Perfusion Cardiac Magnetic Resonance Research Articles

Safety, feasibility, and hemodynamic response of regadenoson for stress perfusion CMR

Owing to its pharmacodynamics and posology, the use of regadenoson for stress cardiac magnetic resonance (CMR) has potential advantages over other vasodilators. We sought to evaluate the safety, hemodynamic response and diagnostic performance of regadenoson stress-CMR in routine clinical practice. All regadenoson stress-CMR examinations performed between May 2017 and July 2020 at our institution were retrospectively reviewed. A total of 698 studies were included for the final analysis. A conventional stress/rest protocol was performed using a 1.5T MRI scanner (Magnetom Aera, Siemens Healthineers, Erlangen, Germany). Adverse events, clinical symptoms, and hemodynamic response were assessed. Diagnostic accuracy of the test was evaluated in patients who underwent invasive coronary angiography. Nearly half of patients (48.5%) remained asymptomatic. Most common clinical symptoms included dyspnea (137, 19.6%), chest pain (116, 16.6%) and flushing (44, 6.3%). Two patients (0.28%) could not complete the examination due to severe hypotension or unbearable chest pain. Overall, an increase in heart rate (HR) response (36.2% [IQR: 22.5?50.9]) and a decrease in systolic and diastolic blood pressure (BP) (median systolic BP response of -5% [IQR: -11.5-0.6]; median diastolic BP response of -6.3 mmHg [IQR: -13.4-0]) was observed. Patients with symptoms induced by regadenoson showed higher HR response (40.3%, IQR: 26.4?56.1 vs. 32.4%, IQR: 19-45.6, p < 0.001), whereas a blunted HR response was observed in diabetic (29.6%, IQR: 18.4?42 p < 0.001), obese (31.7%, IQR: 20.7?46.2 p = 0.005) and patients aged 70 years or older (32.9%, IQR: 22.6?43.1 p < 0.001). Overall, regadenoson stress-CMR showed 95.65% (IQ 91.49?99.81) sensitivity, 54.84% (IQ 35.71?73.97) specificity, 86.99% (IQ 82.74?94.68) positive predictive value, and 77.27% (IQ 57.49?97.06) negative predictive value for detecting significant coronary stenosis as compared with invasive coronary angiography. Regadenoson is a well-tolerated vasodilator that can be safely employed for stress perfusion CMR, with high diagnostic performance.

Machine learning outcome prediction using stress perfusion cardiac magnetic resonance and electronic health records

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Wellcome Trust. Background Stress perfusion cardiac magnetic resonance (SP-CMR) is a well validated and guidelines backed diagnostic test for non-invasive assessment of patients with known or suspected coronary artery disease (CAD)(1). The prognostic value of SP-CMR is enhanced by adding clinical information, however, most electronic health record (EHR) is stored in an unstructured format, therefore limiting access to the information stored when large datasets are concerned. Furthermore, current outcome prediction models rely on linear models, but recent literature has shown stronger prediction using non-linear models (2). Purpose We aimed to address these challenges by using artificial intelligence (AI) tools to extract unstructured data from SP-CMR database and improve outcome prediction. Methods SP-CMR cases from 2011 to 2021 were screened. Data extraction was performed using Cogstack (3), an information retrieval and extraction platform for unstructured data based on natural language processing (NLP). Data were analysed for survival using Log Normal curves. Multivariate analysis was performed using survival Cox model. Different machine learning models were trained to predict survival, and compared using area under the receiver operating characteristic curve (AUC) and the DeLong test. 80% of dataset was used for training and 20% for testing. P value of &amp;lt;0.05 was considered statistically significant. Results 4,188 cases were included in the analysis. Total number of events (deaths) was 252 (6%). Ischaemia on stress perfusion imaging or the presence of myocardial scar on late gadolinium enhancement were significantly associated with events (Logrank p&amp;lt;0.001). Independent predictors from Cox survival analysis used to train machine learning models were: age, chronic kidney disease, hypertension, male gender, smoking, heart failure, positive ischaemic myocardial scar, positive stress perfusion, and ventricular ejection fraction. Considering clinical parameters only, support vector machine survival prediction performed best (AUC 0.76, F1 score 0.24), followed by XGBoost, random forest and ensemble classifier. After adding CMR predictors (stress perfusion, ischaemic myocardial scar, and left ventricular ejection fraction), prediction power improved for all machine learning models, with support vector machine having the best performance (AUC 0.82, F1 score 0.30). After comparing AUCs, non-linear models were better than multilinear regression (p&amp;lt;0.001, Z score −19). Conclusion NLP-based data extraction enables immediate access to unstructured EHR and reveals plausible results, which can be used within an integrated pipeline for data analysis and prediction, and has advantages over structured data due to access to large datasets. Machine learning-based prediction is superior to conventional linear models due to the added ability to model non-linear relationships. CMR predictors improve the survival prediction, compared to clinical variables alone.

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.

Comparison of the diagnostic accuracy of dynamic CT perfusion and cardiac CMR with quantitative perfusion: a subanalysis of ADVANTAGE II study

Abstract Funding Acknowledgements Type of funding sources: None. Background The ADVANTAGE II study has evaluated the performance of dynamic myocardial perfusion assessed by CT (CTP) in stented patient using ICA and in particular invasive coronary physiology (FFR and IMR) as gold-standard. Recently, quantitative myocardial blood flow (MBF) analysis using stress cardiac magnetic resonance (CMR) has been showed to detect obstructive coronary artery disease (CAD) and coronary microvascular dysfunction (CMD). In a substudy of ADVANTAGE II we aimed to evaluate the performance of quantitative stress CMR in comparison to CTP. Methods We present data from 39 subjects with clinically indicated ICA who underwent both vasodilator stress CMR using 1.5T MR scanner (General Electric) and dynamic stress myocardial CTP using a last generation scanner characterized by a 16-cm Z-axis coverage. In CMR Quantitative myocardial perfusion imaging was performed using the dual sequence technique (i.e. low-resolution slice for arterial input function and 2–3 short axis slices for myocardial perfusion). Resting MBF (rMBF), Stress MBF (sMBF), and myocardial perfusion reserve (MPR) were measured using Fermi deconvolution (Circle Cvi42). Quantitative perfusion results were displayed on color-encoded pixel-wise maps and on a 16-segment plot with segmental values listed. Results When FFR was used as gold standard the diagnostic accuracy of CTP was higher than those of CCTA (84.7% vs. 61.5%, p&amp;lt;0.001). When IMR was used as gold standard, diagnostic accuracy of CTP was higher than CCTA (82.9% vs. 59.3%, p&amp;lt;0.01, respectively). When the presence of at least one abnormal physiological parameter among FFR and IMR was used as gold standard, the diagnostic accuracy of CTP was higher than that of CCTA (90.8%vs 68%). Quantitative stress CMR using 2.2 ml/min/g as cut-off has a sensitivity of 83.3%, 77.7% and 100% vs QCA, FFR and IMR, respectively with higher performance of dynamic CTP in comparison to quantitative stress CMR. Conclusions In this substudy of ADVANTAGE II, we showed that global sMBF in MRI can accurately identify patients with CAD. Dynamic CTP seems to offer higher value of diagnostic performance in comparison to quantitative CMR that seems to be very promising, but more data are needed.

Stress computed tomography perfusion versus stress cardiac magnetic resonance for the management of suspected or known coronary artery disease: resources and outcomes impact (STRATEGY II Study)

Abstract Funding Acknowledgements Type of funding sources: None. Background Non-invasive techniques have evolved as "gatekeepers" to invasive coronary angiography (ICA) for symptomatic patients with suspected or known coronary artery disease (CAD). Evaluation of myocardial ischemia with functional tests represents a milestone in CAD detection with proved diagnostic and prognostic power. Coronary computed tomography angiography (CCTA), a non-invasive anatomical assessment, intrinsically lacks physiologic data to categorize the downstream hemodynamic significance of lesions. Stress CT perfusion (stress-CTP) is a recently evolved imaging modality able to assess inducible myocardial perfusion defects. The aim of this study is to compare resources and outcomes Impact of combined CCTA+stress-CTP versus stress cardiovascular magnetic resonance (stress-CMR) in consecutive symptomatic patients with suspected CAD and intermediate to high pre-test likelihood of disease or known CAD or previous history of revascularization. Methods 624 symptomatic patients with intermediate to high risk pre-test likelihood for CAD or previous history of revascularization referred to our hospital for clinically indicated CCTA+stress-CTP or stress-CMR were enrolled. Stress-CTP scans were performed in 223 patients using 256-row whole heart-coverage scanner, static protocol acquisition and vasodilation induced by adenosine. 401 patients with clinically indicated stress-CMR were evaluated in a 1.5-T scanner after vasodilatation induced with dipyridamole. Patient follow-up was performed at 1 year after index test performance. Endpoints were as follow: 1) all cardiac events as a combined endpoint of revascularization, non-fatal MI and death; 2) hard cardiac events as combined endpoint of non-fatal MI and death. Results Stress-CMR group showed lower age, higher prevalence of male gender and higher prevalence of previous revascularization, while CCTA+CTP group showed higher prevalence of family history of CAD and statin use. CCTA was defined positive for obstructive disease in 62% of patients while the addition of CTP on top of CCTA reduced the number of positive patients to 46%. Stress-CMR resulted positive in 23% of subjects. Patients who underwent CCTA+CTP underwent more revascularization (29% versus 7%, p: 0.001) while no differences were found in terms of non-fatal MI and death between the two strategies. According to the predefined endpoints, CCTA+CTP group showed higher rate of all cardiac events (29% vs 8%, p: 0.001) and lower rate of hard cardiac events (0.4% vs 3%, p: 0.033), respectively. Stratifying the baseline characteristics by all cardiac events and hard cardiac events, left ventricle volume and index test strategy predicted all cardiac events while only index test strategy predicted hard cardiac events. Conclusions The use of CCTA+CTP strategy was associated with higher referral to revascularization but with a protective trend in terms of hard cardiac events as compared to the usual strategy with lone functional evaluation.

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.

The Non-Invasive Diagnosis of Chronic Coronary Syndrome: A Focus on Stress Computed Tomography Perfusion and Stress Cardiac Magnetic Resonance.

Coronary artery disease is still a major cause of death and morbidity worldwide. In the setting of chronic coronary disease, demonstration of inducible ischemia is mandatory to address treatment. Consequently, scientific and technological efforts were made in response to the request for non-invasive diagnostic tools with better sensitivity and specificity. To date, clinicians have at their disposal a wide range of stress-imaging techniques. Among others, stress cardiac magnetic resonance (S-CMR) and computed tomography perfusion (CTP) techniques both demonstrated their diagnostic efficacy and prognostic value in clinical trials when compared to other non-invasive ischemia-assessing techniques and invasive fractional flow reserve measurement techniques. Standardized protocols for both S-CMR and CTP usually imply the administration of vasodilator agents to induce hyperemia and contrast agents to depict perfusion defects. However, both methods have their own limitations, meaning that optimizing their performance still requires a patient-tailored approach. This review focuses on the characteristics, drawbacks, and future perspectives of these two techniques.

Cardiac magnetic resonance in ischemic cardiomyopathy: present role and future directions.

Ischemic cardiomyopathy is a significant cause of mortality and morbidity, with peculiar needs for accurate diagnostic and prognostic characterization. Cardiac magnetic resonance (CMR) can help to satisfy these requirements by allowing a comprehensive evaluation of myocardial function, perfusion and tissue composition, with a demonstrated utility in guiding clinical management of patients with known or suspected ischemic cardiomyopathy. When compared with alternative non-invasive imaging modalities, such as stress echocardiography and nuclear techniques, CMR is able to provide accurate (function and perfusion) or peculiar (tissue characterization) information on cardiac pathophysiology, while avoiding exposition to ionizing radiations and overcoming limitations related to the quality of the imaging window. In particular, stress perfusion CMR showed to be accurate, safe, cost-effective, and clinically valuable as a non-invasive test for detecting severity and distribution of myocardial ischemia. In many circumstances, however, local availability of the technique, together with procedural costs, and scanning and post-processing time duration still limit the use of CMR in clinical routine. In the current review, we focused on clinical applications of CMR in ischemic cardiomyopathy. The consolidated role of the technique is described by illustrating both standard and advanced sequences that constitute the current body of a dedicated CMR examination. Ongoing developments and potential future diagnostic and prognostic applications of CMR when assessing ischemic cardiomyopathy are also discussed, with a focus on artificial intelligence-based implementations proposed for refining the efficiency of CMR analysis and reporting.

Microvascular Dysfunction Is Associated With Impaired Myocardial Work in Obstructive and Nonobstructive Hypertrophic Cardiomyopathy: A Multimodality Study

Background Two-dimensional speckle tracking echocardiography has been shown to correlate with microvascular dysfunction, a hallmark of hypertrophic cardiomyopathy (HCM). We hypothesized that there is an association between myocardial work and left ventricular ischemia, with incremental value to global longitudinal strain, in patients with HCM. Methods and Results We performed a prospective assessment of patients with HCM, undergoing 2-dimensional speckle tracking echocardiography and stress perfusion cardiac magnetic resonance. Results were stratified according to obstructive or nonobstructive HCM and the presence of significant replacement fibrosis (late gadolinium enhancement ≥15% of left ventricular mass). Seventy-five patients with HCM (63% men, age 55±15 years) were evaluated, 28% with obstructive HCM (mean gradient 89±60 mm Hg). Perfusion defects were found in 90.7%, involving 22.5±16.9% of left ventricular mass, and 38.7% had late gadolinium enhancement ≥15%. In a multivariable analysis, a lower global work index (r=-0.519, β-estimate -10.822; P=0.001), lower global work efficiency (r=-0.379, β-estimate -0.123; P=0.041), and impaired global constructive work (r=-0.532, β-estimate -13.788; P<0.001) significantly correlated with ischemia. A segmental analysis supported these findings, albeit with lower correlation coefficients. A global work index cutoff ≤1755 mm Hg% was associated with hypoperfusion with a sensitivity of 88% and a specificity of 71%, while the best cutoff for global longitudinal strain (>-15.5%) had a sensitivity of 64% and a specificity of 57%. The association between myocardial work and perfusion defects was significant independently of late gadolinium enhancement ≥15% and obstructive HCM. Conclusions Impaired myocardial work was significantly correlated with the extent of ischemia in cardiac magnetic resonance, independently of the degree of left ventricular hypertrophy or fibrosis, with a higher predictive power than global longitudinal strain.

Sex-Specific Stress Perfusion Cardiac Magnetic Resonance Imaging in Suspected Ischemic Heart Disease: Insights From SPINS Retrospective Registry

BackgroundCardiovascular disease (CVD) remains the leading cause of mortality in women, but current noninvasive cardiac imaging techniques have sex-specific limitations. ObjectivesIn this study, the authors sought to investigate the effect of sex on the prognostic utility and downstream invasive revascularization and costs of stress perfusion cardiac magnetic resonance (CMR) for suspected CVD. MethodsSex-specific prognostic performance was evaluated in a 2,349-patient multicenter SPINS (Stress CMR Perfusion Imaging in the United States [SPINS] Study) Registry. The primary outcome measure was a composite of cardiovascular death and nonfatal myocardial infarction; secondary outcomes were hospitalization for unstable angina or heart failure, and late unplanned coronary artery bypass grafting. ResultsSPINS included 1,104 women (47% of cohort); women had higher prevalence of chest pain (62% vs 50%; P < 0.0001) but lower use of medical therapies. At the 5.4-year median follow-up, women with normal stress CMR had a low annualized rate of primary composite outcome similar to men (0.54%/y vs 0.75%/y, respectively; P = NS). In contrast, women with abnormal CMR were at higher risk for both primary (3.74%/y vs 0.54%/y; P < 0.0001) and secondary (9.8%/y vs 1.6%/y; P < 0.0001) outcomes compared with women with normal CMR. Abnormal stress CMR was an independent predictor for the primary (HR: 2.64 [95% CI: 1.20-5.90]; P = 0.02) and secondary (HR: 2.09 [95% CI: 1.43-3.08]; P < 0.0001) outcome measures. There was no effect modification for sex. Women had lower rates of invasive coronary angiography (3.6% vs 7.3%; P = 0.0001) and downstream costs ($114 vs $171; P = 0.001) at 90 days following CMR. There was no effect of sex on diagnostic image quality. ConclusionsStress CMR demonstrated excellent prognostic performance with lower rates of invasive coronary angiography referral in women. Stress CMR should be considered as a first-line noninvasive imaging tool for the evaluation of women. (Stress CMR Perfusion Imaging in the United States [SPINS] Study [SPINS]; NCT03192891)

Quantifying Myocardial Blood Flow and Resistance Using 4D-Flow Cardiac Magnetic Resonance Imaging.

Ischaemia with nonobstructive coronary arteries is most commonly caused by coronary microvascular dysfunction but remains difficult to diagnose without invasive testing. Myocardial blood flow (MBF) can be quantified noninvasively on stress perfusion cardiac magnetic resonance (CMR) or positron emission tomography but neither is routinely used in clinical practice due to practical and technical constraints. Quantification of coronary sinus (CS) flow may represent a simpler method for CMR MBF quantification. 4D flow CMR offers comprehensive intracardiac and transvalvular flow quantification. However, it is feasibility to quantify MBF remains unknown. Patients with acute myocardial infarction (MI) and healthy volunteers underwent CMR. The CS contours were traced from the 2-chamber view. A reformatted phase contrast plane was generated through the CS, and flow was quantified using 4D flow CMR over the cardiac cycle and normalised for myocardial mass. MBF and resistance (MyoR) was determined in ten healthy volunteers, ten patients with myocardial infarction (MI) without microvascular obstruction (MVO), and ten with known MVO. MBF was quantified in all 30 subjects. MBF was highest in healthy controls (123.8 ± 48.4 mL/min), significantly lower in those with MI (85.7 ± 30.5 mL/min), and even lower in those with MI and MVO (67.9 ± 29.2 mL/min/) (P < 0.01 for both differences). Compared with healthy controls, MyoR was higher in those with MI and even higher in those with MI and MVO (0.79 (±0.35) versus 1.10 (±0.50) versus 1.50 (±0.69), P=0.02). MBF and MyoR can be quantified from 4D flow CMR. Resting MBF was reduced in patients with MI and MVO.

Accuracy of stress perfusion cardiac magnetic resonance imaging in a district hospital.

The European Society of Cardiology has published updated guidelines regarding pathways for diagnosis and management of obstructive coronary artery disease (CAD). Non-invasive functional assessment, for example, by stress perfusion cardiac magnetic resonance (stress pCMR) is recommended in patients with intermediate pretest probability of disease. Previous pCMR studies were mainly performed in high volume university hospitals with experienced radiologists or cardiologists interpreting the images. The aim of the present study was to evaluate the feasibility of establishing a stress pCMR imaging service in a district hospital. One hundred and thirteen patients with intermediate pretest probability of CAD referred for single-photon emission computed tomography (SPECT) at the regional hospital also underwent adenosine stress pCMR locally. The diagnostic analysis was compared to that of an experienced cardiac magnetic resonance (CMR) center serving as a reference. Inter-rater agreement between local readers and the reference reader was substantial to perfect for late gadolinium enhancement (LGE) (weighted kappa = 0.76 and 0.82), but only fair to moderate for pCMR (k = 0.34 and 0.51). No improvement in agreement between reference reader and local reader during the study was demonstrated. CMR is feasible in patients with intermediate pretest probability of obstructive CAD in the setting of a district hospital. However, as opposed to infarct detection with LGE, the interpretation of stress pCMR was more challenging. To establish this method, we suggest obtaining experience in close collaboration with a reference CMR center.

Qualitative and Quantitative Stress Perfusion Cardiac Magnetic Resonance in Clinical Practice: A Comprehensive Review.

Stress cardiovascular magnetic resonance (CMR) imaging is a well-validated non-invasive stress test to diagnose significant coronary artery disease (CAD), with higher diagnostic accuracy than other common functional imaging modalities. One-stop assessment of myocardial ischemia, cardiac function, and myocardial viability qualitatively and quantitatively has been proven to be a cost-effective method in clinical practice for CAD evaluation. Beyond diagnosis, stress CMR also provides prognostic information and guides coronary revascularisation. In addition to CAD, there is a large body of literature demonstrating CMR's diagnostic performance and prognostic value in other common cardiovascular diseases (CVDs), especially coronary microvascular dysfunction (CMD). This review focuses on the clinical applications of stress CMR, including stress CMR scanning methods, practical interpretation of stress CMR images, and clinical utility of stress CMR in a setting of CVDs with possible myocardial ischemia.

Stress CMR T1-mapping technique for assessment of coronary microvascular dysfunction in a rabbit model of type II diabetes mellitus: Validation against histopathologic changes.

Coronary microvascular dysfunction (CMD) is an early character of type 2 diabetes mellitus (T2DM), and is indicative of adverse events. The present study aimed to validate the performance of the stress T1 mapping technique on cardiac magnetic resonance (CMR) for identifying CMD from a histopathologic perspective and to establish the time course of CMD-related parameters in a rabbit model of T2DM. New Zealand white rabbits (n = 30) were randomly divided into a control (n = 8), T2DM 5-week (n = 6), T2DM 10-week (n = 9), and T2DM 15-week (n = 7) groups. The CMR protocol included rest and adenosine triphosphate (ATP) stress T1-mapping imaging using the 5b(20b)3b-modified look-locker inversion-recovery (MOLLI) schema to quantify stress T1 response (stress ΔT1), and first-pass perfusion CMR to quantify myocardial perfusion reserve index (MPRI). After the CMR imaging, myocardial tissue was subjected to hematoxylin-eosin staining to evaluate pathological changes, Masson trichrome staining to measure collagen volume fraction (CVF), and CD31 staining to measure microvascular density (MVD). The associations between CMR parameters and pathological findings were determined using Pearson correlation analysis. The stress ΔT1 values were 6.21 ± 0.59%, 4.88 ± 0.49%, 3.80 ± 0.40%, and 3.06 ± 0.54% in the control, T2DM 5-week, 10-week, and 15-week groups, respectively (p < 0.001) and were progressively weakened with longer duration of T2DM. Furthermore, a significant correlation was demonstrated between the stress ΔT1 vs. CVF and MVD (r = -0.562 and 0.886, respectively; p < 0.001). The stress T1 response correlated well with the histopathologic measures in T2DM rabbits, indicating that it may serve as a sensitive CMD-related indicator in early T2DM.

Cardiovascular Magnetic Resonance Parametric Mapping Techniques for the Assessment of Chronic Coronary Syndromes.

The term chronic coronary syndromes encompasses a variety of clinical presentations of coronary artery disease (CAD), ranging from stable angina due to epicardial coronary artery disease to microvascular coronary dysfunction. Cardiac magnetic resonance (CMR) imaging has an established role in the diagnosis, prognostication and treatment planning of patients with CAD. Recent advances in parametric mapping CMR techniques have added value in the assessment of patients with chronic coronary syndromes, even without the need for gadolinium contrast administration. Furthermore, quantitative perfusion CMR techniques have enabled the non-invasive assessment of myocardial blood flow and myocardial perfusion reserve and can reliably identify multivessel coronary artery disease and microvascular dysfunction. This review summarizes the clinical applications and the prognostic value of the novel CMR parametric mapping techniques in the setting of chronic coronary syndromes and discusses their strengths, pitfalls and future directions.

AI-AIF: artificial intelligence-based arterial input function for quantitative stress perfusion cardiac magnetic resonance.

One of the major challenges in the quantification of myocardial blood flow (MBF) from stress perfusion cardiac magnetic resonance (CMR) is the estimation of the arterial input function (AIF). This is due to the non-linear relationship between the concentration of gadolinium and the MR signal, which leads to signal saturation. In this work, we show that a deep learning model can be trained to predict the unsaturated AIF from standard images, using the reference dual-sequence acquisition AIFs (DS-AIFs) for training. A 1D U-Net was trained, to take the saturated AIF from the standard images as input and predict the unsaturated AIF, using the data from 201 patients from centre 1 and a test set comprised of both an independent cohort of consecutive patients from centre 1 and an external cohort of patients from centre 2 (n = 44). Fully-automated MBF was compared between the DS-AIF and AI-AIF methods using the Mann-Whitney U test and Bland-Altman analysis. There was no statistical difference between the MBF quantified with the DS-AIF [2.77 mL/min/g (1.08)] and predicted with the AI-AIF (2.79 mL/min/g (1.08), P = 0.33. Bland-Altman analysis shows minimal bias between the DS-AIF and AI-AIF methods for quantitative MBF (bias of -0.11 mL/min/g). Additionally, the MBF diagnosis classification of the AI-AIF matched the DS-AIF in 669/704 (95%) of myocardial segments. Quantification of stress perfusion CMR is feasible with a single-sequence acquisition and a single contrast injection using an AI-based correction of the AIF.

Abstract 11544: Prognostic Risk Stratification of Cardiac Metastasis via Quantitative Perfusion Cardiac Magnetic Resonance Imaging

Introduction: Cardiac magnetic resonance (CMR) is widely used to assess cardiac masses, including cardiac metastases (C MET ). Perfusion CMR can quantify magnitude of tumor vascularity; prognostic relevance of lesion perfusion among patients (pts) with C MET is unknown. Methods: The population comprised adult cancer pts with C MET and controls matched for cancer type/stage. Late gadolinium enhancement (LGE) CMR was the reference for C MET . Perfusion CMR quantified vascularity within lesions, including contrast enhancement (CER: maximum vs. baseline) and uptake (CUR [slope] ratios during gadolinium infusion (0.1mmol/kg). Follow-up was performed for mortality. Results: 155 C MET pts (59 ± 15yo, 56% male) and cancer matched controls underwent CMR, including a range of primary cancers (sarcoma 22%, GU 17%, GI &amp; lung 12%). Anti-cancer treatment, cardiac risk factors and LVEF were similar between groups (p=NS). In relation to LGE-CMR, perfusion yielded good performance to distinguish C MET (AUC 0.57-0.97; p &lt; 0.001). During follow-up, C MET pts tended to have higher aggregate 1 year mortality vs. controls (56% vs. 46%; p=0.09); median time to death was 6.8 (2.5, 17.1) months post-CMR. Pts with C MET on perfusion CMR had higher mortality risk than controls (HR 1.41 [1.04-1.92], p=0.03), paralleling LGE-CMR (HR 1.52 [CI 1.14-2.02], p=0.004). C MET mortality increased stepwise with impaired perfusion (Figure A) and was highest among pts in the bottom (vs. top) CER tertile, corresponding to decreased tumor vascularity. Among cancer matched subgroups, pts with C MET in the bottom CER tertile had higher mortality than controls (p &lt; 0.001); prognosis was equivalent to controls (p=NS) among pts with lesions in the highest two CER tertiles (Figure B). Conclusions: Perfusion CMR identifies CMET based on vascularity and stratifies prognosis: Among cancer pts with CMET on LGE, mortality increases in proportion to magnitude of decreased tumor vascularity on perfusion CMR.

Abstract 14447: Multi-Center Evaluation of Stress Myocardial Blood Flow by Cardiac Magnetic Resonance in Known and Suspected Ischemic Heart Disease: Preliminary Findings From the AQUA-MBF Initiative

Introduction: Quantitative myocardial blood flow (MBF) analysis using stress cardiac magnetic resonance (CMR) has been shown to detect obstructive coronary artery disease (CAD) and coronary microvascular dysfunction (CMD) in several mostly small, single-center studies. The AQUA-MBF ( A ssessment of QUA ntitative MBF ) study is a multicenter initiative involving 16 centers. Hypothesis: The goal of this sub-study is to determine if MBF can differentiate CAD, CMD, and normal volunteers in this multicenter setting. Methods: We present data from 53 subjects (15 with CAD, 20 at risk for CMD and 18 controls) who underwent vasodilator stress CMR (Figure) using 1.5T and 3.0T MR scanners (General Electric). At risk for CMD was defined as having diabetes and 2 other risk factors in absence of ≥50% stenosis based on coronary CT. CAD was defined as the presence of stenosis ≥70% based on invasive coronary angiography. Stress perfusion images were acquired using the dual sequence technique. Stress MBF was measured in each of the 16 AHA segments using Fermi deconvolution (Circle Cvi42). In the CAD group, each segment was further classified as having late gadolinium enhancement (LGE), supplied by CAD, or a normal remote territory. The means of the 5 groups were compared using one-way analysis of variance. Results: The segmental stress MBF (ml/g/min) for the 5 groups are shown in figure. Compared to the normal group, segmental stress MBF in 4 disease groups were significantly lower (p&lt;0.001). Segmental MBF in those at risk for CMD was lower than normal segments and greater than CAD segments (p&lt;0.001). LGE and CAD segments had the lowest stress MBF but similar to each other (p=0.9). Conclusions: In this multicenter study, we show that quantification of MBF using the dual sequence stress perfusion CMR technique can differentiate diseased from healthy myocardium and also between obstructive CAD and those at risk for CMD.

Adenosine triphosphate (ATP): a safe and effective vasodilator for stress perfusion cardiac magnetic resonance imaging

To evaluate the efficiency and safety of adenosine triphosphate (ATP) as a stress agent in a cohort of patients undergoing stress perfusion cardiac magnetic resonance imaging (CMRI). This retrospective study was conducted between December 2019 and October 2021. The study recruited patients who underwent stress perfusion CMRI using ATP as a vasodilator. Adverse events, such as chest pain, flushing, dyspnoea, headache, and splenic switch-off (SSO) phenomenon, were evaluated in the patients who underwent stress perfusion CMRI. The study included 107 patients (age range: 53±11 years; male:female, 62%:38%). The haemodynamic response (heart rate increased by≥10 beats/min) was quick and observed within 2 minutes of ATP infusion. Scanning was stopped in three patients because of atrioventricular block. CMRI images of seven out of 104 patients were excluded from the final analysis because of inferior quality. During ATP infusion, 37/107 patients (35%) experienced mild adverse events, such as chest pain, flushing, dyspnoea, headache, and atrioventricular block. Myocardial infarction and bronchospasms were not observed during ATP infusion. SSO, a marker of adequate stress, was observed in 91% (94/103) of the patients who underwent stress perfusion CMRI. As a coronary vasodilator, ATP was safe for stress perfusion CMRI. In addition, the adverse events during ATP infusion were mild, which were relieved within 2 minutes of ATP injection cessation. SSO could serve as an indicator of stress success in ATP stress perfusion CMRI.

Multimodality Imaging in the Detection of Ischemic Heart Disease in Women.

Women with coronary artery disease tend to have a worse short and long-term prognosis relative to men and the incidence of atherosclerotic cardiovascular disease is increasing. Women are less likely to present with classic anginal symptoms when compared with men and more likely to be misdiagnosed. Several non-invasive imaging modalities are available for diagnosing ischemic heart disease in women and many of these modalities can also assist with prognostication and help to guide management. Selection of the optimal imaging modality to evaluate women with possible ischemic heart disease is a scenario which clinicians often encounter. Earlier modalities such as exercise treadmill testing demonstrate significant performance variation in men and women, while newer modalities such as coronary CT angiography, myocardial perfusion imaging and cardiac magnetic resonance imaging are highly specific and sensitive for the detection of ischemia and coronary artery disease with greater parity between sexes. Individual factors, availability, diagnostic performance, and female-specific considerations such as pregnancy status may influence the decision to select one modality over another. Emerging techniques such as strain rate imaging, CT-myocardial perfusion imaging and cardiac magnetic resonance imaging present additional options for diagnosing ischemia and coronary microvascular dysfunction.