Impact of vessel morphology on CT-derived fractional-flow-reserve in non-obstructive coronary artery disease in right coronary artery.

OBJECTIVES: Computed tomography (CT)-derived fractional flow reserve (FFRCT) decreases continuously from proximal to distal segments of the vessel due to the influence of various factors even in non-obstructive coronary artery disease (NOCAD). It is known that FFRCT is dependent on vessel-length, but the relationship with other vessel morphologies remains to be explained. PURPOSE: To investigate morphological aspects of the vessels that influence FFRCT in NOCAD in the right coronary artery (RCA). METHODS: A total of 443 patients who underwent both FFRCT and invasive coronary angiography, with < 50% RCA stenosis, were evaluated. Enrolled RCA vessels were classified into two groups according to distal FFRCT: FFRCT ≤ 0.80 (n = 60) and FFRCT > 0.80 (n = 383). Vessel morphology (vessel length, lumen diameter, lumen volume, and plaque volume) and left-ventricular mass were assessed. The ratio of lumen volume and vessel length was defined as V/L ratio. RESULTS: Whereas vessel-length was almost the same between FFRCT ≤ 0.80 and > 0.80, lumen volume and V/L ratio were significantly lower in FFRCT ≤ 0.80. Distal FFRCT correlated with plaque-related parameters (low-attenuation plaque, intermediate-attenuation plaque, and calcified plaque) and vessel-related parameters (proximal and distal vessel diameter, vessel length, lumen volume, and V/L ratio). Among all vessel-related parameters, V/L ratio showed the highest correlation with distal FFRCT (r = 0.61, p < 0.0001). Multivariable analysis showed that calcified plaque volume was the strongest predictor of distal FFRCT, followed by V/L ratio (ß-coefficient = 0.48, p = 0.03). V/L ratio was the strongest predictor of a distal FFRCT ≤ 0.80 (cut-off 8.1 mm3/mm, AUC 0.88, sensitivity 90.0%, specificity 76.7%, 95% CI 0.84-0.93, p < 0.0001). CONCLUSIONS: Our study suggests that V/L ratio can be a measure to predict subclinical coronary perfusion disturbance. CLINICAL RELEVANCE STATEMENT: A novel marker of the ratio of lumen volume to vessel length (V/L ratio) is the strongest predictor of a distal CT-derived fractional flow reserve (FFRCT) and may have the potential to improve the diagnostic accuracy of FFRCT. KEY POINTS: • Physiological FFRCT decline depends not only on vessel length but also on the lumen volume in non-obstructive coronary artery disease in the right coronary artery. • FFRCT correlates with plaque-related parameters (low-attenuation plaque, intermediate-attenuation plaque, and calcified plaque) and vessel-related parameters (proximal and distal vessel diameter, vessel length, lumen volume, and V/L ratio). • Of vessel-related parameters, V/L ratio is the strongest predictor of a distal FFRCT and an optimal cut-off value of 8.1 mm3/mm.

Impact of Pulmonary Artery-to-Aorta Ratio by CT on the Clinical Outcome in Heart Failure.

INTRODUCTION: Previous studies have indicated that the ratio of pulmonary artery (PA) to ascending aorta (Ao) diameter as measured by computed tomography (PA/Ao) is strongly associated with pulmonary artery pressure. However, the clinical significance of PA/Ao in heart failure (HF) has not been fully characterized. We sought to investigate the prognostic impact of PA/Ao in HF. METHODS: Based on the prospective registry of patients admitted to our institution due to acute decompensated HF (ADHF), the records of the consecutive 761 patients admitted between 2011 and 2016 were reviewed. Thoracic computed tomography data during the hospital stays were obtained from 447 patients (median 78 (70-84) years of age; male, 62.2%). The diameters of PA and Ao were measured at the level of PA bifurcation. The subjects were divided into the H group (PA/Ao ≥ 1.0) and the L group (PA/Ao < 1.0) according to the PA/Ao values. The cutoff value was derived from receiver operating curve analysis. RESULTS: There were no significant differences in age, sex or body mass index between the H and L groups. The H group was associated with significantly larger left atrial dimension (LAD), higher tricuspid regurgitation peak gradient (TRPG) and E/e' (LAD, H, 48 (42-55) mm vs L, 45 (39-50) mm, P < 0.001; TRPG, H, 34 (26-48) mm Hg vs L, 28 (22-38) mm Hg, P < 0.001; E/e', H, 23.3 (42-55) vs L, 18.4 (13.9-25), P < 0.001). Length of hospital stay was significantly longer in the H group than in the L group (H, 19 (14-32) days vs L, 16 (12-23) days, P < 0.001). In-hospital mortality was significantly higher in the H group compared with the L group (H, 5.4% vs L, 1.2%, P = 0.02). Age, sex, LAD and TRPG were independently associated with PA/Ao. The primary endpoint, defined as the composite of all-cause death and ADHF rehospitalization during a median of 479 days after discharge, was significantly more common in the H group (P < 0.001, log-rank test). PA/Ao was independently associated with the primary endpoint, even after adjusting for the other confounding factors (P = 0.002). CONCLUSIONS: PA/Ao is a reliable marker for the prediction of the outcome of patients with ADHF.

Impact of Advanced Extravascular Calcified Plaque on the Assessment of Coronary Stenosis Severity.

Coronary computed tomography angiography (CCTA) and CT-derived fractional flow reserve (FFRCT) provide high diagnostic accuracy for coronary artery disease (CAD), consistent with invasive coronary angiography (ICA), the gold standard diagnostic technique. The presence of calcified components, however, complicates the interpretation of coronary stenosis severity. We present a case where there was a discrepant assessment of coronary stenosis severity between CCTA/FFRCT (indicating significant obstructive CAD) and ICA (showing no apparent obstructive CAD). CCTA/FFRCT revealed that the stenotic lesion, located in the middle segment of the left circumflex artery, was surrounded by plaque components. The proximal and distal portions of the stenotic lesion consisted of 80.9% luminal volume, 0.2% low-attenuation plaque, 13.4% intermediate-attenuation plaque, and 5.5% calcified plaque. In contrast, the stenotic lesion itself contained 50.0% luminal volume, 0.3% low-attenuation plaque, 26.7% intermediate-attenuation plaque, and 22.9% calcified plaque. Invasive coronary angiography showed no apparent obstructive CAD, implying that the lesions appearing as significant obstructive CAD on CCTA/FFRCT were likely overestimated due to the effects of extravascular calcified plaque. Advanced extravascular calcified plaque surrounding the lesion may cause several artifacts (such as blooming and/or beam hardening artifacts) and/or vasodilator dysfunction (either organic and/or functional), potentially leading to an overestimation of the severity of coronary stenosis in CCTA/FFRCT assessments.