Myocardial Perfusion Territories Research Articles

Personalized coronary blood flow model based on CT perfusion to non-invasively calculate fractional flow reserve

Coronary outlet resistance, influenced by quantification and distribution of total hyperemic coronary blood flow, is critical for accurately estimating the computation of fractional flow reserve from computed tomography angiography (FFRCT). However, accurate estimation of FFRCT is still a challenging task due to the impractical of non-invasively measuring coronary outlet resistance in the clinic. While traditional methods have been used to estimate outlet resistance through population-averaged physiological assumption models, individual differences between patients limit the reliability of the models. In this work, we propose a personalized coronary flow model based on dynamic stress computed tomographic perfusion (CTP), called CTPV, to achieve a noninvasive estimation of the outlet resistance and FFRCT. The CTPV model employs myocardial blood flow (MBF) obtained from CTP to quantify the total hyperemic coronary blood flow directly. Then, myocardial perfusion territories corresponding to coronary artery branches are proposed to distribute the outlet coronary blood flow. For this purpose, we use the Voronoi algorithm to segment the myocardial perfusion territory. Finally, the outlet resistance and FFRCT are estimated based on the outlet coronary blood flow. Experiment studies on a clinical dataset consisting of 138 vessels from 86 subjects show the superiority of our CTPV model against the CTPD and LVMD models, including the method of quantifying total hyperemic coronary blood flow based on left ventricular myocardial mass (LVM) and distributing the outlet coronary blood flow based on outlet diameter. The CTPV model estimates a higher AUC for FFRCT (AUC = 0.96) than the CTPD model (AUC = 0.93) and the LVMD model (AUC = 0.92). The accuracies of CTPV, CTPD, and LVMD models are 90.6%, 87.7%, and 84.1%, respectively. Additionally, we use different outlet truncation locations to evaluate the repeatability of the CTPV and CTPD models for estimating FFRCT on a random dataset of 10 vessels. The result shows that the repeatability of the CTPV model is better than the CTPD model. These compelling results evince that the proposed CTPV model can accurately estimate the coronary outlet resistance and improve the diagnostic performance and repeatability of FFRCT.

Abstract 13573: Prediction of Culprit Lesions in Acute Coronary Syndrome Based Upon Myocardial Mass At-Risk From Coronary CT Angiography

Introduction: Stratifying patients with coronary artery disease (CAD) remains challenging. Assessing CAD using myocardial mass at-risk may help identify patients at higher risk of acute coronary syndrome. Hypothesis: This study investigated whether quantitative myocardial mass at-risk (MMAR) can improve prognostication of future culprit coronary lesions at the time of acute coronary syndrome (ACS) events. Methods: From the multicenter, international ICONIC study, 49 patients suspected of coronary artery disease (CAD) going coronary CT angiography imaging (CCTA) were followed to the occurrence of the first ACS. At the time of ACS, culprit lesion was adjudicated by invasive coronary angiography by a group of cardiologists blinded to the previously acquired CCTA. MMAR was calculated for each lesion using the minimum-cost path technique, a previously validated method for calculating myocardial perfusion territories. Left ventricle myocardial segmentation and coronary centerline extraction was performed and used to calculate MMAR distal to all identifiable culprit and non-culprit coronary lesions. Results: In the study sample, 243 coronary lesions were identified on CCTA (194 non-culprit lesions; 49 culprit lesions). The mean MMAR, as a percentage of total left ventricle myocardial mass, for all lesions was 24.6±12.4%. The mean MMAR was 23.1±12.5% and 30.3±10.3% for non-culprit and culprit lesions, respectively (p<0.05). Receiver operating characteristic curve analysis was performed to determine the value of MMAR in predicting a culprit lesion, with an area-under-the-curve analysis for MMAR predicting a culprit lesion of 0.68. Conclusions: MMAR is larger for lesions that will versus will not become culprit at the time of future ACS. The addition of MMAR in the assessment of CAD on CCTA may help stratify the risk of individual coronary lesions.

Coronary CT angiography-based estimation of myocardial perfusion territories for coronary artery FFR and wall shear stress simulation

This study aims to apply a CCTA-derived territory-based patient-specific estimation of boundary conditions for coronary artery fractional flow reserve (FFR) and wall shear stress (WSS) simulation. The non-invasive simulation can help diagnose the significance of coronary stenosis and the likelihood of myocardial ischemia. FFR is often regarded as the gold standard to evaluate the functional significance of stenosis in coronary arteries. In another aspect, proximal wall shear stress (mathrm{{WSS}_{prox}}) can also be an indicator of plaque vulnerability. During the simulation process, the mass flow rate of the blood in coronary arteries is one of the most important boundary conditions. This study utilized the myocardium territory to estimate and allocate the mass flow rate. 20 patients are included in this study. From the knowledge of anatomical information of coronary arteries and the myocardium, the territory-based FFR and the mathrm{{WSS}_{prox}} can both be derived from fluid dynamics simulations. Applying the threshold of distinguishing between significant and non-significant stenosis, the territory-based method can reach the accuracy, sensitivity, and specificity of 0.88, 0.90, and 0.80, respectively. For significantly stenotic cases (mathrm{FFR}_{m}le 0.80), the vessels usually have higher wall shear stress in the proximal region of the lesion.

T2-based area-at-risk and edema are influenced by ischemic duration in acute myocardial infarction

The purpose of our study was to assess whether T2 MRI identifies the infarcted myocardium or the true area-at-risk (AAR) and whether edema is present in the salvageable region following acute myocardial infarction (MI). The study involved a porcine model of MI with a coronary occlusion model of either 60 min or 90 min. Imaging was performed on a 3T MRI pre-occlusion and at day 3 post-MI. Prior-MI, myocardial perfusion territory (MPT) maps were obtained under MRI via direct intracoronary injection of contrast agent. Post-MI, edema extent was quantified by T2 mapping while infarction and microvascular obstruction (MVO) were assessed by late gadolinium enhancement (LGE). Anatomically registered short-axis slices were analyzed for MPT, T2-AAR and infarct areas and T2 relaxation values. Animals were divided into groups with (MVO+) and without MVO (MVO-). T2-AAR area was significantly greater than infarct area in both groups. In the MVO+ group, T2-AAR and MPT were comparable and highly correlated, whereas, in the MVO- group, T2-AAR significantly underestimated MPT without any trend. T2 values in the salvageable myocardium were found to be significantly higher than those in remote myocardium. Our methodology offers the advantage that all images are acquired within the same MRI reference as opposed to complex co-registration with gross pathology. Our study suggests that edema may expand beyond the infarct zone over the entire ischemic bed. T2-AAR may be more clinically relevant than true AAR by perfusion territory since it identifies the “salvageable” myocardium.

3D Printed Heart Models Illustrating Myocardial Perfusion Territories to Augment Echocardiography and Electrocardiography Interpretation

Visualizing the vascular territories of coronary arteries during echocardiography or electrocardiography (ECG) requires trainees to mentally relate and overlay 2D sonographic images or cardiac lead projections with 3D anatomical representations of the ventricular walls and their respective blood supply. To facilitate the acquisition of these competencies, this study focuses on the feasibility of developing low-cost, open-sourced 3D printed heart models with standard ultrasound views or ECG lead projections illustrating the myocardial perfusion territories. A 3D digital heart model was cut to reflect the typical cardiac ultrasound views. The 4-chamber view model was further punctured for the paths of the precordial and limb leads of an ECG. Painting coronary arteries on the surface and internal views of the 3D prints illustrated vessel territories. Students, residents, and staff were surveyed during bedside ultrasound simulation sessions and ECG teaching half-days. Results demonstrated clear appreciation of 3D printed models, which suggests such models can easily be implemented by other institutions to augment trainees' experience during skill acquisition.

Myocardial stunning-induced left ventricular dyssynchrony on gated single-photon emission computed tomography myocardial perfusion imaging.

Myocardial stunning provides additional nonperfusion markers of coronary artery disease (CAD), especially for severe multivessel CAD. The purpose of this study is to assess the influence of myocardial stunning to the changes of left ventricular mechanical dyssynchrony (LVMD) parameters between stress and rest gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). A total of 113 consecutive patients (88 males and 25 females) who had undergone both stress and rest Tc-sestamibi gated SPECT MPI were retrospectively enrolled. Suspected or known patients with CAD were included if they had exercise stress MPI and moderate to severe myocardial ischemia. Segmental scores were summed for the three main coronary arteries according to standard myocardial perfusion territories, and then regional perfusion, wall motion, and wall thickening scores were measured. Myocardial stunning was defined as both ischemia and wall dysfunction within the same coronary artery territory. Patients were divided into the stunning group (n=58) and nonstunning group (n=55). There was no significant difference of LVMD parameters between stress and rest in the nonstunning group. In the stunning group, phase SD and phase histogram bandwidth of contraction were significantly larger during stress than during rest (15.05±10.70 vs. 13.23±9.01 and 46.07±34.29 vs. 41.02±32.16, P<0.05). Phase SD and phase histogram bandwidth of relaxation were also significantly larger during stress than during rest (21.21±13.91 vs. 17.46±10.52 and 59.03±37.82 vs. 52.38±36.89, P<0.05). Both systolic and diastolic LVMD parameters deteriorate with myocardial stunning. This kind of change may have incremental values to diagnose CAD.

Comparative Effectiveness of CT-Derived Atherosclerotic Plaque Metrics for Predicting Myocardial Ischemia

ObjectivesThis study sought to investigate the performance of various cardiac computed tomography (CT)–derived atherosclerotic plaque metrics for predicting provocable myocardial ischemia. BackgroundThe association of coronary arterial diameter stenosis with myocardial ischemia is only modest, but cardiac CT provides several other, readily available atherosclerosis metrics, which may have incremental value. MethodsThe study analyzed 873 nonstented coronary arteries and their myocardial perfusion territories in 356 patients (mean 62 years of age) enrolled in the CORE320 (Coronary Artery Evaluation using 320-row Multidetector Computed Tomography Angiography and Myocardial Perfusion) study. Myocardial perfusion defects in static CT perfusion imaging were graded at rest and after adenosine in 13 myocardial segments using a 4-point scale. The summed difference score was calculated by subtracting the summed rest score from the summed stress score. Reversible ischemia was defined as summed difference score ≥1. In a sensitivity analysis, results were also provided using single-photon emission computed tomography (SPECT) as the reference standard. Vessel based predictor variables included maximum percent diameter stenosis, lesion length, coronary calcium score, maximum cross-sectional calcium arc, percent atheroma volume (PAV), low-attenuation atheroma volume, positive (external) vascular remodeling, and subjective impression of “vulnerable plaque.” The study used logistic regression models to assess the association of plaque metrics with myocardial ischemia. ResultsIn univariate analysis, all plaque metrics were associated with reversible ischemia. In the adjusted logistic model, only maximum percent diameter stenosis (1.26; 95% confidence interval: 1.15 to 1.38) remained an independent predictor. With SPECT as outcome variable, PAV and “vulnerable” plaque remained predictive after adjustment. In vessels with intermediate stenosis (40% to 70%), no single metric had clinically meaningful incremental value. ConclusionsVarious plaque metrics obtained by cardiac CT predict provocable myocardial ischemia by CT perfusion imaging through their association with maximum percent stenosis, while none had significant incremental value. With SPECT as reference standard, PAV and “vulnerable plaque” remained predictors of ischemia after adjustment but the predictive value added to stenosis assessment alone was small.

Assessment of segmental myocardial blood flow and myocardial perfusion reserve by adenosine-stress myocardial arterial spin labeling perfusion imaging.

To determine the feasibility of measuring increases in myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) on a per-segment basis using arterial spin labeled (ASL) magnetic resonance imaging (MRI) with adenosine vasodilator stress in normal human myocardium. Myocardial ASL scans at rest and during adenosine infusion were incorporated into a routine 3T MR adenosine-induced vasodilator stress protocol and were performed in 10 healthy human volunteers. Myocardial ASL was performed using single-gated flow-sensitive alternating inversion recovery (FAIR) tagging and balanced steady-state free precession (bSSFP) imaging at 3T. A T2 -prep blood oxygen level-dependent (BOLD) SSFP sequence was used to concurrently assess segmental myocardial oxygenation with BOLD signal intensity (SI) percent change in the same subjects. There was a statistically significant difference between MBF measured by ASL at rest (1.75 ± 0.86 ml/g/min) compared to adenosine stress (4.58 ± 2.14 ml/g/min) for all wall segments (P < 0.0001), yielding a per-segment MPR of 3.02 ± 1.51. When wall segments were divided into specific segmental myocardial perfusion territories (ie, anteroseptal, anterior, anterolateral, inferolateral, inferior, and inferoseptal), the differences between rest and stress regional MBF for each territory remained consistently statistically significant (P < 0.001) after correcting for multiple comparisons. This study demonstrates the feasibility of measuring MBF and MPR on a segmental basis by single-gated cardiac ASL in normal volunteers. Second, this study demonstrates the feasibility of performing the ASL sequence and T2 -prepared SSFP BOLD imaging during a single adenosine infusion. 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:413-420.

Successful transcatheter closure of coronary artery fistula in a child with single coronary artery: A heavy load and a long road

Single coronary artery is an uncommon variation of the coronary circulation. After transposition of great arteries, coronary artery fistulas are the most common associated cardiac anomalies in these patients. Transcatheter closure of coronary artery fistula (CAF) involving single coronary artery is a challenging intervention. In the absence of contralateral coronary artery, a complex anatomy of the CAF and a large myocardial perfusion territory of the dominant circulation pose an additional risk during interventional procedure. We report our experience of a successful transcatheter closure of a coronary artery fistula in a patient with single coronary artery.

The effect of distal coronary embolization on infarct size in a porcine acute myocardial infarction model

Background Reperfusion no-reflow (R-NR), characterized by TIMI 0/1 flow grade, is a phenomenon that occurs in up to 20% of percutaneous coronary intervention cases for acute myocardial infarction (AMI). R-NR involves reduced myocardial tissue perfusion in the presence of a reperfused and patent epicardial coronary artery. This phenomenon is associated with worse patient outcome and increased mortality. Potential contributing factors of R-NR include the initial ischemic insult, injury as a result of reperfusion, and possibly distal coronary embolization (DCE) of thrombotic material. The objective of this study was to develop a novel large animal model to investigate the effects of DCE in the setting of ischemia-reperfusion using microthrombi derived from autologous porcine blood. Methods 3.0 T CMR was performed on 25-30kg female Yorkshire pigs to determine baseline values of cardiac function, as well as the myocardial perfusion territory at risk using direct intracoronary injection of dilute GadoliniumDTPA. Pigs were then subjected to balloon occlusion mediated myocardial ischemia distal to the second diagonal branch of the left anterior descending coronary artery (LAD) for 60 minutes. Following reperfusion, intracoronary injection of sterile saline (n=4) or microthrombi particles to simulate DCE (n=7) was performed. Epicardial coronary blood flow was assessed at each stage using x-ray angiography. At 72 hours following ischemia-reperfusion, CMR was used to assess changes in cardiac function, extent of edema/hemorrhage using T2/T2* relaxation times, evaluate infarct size, and to determine the presence/absence of microvascular obstruction (MVO). Myocardial tissue samples were subsequently collected for biochemical and histological analysis.

288 Development of a Porcine No-Reflow Model to Investigate The Impact of Distal Coronary Embolization in Acute Myocardial Infarction

288 Development of a Porcine No-Reflow Model to Investigate The Impact of Distal Coronary Embolization in Acute Myocardial Infarction

Aligning Coronary Anatomy and Myocardial Perfusion Territories

Background— Appropriate clinical decisions concerning diagnosis and treatment of coronary artery disease rely on correct integration of data on coronary anatomy and myocardial perfusion. The purpose of this article is to introduce a new left ventricular segmentation model for improved alignment of coronary arterial segments and myocardial perfusion territories, designed for the CORE320 study. Methods and Results— CORE320 is a prospective, multicenter study with a primary objective to evaluate the diagnostic accuracy of 320-row detector computed tomography (CT) to detect coronary artery luminal stenosis and corresponding myocardial perfusion deficits in patients with suspected coronary artery disease compared with the gold standard of conventional coronary angiography and single-photon emission CT myocardial perfusion imaging. We describe a 19-coronary segment and 13-myocardial territory alignment model, its application in both standard and CT image data sets, and the adjudication process of the initial cohort of patients recruited for the CORE320 study. Adjudication committees reviewed the images of the first 101 gold standard and 107 CT data sets. On the basis of the presented model and rules, all cases for adjudication were correctly identified. During image review, 6 (5.9%) gold standard and 9 (8.4%) CT data sets needed further realignment not triggered by the algorithm. Conclusions— We present a vascular territory distribution model developed for the CORE320 multicenter study, which accounts for variability in coronary anatomy and potential myocardial perfusion territory overlap. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00934037.

C-Reactive Protein

See related article, pp 208–215 In response to inflammatory stress, C-reactive protein (CRP) is predominantly secreted from the liver and adipose tissue(s), and an independent relationship exists between different markers of overweight/obesity and elevated high sensitive (hs) CRP levels (Figure). Figure. CRP is predominantly secreted from the liver and adipose tissue(s) in response to inflammatory stress resulting from plaque rupture and subsequent microembolization. High levels of CRP induce endothelial dysfunction, activate platelets, and aggravate stress-induced alterations in cardiac function and morphology (ie, cardiomyocyte apoptosis and hypertrophy, fibrosis, and LV dilatation). NFkB indicates nuclear factor κB; iNOS, inducible nitric oxide synthase; LV, left ventricle; IL-6, interleukin 6. Higher hsCRP levels predict incident myocardial infarction (MI), stroke, peripheral arterial disease, sudden cardiac death, and all-cause mortality in healthy individuals with no history of cardiovascular disease.1,2 hsCRP at admission predicts in-hospital outcome, and hsCRP at discharge predicts 6-month event rate and 30-day mortality (Global Utilization of Strategies To Open occluded arteries [GUSTO] IV) in patients with an acute coronary syndrome. Indeed, adding hsCRP levels to the Global Registry in Acute Coronary Events (GRACE) acute coronary syndrome risk model improves the prediction of 30-day mortality. In patients with non-ST-elevated MI, an increased hsCRP level predicts the death rate even at 20-month follow-up but does not predict stent-related complications. The question of whether CRP, apart from serving …

Reduction in Myocardial Perfusion Territory and its Effect on the Physiological Severity of a Coronary Stenosis

Received August 22, 2009; accepted December 3, 2009. A man aged 56 years presented with worsening exertional angina. Coronary angiography showed a moderate-to-severe stenosis in the midleft anterior descending artery (LAD) [Figure 1a]. The right coronary artery (RCA) was chronically occluded (Figure 1b). A coronary pressure wire assessment of the mid-LAD lesion yielded a fractional flow reserve (FFR) of 0.72, indicating this to be functionally significant (Figure 2a). The patient did not wish to have cardiac surgery, and thus, a percutaneous revascularization strategy was proposed. The RCA was successfully revascularized with 2 drug-eluting stents (Figure 1e). Repeat coronary pressure assessment of the mid-LAD lesion yielded an FFR of 0.84, indicating this to be no longer functionally significant (Figure 2b). Given this result, we decided not to proceed with …

Drug-eluting stenting of saphenous vein graft vs. native coronary artery of the same myocardial perfusion territory: a retrospective 12-month follow-up

Drug-eluting stenting of saphenous vein graft vs. native coronary artery of the same myocardial perfusion territory: a retrospective 12-month follow-up

Novel revascularization therapies--TMLR and growth factor-induced angiogenesis monitored with cardiac MRI.

Employment of cardiac MRI techniques (cine MRI, wall thickening analysis, quantitative MRFPP, MR tissue tagging) allowed non-invasive localization and assessment of early and late changes in myocardial function and perfusion produced by these new approaches of myocardial revascularization. With its precision in assessment of myocardial perfusion and collateral-dependent territories, cardiac MRI techniques may be of excellent use for the evaluation of effects on myocardial function and perfusion as well as longitudinal outcomes in clinical trials with TMLR and angiogenesis therapies in patients with CAD. As growth factor therapies approach phase III clinical trials, such vital questions as the most effective delivery system, dosages and techniques used for treatment-monitoring parameters remain unanswered. In addition, better definitions of patient selection criteria for TMLR and angiogenesis therapies for both short- and long-term maximum benefits are needed at this time. Large-scale clinical trials with cardiac MRI techniques are needed to reliably assess functional and perfusion reserves of the myocardium pre and post TMLR and angiogenesis therapies. MR-based outcome parameters may aid in answering questions pertinent to the new revascularization treatments.

703-6 Three-dimensional Echocardiographic Delineation of Myocardial Perfusion Territories: Description of a New 3-D Image Processing Approach with a New Ultrasound Contrast Agent

Previous work dealing with contrast echo evaluation of myocardial perfusion has relied only on 2-D echo images, which do not provide a comprehensive description of perfusion territories of the whole LV. Since every facet of LV perfusion is multidimensional, 3-dimensional assessment of perfusion territories would be more relevant clinically. 2 problems have hampered advances in this area: (1) Lack of image processing algorithms that can automatically segment out regions of contrast enhancement in volume-rendered 3DE, and (2) Lack of a stable contrast agent that would show persistent opacification allowing for acquisition of multiple 2DE slices required for 3DE. In this study we explored the feasibility of defining perfusion territories using newly developed 3DE segmentation and extraction software and a newer stable contrast agent FS069. In 8 anesthetized dogs, using a computer-driven motor, we obtained parallel (1 mm intervals) short-axis images of the heart, in base-line, and with a small dose of the contrast agent FS069 (MBI) injected in the aortic root. This process was repeated with administration of FS069 after occlusion and release of various coronary arterial branches. 3DE was performed from all collected data. Contrast enhancements and perfusion defects persisted long enough for 3DE data acquisition (average 2 min). FS069 demonstrated excellent contrast enhancement of the LV myocardium not only in 2DE but also in digitally reformatted 3DE data matrix. Contrast defects during coronary occlusion were crisply defined as well. In all the 3DE studies, recently developed image processing algorithms allowed extraction of myocardium alone and exclusion of contrast in the cavity. In addition, use of various thresholding and opacification schema permitted discrimination of perfused and non-perfused territories. When viewed against the baseline 3DE, hypoperfused regions appeared as gaps of missing myocardial regions. The hypoperfused regions could be extracted discretely and visualized separately in 3D (with retained gray scale data) in dynamic forms from different orientations. We conclude that the advanced 3DE image processing approach and the new generation contrast agent FS069 allow three-dimensional appraisal of myocardial perfusion territories.

Relationship of coronary flow and perfusion territory in dogs.

In this study the relationship between myocardial flow and perfusion territory at maximal vasodilation was examined for the left anterior descending (A), circumflex (C), right (R), and septal (S) coronary arteries. Average flows to A, C, R, and S were 31.2 +/- 1.5 (SE), 41.2 +/- 13.5 +/- 0.6, and 14.1 +/- 0.6% of total coronary flow. Strong correlations were found between weight and volume, weight and coronary flow, and weight and resistance of the perfusion territories of A, C, R, and S. However, coronary flow (milliliter per minute per gram) to the right ventricle was significantly lower than to the left ventricle. Examination of the distribution of perfusion territories from base to apex of the heart showed that the anterior descending territory increases from base to apex, whereas the right decreases from base to apex. Circumflex flow distribution is relatively uniform between these limits, and the septal artery is most pronounced at midlevel and tapers toward the apex and base.