Perfusion Cardiac Magnetic Resonance Research Articles

Non-invasive electrocardiographic assessment of arrhythmic risk in ischaemic cardiomyopathy patients undergoing revasularisation

Abstract Background Ventricular arrhythmias are a leading cause of death in patients with ischaemic cardiomyopathy (ICM). Ischaemia is thought to increase arrhythmic risk and coronary revascularisation is frequently undertaken to reduce this risk, although the recent REVIVED-BCIS2 trial did not show a difference in the incidence of death, device therapies or sustained arrhythmias in patients assigned to have percutaneous coronary intervention (PCI) compared to optimal medical therapy alone(1). Purpose We assessed the mechanistic effects of revascularisation on arrhythmic risk in patients with ICM using non-invasive electrocardiographic imaging (ECGi). Methods Patients were eligible if they had a left ventricular ejection fraction (LVEF) <40%, extensive coronary disease (BCIS Jeopardy Score≥6) and were scheduled to undergo revascularisation with coronary artery bypass grafting or PCI. ECGi assessment was performed using a 252-electrode vest with anatomical co-registration using a CT thorax. Patients underwent stress perfusion cardiac magnetic resonance (CMR) imaging; both ECGi and CMR were conducted at baseline and 3 months post revascularisation(Figure 1). The primary outcome measure was dispersion of repolarisation measured using global activation recovery interval (ARI) dispersion. Secondary outcome measures included repolarisation time (RT) dispersion, mean ARI and LV ARI dispersion. We also assessed the relationship between ARI dispersion, revascularisation and left ventricular scar burden. Data are presented as mean ± SD or median [IQR]. Results Thirty patients were recruited between 2020-2023; age 67±11 years, 90% male, BMI 28±5 and baseline LVEF was 29±8%. Twelve patients underwent CABG, 18 (60%) had PCI. The BCIS jeopardy score was 10 [9-11] at enrolment and decreased to 2 [0-4] after revascularisation. The LV scar burden at baseline was 15.1±6.5% and the change at 3 months was -0.5±5% (p=0.70). ARI dispersion and LV ARI dispersion were correlated with LV scar burden (r=0.62,p=0.01 and 0.71,p=0.002 respectively). No differences were seen in ARI dispersion (44.5 vs 44.1, p=0.86) or secondary outcome measures before and after revascularisation (RT dispersion: 45.5 vs 44.7, p=0.49; Mean ARI: 281.3 vs 282.6, p=0.74; ARI dispersion: 44.5 vs 44.1, p=0.86; LV ARI dispersion: 38.4 vs 36.7, p=0.39)(Figure 2). The LVEF change on CMR at 3 months was +6.9±10%; no relationship was seen between change in LVEF and ARI dispersion. Conclusion Arrhythmic risk assessed by non-invasive ECGi was not altered by coronary revascularisation. LV ARI dispersion was highly correlated with scar burden, which is not altered by revascularisation. Future work includes analysis of perfusion data. Our results support the findings of the REVIVED arrhythmia study that revascularisation does not reduce arrhythmic risk in patients with ICM(1). ECGi derived LV ARI dispersion correlates with scar and may represent a non-invasive arrhythmic risk assessment tool.Figure 1Figure 2

Pulmonary Artery Angioplasty for Improving Ipsilateral Lung Perfusion in Adolescent and Adult Patients: An Analysis Based on Cardiac Magnetic Resonance Imaging and Lung Perfusion Scanning.

The left pulmonary artery (LPA) may be kinked and stenotic, especially in tetralogy of Fallot, because of ductal tissue and anterior deviation of the conal septum. If LPA stenosis is not effectively treated during total correction, surgical angioplasty is occasionally performed. However, whether pulmonary artery (PA) angioplasty in adolescents or adults improves perfusion in the ipsilateral lung remains unclear. This retrospective review enrolled patients who underwent PA angioplasty for LPA stenosis between 2004 and 2019. Among patients who underwent a lung perfusion scan (LPS) or cardiac magnetic resonance imaging (cMRI) pre- and post-pulmonary angioplasty, those aged >13 years with <40% left lung perfusion (p-left) in the pre-angioplasty study were included. Preoperative and postoperative computed tomography, LPS, and cMRI data were collected. The perfusion ratio was analyzed according to the LPA's anatomical characteristics. Seventeen adolescents and 16 adults (≥18 years old) were finally included (median age, 17 years). The most common primary diagnosis was tetralogy of Fallot (87.9%). In all patients, LPA angioplasty was performed concomitantly with right ventricular outflow tract reconstruction. No patients died. Preoperative p-left was not significantly different between adolescents and adults; however, adolescents had significantly higher postoperative p-left than adults. P-left significantly increased in adolescents, but not in adults. Seven patients had significant stenosis (z-score <-2.0) confined only to the proximal LPA and demonstrated significantly increased p-left. PA angioplasty significantly increased ipsilateral lung perfusion in adolescents. If focal stenosis is confined to the proximal LPA, PA angioplasty may improve ipsilateral lung perfusion, regardless of age.

Coronary sinus reducer for the treatment of refractory angina (ORBITA-COSMIC): a randomised, placebo-controlled trial

The coronary sinus reducer (CSR) is proposed to reduce angina in patients with stable coronary artery disease by improving myocardial perfusion. We aimed to measure its efficacy, compared with placebo, on myocardial ischaemia reduction and symptom improvement. ORBITA-COSMIC was a double-blind, randomised, placebo-controlled trial conducted at six UK hospitals. Patients aged 18 years or older with angina, stable coronary artery disease, ischaemia, and no further options for treatment were eligible. All patients completed a quantitative adenosine-stress perfusion cardiac magnetic resonance scan, symptom and quality-of-life questionnaires, and a treadmill exercise test before entering a 2-week symptom assessment phase, in which patients reported their angina symptoms using a smartphone application (ORBITA-app). Patients were randomly assigned (1:1) to receive either CSR or placebo. Both participants and investigators were masked to study assignment. After the CSR implantation or placebo procedure, patients entered a 6-month blinded follow-up phase in which they reported their daily symptoms in the ORBITA-app. At 6 months, all assessments were repeated. The primary outcome was myocardial blood flow in segments designated ischaemic at enrolment during the adenosine-stress perfusion cardiac magnetic resonance scan. The primary symptom outcome was the number of daily angina episodes. Analysis was done by intention-to-treat and followed Bayesian methodology. The study is registered with ClinicalTrials.gov, NCT04892537, and completed. Between May 26, 2021, and June 28, 2023, 61 patients were enrolled, of whom 51 (44 [86%] male; seven [14%] female) were randomly assigned to either the CSR group (n=25) or the placebo group (n=26). Of these, 50 patients were included in the intention-to-treat analysis (24 in the CSR group and 26 in the placebo group). 454 (57%) of 800 imaged cardiac segments were ischaemic at enrolment, with a median stress myocardial blood flow of 1·08 mL/min per g (IQR 0·77-1·41). Myocardial blood flow in ischaemic segments did not improve with CSR compared with placebo (difference 0·06 mL/min per g [95% CrI -0·09 to 0·20]; Pr(Benefit)=78·8%). The number of daily angina episodes was reduced with CSR compared with placebo (OR 1·40 [95% CrI 1·08 to 1·83]; Pr(Benefit)=99·4%). There were two CSR embolisation events in the CSR group, and no acute coronary syndrome events or deaths in either group. ORBITA-COSMIC found no evidence that the CSR improved transmural myocardial perfusion, but the CSR did improve angina compared with placebo. These findings provide evidence for the use of CSR as a further antianginal option for patients with stable coronary artery disease. Medical Research Council, Imperial College Healthcare Charity, National Institute for Health and Care Research Imperial Biomedical Research Centre, St Mary's Coronary Flow Trust, British Heart Foundation.

Hybrid artificial intelligence outcome prediction using features extraction from stress perfusion cardiac magnetic resonance images and electronic health records.

Prediction of clinical outcomes in coronary artery disease (CAD) has been conventionally achieved using clinical risk factors. The relationship between imaging features and outcome is still not well understood. This study aims to use artificial intelligence to link image features with mortality outcome. A retrospective study was performed on patients who had stress perfusion cardiac magnetic resonance (SP-CMR) between 2011 and 2021. The endpoint was all-cause mortality. Convolutional neural network (CNN) was used to extract features from stress perfusion images, and multilayer perceptron (MLP) to extract features from electronic health records (EHRs), both networks were concatenated in a hybrid neural network (HNN) to predict study endpoint. Image CNN was trained to predict study endpoint directly from images. HNN and image CNN were compared with a linear clinical model using area under the curve (AUC), F1 scores, and McNemar's test. Total of 1,286 cases were identified, with 201 death events (16%). The clinical model had good performance (AUC =80%, F1 score =37%). Best Image CNN model showed AUC =72% and F1 score =38%. HNN outperformed the other two models (AUC =82%, F1 score =43%). McNemar's test showed statistical difference between image CNN and both clinical model (P<0.01) and HNN (P<0.01). There was no significant difference between HNN and clinical model (P=0.15). Death in patients with suspected or known CAD can be predicted directly from stress perfusion images without clinical knowledge. Prediction can be improved by HNN that combines clinical and SP-CMR images.

Comparison of machine learning-based CT fractional flow reserve with cardiac MR perfusion mapping for ischemia diagnosis in stable coronary artery disease.

To compare the diagnostic performance of machine learning (ML)-based computed tomography-derived fractional flow reserve (CT-FFR) and cardiac magnetic resonance (MR) perfusion mapping for functional assessment of coronary stenosis. Between October 2020 and March 2022, consecutive participants with stable coronary artery disease (CAD) were prospectively enrolled and underwent coronary CTA, cardiac MR, and invasive fractional flow reserve (FFR) within 2weeks. Cardiac MR perfusion analysis was quantified by stress myocardial blood flow (MBF) and myocardial perfusion reserve (MPR). Hemodynamically significant stenosis was defined as FFR ≤ 0.8 or > 90% stenosis on invasive coronary angiography (ICA). The diagnostic performance of CT-FFR, MBF, and MPR was compared, using invasive FFR as a reference. The study protocol was completed in 110 participants (mean age, 62years ± 8; 73 men), and hemodynamically significant stenosis was detected in 36 (33%). Among the quantitative perfusion indices, MPR had the largest area under receiver operating characteristic curve (AUC) (0.90) for identifying hemodynamically significant stenosis, which is in comparison with ML-based CT-FFR on the vessel level (AUC 0.89, p = 0.71), with comparable sensitivity (89% vs 79%, p = 0.20), specificity (87% vs 84%, p = 0.48), and accuracy (88% vs 83%, p = 0.24). However, MPR outperformed ML-based CT-FFR on the patient level (AUC 0.96 vs 0.86, p = 0.03), with improved specificity (95% vs 82%, p = 0.01) and accuracy (95% vs 81%, p < 0.01). ML-based CT-FFR and quantitative cardiac MR showed comparable diagnostic performance in detecting vessel-specific hemodynamically significant stenosis, whereas quantitative perfusion mapping had a favorable performance in per-patient analysis. ML-based CT-FFR and MPR derived from cardiac MR performed well in diagnosing vessel-specific hemodynamically significant stenosis, both of which showed no statistical discrepancy with each other. • Both machine learning (ML)-based computed tomography-derived fractional flow reserve (CT-FFR) and quantitative perfusion cardiac MR performed well in the detection of hemodynamically significant stenosis. • Compared with stress myocardial blood flow (MBF) from quantitative perfusion cardiac MR, myocardial perfusion reserve (MPR) provided higher diagnostic performance for detecting hemodynamically significant coronary artery stenosis. • ML-based CT-FFR and MPR from quantitative cardiac MR perfusion yielded similar diagnostic performance in assessing vessel-specific hemodynamically significant stenosis, whereas MPR had a favorable performance in per-patient analysis.

Coronary microvascular dysfunction: prevalence and aetiology in patients with suspected myocardial ischaemia

To evaluate the prevalence, aetiology, and corresponding morbidity of coronary microvascular dysfunction (CMD) in patients with suspected myocardial ischaemia. The present study included 115 patients with suspected myocardial ischaemia who underwent stress perfusion cardiac magnetic resonance imaging. CMD was assessed visually based on the myocardial perfusion results. The CMR-derived myocardial perfusion reserve index (MPRI) and left ventricular (LV) strain parameters obtained using the post-processing software CVI42 were employed to evaluate LV myocardial perfusion and deformation. LV strain parameters included global longitudinal, circumferential, and radial strain (GLS, GCS, and GRS), global systolic/diastolic longitudinal, circumferential, and radial strain rates (SLSR, SCSR, SRSR, DLSR, DCSR, and DRSR). Of the 115 patients, 12 patients were excluded and 103 patients were finally included in the study. CMD was observed in 79 % (81 patients, aged 53±12 years) of patients. Regarding aetiology, 91 (88 %) patients had non-obstructive coronary artery disease (CAD), eight (8 %) had obstructive CAD, and four (4 %) had hypertrophic cardiomyopathy (HCM). The incidence of CMD was highest (100 %) in patients with HCM, followed by those with non-obstructive CAD (up to 79 %). There were no statistical differences between CMD and non-CMD groups in GCS, GRS, GLS, SRSR, SCSR, SLSR, DCSR, DRSR and DLSR. The incidence of CMD was higher in patients with signs and symptoms of ischaemia. CMD occurred with non-obstructive CAD, obstructive CAD, and HCM, with the highest prevalence of CMD in HCM.

High-resolution quantification of stress perfusion defects by cardiac magnetic resonance.

Quantitative stress perfusion cardiac magnetic resonance (CMR) is becoming more widely available, but it is still unclear how to integrate this information into clinical decision-making. Typically, pixel-wise perfusion maps are generated, but diagnostic and prognostic studies have summarized perfusion as just one value per patient or in 16 myocardial segments. In this study, the reporting of quantitative perfusion maps is extended from the standard 16 segments to a high-resolution bullseye. Cut-off thresholds are established for the high-resolution bullseye, and the identified perfusion defects are compared with visual assessment. Thirty-four patients with known or suspected coronary artery disease were retrospectively analysed. Visual perfusion defects were contoured on the CMR images and pixel-wise quantitative perfusion maps were generated. Cut-off values were established on the high-resolution bullseye consisting of 1800 points and compared with the per-segment, per-coronary, and per-patient resolution thresholds. Quantitative stress perfusion was significantly lower in visually abnormal pixels, 1.11 (0.75-1.57) vs. 2.35 (1.82-2.9) mL/min/g (Mann-Whitney U test P < 0.001), with an optimal cut-off of 1.72 mL/min/g. This was lower than the segment-wise optimal threshold of 1.92 mL/min/g. The Bland-Altman analysis showed that visual assessment underestimated large perfusion defects compared with the quantification with good agreement for smaller defect burdens. A Dice overlap of 0.68 (0.57-0.78) was found. This study introduces a high-resolution bullseye consisting of 1800 points, rather than 16, per patient for reporting quantitative stress perfusion, which may improve sensitivity. Using this representation, the threshold required to identify areas of reduced perfusion is lower than for segmental analysis.

CMR 2-45 - Stress Computed Tomography Perfusion versus Stress Cardiac Magnetic Resonance for the Management of Suspected or Known Coronary Artery Disease: Resources and Outcomes Impact - The STRATEGY II Study

CMR 2-45 - Stress Computed Tomography Perfusion versus Stress Cardiac Magnetic Resonance for the Management of Suspected or Known Coronary Artery Disease: Resources and Outcomes Impact - The STRATEGY II Study

Enhanced External Counterpulsation for Management of Postacute Sequelae of SARS-CoV-2 Associated Microvascular Angina and Fatigue: An Interventional Pilot Study.

Postacute sequelae of SARS-CoV-2 infection (PASC) are a novel clinical syndrome characterized in part by endothelial dysfunction. Enhanced external counterpulsation (EECP) produces pulsatile shear stress, which has been associated with improvements in systemic endothelial function. To explore the effects of EECP on symptom burden, physical capacity, mental health, and health-related quality of life (HRQoL) in patients with PASC-associated angina and microvascular dysfunction (MVD). An interventional pilot study was performed, including 10 patients (male = 5, mean age 50.3 years) recruited from a tertiary specialized PASC clinic. Patients with angina and MVD, defined as index of microcirculatory resistance (IMR) ≥25 and/or diagnosed through stress perfusion cardiac magnetic resonance imaging, were included. Patients underwent one modified EECP course (15 one-hour sessions over five weeks). Symptom burden, six-minute walk test, and validated generic self-reported instruments for measuring psychological distress and HRQoL were assessed before and one month after treatment. At baseline, most commonly reported PASC symptoms were angina (100%), fatigue (80%), and dyspnea (80%). Other symptoms included palpitations (50%), concentration impairment (50%), muscle pain (30%), and brain fog (30%). Mean IMR was 63.6. After EECP, 6MWD increased (mean 29.5 m, median 21 m) and angina and fatigue improved. Mean depression scores showed reduced symptoms (-0.8). Mean HRQoL scores improved in seven out of eight subscales (+0.2 to 10.5). Patients with PASC-associated angina and evidence of MVD experienced subjective and objective benefits from EECP. The treatment was well-tolerated. These findings warrant controlled studies in a larger cohort.

Machine learning outcome prediction using stress perfusion cardiac magnetic resonance reports and natural language processing of electronic health records

Machine learning outcome prediction using stress perfusion cardiac magnetic resonance reports and natural language processing of electronic health records

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 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.

The left main coronary artery (LMCA) physiology study: comprehensive clinical haemodynamic evaluation of physiology and pathophysiology

Abstract Background &amp; Purpose At present, physiological evaluation of left main coronary artery (LMCA) disease is based on the assumption that pressure-based indices are agnostic to the vessel being assessed. We conducted mechanistic studies to determine whether pressure-based indices in the left anterior descending (LAD) and left circumflex (LCx) arteries are different and if so, the basis of this discrepancy, in patients with normal coronary arteries (LMCA Physiology Study) and in those with isolated LMCA disease (LMCA Pathophysiology Study). Methods Patients with exertional angina were prospectively enrolled after baseline investigation of computed tomography or invasive angiography and those with left ventricular impairment were excluded. Eligibility for the Physiology Study required the absence of epicardial disease on angiography and/or fractional flow reserve or significant coronary microvascular disease (LAD coronary flow reserve (CFR) &amp;lt;2.0). Simultaneous intracoronary pressure and Doppler measurements were performed in the LAD and LCx arteries, at rest and adenosine mediated hyperaemia. A subset also underwent 3-Tesla quantitative stress perfusion cardiac magnetic resonance imaging. Eligibility for the Pathophysiology Study required isolated LMCA disease, which was verified physiologically by pressure wire pullback according to predefined criteria of 1) ≥80% of total FFR arising from the left main coronary artery disease and 2) ≤0.05 FFR gradient distal to the left main coronary artery disease in both vessels. A paired 2-tailed test for significance was performed for all analyses. The protocols were approved by the UK National research ethics committee. Results 71 patients were prospectively enrolled, 28 in the Physiology Study and 43 in the Pathophysiology Study (Table 1). In the LMCA Physiology Study, CFR was higher and hyperaemic microvascular resistance (hMR) lower in the LAD compared to the LCx. In the LMCA Pathophysiology Study, the contribution to total FFR of downstream disease was negligible and comparable in both branches. Moreover, hyperaemic, and non-hyperaemic pressure-based indices were all significantly lower in the LAD, compared to the LCx. In addition, CFR was higher and hMR lower in the LAD compared to the LCx. Correlations are outlined in Figure 1. Differences in pressure-derived measurements remained after correction for the influence of hydrostatic pressures. However, when adjusted for subtended myocardial mass, there was no significant difference in invasive hemodynamic indices or quantitative perfusion analysis-derived myocardial perfusion reserve index. Conclusions Commonly used indices of stenosis severity are not agnostic to the vessel assessed due to differences in myocardial mass and microvascular resistances. The need for vessel-specific thresholds has significant implications on LMCA disease assessment and potentially, interpretation of the existing evidence base on physiological assessment of non-LMCA disease.Table 1Figure 1

Hybrid Artificial Intelligence Outcome Prediction Using Feature Extraction from Stress Perfusion Cardiac Magnetic Resonance Images and Electronic Health Records

Abstract Background Prediction of mortality and cardiovascular (CVS) events in coronary artery disease (CAD) has been conventionally achieved using clinical risk factors. Conventional qualitative visual assessment and quantitative analysis of stress perfusion cardiac magnetic resonance (SP-CMR) has previously been shown to have independent prognostic value (1), but the relationship between hidden or recognised imaging features and mortality outcome is still not well understood. Purpose To use deep learning with hybrid neural networks to combine image pixel data and clinical information for outcome prediction. Methods A retrospective study was performed on patients who had SP-CMR between 2011 and 2021. Ethical approval was obtained under the Research Ethics Committee in compliance with the Declaration of Helsinki. Clinical characteristics and CVS risk factors were extracted by using CogStack (2), a natural language processing (NLP) application to extract and analyse clinical data. SP-CMR images were extracted from patients who had mortality events, and from equally random sample without the events for class balance. Data were split into 70% for training, 15% for validation, and 15% for testing. A hybrid neural network (HNN), which combined convolutional neural network (CNN) and multilayer perceptron (MLP), was developed to predict the mortality outcome. The CNN and MLP were trained to extract image features and clinical data, respectively, followed by prediction from concatenated features. This prediction was compared with two models, one CNN model trained on images only and another linear model trained on clinical data including CMR reports findings. DeLong test was used to compare AUC and F1 scores. All deep learning techniques was performed using Python 3.7 and Tensorflow library. Results A total of 4,188 patients were identified, a subset of 500 patients were included in training the networks, including 220 patients with positive mortality events (44%). There were more males than females (73% vs 27%), approximately 36% of patients had history of myocardial infarction (MI), and there was a significant number of patients who had positive ischaemia on SP-CMR (40%), and/or evidence of ischaemic scar (48%). Mean left ventricular ejection fraction (LVEF) was 51 ± 16 %. Area under the curve (AUC) was found to be higher in HNN (80%) followed by clinical data prediction model (78%), and superior to image CNN (63%). There was no significant AUC difference between HNN and clinical model (p=0.072). However, the F1 score showed significant improvement in precision in HNN model (72%) followed by image CNN model (52%), overtaking clinical data prediction model (21%). There was significant F1 score difference between HNN and clinical model (p&amp;lt;0.001). Conclusion Death in patients with suspected or known CAD can be better predicted by a hybrid neural network that combines clinical and SP-CMR image data than by using clinical data alone.Full pipeline for hybrid neural networkAUC and F1 Score comparisons

Adenosine-induced splenic switch-off on [15O]H2O PET perfusion for the assessment of vascular vasodilatation

BackgroundSplenic switch-off (SSO) is a marker of adequate adenosine-induced vasodilatation on cardiac magnetic resonance perfusion imaging. We evaluate the feasibility of quantitative assessment of SSO in myocardial positron emission tomography (PET) perfusion imaging using [15O]H2O.MethodsThirty patients underwent [15O]H2O PET perfusion with adenosine stress. Time-activity curves, as averaged standardized uptake values (SUVavg), were extracted from dynamic PET for spleen and liver. Maximum SUVavg, stress and rest spleen-to-liver ratio (SLR), and the splenic activity concentration ratio (SAR) were computed. Optimal cut-off values for SSO assessment were estimated from receiver operating characteristics (ROC) curve for maximum SUVavg and SLR. Also, differences between coronary artery disease, myocardial ischemia, beta-blockers, and diabetes were assessed. Data are presented as median [interquartile range].ResultsIn concordance with the SSO phenomenon, both the spleen maximum SUVavg and SLR were lower in adenosine stress when compared to rest perfusion (8.1 [6.5, 9.2] versus 16.4 [13.4, 19.0], p < 0.001) and (0.81 [0.63, 1.08] versus 1.86 [1.73, 2.06], p < 0.001), respectively. During adenosine stress, the SSO effect was most prominent 40–160 s after radiotracer injection. Cut-off values of 12.6 and 1.57 for maximum SUVavg and SLR, respectively, were found based on ROC analysis. No differences in SAR, SLRRest, or SLRStress were observed in patients with coronary artery disease, myocardial ischemia, or diabetes.ConclusionsSSO can be quantified from [15O]H2O PET perfusion and used as a marker for adequate adenosine-induced vasodilatation response. In contrary to other PET perfusion tracers, adenosine-induced SSO is time dependent with [15O]H2O.

Abstract 11609: Developing a Novel Method for Measuring Relative Lung Perfusion at the Catheterization Laboratory

Background: Maldistribution of pulmonary blood flow (Qp) is common in patients with congenital heart disease and is associated with worse clinical outcomes. Currently, measurement of Qp-split can only be performed outside the catheterization laboratory, using either lung perfusion scans or cardiac magnetic resonance imaging. Aim: We sought to develop and evaluate a tool for measuring Qp-split using readily available fluoroscopy sequences. Methods: A retrospective cohort study of patients with conotruncal anomalies who underwent perfusion scan and subsequent cardiac catheterization. Inclusion criteria were non-selective angiogram of pulmonary vasculature, oblique angulation ≤20°, and an adequate view of both lung fields. A method was developed and implemented in 3D Slicer to calculate the amount of contrast that entered each lung field from the start of contrast-injection and until the onset of levophase. The predicted perfusion distribution was compared to the distribution measured by lung scan. Results: In total 32% (79/249) of screened studies met inclusion criteria. There was strong correlation between the predicted Qp-split and the measured Qp-split (R 2 =0.83, p&lt;0.001) with median absolute error (MAE) of 6%. Bias was not systematically worse at either extreme of flow distribution. Factors associated with better prediction were smaller BSA, younger age, right ventricle (vs. pulmonary artery) angiograms, and cranial angulations ≤20°. In cases with one or more of these conditions (n=40), the prediction achieved R 2 =0.87, MAE of 5.5%, and 78% of predictions were within 10% of true flow. Conclusions: Data from conventional angiograms can be used to provide accurate real-time measurement of relative perfusion of the left and right lungs. This has the potential to reduce unnecessary testing, associated costs, and radiation exposure.

Abstract 17534: Safety and Feasibility of Adenosine Stress CMR for CAV Detection in Orthotopic Heart Transplant Recipients

Background: Stress perfusion cardiac magnetic resonance (CMR) imaging is recommended in international guidelines in class I in patients with known or suspected CAD. Patients undergoing cardiac transplantation (OHT) are at risk of developing cardiac allograft vasculopathy (CAV). Adenosine is relatively contraindicated after transplantation because of a presumed risk of atrioventricular block in denervated hearts. We sought to evaluate the safety and feasibility of adenosine stress CMR in patients with OHT and suspected CAV. Methods: In an outpatient cohort study, we measured the incidence of adverse effects of adenosine stress CMR in consecutive OHT recipients undergoing quantitative stress perfusion CMR for suspected CAV. We additionally stratified patients based on presence of significant CAV (grades 2-3 versus 0-1) on either invasive or computed tomography coronary angiography to evaluate potential CMR biomarkers of significant coronary disease in this population. Results: We identified 50 adenosine stress CMR studies performed in 45 individual patients at a median of 19 years after transplantation (IQR 4.7-24.4); 9% of studies were conducted within the first year post-transplantation. No life-threatening adverse events, brief or prolonged atrioventricular block or other arrythmias occurred after adenosine infusion. Significant myocardial ischemia (≥ 1.5 segments) was reported in 17% of patients. When stratified by CAV severity, stress MBF index, but not inducible ischemia on visual inspection, was found to significantly differentiate patients with severe CAV from those without significant coronary disease (ANOVA p = 0.028). Conclusion: Adenosine stress perfusion CMR is safe and feasible in OHT recipients. Quantitative measurement of stress MBF index may represent a promising marker of coronary disease with incremental value over qualitative assessment of ischemia, and should be evaluated in future studies.

Abstract 18068: Isometric Handgrip Exercise Myocardial Perfusion Reserve Correlates With Coronary Microvascular Dysfunction and Abnormal Left Ventricular Strain: A Report From the Women’s Ischemia Syndrome Evaluation Pre-Heart Failure With Preserved Ejection Fraction Study

Background: Impaired coronary artery response to isometric handgrip exercise (IHE) has previously been demonstrated to reflect endothelial dysfunction, an important contributor to ischemia with no obstructive coronary arteries (INOCA) and coronary microvascular dysfunction (CMD). Stress perfusion cardiac magnetic resonance (CMR) imaging is typically performed with pharmacologic stress using myocardial perfusion reserve index (MPRI) as a measure of CMD. IHE-MPRI has not been comprehensively studied in patients with INOCA, who are at risk for heart failure with preserved ejection fraction (HFpEF). Hypothesis: IHE-MPRI is related to CMD measured by pharm-MPRI and left ventricular (LV) structural and functional abnormalities in INOCA patients at risk for HFpEF. Methods: Participants with INOCA underwent comprehensive CMR with first-pass perfusion with adenosine or regadenoson, rest, and IHE. MPRI was adjusted to rest rate-pressure product (RPP). Lack of a satisfactory IHE response (defined as increase in heart rate≥10 bpm or systolic blood pressure ≥10 mmHg) was excluded. CMR measures of LV structure, function, MPRI, T1 and T2 mapping were analyzed using commercial software, blinded to clinical data. Pearson correlations were performed. Results: Of the participants (n=44) with IHE-MPRI, mean age was 55±11 years, body mass index 27±7 kg/m 2 , and 98% female, 31% hypertension, 12.5% diabetes, 19% hyperlipidemia. IHE-MPRI adjusted for rest RPP significantly correlated positively with pharm-MPRI and inversely with time to peak strain, diastolic strain measures and myocardial T2 ( Figure ). IHE-MPRI was not related to resting or IHE heart rate, systolic strain, LV mass, volumes, mass-volume ratio, native T1 or extracellular volume. Conclusion: IHE-MPRI relates to CMD and LV strain among patients with INOCA. Measurement of IHE-MPRI may improve understanding of CMD and LV structural and functional abnormalities that may contribute to development of HFpEF.

Abstract 15210: Qualitative Stress Perfusion American Heart Association Plot and Outcome Prediction Using Artificial Intelligence

Introduction: Stress perfusion cardiac magnetic resonance (CMR) is a guidelines-backed non-invasive test for the assessment of coronary artery disease (CAD), and its prognostic value is well validated. However, image interpretation requires a high level of expertise. Furthermore, the direct relationship between image pixels and outcome is not well understood. Hypothesis: Qualitative stress perfusion map based on American Heart Association (AHA) segmentation and direct linkage with outcome can be achieved using artificial intelligence. Methods: Retrospective CMR data collection was performed in one center between 2011 and 2021. Cases with death events were identified. Mean time to event was considered as a follow-up period, and cases without events and with shorter duration from CMR to collection date were excluded. Stress perfusion images were selected from 3 left ventricular (LV) levels: basal, mid and apical. Clinical CMR reports with binary AHA perfusion values were available. Six convolutional neural networks (CNNs) were trained to predict AHA segments values for each level and merged into four CNNs for the apical level. Perfusion, scar image pixels and clinical data were transformed into features, and a hybrid CNN (HNN) was trained to predict mortality. Training, validation, and test split was 70%, 15%, and 15%, respectively. Evaluation metrics included area under curve (AUC). Results: Total number of cases included for AHA plot classification were 2139 (6417 perfusion images). The average AUC for AHA perfusion classifiers was 61%, an example with correct predictions is presented. Follow-up period was calculated at 999 days. Total number of cases included for HNN development was 1294. HNN achieved high prediction value with AUC of 81%. Conclusions: Qualitative AHA stress perfusion map was feasible using artificial intelligence. Outcome prediction with HNN was a powerful new approach for risk stratifying patients with known or suspected CAD.

Stress Perfusion Cardiac Magnetic Resonance vs SPECT Imaging for Detection of Coronary Artery Disease

BackgroundGadaCAD2 was 1 of 2 international, multicenter, prospective, Phase 3 clinical trials that led to U.S. Food and Drug Administration approval of gadobutrol to assess myocardial perfusion and late gadolinium enhancement (LGE) in adults with known or suspected coronary artery disease (CAD). ObjectivesA prespecified secondary objective was to determine if stress perfusion cardiovascular magnetic resonance (CMR) was noninferior to single-photon emission computed tomography (SPECT) for detecting significant CAD and for excluding significant CAD. MethodsParticipants with known or suspected CAD underwent a research rest and stress perfusion CMR that was compared with a gated SPECT performed using standard clinical protocols. For CMR, adenosine or regadenoson served as vasodilators. The total dose of gadobutrol was 0.1 mmol/kg body weight. The standard of reference was a 70% stenosis defined by quantitative coronary angiography (QCA). A negative coronary computed tomography angiography could exclude CAD. Analysis was per patient. CMR, SPECT, and QCA were evaluated by independent central core lab readers blinded to clinical information. ResultsParticipants were predominantly male (61.4% male; mean age 58.9 ± 10.2 years) and were recruited from the United States (75.0%), Australia (14.7%), Singapore (5.7%), and Canada (4.6%). The prevalence of significant CAD was 24.5% (n = 72 of 294). Stress perfusion CMR was statistically superior to gated SPECT for specificity (P = 0.002), area under the receiver operating characteristic curve (P < 0.001), accuracy (P = 0.003), positive predictive value (P < 0.001), and negative predictive value (P = 0.041). The sensitivity of CMR for a 70% QCA stenosis was noninferior and nonsuperior to gated SPECT. ConclusionsVasodilator stress perfusion CMR, as performed with gadobutrol 0.1 mmol/kg body weight, had superior diagnostic accuracy for diagnosis and exclusion of significant CAD vs gated SPECT.

Safety and clinical impact of adenosine stress perfusion cardiac magnetic resonance in Asian patients with known or suspected coronary artery disease.

Adenosine stress cardiac magnetic resonance (CMR) imaging is increasingly utilized for evaluating patients with known or suspected coronary artery disease (CAD). This study aims to assess the safety and clinical impact of adenosine stress CMR in a tertiary care setting in Thailand. A total of 3,768 consecutive patients aged 18 years and above who underwent adenosine stress CMR between 2017 and 2020 were included in the study. Patient records were reviewed to collect data on clinical characteristics, hemodynamic measurements, complications during or immediately after CMR, and the rates of clinical changes resulting from CMR. Among the included patients, the primary indications for adenosine stress CMR were risk stratification in suspected CAD (70.8%) and the assessment of myocardial ischemia/viability in patients with known CAD (26.5%). There were no reported deaths or acute myocardial infarctions during the procedure. Major complications, specifically acute pulmonary edema requiring hospital observation or admission for further management, occurred in four patients (0.11%), all of whom were elderly (ranging from 75 to 91 years) with a history of heart failure. Non-major complications were observed in 13.7% of patients, with dyspnea (9.8%) and mild chest pain (5.6%) being the most common. CMR provided a completely new diagnosis in 26.2% of patients. Overall, stress CMR resulted in a change in diagnosis or management for 48% of patients. Adenosine stress CMR was found to be safe and to have a significant impact on clinical management in Asian patients with known or suspected CAD. These findings support the use of adenosine stress CMR as a valuable tool for evaluating and guiding treatment decisions in this patient population.