Cardiac Magnetic Resonance Myocardial Perfusion Research Articles

Myocardial perfusion impairment in children with Kawasaki disease: assessment with cardiac magnetic resonance first-pass perfusion.

Kawasaki disease (KD) potentially increases the risk of myocardial ischemia. This study aimed to semi-quantitatively evaluate myocardial perfusion impairment using cardiac magnetic resonance (CMR) first-pass perfusion in children with KD and explore the association between coronary artery (CA) dilation and myocardial perfusion. From December 2018 to July 2021, 77 patients with KD (48 male, 5.71±2.80 years) and 37 age- and sex-matched normal controls (20 male, 6.19±3.32 years) who underwent CMR in West China Second University Hospital were enrolled in this cross-sectional study with prospective data collection. A total of 30 of these patients completed the follow-up CMR, with a median interval of 13 months. Myocardial perfusion parameters including perfusion index (PI) and maximum signal intensity (Max SI) were obtained through rest first-pass perfusion. The internal diameter of the CA was assessed via coronary magnetic resonance angiography (CMRA) to calculate the coronary Z score. The global and regional myocardial parameters among the subgroups were compared. Statistical analysis included one-way analysis of variance (ANOVA), Pearson's correlation, and multivariate linear regression. The global Max SI and regional Max SI of all segments in patients with and without CA dilation decreased compared with those in controls (P=0.19 and P<0.001, respectively). The global PI of patients with CA dilation and regional PI in segments subtended by dilated CA were lower than that of controls (P=0.002 and P<0.001, respectively) and were negatively correlated with the Z score (global: r=-0.576; regional: r=-0.351, both P<0.001). Multivariate analysis revealed that the Z score was negatively associated with global PI in KD (β=-0.409, P=0.02, model R2=0.170). The global Max SI of patients with and without CA dilation during the follow-up CMR decreased compared with that of the first CMR (42.18±9.84 vs. 34.48±8.24, P=0.02; 44.82±7.13 vs. 36.61±7.67, P=0.03, respectively). CMR myocardial first-pass perfusion imaging can semi-quantitatively evaluate impaired myocardial perfusion in KD patients. Not only patients with CA dilation and segments subtended by dilated CA but also those without CA dilation and segments subtended by non-dilated CA developed myocardial perfusion impairment, the severity of myocardial perfusion impairment is associated with the degree of CA dilation.

Comparison of dual-bolus versus dual-sequence techniques for determining myocardial blood flow and myocardial perfusion reserve by cardiac magnetic resonance stress perfusion: From the Automated Quantitative analysis of myocardial perfusion cardiac Magnetic Resonance Consortium

BackgroundQuantitative stress cardiac magnetic resonance (CMR) can be performed using the dual sequence (DS) technique or dual bolus (DB) method. It is unknown if DS and DB produce similar results for myocardial blood flow (MBF) and myocardial perfusion reserve (MPR). The study objective is to investigate if there are any differences between DB and DS derived MBF and MPR. MethodsRetrospective observational study with 168 patients underwent stress CMR. Dual bolus and dual sequence methods were simultaneously performed on each patient on the same day. Global and segmental stress MBF and rest MBF values were collected. ResultsUsing Bland-Altman analysis, segmental and global stress MBF values were higher in DB than DS (0.22 + 0.60ml/g/min, p<0.001 and 0.20 + 0.48ml/g/min, p=0.005 respectively) with strong correlation (r = 0.81, p < 0.001 for segmental and r = 0.82, p < 0.001 for global). In rest MBF, segmental and global DB values were higher than by DS (0.15 + 0.51ml/g/min, p<0.001 and 0.14 + 0.36ml/g/min, p=0.011 respectively) with strong correlation (r = 0.81, p < 0.001 and r = 0.77, p < 0.001). Mean difference between MPR by DB and DS was -0.02 + 0.68ml/g/min (p=0.758) for segmental values and -0.01 + 0.49ml/g/min (p=0.773) for global values. MPR values correlated strongly as well in both segmental and global, both (r = 0.74, p < 0.001) and (r = 0.75, p < 0.001) respectively. ConclusionsThere is very good correlation between DB and DS derived MBF and MPR values. However, there are significant differences between DB and DS derived global stress and rest MBF. Whilst MPR values did not show statistically significant differences between DB and DS methods.

Automated quantitative myocardial perfusion cardiac magnetic resonance with artificial intelligence-based arterial input function correction versus fractional flow reserve

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Wellcome Trust. Background Quantitative myocardial perfusion cardiac magnetic resonance (QP-CMR) is gaining importance in clinical practice due to the increasing availability of automated processing software. However, a significant obstacle in the widespread deployment of QP-CMR is the accurate estimation of the arterial input function (AIF), as this is precluded by the non-linear relationship between observed MR signal and the concentration of contrast agent. Modern solutions favour a dual-saturation acquisition sequence, acquiring specific low-resolution images with a short saturation time to minimise the signal saturation of the AIF. However, this approach is limited by the availability of the pulse sequence. Recently, the AI-AIF has been proposed (1), which uses an artificial intelligence (AI)-based correction of the AIF, without the need for a dual-sequence or dual-bolus acquisition. Purpose In this work, we compare QP-CMR values, quantified with the AI-AIF versus the invasive reference standard: fractional flow reserve (FFR), to identify diagnostically significant coronary artery disease (CAD), as defined by FFR &amp;lt; 0.80. Methods This study enrolled 18 patients (mean age 65 (± 11), 8 female) who underwent stress perfusion CMR (Philips Achieva 3T) and invasive FFR assessment of at least one coronary artery. Perfusion was quantified in a fully-automated manner with motion compensation (2) and AI-based segmentation and processing (3), using a Fermi function-constrained deconvolution. Fully automated pixelwise perfusion maps were generated, and further subdivided into 16 myocardial segments. Segments were assigned to their respective perfusion territory (4) and the QP value for a territory is given as the mean of its two lowest segments. Receiver operating characteristic (ROC) analysis was performed to identify cut-off thresholds and report the diagnostic accuracy of the proposed approach. Results The overall mean QP-CMR value was 2.29 ml/min/g (± 0.32). Figure 1 shows QP maps and FFR values for 3 example patients. The mean QP-CMR value was 2.09 ml/min/g (± 0.36) in patients with significant CAD and 2.95 ml/min/g (± 0.48) in patients without significant CAD. In total, 28 vessels underwent FFR assessment with 12 vessels in 10 patients being positive for significant CAD (FFR &amp;lt; 0.80). The mean QP-CMR value in FFR-positive coronary territories was 1.76 ml/min/g (± 0.37). The ROC curves are shown in Figure 2 on a per-vessel (left) and per-patient (right) level. The optimal QP threshold on a per-vessel level is 2.11 ml/min/g and on a per-patient level is 1.96 ml/min/g. Conclusion QP-CMR is feasible with the AI-AIF and does not require dual-sequence acquisition or a dual contrast injection. The QP values derived after the AI-based correction of the AIF show good agreement with FFR assessment of epicardial coronary disease. However, due to the limited sample size, further work is required to confirm these findings.

Cardiac fibroblast activation after acute myocardial infarction: pilot study using technetium 99m-iFAP SPECT

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Instituto Nacional de Investigaciones Nucleares (ININ). Background/Introduction Excessive fibrosis and persistent active fibroblasts can lead to increased left ventricular stiffness and, thus, heart failure. Cardiac remodeling is an important factor in the prognosis of patients after an acute myocardial infarction (AMI), and fibroblast activation is mandatory for repair and regeneration of the damage. There's an increasing use of molecular imaging in cardiovascular processes, such as molecules targeting fibroblast activation protein (FAP). FAP inhibitors (iFAP) radiolabeled with 68Ga in PET/CT have demonstrated adequate biodistribution and high uptake by activated fibroblasts in patients with cardiovascular risk factors and after acute myocardial infarction. Unfortunately, PET is not always widely available or cost-effective. Purpose This pilot study evaluates the feasibility of imaging activated fibroblast using 99mTc-iFAP SPECT in patients after AMI and its correlation with myocardial perfusion imaging (MPI), cardiac magnetic resonance (CMR) and invasive coronary angiography (ICA). Methods A prospective study with recent first AMI and non-previous known coronary artery disease patients were included. They underwent 99mTc-MIBI MPI SPECT and 99mTc-iFAP SPECT (including whole-body scan and thorax anterior static image acquired at 20, 60, and 120 min for the iFAP) and CMR/ICA within 14 days (+-2) after AMI. Qualitative and quantitative analysis was performed using a 17 segments model using QPS (Cedars Sinai) to determine the infarct extension from MPI and the correlation with the 99mTc-iFAP uptake pattern. A visual grading scale was established to assess localized tracer uptake and segments belonging to the hypoperfused area of the culprit's vessel. CMR yielded an area of injury with late gadolinium enhancement (LGE) and correlated with MPI studies. Results Five patients with STEMI were included (mean age of 63). Localized uptake of 99mTc-iFAP was observed in all patients with according to the affected coronary territory detected by ICA in 100% of patients (four anterior STEMI, one inferior STEMI). No radiotracer uptake was observed in the non-infarcted territories. Agreement between myocardial iFAP uptake, MIBI myocardial perfusion defect, CMR LGE, and ICA findings are presented in figure 1. An agreement of mismatch in polar maps between iFAP and MPI was performed, obtaining an excellent mismatch pattern in all patients, especially in transmural infarct segments. The best quality image was obtained at 60 minutes. Conclusions We successfully carried out the first pilot study with the patented 99mTc-iFAP molecule with SPECT technique. 99mTc-iFAP is a promising novel biomarker in assessing myocardial injury in sites where PET/CT is unavailable. There is an excellent correlation between iFAP uptake with the perfusion defect, LGE, and invasive anatomical obstruction findings. It is feasible and necessary to extend the inclusion of patients to a larger sample.

Autoimmune rheumatic diseases in women with coronary microvascular dysfunction: a report from the Women's Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction (WISE-CVD) project.

While autoimmune rheumatic diseases (ARDs) have been linked with coronary microvascular dysfunction (CMD), the relationship between ARD and CMD in women with signs and symptoms of ischemia and no obstructive arteries (INOCA) are not well described. We hypothesized that among women with CMD, those with ARD history have greater angina, functional limitations, and myocardial perfusion compromise compared to those without ARD history. Women with INOCA and confirmed CMD by invasive coronary function testing were included from the Women's Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction (WISE-CVD) project (NCT00832702). Seattle Angina Questionnaire (SAQ), Duke Activity Status Index (DASI), and cardiac magnetic resonance myocardial perfusion reserve index (MPRI) were collected at baseline. Chart review was performed to confirm self-reported ARD diagnosis. Of the 207 women with CMD, 19 (9%) had a confirmed history of ARD. Compared to those without ARD, women with ARD were younger (p = 0.04). In addition, they had lower DASI-estimated metabolic equivalents (p = 0.03) and lower MPRI (p = 0.008) but similar SAQ scores. There was a trend towards increased nocturnal angina and stress-induced angina in those with ARD (p = 0.05 for both). Invasive coronary function variables were not significantly different between groups. Among women with CMD, women with a history of ARD had lower functional status and worse myocardial perfusion reserve compared to women without ARD. Angina-related health status and invasive coronary function were not significantly different between groups. Further studies are warranted to understand mechanisms contributing to CMD among women with ARDs with INOCA.

Value of myocardial deformation parameters for detecting significant coronary artery disease.

Introduction: The study aimed to evaluate the diagnostic value of global and regional myocardial deformation parameters derived from two-dimensional speckle-tracking echocardiography to detect functionally significant coronary artery stenosis. Methods: Dobutamine stress echocardiography and cardiac magnetic resonance myocardial perfusion imaging (CMR-MPI) were performed on 145 patients with a moderate and high probability of coronary artery disease (CAD) and LVEF≥55%. Significant CAD was defined as>50% stenosis of the left main stem,>70% stenosis in a major coronary vessel, or in the presence of intermediate stenosis (50-69%) validated as hemodynamically significant by CMRMPI. Patients were divided in two groups: non-pathological (48.3%) vs pathological (51.7%), according to CAG and CMR-MPI results. Afterwards, off-line speckle-tracking analysis was performed to analyse myocardial deformation parameters. Results: There were no differences in myocardial deformation parameters at rest between groups, except global longitudinal strain (GLS) and global radial strain (GRS) were significantly lower in the CAD (+) group: -21.3±2.2 vs.-16.3±2.3 (P<0.001) and 39.7±23.2 vs. 24.5±15.8 (P<0.001). GLS and regional longitudinal strain rate (SR) had the highest diagnostic value at high dobutamine dose with AUC of 0.902 and 0.878, respectively. At early recovery, GLS was also found to be the best myocardial deformation parameter with a sensitivity of 78%, specificity 67%, AUC 0.824. Conclusion: Global and regional myocardial deformation parameters are highly sensitive and specific in detecting functionally significant CAD. The combination of deformation parameters and WMA provides an incremental diagnostic value for patients with a moderate and high probability of CAD, especially the combination with regional longitudinal SR.

Splenic T1-Mapping for Predicting Adenosine Stress Adequacy in Cardiac Magnetic Resonance Myocardial Perfusion Imaging: A Validation and Reproducibility Study

Splenic T1-Mapping for Predicting Adenosine Stress Adequacy in Cardiac Magnetic Resonance Myocardial Perfusion Imaging: A Validation and Reproducibility Study

Automated Quantitative Stress Perfusion Cardiac Magnetic Resonance in Pediatric Patients.

Background: Myocardial ischemia occurs in pediatrics, as a result of both congenital and acquired heart diseases, and can lead to further adverse cardiac events if untreated. The aim of this work is to assess the feasibility of fully automated, high resolution, quantitative stress myocardial perfusion cardiac magnetic resonance (CMR) in a cohort of pediatric patients and to evaluate its agreement with the coronary anatomical status of the patients.Methods: Fourteen pediatric patients, with 16 scans, who underwent dual-bolus stress perfusion CMR were retrospectively analyzed. All patients also had anatomical coronary assessment with either CMR, CT, or X-ray angiography. The perfusion CMR images were automatically processed and quantified using an analysis pipeline previously developed in adults.Results: Automated perfusion quantification was successful in 15/16 cases. The coronary perfusion territories supplied by vessels affected by a medium/large aneurysm or stenosis (according to the AHA guidelines), induced by Kawasaki disease, an anomalous origin, or interarterial course had significantly reduced myocardial blood flow (MBF) (median (interquartile range), 1.26 (1.05, 1.67) ml/min/g) as compared to territories supplied by unaffected coronaries [2.57 (2.02, 2.69) ml/min/g, p < 0.001] and territories supplied by vessels with a small aneurysm [2.52 (2.45, 2.83) ml/min/g, p = 0.002].Conclusion: Automatic CMR-derived MBF quantification is feasible in pediatric patients, and the technology could be potentially used for objective non-invasive assessment of ischemia in children with congenital and acquired heart diseases.

Commentary: Vasodilator Myocardial Perfusion Cardiac Magnetic Resonance Imaging Is Superior to Dobutamine Stress Echocardiography in the Detection of Relevant Coronary Artery Stenosis: A Systematic Review and Meta-Analysis on Their Diagnostic Accuracy.

Commentary: Vasodilator Myocardial Perfusion Cardiac Magnetic Resonance Imaging Is Superior to Dobutamine Stress Echocardiography in the Detection of Relevant Coronary Artery Stenosis: A Systematic Review and Meta-Analysis on Their Diagnostic Accuracy.

Advances in Myocardial Perfusion MR Imaging: Physiological Implications, the Importance of Quantitative Analysis, and Impact on Patient Care in Coronary Artery Disease.

Stress myocardial perfusion imaging (MPI) is the preferred test in patients with intermediate-to-high clinical likelihood of coronary artery disease (CAD) and can be used as a gatekeeper to avoid unnecessary revascularization. Cardiac magnetic resonance (CMR) has a number of favorable characteristics, including: (1) high spatial resolution that can delineate subendocardial ischemia; (2) comprehensive assessment of morphology, global and regional cardiac functions, tissue characterization, and coronary artery stenosis; and (3) no radiation exposure to patients. According to meta-analysis studies, the diagnostic accuracy of perfusion CMR is comparable to positron emission tomography (PET) and perfusion CT, and is better than single-photon emission CT (SPECT) when fractional flow reserve (FFR) is used as a reference standard. In addition, stress CMR has an excellent prognostic value. One meta-analysis study demonstrated the annual event rate of cardiovascular death or non-fatal myocardial infarction was 4.9% and 0.8%, respectively, in patients with positive and negative stress CMR. Quantitative assessment of perfusion CMR not only allows the objective evaluation of regional ischemia but also provides insights into the pathophysiology of microvascular disease and diffuse subclinical atherosclerosis. For accurate quantification of myocardial perfusion, saturation correction of arterial input function is important. There are two major approaches for saturation correction, one is a dual-bolus method and the other is a dual-sequence method. Absolute quantitative mapping with myocardial perfusion CMR has good accuracy in detecting coronary microvascular dysfunction. Flow measurement in the coronary sinus (CS) with phase contrast cine CMR is an alternative approach to quantify global coronary flow reserve (CFR). The measurement of global CFR by quantitative analysis of perfusion CMR or flow measurement in the CS permits assessment of microvascular disease and diffuse subclinical atherosclerosis, which may provide improved prediction of future event risk in patients with suspected or known CAD. Multi-institutional studies to validate the diagnostic and prognostic values of quantitative perfusion CMR approaches are required.

Direct Comparison of Bayesian and Fermi Deconvolution Approaches for Myocardial Blood Flow Quantification: In silico and Clinical Validations.

Cardiac magnetic resonance myocardial perfusion imaging can detect coronary artery disease and is an alternative to single-photon emission computed tomography or positron emission tomography. However, the complex, non-linear MR signal and the lack of robust quantification of myocardial blood flow have hindered its widespread clinical application thus far. Recently, a new Bayesian approach was developed for brain imaging and evaluation of perfusion indexes (Kudo et al., 2014). In addition to providing accurate perfusion measurements, this probabilistic approach appears more robust than previous approaches, particularly due to its insensitivity to bolus arrival delays. We assessed the performance of this approach against a well-known and commonly deployed model-independent method based on the Fermi function for cardiac magnetic resonance myocardial perfusion imaging. The methods were first evaluated for accuracy and precision using a digital phantom to test them against the ground truth; next, they were applied in a group of coronary artery disease patients. The Bayesian method can be considered an appropriate model-independent method with which to estimate myocardial blood flow and delays. The digital phantom comprised a set of synthetic time-concentration curve combinations generated with a 2-compartment exchange model and a realistic combination of perfusion indexes, arterial input dynamics, noise and delays collected from the clinical dataset. The myocardial blood flow values estimated with the two methods showed an excellent correlation coefficient (r2 > 0.9) under all noise and delay conditions. The Bayesian approach showed excellent robustness to bolus arrival delays, with a similar performance to Fermi modeling when delays were considered. Delays were better estimated with the Bayesian approach than with Fermi modeling. An in vivo analysis of coronary artery disease patients revealed that the Bayesian approach had an excellent ability to distinguish between abnormal and normal myocardium. The Bayesian approach was able to discriminate not only flows but also delays with increased sensitivity by offering a clearly enlarged range of distribution for the physiologic parameters.

Ischemia and Viability Testing in New-Onset Heart Failure.

To examine the utility and methods of coronary artery disease (CAD) assessment in patients with new-onset heart failure with reduced ejection fraction (HFrEF) of unclear etiology. Moreover, we sought to review the role and techniques of assessing myocardial viability to guide coronary revascularization in patients with established ischemic cardiomyopathy. Data indicates that surgical coronary revascularization in patients with HFrEF due to ischemic cardiomyopathy leads to lower long-term all-cause mortality and cardiovascular hospitalizations. Thus, identifying ischemic heart disease in patients with new-onset HFrEF is essential. In addition to invasive coronary angiography (ICA), radionuclide myocardial perfusion imaging, coronary CT angiography (CCTA), and cardiac magnetic resonance (CMR) imaging have emerged as effective non-invasive tools in the assessment of CAD in this population. Viability testing remains an area of particular interest and debate and its full potential has not been fully addressed. We propose stepwise algorithms for CAD and viability assessment in this patient population. Non-invasive testing with radionuclide myocardial perfusion imaging, CCTA, and CMR is an alternative to ICA for CAD assessment in patients with new-onset HFrEF of unclear etiology. Several non-invasive imaging modalities have proved to be effective in detecting viable myocardium in patients with ischemic cardiomyopathy. The use of viability imaging to guide coronary revascularization should be individualized.

Myocardial first pass perfusion assessed by cardiac magnetic resonance and coronary microvascular dysfunction in women with angina and no obstructive coronary artery disease

Coronary microvascular dysfunction (CMD) is associated with a poor prognosis even in absence of obstructive coronary artery disease. CMD can be assessed as a myocardial blood flow reserve by positron emission tomography (PETMBFR) and as coronary flow velocity reserve by transthoracic Doppler echocardiography (TTDECFVR). Impaired first-pass perfusion assessed by cardiac magnetic resonance (CMR) is an early sign of ischemia. We aimed to investigate the association between CMD and CMR first-pass perfusion. Women (n = 66) with angina pectoris and an invasive coronary angiogram (<50% stenosis) were assessed by TTDECFVR and in a subgroup of these (n = 54) also by PETMBFR. Semi-quantitative evaluation of first-pass perfusion at rest and adenosine stress was assessed by gadolinium CMR in all 66 women. Four measures of CMR perfusion reserve were calculated using contrast upslope, maximal signal intensity and both indexed to arterial input. Mean (standard deviation) age was 62 (8) years. Median (interquartile range) TTDECFVR was 2.3 (1.8;2.7) and PETMBFR was 2.7 (2.2;3.1). Using a cut-off of 2.0 for TTDECFVR and 2.5 for PETMBFR, 25 (38%) and 21 (39%) had CMD, respectively. CMR myocardial perfusion reserve from contrast upslope (CMR_MPRupslope) showed moderate but significant correlation with PETMBFR (R = .46, p < .001) while none of the other CMR variables were associated with CMD. A CMR_MPRupslope cut-off of 0.78 identified CMD, area under the curve 0.73 (p = .001). The results indicate that CMR_MPRupslope may be associated to PETMBFR; a measure of CMD. Further research is needed to validate and implement the use of CMR first pass perfusion in this population.

Contemporary Issues in Quantitative Myocardial Perfusion CMR Imaging

This review highlights the development and application of quantitative myocardial perfusion by cardiac magnetic resonance (CMR) and discusses recent innovations in this area. First pass, contrast-enhanced CMR can accurately quantify myocardial perfusion in order to diagnose obstructive coronary artery disease and microvascular dysfunction. Quantitative analysis conveys additional prognostic information beyond other CMR findings. New, fully automated techniques may aid standardization of methods across centers. CMR quantitative perfusion has robust performance for the diagnosis of obstructive coronary disease and microvascular dysfunction and conveys prognostic information. Adoption of automated post-processing and standardized protocols will further strengthen CMR in its position as the modality of choice for the evaluation of possible myocardial ischemia.

Cardiac magnetic resonance myocardial perfusion reserve index is reduced in women with coronary microvascular dysfunction. A National Heart, Lung, and Blood Institute-sponsored study from the Women's Ischemia Syndrome Evaluation.

Women with signs and symptoms of ischemia and no obstructive coronary artery disease often have coronary microvascular dysfunction (CMD), diagnosed by invasive coronary reactivity testing (CRT). Although traditional noninvasive stress imaging is often normal in CMD, cardiac MRI may be able to detect CMD in this population. Vasodilator stress cardiac MRI was performed in 118 women with suspected CMD who had undergone CRT and 21 asymptomatic reference subjects. Semi-quantitative evaluation of the first-pass perfusion images was completed to determine myocardial perfusion reserve index (MPRI). The relationship between CRT findings and MPRI was examined by Pearson correlations, logistic regression, and sensitivity/specificity. Symptomatic women had lower mean pharmacological stress MPRI compared with reference subjects (1.71±0.43 versus 2.23±0.37; P<0.0001). Lower MPRI was predictive of ≥1 abnormal CRT variables (odds ratio =0.78 [0.70, 0.88], P<0.0001, c-statistic 0.78 [0.68, 0.88]). An MPRI threshold of 1.84 predicted CRT abnormality with sensitivity 73% and specificity 74%. Noninvasive cardiac MRI MPRI can detect CMD defined by invasive CRT. Further work is aimed to optimize the noninvasive identification and management of CMD patients. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00832702.

Head-to-head comparison of myocardial perfusion SPECT and CMR for assessment of myocardial ischemia

Background Myocardial perfusion single photon emission computed tomography (MPS) and cardiac magnetic resonance (CMR) can be used for assessment of myocardial ischemia. The methods reveal different aspects of the pathophysiology associated with myocardial ischemia where MPS is based on uptake of a perfusion tracer in viable mitochondria whereas CMR is based on firstpass perfusion reflecting coronary in-flow kinetics. The aim of this study was to perform a head-to-head comparison between MPS and CMR for assessment of myocardial ischemia under identical perfusion conditions at stress.

The prominent role of cardiac magnetic resonance imaging in coronary artery disease

The role of cardiac magnetic resonance (CMR) in coronary artery disease is prominent. CMR provides functional and structural heart disease assessment with high accuracy. It allows accurate cardiac volume and flow quantification and wall motion analysis both at rest and at stress. CMR myocardial perfusion studies detect myocardial ischemia and provide insights into the morphology of the myocardial tissue. CMR imaging noninvasively differentiates causes of myocardial injury such as ischemia or inflammation; stages of myocardial injury, such as acute or chronic; grade of myocardial damage, such as reversible or irreversible; myocardial fibrosis or scar. There is an emerging role of CMR in patients with acute chest presentation since it can demonstrate causes of chest pain other than coronary artery disease such as myocarditis, pericarditis, aortic dissection and pulmonary embolism. CMR is noninvasive and radiation-free. It’s combined approach of functional and structural cardiac assessment makes it unique compared with other imaging modalities.

Cardiac MR Imaging to Measure Myocardial Blood Flow Response to the Cold Pressor Test in Healthy Smokers and Nonsmokers

To determine if myocardial perfusion cardiac magnetic resonance (MR) imaging can show changes in myocardial blood flow (MBF) during the cold pressor test (CPT) and can allow identification of the differing endothelial function of smokers and nonsmokers when compared during adenosine stress. The study was approved by the institutional ethics review board and all participants gave informed written consent. Twenty-nine healthy volunteers (19 nonsmokers, 10 smokers; mean age ± standard deviation, 22 years ± 4) underwent 1.5-T MR imaging and analysis. Myocardial perfusion was assessed during rest, peak CPT, and adenosine hyperemia with a saturation-recovery gradient-echo pulse sequence (spatial resolution, 2.4 × 2.4 × 10 mm). Global, endocardial, and epicardial MBF were calculated by using Fermi-constrained deconvolution. Paired and independent t test statistical analyses were used to compare the responses between tests and groups. Regression analysis was performed to identify predictors of MBF change. MBF at rest was similar between the nonsmoking and smoking groups (0.97 mL/g/min ± 0.4 vs 0.96 mL/g/min ± 0.3, respectively; P = .96). Nonsmokers responded to CPT with a 47% increase in MBF (1.43 mL/g/min ± 0.5) and smokers responded with a 27% increase (1.22 mL/g/min ± 0.4; P < .001). An endocardial-to-epicardial gradient existed at rest (nonsmokers, 1.10 [P = .002]; smokers, 1.30 [P = .01]) and CPT (nonsmokers, 1.19 [P < .001] smokers, 1.28 [P = .04]) but reversed during adenosine stress (nonsmokers, 0.89 [P = .03]; smokers, 0.92 [P = .42]). Myocardial perfusion cardiac MR imaging during CPT can allow assessment of changes in MBF globally and in the separate myocardial layers in healthy smokers and nonsmokers. This allows the combined assessment of endothelium-dependent (CPT) and endothelium-independent (adenosine stress test) MBF reserve in a single study.

Incremental value of adenosine stress cardiac magnetic resonance in coronary artery disease detection

Cardiac magnetic resonance myocardial perfusion imaging (CMR-MPI) is considered a state-of-the-art non-invasive modality for ischemia detection but its additive value in a multiple-test strategy in patients with suspected coronary artery disease (CAD) is not fully validated. We aimed to evaluate CMR-MPI integration with exercise treadmill test (ETT) for the diagnostic workup of patients with suspected CAD, having invasive fractional flow reserve (FFR) as reference standard. In this prospective single-center study, patients with suspected CAD underwent sequential ETT, CMR-MPI and X-ray invasive coronary angiography (XA). Significant CAD was defined by the presence of stenosis >40% with FFR ≤ 0.8 in vessels >2 mm or ≥90% stenosis/occlusion. 80 symptomatic patients (68% male, 61 ± 8 years) were enrolled. Compared to ETT, CMR-MPI showed similar sensitivity (81%) and higher specificity (93 vs. 58%, p < 0.001) for CAD detection (prevalence = 46%) translating into better diagnostic performance (AUC 0.87 vs. 0.70; p = 0.002). CMR-MPI improved accuracy independently of ETT in all patients with high pre-test probability and in intermediate-probability patients but those with a clearly positive-ETT (symptoms + ST-shift), in whom ETT correctly identified CAD. In the low-probability group CMR-MPI was useful as a gatekeeper for XA after a positive-ETT. The best integrating protocol achieved a global accuracy of 89% (AUC 0.88) and was clearly superior to an approach based solely in ETT (AUC 0.70, p < 0.001), yet similar to isolated CMR-MPI (AUC 0.87, p = ns). CMR-MPI has high sensitivity and specificity for CAD detection and may be combined with ETT in a diagnostic workflow aiming to increase accuracy and reduce the number of unnecessary catheterizations.

Magnetic resonance myocardial perfusion imaging at 3.0 Tesla for the identification of myocardial ischaemia: comparison with coronary catheter angiography and fractional flow reserve measurements

To assess image quality and diagnostic performance of 3.0 Tesla (3T) cardiac magnetic resonance (CMR) myocardial perfusion imaging with a dual radiofrequency source to detect functional relevant coronary artery disease (CAD), using coronary angiography and invasive pressure-derived fractional flow reserve (FFR) as reference standard. We included 116 patients with suspected or known CAD, who underwent 3T adenosine myocardial perfusion CMR (resolution 2.97 × 2.97 mm) and coronary angiography plus FFR measurements in intermediate lesions. Image quality of myocardial perfusion CMR was graded on a 4-point scale (1 = poor to 4 = excellent). Diagnostic accuracy was assessed by ROC analyses using a 16-myocardial segment-based summed perfusion score (0 = normal to 3 = transmural perfusion defect) and by determining sensitivity, specificity, positive and negative predictive value on the coronary vessel territory and the patient level. Diagnostic image quality was achieved for all stress myocardial perfusion CMR studies with an average quality score of 2.5, 3.1, and 3.0 for LAD, LCX, and RCA territories. The ability of the myocardial perfusion CMR perfusion score to detect significant coronary artery stenosis yielded an area under the curve of 0.93 on ROC analysis. Values for sensitivity, specificity, positive and negative predictive value on a vessel territory level and the patient level were 89, 95, 87, 96% and 85, 87, 77, 92%, respectively. In patients with suspected or known significant CAD, 3T myocardial perfusion CMR with standard perfusion protocols provides consistently high image quality and an excellent diagnostic performance.