burden (WB) (wall/wall + lumen volumes; %), and assessed proportions of calcified, fibrotic, fibro-fatty, and low-attenuation tissue (%) in coronary wall. We rendered independent CTA measures associated with CAV by ICA, tested their discriminatory capacity, and assessed concordance between CTA and ICA.

Results: Among 50 patients (84% men; 53.6 ± 11.9 years), we analyzed 632 coronary segments. Mean interval between HTX and CTA was 6.7 ± 4.7 years and between ICA and CTA 1 (0-1) day. Segmental VLR, WB, and proportion of fibrotic tissue were independently associated with CAV (OR = 1.06-1.27; p ≤ 0.002), reaching a high discriminatory capacity (combination of all three: AUC = 0.84; 95%CI, 0.75-0.90). Concordance between CTA and ICA was higher in advanced CAV (88%) compared with that in none (37%) and mild (19%) CAV. Discordance was primarily driven by a large number of segments with coronary wall changes on CTA but without luminal stenoses on ICA (177/591; 25%).

Conclusion: CTA-derived coronary wall VLR, WB, and the proportion of fibrotic tissue are independent markers of CAV. Combination of these three parameters may aid the detection of early CAV not detected by ICA, the current standard of care.

Key points: • Coronary CTA detects CAV in HTX patients. • Coronary wall volume-length ratio, wall burden, and proportion of fibrotic tissue are independently associated with CAV. • In contrast to ICA, coronary CTA may identify the early stages of CAV.

Keywords: Cardiac allograft vasculopathy; Computed tomography angiography; Heart transplantation; Invasive coronary angiography.

Fig. 1

Discriminatory capacity of quantitative CTA for the detection of CAV. Receiver operator characteristics curves for individual quantitative CTA measures (coronary wall volume-length ratio (VLR; mm³/mm), wall burden (%), and fibrotic tissue proportion (%)) and the composite of all three parameters (i.e., logistic regression–based probability). The composite reached the highest discriminatory capacity. p values indicate significantly larger AUC (0.83) compared with the AUCs of the individual CTA measures. VLR, volume-length ratio

Fig. 2

Imaging examples stratified by CAV status. Left coronary arteries of three patients with (a) CAV on ICA and CTA, corresponding luminal stenoses on ICA and wall thickening on CTA; (b) patient without signs of CAV, with normal coronary lumen on ICA and thin coronary wall on CTA; and (c) patient with normal coronary lumen on ICA (also no stenosis on CTA), but wall thickening (red arrowheads) on CTA. Red dotted lines mark the reference areas of interest. CAV, cardiac allograft vasculopathy; CTA, computed tomography angiography; ICA, invasive coronary angiography