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Objectives: To investigate the additional value of transmural perfusion ratio (TPR) in dynamic CT myocardial perfusion imaging for detection of haemodynamically significant coronary artery disease compared with fractional flow reserve (FFR).Methods: Subjects with suspected or known coronary artery disease were prospectively included and underwent a CT-MPI examination. From the CT-MPI time-point data absolute myocardial blood flow (MBF) values were temporally resolved using a hybrid deconvolution model. An absolute MBF value was measured in the suspected perfusion defect. TPR was defined as the ratio between the subendocardial and subepicardial MBF. TPR and MBF results were compared with invasive FFR using a threshold of 0.80.Results: Forty-three patients and 94 territories were analysed. The area under the receiver operator curve was larger for MBF (0.78) compared with TPR (0.65, P = 0.026). No significant differences were found in diagnostic classification between MBF and TPR with a territory-based accuracy of 77 % (67-86 %) for MBF compared with 70 % (60-81 %) for TPR. Combined MBF and TPR classification did not improve the diagnostic classification.Conclusions: Dynamic CT-MPI-based transmural perfusion ratio predicts haemodynamically significant coronary artery disease. However, diagnostic performance of dynamic CT-MPI-derived TPR is inferior to quantified MBF and has limited incremental value.Key Points: • The transmural perfusion ratio from dynamic CT-MPI predicts functional obstructive coronary artery disease • Performance of the transmural perfusion ratio is inferior to quantified myocardial blood flow • The incremental value of the transmural perfusion ratio is limited. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study is to assess the effect of blood pressure (BP) on coronary computed tomography angiography (CTA) derived computational fractional flow reserve (CTA-FFR).Materials and Methods: Twenty-one patients who underwent coronary CTA and invasive FFR were retrospectively identified. Ischemia was defined as invasive FFR ≤0.80. Using a work-in-progress computational fluid dynamics algorithm, CTA-FFR was computed with BP measured before CTA, and simulated BPs of 60/50, 90/60, 110/70, 130/80, 150/90, and 180/100 mmHg respectively. Correlation between CTA-FFR and invasive FFR was assessed using Pearson test. The repeated measuring test was used for multiple comparisons of CTA-FFR values by simulated BP inputs.Results: Twenty-nine vessels (14 with invasive FFR ≤0.80) were assessed. The average CTA-FFR for measured BP (134 ± 20/73 ± 12 mmHg) was 0.77 ± 0.12. Correlation between CTA-FFR by measured BP and invasive FFR was good (r = 0.735, P < 0.001). For simulated BPs of 60/50, 90/60, 110/70, 130/80, 150/90, and 180/100 mmHg, the CTA-FFR increased: 0.69 ± 0.13, 0.73 ± 0.12, 0.75 ± 0.12, 0.77 ± 0.11, 0.79 ± 0.11, and 0.81 ± 0.10 respectively (P < 0.05).Conclusion: Measurement of the BP just before CTA is preferred for accurate CTA-FFR simulation. BP variations in the common range slightly affect CTA-FFR. However, inaccurate BP assumptions differing from the patient-specific BP could cause misinterpretation of borderline significant lesions.Key Points: • The blood pressure (BP) affects the CTA-FFR computation. • Measured BP before CT examination is preferable for accurate CTA-FFR simulation. • Inaccurate BP assumptions can cause misinterpretation of borderline significant lesions. [ABSTRACT FROM AUTHOR]

The aim of this research was finding the influence of anatomy-based and functional-based outflow boundary conditions for computational fluid dynamics (CFD) on fractional flow reserve (FFR) and wall shear stress (WSS) in mildly diseased coronary bifurcations. For 10 patient-specific bifurcations three simulations were set up with different outflow conditions, while the inflow was kept constant. First, the outflow conditions were based on the diameter of the outlets. Second, they were based on the volume estimates of the myocardium that depended on the outlets. Third, they were based on a myocardial flow measure derived from computed tomography perfusion imaging (CTP). The difference in outflow ratio between the perfusion-based and the diameter-based approach was −7 p.p. [−14 p.p.:7 p.p.] (median percentage point and interquartiles), and between the perfusion-based and volume-based this was −2 p.p. [−2 p.p.:1 p.p.]. Despite of these differences the computed FFRs matched very well. A quantitative analysis of the WSS results showed very high correlations between the methods with an r 2 ranging from 0.90 to 1.00. But despite the high correlations the diameter-based and volume-based approach generally underestimated the WSS compared to the perfusion-based approach. These differences disappeared after normalization. We demonstrated the potential of CTP for setting patient-specific boundary conditions for atherosclerotic coronary bifurcations. FFR and normalized WSS were unaffected by the variations in outflow ratios. In order to compute absolute WSS a functional measure to set the outflow ratio might be of added value in this type of vessels. [ABSTRACT FROM AUTHOR]

Key Clinical Message ST-T segment depression during right-sided endovascular catheter ablation is not only caused by obstructive coronary artery disease or (induced) tachycardia. Clinicians should also consider coronary artery spasms evoked by manipulation of nearby catheters, especially in patients with abnormal coronary artery anatomy. [ABSTRACT FROM AUTHOR]

Purpose Myocardial blood flow ( MBF) obtained by dynamic CT perfusion ( CTP) has been recently introduced to assess hemodynamic significance of coronary stenosis in coronary artery disease. The diagnostic performance of dynamic CTP MBF is limited due to subjective interpretation of MBF maps and MBF variations caused by physiological, methodological, and technical issues. In this paper, we introduce a novel method to quantify the hypoperfused volume ( HPV) in myocardial territories derived from CT angiography ( CTA) to overcome the limitations of current dynamic CTP MBF analysis methods. Methods The diagnostic performance of HPV in classifying significant stenoses was evaluated on 22 patients (57 vessels) that underwent CTA, CTP and invasive fractional flow reserve ( FFR). FFR was used as the standard of reference to determine stenosis significance. The diagnostic performance was compared to that of the mean MBF computed in regions manually annotated by an expert ( MA- MBF). HPV was derived by thresholding the MBF in myocardial territories constructed from CTA by locating the closest artery. Diagnostic performance was evaluated using leave-one-case out cross-validation. Inter-observer reproducibility was assessed by performing annotations of coronary seeds ( HPV) and manual regions ( MA- MBF) with two users. In addition, the influence of different parameter settings on the diagnostic performance of HPV was assessed. Results Leave-one-case out cross-validation showed that HPV has an accuracy of 72% (58-83%) with sensitivity of 72% (47-90%) and specificity of 72% (58-83%). The accuracy of MA- MBF was 70% (57-82%) with a sensitivity of 50% (26-74%) and a specificity of 79% (64-91%). The Spearman correlation and the kappa statistic was ( ρ = 0.94, κ = 0.86) for HPV and ( ρ = 0.72, κ = 0.82) for MA- MBF. The influence of parameter settings on HPV based diagnostic performance was not significant. Conclusions The proposed HPV accurately classifies hemodynamically significant stenoses with a level of accuracy comparable to the mean MBF in regions annotated by an expert. HPV improves inter-observer reproducibility as compared to MA- MBF by providing a more objective criterion to associate the stenotic coronary with the supplied myocardial territory. [ABSTRACT FROM AUTHOR]

Aims Atherosclerotic plaque development has been associated with wall shear stress (WSS). However, the multidirectionality of blood flow, and thus of WSS, is rarely taken into account. The purpose of this study was to comprehensively compare five metrics that describe (multidirectional) WSS behaviour and assess how WSS multidirectionality affects coronary plaque initiation and progression. Methods and results Adult familial hypercholesterolaemic pigs (n  = 10) that were fed a high-fat diet, underwent imaging of the three main coronary arteries at three-time points [3 (T1), 9 (T2), and 10–12 (T3) months]. Three-dimensional geometry of the arterial lumen, in combination with local flow velocity measurements, was used to calculate WSS at T1 and T2. For analysis, arteries were divided into 3 mm/45° sectors (n  = 3648). Changes in wall thickness and final plaque composition were assessed with near-infrared spectroscopy–intravascular ultrasound, optical coherence tomography imaging, and histology. Both in pigs with advanced and mild disease, the highest plaque progression rate was exclusively found at low time-averaged WSS (TAWSS) or high multidirectional WSS regions at both T1 and T2. However, the eventually largest plaque growth was located in regions with initial low TAWSS or high multidirectional WSS that, over time, became exposed to high TAWSS or low multidirectional WSS at T2. Besides plaque size, also the presence of vulnerable plaque components at the last time point was related to low and multidirectional WSS. Almost all WSS metrics had good predictive values for the development of plaque (47–50%) and advanced fibrous cap atheroma (FCA) development (59–61%). Conclusion This study demonstrates that low and multidirectional WSS promote both initiation and progression of coronary atherosclerotic plaques. The high-predictive values of the multidirectional WSS metrics for FCA development indicate their potential as an additional clinical marker for the vulnerable disease. [ABSTRACT FROM AUTHOR]

Background To evaluate the combined diagnostic accuracy of coronary computed tomography angiography (CCTA) and computed tomography derived fractional flow reserve (FFRct) in patients with suspected or known coronary artery disease (CAD). Methods PubMed, The Cochrane library, Embase and OpenGray were searched to identify studies comparing diagnostic accuracy of CCTA and FFRct. Diagnostic test measurements of FFRct were either extracted directly from the published papers or calculated from provided information. Bivariate models were conducted to synthesize the diagnostic performance of combined CCTA and FFRct at both “per-vessel” and “per-patient” levels. Results 7 articles were included for analysis. The combined diagnostic outcomes from “both positive” strategy, i.e. a subject was considered as “positive” only when both CCTA and FFRct were “positive”, demonstrated relative high specificity (per-vessel: 0.91; per-patient: 0.81), high positive likelihood ratio (LR +, per-vessel: 7.93; per-patient: 4.26), high negative likelihood ratio (LR −, per-vessel: 0.30; per patient: 0.24) and high accuracy (per-vessel: 0.91; per-patient: 0.81) while “either positive” strategy, i.e. a subject was considered as “positive” when either CCTA or FFRct was “positive”, demonstrated relative high sensitivity (per-vessel: 0.97; per-patient: 0.98), low LR + (per-vessel: 1.50; per-patient: 1.17), low LR − (per-vessel: 0.07; per-patient: 0.09) and low accuracy (per-vessel: 0.57; per-patient: 0.54). Conclusion “Both positive” strategy showed better diagnostic performance to rule in patients with non-significant stenosis compared to “either positive” strategy, as it efficiently reduces the proportion of testing false positive subjects. [ABSTRACT FROM AUTHOR]

Objectives: In this study, we evaluated a cloud-based platform for cardiac magnetic resonance (CMR) four-dimensional (4D) flow imaging, with fully integrated correction for eddy currents, Maxwell phase effects, and gradient field non-linearity, to quantify forward flow, regurgitation, and peak systolic velocity over the pulmonary artery.Methods: We prospectively recruited 52 adult patients during one-year period from July 2014. The 4D flow and planar (2D) phase-contrast (PC) were acquired during same scanning session, but 4D flow was scanned after injection of a gadolinium-based contrast agent. Eddy-currents were semi-automatically corrected using the web-based software. Flow over pulmonary valve was measured and the 4D flow values were compared against the 2D PC ones.Results: The mean forward flow was 92 (±30) ml/cycle measured with 4D flow and 86 (±29) ml/cycle measured with 2D PC, with a correlation of 0.82 and a mean difference of -6ml/cycle (-41-29). For the regurgitant fraction the correlation was 0.85 with a mean difference of -0.95% (-17-15). Mean peak systolic velocity measured with 4D flow was 92 (±49) cm/s and 108 (±56) cm/s with 2D PC, having a correlation of 0.93 and a mean difference of 16cm/s (-24-55).Conclusion: 4D flow imaging post-processed with an integrated cloud-based application accurately quantifies pulmonary flow. However, it may underestimate the peak systolic velocity. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study was to estimate the myocardial area at risk (MAAR) using coronary computed tomography angiography (CTA) and Voronoi algorithm-based myocardial segmentation in comparison with single-photon emission computed tomography (SPECT). Methods: Thirty-four patients with coronary artery disease underwent 128-slice coronary CTA, stress/rest thallium-201 SPECT, and coronary angiography (CAG). CTA-based MAAR was defined as the sum of all CAG stenosis (>50 %) related territories (the ratio of the left ventricular volume). Using automated quantification software (17-segment model, 5-point scale), SPECT-based MAAR was defined as the number of segments with a score above zero as compared to the total 17 segments by summed stress score (SSS), difference (SDS) score map, and comprehensive SPECT interpretation with either SSS or SDS best correlating CAG findings (SSS/SDS). Results were compared using Pearson's correlation coefficient. Results: Forty-nine stenoses were observed in 102 major coronary territories. Mean value of CTA-based MAAR was 28.3 ± 14.0 %. SSS-based, SDS-based, and SSS/SDS-based MAAR was 30.1 ± 6.1 %, 20.1 ± 15.8 %, and 26.8 ± 15.7 %, respectively. CTA-based MAAR was significantly related to SPECT-based MAAR ( r = 0.531 for SSS; r = 0.494 for SDS; r = 0.814 for SSS/SDS; P < 0.05 in each). Conclusions: CTA-based Voronoi algorithm myocardial segmentation reliably quantifies SPECT-based MAAR. Key points: • Voronoi algorithm allows for three-dimensional myocardial segmentation of coronary CT angiography • Stenosis-related CT myocardial territories correlate to SPECT based area at risk • CT angiography myocardial segmentation may assist in clinical decision-making [ABSTRACT FROM AUTHOR]

Purpose: This study investigated the impact of gender differences on the diagnostic performance of machine-learning based coronary CT angiography (cCTA)-derived fractional flow reserve (CT-FFRML) for the detection of lesion-specific ischemia.Method: Five centers enrolled 351 patients (73.5% male) with 525 vessels in the MACHINE (Machine leArning Based CT angiograpHy derIved FFR: a Multi-ceNtEr) registry. CT-FFRML and invasive FFR ≤ 0.80 were considered hemodynamically significant, whereas cCTA luminal stenosis ≥50% was considered obstructive. The diagnostic performance to assess lesion-specific ischemia in both men and women was assessed on a per-vessel basis.Results: In total, 398 vessels in men and 127 vessels in women were included. Compared to invasive FFR, CT-FFRML reached a sensitivity, specificity, positive predictive value, and negative predictive value of 78% (95%CI 72-84), 79% (95%CI 73-84), 75% (95%CI 69-79), and 82% (95%CI: 76-86) in men vs. 75% (95%CI 58-88), 81 (95%CI 72-89), 61% (95%CI 50-72) and 89% (95%CI 82-94) in women, respectively. CT-FFRML showed no statistically significant difference in the area under the receiver-operating characteristic curve (AUC) in men vs. women (AUC: 0.83 [95%CI 0.79-0.87] vs. 0.83 [95%CI 0.75-0.89], p = 0.89). CT-FFRML was not superior to cCTA alone [AUC: 0.83 (95%CI: 0.75-0.89) vs. 0.74 (95%CI: 0.65-0.81), p = 0.12] in women, but showed a statistically significant improvement in men [0.83 (95%CI: 0.79-0.87) vs. 0.76 (95%CI: 0.71-0.80), p = 0.007].Conclusions: Machine-learning based CT-FFR performs equally in men and women with superior diagnostic performance over cCTA alone for the detection of lesion-specific ischemia. [ABSTRACT FROM AUTHOR]