Transmural Perfusion Ratio Research Articles

Myocardial perfusion segmentation and partitioning methods in personalized models of coronary blood flow

Abstract In this work we present methods and algorithms for construction of a personalized model of coronary haemodynamics based on computed tomography images. This model provides estimations of fractional flow reserve, coronary flow reserve, and instantaneous wave-free ratio taking into account transmural perfusion ratio indices obtained from perfusion images. The presented pipeline consists of the following steps: aorta segmentation, left ventricle wall segmentation, coronary arteries segmentation, construction of 1D network of vessels, partitioning of left ventricle wall, and personalization of the model parameters. We focus on a new technique, which generates specific perfusion zones and computes transmural perfusion ratio according to the quality of available medical images with a limited number of visible terminal coronary vessels. Numerical experiments show that accurate evaluation of stenosis before precutaneous coronary intervention should take into account both fractional flow reserve indices and myocardial perfusion, as well as other indices, in order to avoid misdiagnosis. The presented model provides better understanding of the background of clinical recommendations for possible surgical treatment of a stenosed coronary artery.

Personalized computational estimation of relative change in coronary blood flow after percutaneous coronary intervention in short-term and long-term perspectives

Abstract Coronary artery disease is the leading cause of mortality worldwide, accounting for 12.8% of all deaths. Although the clinical benefits of treating stenosis with percutaneous coronary intervention (PCI) have been extensively demonstrated, residual myocardial ischemia remains in about 30–50% of patients even after a formally successful PCI. We apply previously developed and validated 1D model of haemodynamics, which distributes terminal hydraulic resistance based on the diameters of the parent vessels and Murray’s law by a recursive algorithm. In our new model the terminal resistance is decreased according to a transmural perfusion ratio increase. In contrast to our previous work we calculate the transmural perfusion ratio for personally defined zones. Thus, peripheral hydraulic resistance of myocardial perfusion is personalized based on patient data, whichwere extracted from computed tomography perfusion images. The model serves as a computational tool for simulating pre- to post-PCI changes in coronary haemodynamics of four patients. We simulate fractional flow reserve (FFR), coronary flow reserve (CFR), instantaneous wave-free ratio (iFR), average flow in selected arteries in hyperemic and rest conditions before PCI and after PCI immediately after the surgery (in a short-term) and in a long-term (several months) perspectives. We conclude that high FFR and iFR values in short-term and long-term perspectives are not necessary correlate with CFR improvement and long-term blood flow recovery in coronary arteries.

A Novel Quantitative Parameter for Static Myocardial Computed Tomography: Myocardial Perfusion Ratio to the Aorta.

We evaluated the feasibility of myocardial perfusion ratio to the aorta (MPR) in static computed tomography perfusion (CTP) for detecting myocardial perfusion abnormalities assessed by single-photon emission computed tomography (SPECT). Twenty-five patients with suspected coronary artery disease who underwent dynamic CTP and SPECT were retrospectively evaluated. CTP images scanned at a sub-optimal phase for detecting myocardial perfusion abnormalities were selected from dynamic CTP images and used as static CTP images in the present study. The diagnostic accuracy of MPR derived from static CTP was compared to those of visual assessment and conventional quantitative parameters such as myocardial CT attenuation (HU) and transmural perfusion ratio (TPR). The area under the curve of MPR (0.84; 95% confidence interval [CI], 0.76–0.90) was significantly higher than those of myocardial CT attenuation (0.73; 95% CI, 0.65–0.79) and TPR (0.76; 95% CI, 0.67–0.83) (p < 0.05). Sensitivity and specificity were 67% (95% CI, 54–77%) and 90% (95% CI, 86–92%) for visual assessment, 51% (95% CI, 39–63%) and 86% (95% CI, 82–89%) for myocardial CT attenuation, 63% (95% CI, 51–74%) and 84% (95% CI, 80–88%) for TPR, and 78% (95% CI, 66–86%) and 84% (95% CI, 80–88%) for MPR, respectively. MPR showed higher diagnostic accuracy for detecting myocardial perfusion abnormality compared with myocardial CT attenuation and TPR.

Numerical evaluation of the effectiveness of coronary revascularization

Abstract In the present paper we construct the model of coronary flow which utilizes the patient’s CT data on both large CA and perfusion. We reconstruct large coronary vessels based on the CT data and extrude possibly invisible vessels from the branches of the left coronary artery so that every terminal point supply every of standardized zone of myocardium. We apply a previously developed and validated 1D model of haemodynamics. Utilizing the patient-specific CTP data for modifying outflow terminal resistance at rest and under stress conditions is the major novelty of the present work. From our results it follows that acceptable values of fractional flow reserve (FFR) after the stenotic treatment may produce false negative output. Therefore healthy FFR values may be observed after ineffective revascularization. We also conclude that microvascular perfusion impairment plays significant role in correct computational estimation of haemodynamic indices before stenotic treatment. The advantage of the presented approach is the availability of transmural perfusion ratio assessment in everyday practice.

Modeling Left Ventricle Perfusion in Healthy and Stenotic Conditions.

A theoretical fluid mechanical model is proposed for the investigation of myocardial perfusion in healthy and stenotic conditions. The model hinges on Terzaghi’s consolidation theory and reformulates the related unsteady flow equation for the simulation of the swelling–drainage alternation characterizing the diastolic–systolic phases. When compared with the outcome of experimental in vivo observations in terms of left ventricle transmural perfusion ratio (T.P.R.), the analytical solution provided by the present study for the time-dependent blood pressure and flow rate across the ventricle wall proves to consistently reproduce the basic mechanisms of both healthy and ischemic perfusion. Therefore, it could constitute a useful interpretative support to improve the comprehension of the basic hemodynamic mechanisms leading to the most common cardiac diseases. Additionally, it could represent the mathematical basis for the application of inverse methods aimed at estimating the characteristic parameters of ischemic perfusion (i.e., location and severity of coronary stenoses) via downstream ventricular measurements, possibly inspiring their assessment via non-invasive myocardial imaging techniques.

Diagnostic value of quantitative parameters for myocardial perfusion assessment in patients with suspected coronary artery disease by single- and dual-energy computed tomography myocardial perfusion imaging.

PurposeTo compare performance of visual and quantitative analyses for detecting myocardial ischaemia from single- and dual-energy computed tomography (CT) in patients with suspected coronary artery disease (CAD).MethodsEighty-four patients with suspected CAD were scheduled for dual-energy cardiac CT at rest (CTA) and pharmacological stress (CTP). Myocardial CT perfusion was analysed visually and using three parameters: mean attenuation density (MA), transmural perfusion ratio (TPR) and myocardial perfusion reserve index (MPRI), on both single-energy CT and CT-based iodine images. Significant CAD was defined in AHA-segments by concomitant myocardial hypoperfusion identified visually or quantitatively (parameter < threshold) and coronary stenosis detected by CTA. Single-photon emission CT and invasive coronary angiography were used as reference. Perfusion-parameter cut-off values were calculated in a randomly-selected subgroup of 30 patients.ResultsThe best-performing thresholds for TPR, MPRI and MA were 0.96, 23 and 0.5 for single-energy CT and 0.97, 47 and 0.3 for iodine imaging. For both CT-imaging modalities, TPR yielded the highest area under receiver operating characteristic curve (AUC) (0.99 and 0.97 for single-energy CT and iodine imaging, respectively, in vessel-based analysis) compared to visual analysis, MA and MPRI. Visual interpretation on iodine imaging resulted in higher AUC compared to that on single-energy CT in per-vessel (AUC: 0.93 vs 0.86, respectively) and per-patient (0.94 vs 0.93) analyses.ConclusionTransmural perfusion ratio on both CT-imaging modalities is the best-performing parameter for detecting myocardial ischaemia compared to visual method and other perfusion parameters. Visual analysis on CT-based iodine imaging outperforms that on single-energy CT.

Assessment of Semi-automated Computed Tomographic Measures of Segmental Perfusion Defects in a Swine Model (Sus scrofa) of Intermediate Coronary Lesions.

Computed tomographic myocardial perfusion (CTP) imaging is a tool that shows promise in emergent settings for defining the hemodynamic significance of coronary artery disease. In this study, we examined the accuracy with which the transmural perfusion ratio (TPR) derived through semiautomated CTP analysis reflected segmental perfusion defects associated with intermediate coronary artery lesions in swine. Lesions (diameter stenosis, 65% ± 11%) of the left anterior descending coronary artery (LAD) were created in 10 anesthetized female swine (weight, 47.5 ± 1.9 kg) by using a pneumatic occlusion device implanted on the LAD. Occluder inflation pressures were adjusted to maintain fractional flow reserve (FFR, 74.3 ± 1.7) during adenosine infusion (140ug/kg/min). Static CTP imaging using a stress-rest protocol and segmental TPR derived from semiautomated CT perfusion software was compared with microsphere-derived TPR (mTPR) by using a 16-segment model and polar mapping. Intermediate LAD stenosis was verified through multiplanar coronary CT angiography. Receiver operating characteristic analysis identified an optimal threshold for segmental perfusion defects for intermediate lesions (TPR threshold, ≤0.80); however, the area under the receiver operating characteristic curve was 0.58, and the overall accuracy was 63%. At this threshold, the sensitivity and specificity were 65% and 61%, and the positive and negative predictive values were 61% and 65%, respectively. Although CTP-TPR illustrated segmental perfusion defects with intermediate lesions, the disparity between CTP-TPR and mTPR measures of segmental perfusion suggests that further advances in analysis software may be necessary to improve the localization of segmental defects for intermediated lesions.

Achieving Low Radiation Dose in “One-Stop” Myocardial Computed Tomography Perfusion Imaging in Coronary Artery Disease Using 16-cm Wide Detector CT

To investigate the feasibility of "one-stop" myocardial computed tomography perfusion (CTP) imaging (combined anatomy, perfusion, and function) in coronary artery disease using 16-cm wide detector CT, compared to conventional coronary CT angiography (CCTA). 442 patients with suspected coronary artery disease were randomly divided into two groups. Patients in group A underwent "one-stop" CTP, whereas group B underwent conventional CCTA. Image quality of CT images was assessed. Radiation and contrast medium doses and scan time of the two groups were recorded. Group A was further divided into four subgroups according to the degree of coronary artery stenosis, for which transmural perfusion ratio (TPR) and left ventricular ejection fraction (LVEF) were measured. Scan time was 73.1 ± 7.3 (s) longer in group A than in group B with 11.7% reduction of radiation dose (p < 0.001) and no significant difference in image quality was noted. Significant differences regarding the minimum TPR (F = 24.657, p < 0.001) and LVEF (χ2 =36.98, p < 0.001) were observed among four subgroups. A negative correlation was found between the degree of coronary artery stenosis and TPR of the corresponding myocardial segments (r = -0.55, p < 0.001). Patients with moderate to severe arterial stenosis exhibited a decreased LVEF compared to those with normal coronary arteries (48.0% vs 56.5%, p < 0.001). Compared to conventional CCTA, our new developed "one-stop" CTP may provide more comprehensive information on myocardial perfusion, coronary artery stenosis, and LV cardiac function with reduced radiation and contrast medium doses.

Normal patterns of left ventricle rest myocardial perfusion assessed by third-generation cardiac computed tomography.

To investigate diastolic and systolic patterns of segmental and transmural rest perfusion of the left ventricle (LV) in normal subjects (NS) undergoing third-generation dual-source cardiac computed tomography (CCT). Forty consecutive NS, with normal coronary arteries and cardiac chambers both anatomically and functionally on the basis of CCT, were retrospectively enrolled in the study. Relative normalized myocardial attenuation density (rnMAD) and transmural perfusion ratio (TPR) were calculated in diastole and systole for each segment and layer of the LV and then pooled into territories. Statistical analysis showed that sub-endocardial rnMAD was significantly higher than intra-myocardial and sub-epicardial for all myocardial territories both in systolic and diastolic phases (P<0·001). Basal and mid-ventricular rnMAD were higher than apical for all myocardial layers (P<0·001). Septum displayed higher rnMAD in intra-myocardium and sub-epicardium (179±61 and 170±59 in diastole and 172±60 and 166±58 in systole, respectively) than the anterior, lateral and inferior wall (P<0·001). Diastolic and systolic TPR were significantly different for the anterior and lateral wall (P<0·001), while septal TPR (1·06±0·06 in diastole and 1·05±0·06 in systole, respectively) was the lowest as compared to other territories' TPR. Finally, basal, mid-ventricular and apical TPR showed a significant linear trend with basal lower than mid-ventricular and apical values. Inter-territory and inter-layer myocardial perfusion differences can be accurately assessed with CCT in NS. This assessment is the basic step to further evaluate abnormal rest perfusion patterns in ischaemic and non-ischaemic diseases.

Non-invasive CT-derived fractional flow reserve and static rest and stress CT myocardial perfusion imaging for detection of haemodynamically significant coronary stenosis

Computed tomography derived fractional flow reserve (FFRCT) and computed tomography stress myocardial perfusion imaging (CTP) are techniques to assess haemodynamic significance of coronary stenosis. To compare the diagnostic performance of FFRCT and static rest/stress CTP in detecting fractional flow reserve (FFR) defined haemodynamically-significant stenosis (FFR ≤ 0.8). Fifty-one patients (96 vessels) with suspected coronary artery disease from a single institution planned for elective invasive-angiography prospectively underwent research indicated 320-detector-CT-coronary-angiography (CTA) and adenosine-stress CTP and invasive FFR. Analyses were performed in separate core-laboratories for FFRCT and CTP blinded to FFR results. Myocardial perfusion was assessed visually and semi-quantitatively by transmural perfusion ratio (TPR). Invasive FFR ≤ 0.8 was present in 33% of vessels and 49% of patients. FFRCT, visual CTP and TPR analysis was feasible in 96%, 92% and 92% of patients respectively. Overall per-vessel sensitivity, specificity and diagnostic accuracy for FFRCT were 81%, 85%, 84%, for visual CTP were 50%, 89%, 75% and for TPR were 69%, 48%, 56% respectively. Receiver-operating-characteristics curve analysis demonstrated larger per vessel area-under-curve (AUC) for FFRCT (0.89) compared with visual CTP (0.70; p < 0.001), TPR (0.58; p < 0.001) and CTA (0.70; p = 0.0007); AUC for CTA + FFRCT (0.91) was higher than CTA + visual CTP (0.77, p = 0.008) and CTA + TPR (0.74, p < 0.001). Per-patient AUC for FFRCT (0.90) was higher than visual CTP (0.69; p = 0.0016), TPR (0.56; p < 0.0001) and CTA (0.68; p = 0.001). Based on this selected cohort of patients FFRCT is superior to visually and semi-quantitatively assessed static rest/stress CTP in detecting haemodynamically-significant coronary stenosis as determined on invasive FFR.

Myocardial perfusion assessed with cardiac computed tomography in women without coronary heart disease

Combined coronary CT angiography and CT perfusion (CTP) is a novel, non-invasive, 'one-stop' diagnostic tool to rule out ischaemia in patients suspected for coronary artery disease (CAD). However, the normal myocardial perfusion pattern by static CTP in humans is poorly described. We aimed to investigate global and regional myocardial perfusion during rest and adenosine-induced hyperaemia in asymptomatic women without history of coronary heart disease (CHD). Using a 320-row CT scanner with a static protocol, semi-quantitative assessment of rest and stress CTP was performed in 34 asymptomatic middle-aged women without obstructive CAD (<50% stenosis) or history of CHD, and with normal exercise stress test and left ventricular (LV) function. Using a 16-segment model, we assessed global and regional values of LV myocardial perfusion reserve (MPR) and transmural perfusion ratio (TPR). Mean±SD age was 56±13years. Resting and hyperaemic myocardial perfusion was heterogeneously distributed throughout the LV myocardium. During hyperaemia, global MPR increased by median (IQR) 158% (144-176) with the highest increase in the right coronary artery territory (171%; P<0.02). Rest and stress segmental TPR values ranged between 0.93-1.26 and 0.99-1.13, respectively, with the lowest values detected in the inferoseptal segments. No differences in perfusion parameters were found between participants with normal epicardial arteries and participants with non-significant epicardial atheromatosis (all P>0.05). Global perfusion parameters were not associated with age or menopausal status (all P>0.05). This descriptive study presents data on global and regional myocardial perfusion in a cohort of healthy middle-aged women.

Myocardial perfusion at rest in uncomplicated type 2 diabetes patients without coronary artery disease evaluated by 320-multidetector computed tomography: A pilot study.

Using computed tomography myocardial perfusion imaging (CTP) to investigate resting myocardial perfusion alterations in uncomplicated type 2 diabetes mellitus (T2DM) patients without obstructive coronary artery disease (CAD).A total of 34 participants with 544 myocardial segments were included prospectively: 17 uncomplicated T2DM patients with no significant coronary artery stenosis on coronary computed tomography angiography and 17 healthy controls. Myocardial perfusion was evaluated by transmural perfusion ratio (TPR). Parameters of cardiac structure and function were measured for cardiac comprehensive assessment. Analyses included descriptive statistics and group comparisons.TPR of segments 5, 7, 9, 10 to 14 were significantly reduced in T2DM group compared with controls (P < .05). When 16 myocardial segments were localized into different areas according to the wall orientations, axial levels of left ventricle and coronary artery territories, respectively, TPR of each area in T2DM group were significantly lower than those in the control group (P < .05). No significant differences were found in cardiac anatomy and function analyses between 2 groups.In uncomplicated T2DM patients without obstructive CAD, myocardial perfusion impairments were present and may develop prior to cardiac morphological and functional abnormalities, which can be early detected by CTP.

Geographic and demographic variabilities of quantitative parameters in stress myocardial computed tomography perfusion.

Background/AimsTo evaluate the geographic and demographic variabilities of the quantitative parameters of computed tomography perfusion (CTP) of the left ventricular (LV) myocardium in patients with normal coronary artery on computed tomography angiography (CTA).MethodsFrom a multicenter CTP registry of stress and static computed tomography, we retrospectively recruited 113 patients (mean age, 60 years; 57 men) without perfusion defect on visual assessment and minimal (< 20% of diameter stenosis) or no coronary artery disease on CTA. Using semiautomatic analysis software, quantitative parameters of the LV myocardium, including the myocardial attenuation in stress and rest phases, transmural perfusion ratio (TPR), and myocardial perfusion reserve index (MPRI), were evaluated in 16 myocardial segments.ResultsIn the lateral wall of the LV myocardium, all quantitative parameters except for MPRI were significantly higher compared with those in the other walls. The MPRI showed consistent values in all myocardial walls (anterior to lateral wall: range, 25% to 27%; p = 0.401). At the basal level of the myocardium, all quantitative parameters were significantly lower than those at the mid- and apical levels. Compared with men, women had significantly higher values of myocardial attenuation and TPR. Age, body mass index, and Framingham risk score were significantly associated with the difference in myocardial attenuation.ConclusionsGeographic and demographic variabilities of quantitative parameters in stress myocardial CTP exist in healthy subjects without significant coronary artery disease. This information may be helpful when assessing myocardial perfusion defects in CTP.

Prediction of clinical outcome by myocardial CT perfusion in patients with low-risk unstable angina pectoris.

The prognostic implications of myocardial computed tomography perfusion (CTP) analyses are unknown. In this sub-study to the CATCH-trial we evaluate the ability of adenosine stress CTP findings to predict mid-term major adverse cardiac events (MACE). In 240 patients with acute-onset chest pain, yet normal electrocardiograms and troponins, a clinically blinded adenosine stress CTP scan was performed in addition to conventional diagnostic evaluation. A reversible perfusion defect (PD) was found in 38 patients (16 %) and during a median follow-up of 19 months (range 12-22 months) 25 patients (10 %) suffered a MACE (cardiac death, non-fatal myocardial infarction and revascularizations). Accuracy for the prediction of MACE expressed as the area under curve (AUC) on receiver-operating characteristic curves was 0.88 (0.83-0.92) for visual assessment of a PD and 0.80 (0.73-0.85) for stress TPR (transmural perfusion ratio). After adjustment for the pretest probability of obstructive coronary artery disease, both detection of a PD and stress TPR were significantly associated with MACE with an adjusted hazard ratio of 39 (95 % confidence interval 11-134), p < 0.0001, for visual interpretation and 0.99 (0.98-0.99) for stress TPR, p < 0.0001. Patients with a PD volume covering >10 % of the LV myocardium had a worse prognosis compared to patients with a PD covering <10 % of the LV myocardium, p = 0.0002. The optimal cut-off value of the myocardial PD extent to predict MACE was 5.3 % of the left ventricle [sensitivity 84 % (64-96), specificity 95 % (91-97)]. Myocardial CT perfusion parameters predict mid-term clinical outcome in patients with recent acute-onset chest pain.

Diagnostic value of transmural perfusion ratio derived from dynamic CT-based myocardial perfusion imaging for the detection of haemodynamically relevant coronary artery stenosis

ObjectivesTo 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).MethodsSubjects 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.ResultsForty-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.ConclusionsDynamic 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

An anomalous left coronary artery with a malignant course: coronary angiography and myocardial perfusion imaging with computed tomography

A 41-year old woman presented at the emergency department because of collapse during running. Coronary computed tomography angiography (CTA) showed no atherosclerosis (Fig. 1). However, as demonstrated by the double oblique view of the sinus of Valsalva in Panel A and 3D-rendering of Panel B, the left coronary artery (LCA) originated from the right coronary sinus. The LCA has an acute angle and a ‘slitlike’ ostium which can collapse in a valve-like manner during exercise. The incidence of this finding on CTA ranges from 0.7– 6.6 % [1, 2]. Adenosine stress CT myocardial perfusion imaging (CTP) was performed. Panel C demonstrates a sub-endocardial perfusion defect in the LCA region (white arrows). Panel D represents the polar map of the transmural perfusion ratio. Surgical unroofing was performed successfully and no further events have occurred [3]. In patients presenting with collapse a malignant coronary anomaly can be observed. CTP can subsequently be performed to detect myocardial ischaemia. Fig. 1 Computed tomography coronary angiography and myocardial perfusion imaging

Rest-Only Myocardial CT Perfusion in Acute Chest Pain.

Cardiac computed tomography perfusion (CTP) using stress testing is an emerging application in the field of cardiac computed tomography. We evaluated patients with acute chest pain (CP) in the emergency department (ED) with evidence of obstructive coronary artery disease (CAD), defined as >70% stenosis on coronary computed tomography angiography (CCTA) and confirmed by invasive coronary angiography (ICA), to evaluate the applicability of resting CTP in the acute CP setting. From January to December 2013, 183 low-intermediate risk symptomatic patients with negative cardiac biomarkers and no known CAD underwent a rapid CCTA protocol in the ED. Of these, 4 patients (1.4%) had obstructive CAD (≥70% stenosis) on CCTA confirmed by ICA. All 183 CCTA studies were evaluated retrospectively with CTP software by a transmural perfusion ratio (TPR) method with a superimposed 17-segment model. A TPR value <0.99 was considered abnormal based on previously published data. A total of four patients were included in this pilot analysis. The duration from resolution of CP to performance of CCTA ranged from 1.6 to 5.0 hours. Three patients underwent revascularization, two with percutaneous coronary intervention (PCI) and one with coronary artery bypass grafting. The fourth patient was managed with aggressive medical therapy. Two patients had multivessel obstructive CAD and two patients had single-vessel CAD. The first patient underwent CCTA 5 hours after resolution of CP symptoms. CCTA demonstrated noncalcified obstructive CAD in the mid-LAD and mid-right coronary artery. ICA showed good correlation by quantitative coronary assessment (QCA) in both vessels and the patient underwent PCI. CTP analysis demonstrated perfusion defects in the LAD and right coronary artery territories. The second patient underwent CCTA 1.6 hours after resolution of CP symptoms with findings of obstructive ostial left main CAD. ICA confirmed obstructive left main CAD by QCA and intravascular ultrasound. The patient underwent revascularization with coronary artery bypass grafting. CTP demonstrated perfusion defects in the anterior and lateral wall segments. The third patient was evaluated for CP in the ED with CCTA demonstrating single-vessel CAD 10 hours after resolution of symptoms with findings of a noncalcified obstructive stenosis in the mid-LAD. The patient subsequently underwent ICA demonstrating good correlation to the CCTA findings in the LAD by QCA. CTP analysis revealed perfusion defects in LAD territory. He was successful treated with PCI. The final patient underwent CCTA 5.4 hours following resolution of CP with the finding of an intermediate partially calcified stenosis in the distal LAD. ICA was performed, with fractional flow reserve demonstrating a hemodynamically insignificant distal LAD at 0.86. CTP detected a perfusion defect in the LAD territory. When positive, rest CTP may have value in the risk stratification of patients presenting to the ED with nontraumatic acute CP.

Myocardial perfusion analysis in cardiac computed tomography angiographic images at rest.

Cardiac computed tomography angiography (CTA) is a non-invasive method for anatomic evaluation of coronary artery stenoses. However, CTA is prone to artifacts that reduce the diagnostic accuracy to identify stenoses. Further, CTA does not allow for determination of the physiologic significance of the visualized stenoses. In this paper, we propose a new system to determine the physiologic manifestation of coronary stenoses by assessment of myocardial perfusion from typically acquired CTA images at rest. As a first step, we develop an automated segmentation method to delineate the left ventricle. Both endocardium and epicardium are compactly modeled with subdivision surfaces and coupled by explicit thickness representation. After initialization with five anatomical landmarks, the model is adapted to a target image by deformation increments including control vertex displacements and thickness variations guided by trained AdaBoost classifiers, and regularized by a prior of deformation increments from principal component analysis (PCA). The evaluation using a 5-fold cross-validation demonstrates the overall segmentation error to be 1.00 ± 0.39 mm for endocardium and 1.06 ± 0.43 mm for epicardium, with a boundary contour alignment error of 2.79 ± 0.52. Based on our LV model, two types of myocardial perfusion analyzes have been performed. One is a perfusion network analysis, which explores the correlation (as network edges) pattern of perfusion between all pairs of myocardial segments (as network nodes) defined in AHA 17-segment model. We find perfusion network display different patterns in the normal and disease groups, as divided by whether significant coronary stenosis is present in quantitative coronary angiography (QCA). The other analysis is a clinical validation assessment of the ability of the developed algorithm to predict whether a patient has significant coronary stenosis when referenced to an invasive QCA ground truth standard. By training three machine learning techniques using three features of normalized perfusion intensity, transmural perfusion ratio, and myocardial wall thickness, we demonstrate AdaBoost to be slightly better than Naive Bayes and Random Forest by the area under receiver operating characteristics (ROC) curve. For the AdaBoost algorithm, an optimal cut-point reveals an accuracy of 0.70, with sensitivity and specificity of 0.79 and 0.64, respectively. Our study shows perfusion analysis from CTA images acquired at rest is useful for providing physiologic information in diagnosis of obstructive coronary artery stenoses.

Stress Myocardial Perfusion CT in Patients Suspected of Having Coronary Artery Disease: Visual and Quantitative Analysis-Validation by Using Fractional Flow Reserve.

To assess the diagnostic accuracy of stress myocardial perfusion computed tomography (CT) by using visual and quantitative analytic methods in patients with coronary artery disease, with fractional flow reserve (FFR) as a reference standard. The institutional review board approved the study, and written informed consent was obtained from all patients. The diagnostic accuracy of myocardial perfusion CT was assessed for 75 patients who underwent myocardial perfusion CT and conventional coronary angiography with reference to hemodynamically significant stenosis, defined as the presence of an FFR of 0.8 or less or an angiographically severe (≥90%) stenosis. Results of quantitative analysis of myocardial perfusion CT data were compared with those of visual analysis by using areas under the receiver operating characteristic curve (AUCs). Among the 75 patients and 210 epicardial arteries, 61 patients (81%) with 86 arteries (41%) had hemodynamically significant stenosis. The per-patient sensitivity and specificity of the visual assessment of myocardial perfusion CT data for all patients were 89% and 86%, respectively. At per-vessel analysis, the sensitivities and specificities, respectively, of myocardial perfusion CT were 80% and 95% for all vessels, 85% and 100% for 63 vessels with severe coronary calcification (defined as an Agatston score > 400), and 76% and 91% for 56 vessels in patients with multivessel disease. In severely calcified vessels, visual assessment of myocardial perfusion CT data in combination with CT angiography provided incremental value over CT angiography alone for the detection of myocardial ischemia (integrated discrimination improvement index, 0.38; P < .001). Quantitative assessment of transmural perfusion ratio had a lower AUC than visual analysis of myocardial perfusion CT (0.759 vs 0.877, P = .002). Stress myocardial perfusion CT provides incremental value over CT angiography in patients with a high calcium score for the detection of myocardial ischemia as defined by FFR.

Transmural myocardial perfusion gradients in relation to coronary artery stenoses severity assessed by cardiac multidetector computed tomography.

To assess the relationship between epicardial coronary artery stenosis severity and the corresponding regional transmural perfusion at rest and during adenosine stress, using multidetector computed tomography (MDCT). We evaluated the relationship between the severity of coronary artery diameter stenosis assessed by MDCT angiography and semi-quantitative myocardial MDCT perfusion in 200 symptomatic patients. The perfusion index (PI=mean myocardial attenuation density/mean left ventricular lumen attenuation density) at rest and during adenosine stress, the myocardial perfusion reserve (MPR=stress-PI/rest-PI), and the transmural perfusion ratio (TPR=subendocardium/subepicardium) were calculated. A coronary artery stenosis ≥50% was present in 49 patients (25%). Rest-PI and rest-TPR values were similar in patients with and without a coronary artery stenosis ≥50%, whereas stress-PI, stress-TPR and MPR were significantly reduced in patients with a stenosis ≥50% (p<0.001, p<0.0001 and p=0.02, respectively). Subendocardial PI was significantly higher than subepicardial PI at rest and during stress for patients without a significant stenosis, whereas this difference was blurred during stress in patients with ≥50% stenosis. In a broad spectrum of stenosis severity groups, TPR at rest remained unchanged until the group of patients with total occlusions, whereas TPR during stress decreased progressively when a threshold of 50% was superseded. In this study we establish the relationship between semi-quantitative perfusion measurements by MDCT and severity of coronary artery stenoses and find the transmural myocardial perfusion ratio to be a potential strong functional index of the hemodynamic significance of coronary artery atherosclerotic lesions.