Sex- and age-specific normal values for automated quantitative pixel-wise myocardial perfusion cardiovascular magnetic resonance

Invasive coronary angiography has limited diagnostic accuracy for detecting reduction of myocardial perfusion assessed by cardiac magnetic resonance

The relationship between degree of coronary artery stenosis and its effect on myocardial perfusion is complex and constitutes a clinical challenge. The aim of this study was to assess diagnostic accuracy of visual assessment of invasive coronary angiography (ICA) for detecting reduced myocardial perfusion determined by quantitative first-pass perfusion (qFPP) cardiac magnetic resonance (CMR) in patients with suspected or established chronic coronary syndrome (CCS). Forty-nine patients with suspected or established CCS were included from the elective ICA list in this prospective, observational study and underwent qFPP CMR prior to ICA. Myocardial perfusion at stress and myocardial perfusion reserve (MPR) were assessed for each vessel territory. Myocardial perfusion at stress <2.0 ml/min/g and MPR <2.4 were considered abnormal. Visually assessed coronary artery stenoses from ICA were considered significant if ≥70%. Sensitivity and specificity of visual assessment of ICA for detecting significant reduction of myocardial perfusion ranged between 32-41% and 70-76% on a per vessel level depending on myocardial perfusion measure used as reference. Accuracy ranged between 0.48-0.64. In 59-68% of vessel territories with reduced stress perfusion or MPR, no significant stenosis was found. Thus, visual assessment of invasive coronary angiography has limited diagnostic accuracy for detecting significant reduction of myocardial perfusion assessed by qFPP CMR in patients with suspected or established CCS. Hence, quantitative myocardial perfusion is required when evaluating the cause of angina to distinguish between coronary stenosis, microvascular dysfunction and non-cardiac causes of chest pain.

Impact of physiological and coronary artery disease risk factors on myocardial perfusion in stress computed tomography myocardial perfusion imaging

To analyze the correlation between the main perfusion parameters of the left ventricle and various physiological and coronary artery disease (CAD) risk factors or comorbidities using dynamic stress computed tomography myocardial perfusion imaging (CT-MPI) in patients without obstructive coronary stenosis. This retrospective analysis included 119 patients without obstructive coronary artery stenosis in computed tomography angiography (CTA), and without perfusion defects in CT-MPI. Patients were categorized into groups based on the presence or absence of physiological and CAD risk factors or comorbidities. The global myocardial blood flow (MBF), myocardial blood volume (MBV), and perfused capillary blood volume (PCBV) of the left ventricle were compared between groups, and correlations with continuous variables were analyzed. Multivariate linear regression was used to identify independent factors. Perfusion parameters were higher (MBF, 149.41 ± 26.38 vs. 159.20 ± 21.31 ml/100 ml/min, MBV, 17.09 ± 2.37 vs.18.84 ± 1.89, and PCBV, 9.82 ± 2.21 vs. 11.47 ± 1.79 ml/100 ml [all P < 0.05]) in female patients than in male patients. Hypertension and overweight/obesity resulted in lower perfusion parameters (hypertension vs. normotension: MBF, 148.09 ± 21.15 vs. 161.47 ± 25.13 ml/100 ml/min, PCBV, 10.25 ± 2.23 vs. 11.22 ± 1.96 ml/100 ml; overweight/obesity vs. none: MBF, 148.82 ± 20.98 vs. 159.51 ± 25.44 ml/100 ml/min, PCBV, 10.20 ± 1.93 vs. 11.15 ± 2.22 ml/100 ml [all P < 0.05]). Body surface area (BSA), body mass index, stress heart rate (HR), incremental HR, coronary total plaque volume, and stress systolic blood pressure were significantly correlated with perfusion parameters (all P < 0.05). Stress HR, BSA, and hypertension were independent predictors of MBF, stress HR and sex were independent predictors of MBV, and stress HR and BSA were independent predictors of PCBV. Dynamic stress CT-MPI myocardial perfusion is affected by stress HR, sex, and BSA, and can identify early perfusion distribution in hypertension and obesity/overweight.

The Protocol for the Multi-Ethnic, multi-centre raNdomised controlled trial of a low-energy Diet for improving functional status in heart failure with Preserved ejection fraction (AMEND Preserved)

INTRODUCTION

Heart failure with preserved ejection fraction (HFpEF) is characterised by severe exercise intolerance, particularly in those living with obesity. Low-energy meal-replacement plans (MRPs) have shown significant weight loss and potential cardiac remodelling benefits. This pragmatic randomised trial aims to evaluate the efficacy of MRP-directed weight loss on exercise intolerance, symptoms, quality of life and cardiovascular remodelling in a multiethnic cohort with obesity and HFpEF.

METHODS AND ANALYSIS

Prospective multicentre, open-label, blinded endpoint randomised controlled trial comparing low-energy MRP with guideline-driven care plus health coaching. Participants (n=110, age ≥18 years) with HFpEF and clinical stability for at least 3 months will be randomised to receive either MRP (810 kcal/day) or guideline-driven care for 12 weeks. Randomisation is stratified by sex, ethnicity, and baseline Sodium Glucose Cotransporter-2 inhibitor (SGLT2-i) use, using the electronic database RedCap with allocation concealment. Key exclusion criteria include severe valvular, lung or renal disease, infiltrative cardiomyopathies, symptomatic biliary disease or history of an eating disorder. Participants will undergo glycometabolic profiling, echocardiography, MRI for cardiovascular structure and function, body composition analysis (including visceral and subcutaneous adiposity quantification), Kansas City Cardiomyopathy Questionnaire (KCCQ) and Six-Minute Walk Test (6MWT), at baseline and 12 weeks. An optional 24-week assessment will include non-contrast CMR, 6MWT, KCCQ score. Optional substudies include a qualitative study assessing participants' experiences and barriers to adopting MRP, and skeletal muscle imaging and cardiac energetics using 31Phosphorus MR spectroscopy.

STATISTICAL ANALYSIS

Complete case analysis will be conducted with adjustment for baseline randomisation factors including sex, ethnicity and baseline SGLT2-i use. The primary outcome is the change in distance walked during the 6MWT. The primary imaging endpoint is the change in left atrial volume indexed to height on cardiac MRI. Key secondary endpoints include symptoms and quality of life measured by the KCCQ score.

ETHICS AND DISSEMINATION

The Health Research Authority Ethics Committee (REC reference 22/EM/0215) has approved the study. The findings of this study will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05887271.

Abnormal skeletal muscle and myocardial vasoreactivity manifests prior to heart failure in a diabetic cardiomyopathy rat model

Background

Microvascular dysfunction (MVD) is a recognized sign of disease in heart failure progression. Intact blood vessels exhibit abnormal vasoreactivity in early stage, subsequently deteriorating to rarefaction and reduced perfusion. In managing heart failure with preserved ejection fraction (HFpEF), earlier diagnosis is key to improving management. In this study, we applied a steady-state blood-pool magnetic resonance imaging (MRI) method to investigate if it can sensitively detect abnormal leg muscle vasoreactivity, a sign of MVD, posited to manifest before structural and functional cardiac changes emerge in a diabetes model of HFpEF.

Methods

Male and female Sprague-Dawley rats were maintained on either a high-fat, high-sugar diet or a control diet for 6 months after the induction of diabetes (n = 5 per group). Beginning at month 1 or 2 post-diabetes and every 2 months thereafter, rats underwent steady-state blood-pool MRI to assess vasoreactivity in the heart or skeletal muscle, respectively. A T1-reducing blood-pool agent was administered and the T1 relaxation time dynamically measured as animals breathed in elevated CO2 levels to modulate vessels.

Results

In male rats, the normally unresponsive heart to 10% CO2 revealed a pro-vasoconstriction response beginning at 5 months post-diabetes. Abnormal leg skeletal muscle vasoreactivity appeared even earlier, at 2 months: the usual vasodilatory response to 5% CO2 was interrupted with periods of vasoconstriction in diseased rats. In female rats, differences were observed between healthy and diseased animals only in the first 2 months post-diabetes and not later. In the heart, vasodilation to 10% CO2 seen in healthy females was abolished in diabetic females. In skeletal muscle, 5% CO2 was suboptimal in inducing reproducible vasoreactivity, but young diabetic females responded by vasodilation only.

Conclusions

Abnormal vasoreactivity presented earlier than overt functional changes in both heart and skeletal muscle in diabetic cardiomyopathy, and steady-state blood-pool MRI offered early diagnosis of microvascular dysfunction.

Coronary Microvascular Function in Asymptomatic Middle-Aged Individuals With Cardiometabolic Risk Factors

BACKGROUND

In patients with ischemic heart disease, coronary microvascular dysfunction is associated with cardiovascular risk factors and poor prognosis; however, data from healthy individuals are scarce.

OBJECTIVES

The purpose of this study was to assess the impact of cardiovascular risk factors and subclinical atherosclerosis on coronary microvascular function in middle-aged asymptomatic individuals.

METHODS

Myocardial perfusion was measured at rest and under stress using cardiac magnetic resonance in 453 individuals and used to generate myocardial blood flow (MBF) maps and calculate myocardial perfusion reserve (MPR). Subclinical atherosclerosis was assessed using 3-dimensional vascular ultrasound of the carotid and femoral arteries and coronary artery calcium scoring at baseline and at 3-year follow-up.

RESULTS

Median participant age was 52.6 years (range: 48.9-55.8 years), and 84.5% were male. After adjusting for age and sex, rest MBF was directly associated with the number of the metabolic syndrome components present (elevated waist circumference, systolic and diastolic blood pressure, fasting glucose, and triglycerides and low high-density lipoprotein cholesterol), insulin resistance (homeostatic model assessment for insulin resistance), and presence of diabetes. MPR was reduced in the presence of several metabolic syndrome components, elevated homeostatic model assessment for insulin resistance, and diabetes. Stress MBF was inversely associated with coronary artery calcium presence and with global plaque burden. Higher stress MBF and MPR were associated with less atherosclerosis progression (increase in plaque volume) at 3 years.

CONCLUSIONS

In asymptomatic middle-aged individuals free of known cardiovascular disease, the presence of cardiometabolic risk factors and systemic (poly-vascular) subclinical atherosclerosis are associated with impaired coronary microvascular function. Better coronary microvascular function reduces atherosclerosis progression at follow-up. (Progression of Early Subclinical Atherosclerosis [PESA]; NCT01410318).

Impact of exercise training in combination with dapagliflozin on physical function in adults with type 2 diabetes mellitus: study protocol for the Dapagliflozin, Exercise Training and physicAl function (DETA) randomised controlled trial

INTRODUCTION

Sodium-glucose co-transporter 2 inhibitors (SGLT2i) are associated with weight loss, diverse cardiorenal benefits and improved glycaemic control. However, the effects of SGLT2i on physical function and fitness are uncertain. The Dapagliflozin, Exercise Training and physicAl function trial investigates whether the SGLT2i dapagliflozin, alone or in combination with structured exercise training, improves physical function compared with diet-induced weight loss in adults with type 2 diabetes mellitus (T2DM), overweight/obesity and impaired physical function.

METHODS AND ANALYSIS

This single-centre randomised controlled trial will assign 1:1:1, 135 adults with T2DM and low physical function to receive one of three treatments: (1) dapagliflozin (10 mg once-daily) alone, (2) dapagliflozin (10 mg once-daily) plus structured exercise training or (3) diet control (where participants are supported to achieve 3% weight loss, equivalent to estimated weight loss with dapagliflozin treatment). Primary and secondary outcomes will be assessed at baseline, 12 and 24 weeks. The primary outcome is the difference in physical function, assessed using the modified Physical Performance Test, between the treatment groups and diet control at 24 weeks. Secondary outcomes include MRI-measured cardiac structure and function, maximal aerobic capacity, resting metabolic rate, device-measured physical activity and sleep, body composition, haemoglobin A1c and cardiovascular risk markers.

ETHICS AND DISSEMINATION

The Heath Research Authority (HRA) and the Medicines and Healthcare Products Regulatory Authority (MHRA) Research Ethics Committee have approved the study. The findings of the study will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ISRCTN11459997.

EUDRACT NUMBER

2019-004586-41.

The Impact of Bariatric Surgery on Coronary Microvascular Function Assessed Using Automated Quantitative Perfusion CMR

BACKGROUND

Coronary microvascular function is impaired in patients with obesity, contributing to myocardial dysfunction and heart failure. Bariatric surgery decreases cardiovascular mortality and heart failure, but the mechanisms are unclear.

OBJECTIVES

The authors studied the impact of bariatric surgery on coronary microvascular function in patients with obesity and its relationship with metabolic syndrome.

METHODS

Fully automated quantitative perfusion cardiac magnetic resonance and metabolic markers were performed before and 6 months after bariatric surgery.

RESULTS

Compared with age- and sex-matched healthy volunteers, 38 patients living with obesity had lower stress myocardial blood flow (MBF) (P = 0.001) and lower myocardial perfusion reserve (P < 0.001). A total of 27 participants underwent paired follow-up 6 months post-surgery. Metabolic abnormalities reduced significantly at follow-up including mean body mass index by 11 ± 3 kg/m2 (P < 0.001), glycated hemoglobin by 9 mmol/mol (Q1-Q3: 4-19 mmol/mol; P < 0.001), fasting insulin by 142 ± 131 pmol/L (P < 0.001), and hepatic fat fraction by 5.6% (Q1-Q3: 2.6%-15.0%; P < 0.001). Stress MBF increased by 0.28 mL/g/min (Q1-Q3: -0.02 to 0.75 mL/g/min; P = 0.003) and myocardial perfusion reserve by 0.13 (Q1-Q3: -0.25 to 1.10; P = 0.036). The increase in stress MBF was lower in those with preoperative type 2 diabetes mellitus (0.1 mL/g/min [Q1-Q3: -0.09 to 0.46 mL/g/min] vs 0.75 mL/g/min [Q1-Q3: 0.31-1.25 mL/g/min]; P = 0.002). Improvement in stress MBF was associated with reduction in fasting insulin (beta = -0.45 [95% CI: -0.05 to 0.90]; P = 0.03).

CONCLUSIONS

Coronary microvascular function is impaired in patients with obesity, but can be improved significantly with bariatric surgery. Improvements in microvascular function are associated with improvements in insulin resistance but are attenuated in those with preoperative type 2 diabetes mellitus.

Age- and Sex-Specific Myocardial Blood Flow Values in Patients Without Coronary Atherosclerosis on Rb-82 PET Myocardial Perfusion Imaging

BACKGROUND

Quantitative myocardial blood flow (MBF) on positron-emission tomography myocardial perfusion imaging is a measure of the overall health of the coronary circulation. The ability to adequately augment blood flow, measured by myocardial blood flow reserve (MBFR), is associated with lower major adverse cardiovascular events and all-cause mortality. The age-specific ranges of MBFR in patients without demonstrable coronary artery disease have not been well established. We aimed to determine the effect of age and sex on MBF in a cohort of patients without demonstrable coronary artery disease.

METHODS

Patients who underwent positron-emission tomography myocardial perfusion imaging studies from 2012 to 2022 on positron-emission tomography/computed tomography cameras were included if the summed stress score was 0, the coronary calcium score was 0, and the left ventricular ejection fraction was ≥50%. Those with known coronary artery disease, prior history of coronary intervention, diabetes, heart/kidney/liver transplant, cirrhosis, or chronic kidney disease stage IV+ were excluded. MBF was calculated using a net retention model (ImagenQ, Cardiovascular Imaging Technologies, Kansas City), and quantile regression models were developed to predict MBF.

RESULTS

Among 2789 patients (age 59.9±13.0 years, 76.4% females), median rest MBF was 0.73 (0.60-0.91) mL/min·g, stress MBF was 1.72 (1.41-2.10) mL/min·g, and MBFR was 2.31 (1.96-2.74). Across all ages, males augmented MBF in response to vasodilator stress to a greater degree than females but achieved lower absolute stress MBF. Younger males in particular achieved a higher MBFR than their female counterparts, and this gap narrowed with increasing age. Predicted MBFR for a 20-year-old male was 3.18 and female was 2.50, while predicted MBFR for an 80-year-old male was 2.17 and female was 2.02.

CONCLUSIONS

In patients without demonstrable coronary artery disease, MBFR is higher in younger males than younger females and decreases with age in both sexes. Age- and sex-specific MBFR may be important in risk prediction and guidance for revascularization and warrant further study.

High-resolution free-breathing automated quantitative myocardial perfusion by cardiovascular magnetic resonance for the detection of functionally significant coronary artery disease

AIMS

Current assessment of myocardial ischaemia from stress perfusion cardiovascular magnetic resonance (SP-CMR) largely relies on visual interpretation. This study investigated the use of high-resolution free-breathing SP-CMR with automated quantitative mapping in the diagnosis of coronary artery disease (CAD). Diagnostic performance was evaluated against invasive coronary angiography (ICA) with fractional flow reserve (FFR) measurement.

METHODS AND RESULTS

Seven hundred and three patients were recruited for SP-CMR using the research sequence at 3 Tesla. Of those receiving ICA within 6 months, 80 patients had either FFR measurement or identification of a chronic total occlusion (CTO) with inducible perfusion defects seen on SP-CMR. Myocardial blood flow (MBF) maps were automatically generated in-line on the scanner following image acquisition at hyperaemic stress and rest, allowing myocardial perfusion reserve (MPR) calculation. Seventy-five coronary vessels assessed by FFR and 28 vessels with CTO were evaluated at both segmental and coronary territory level. Coronary territory stress MBF and MPR were reduced in FFR-positive (≤0.80) regions [median stress MBF: 1.74 (0.90-2.17) mL/min/g; MPR: 1.67 (1.10-1.89)] compared with FFR-negative regions [stress MBF: 2.50 (2.15-2.95) mL/min/g; MPR 2.35 (2.06-2.54) P < 0.001 for both]. Stress MBF ≤ 1.94 mL/min/g and MPR ≤ 1.97 accurately detected FFR-positive CAD on a per-vessel basis (area under the curve: 0.85 and 0.96, respectively; P < 0.001 for both).

CONCLUSION

A novel scanner-integrated high-resolution free-breathing SP-CMR sequence with automated in-line perfusion mapping is presented which accurately detects functionally significant CAD.

Clinical implementation of a fully automated quantitative perfusion cardiovascular magnetic resonance imaging workflow with a simplified dual-bolus contrast administration scheme

This study clinically implemented a ready-to-use quantitative perfusion (QP) cardiovascular magnetic resonance (QP CMR) workflow, encompassing a simplified dual-bolus gadolinium-based contrast agent (GBCA) administration scheme and fully automated QP image post-processing. Twenty-five patients with suspected obstructive coronary artery disease (CAD) underwent both adenosine stress perfusion CMR and an invasive coronary angiography or coronary computed tomography angiography. The dual-bolus protocol consisted of a pre-bolus (0.0075 mmol/kg GBCA at 0.5 mmol/ml concentration + 20 ml saline) and a main bolus (0.075 mmol/kg GBCA at 0.5 mmol/ml concentration + 20 ml saline) at an infusion rate of 3 ml/s. The arterial input function curves showed excellent quality. Stress MBF ≤ 1.84 ml/g/min accurately detected obstructive CAD (area under the curve 0.79; 95% Confidence Interval: 0.66 to 0.89). Combined visual assessment of color pixel QP maps and conventional perfusion images yielded a diagnostic accuracy of 84%, sensitivity of 70% and specificity of 93%. The proposed easy-to-use dual-bolus QP CMR workflow provides good image quality and holds promise for high accuracy in diagnosis of obstructive CAD. Implementation of this approach has the potential to serve as an alternative to current methods thus increasing the accessibility to offer high-quality QP CMR imaging by a wide range of CMR laboratories.

Misclassification of females and males in cardiovascular magnetic resonance parametric mapping: the importance of sex-specific normal ranges for diagnosis of health vs. disease

AIMS

Cardiovascular magnetic resonance parametric mapping enables non-invasive quantitative myocardial tissue characterization. Human myocardium has normal ranges of T1 and T2 values, deviation from which may indicate disease or change in physiology. Normal myocardial T1 and T2 values are affected by biological sex. Consequently, normal ranges created with insufficient numbers of each sex may result in sampling biases, misclassification of healthy values vs. disease, and even misdiagnoses. In this study, we investigated the impact of using male normal ranges for classifying female cases as normal or abnormal (and vice versa).

METHODS AND RESULTS

One hundred and forty-two healthy volunteers (male and female) were scanned on two Siemens 3T MR systems, providing averaged global myocardial T1 and T2 values on a per-subject basis. The Monte Carlo method was used to generate simulated normal ranges from these values to estimate the statistical accuracy of classifying healthy female or male cases correctly as 'normal' when using sex-specific vs. mixed-sex normal ranges. The normal male and female T1- and T2-mapping values were significantly different by sex, after adjusting for age and heart rate.

CONCLUSION

Using 15 healthy volunteers who are not sex specific to establish a normal range resulted in a typical misclassification of up to 36% of healthy females and 37% of healthy males as having abnormal T1 values and up to 16% of healthy females and 12% of healthy males as having abnormal T2 values. This paper highlights the potential adverse impact on diagnostic accuracy that can occur when local normal ranges contain insufficient numbers of both sexes. Sex-specific reference ranges should thus be routinely adopted in clinical practice.

Myocardial perfusion in cardiac amyloidosis

AIMS

Cardiac involvement is the main driver of clinical outcomes in systemic amyloidosis and preliminary studies support the hypothesis that myocardial ischaemia contributes to cellular damage. The aims of this study were to assess the presence and mechanisms of myocardial ischaemia using cardiovascular magnetic resonance (CMR) with multiparametric mapping and histopathological assessment.

METHODS AND RESULTS

Ninety-three patients with cardiac amyloidosis (CA) (light-chain amyloidosis n = 42, transthyretin amyloidosis n = 51) and 97 without CA (three-vessel coronary disease [3VD] n = 47, unobstructed coronary arteries n = 26, healthy volunteers [HV] n = 24) underwent quantitative stress perfusion CMR with myocardial blood flow (MBF) mapping. Twenty-four myocardial biopsies and three explanted hearts with CA were analysed histopathologically. Stress MBF was severely reduced in patients with CA with lower values than patients with 3VD, unobstructed coronary arteries and HV (CA: 1.04 ± 0.51 ml/min/g, 3VD: 1.35 ± 0.50 ml/min/g, unobstructed coronary arteries: 2.92 ± 0.52 ml/min/g, HV: 2.91 ± 0.73 ml/min/g; CA vs. 3VD p = 0.011, CA vs. unobstructed coronary arteries p < 0.001, CA vs. HV p < 0.001). Myocardial perfusion abnormalities correlated with amyloid burden, systolic and diastolic function, structural parameters and blood biomarkers (p < 0.05). Biopsies demonstrated abnormal vascular endothelial growth factor staining in cardiomyocytes and endothelial cells, which may be related to hypoxia conditions. Amyloid infiltration in intramural arteries was associated with severe lumen reduction and severe reduction in capillary density.

CONCLUSION

Cardiac amyloidosis is associated with severe inducible myocardial ischaemia demonstrable by histology and CMR stress perfusion mapping. Histological evaluation indicates a complex pathophysiology, where in addition to systolic and diastolic dysfunction, amyloid infiltration of the epicardial arteries and disruption and rarefaction of the capillaries play a role in contributing to myocardial ischaemia.

Improved reproducibility for myocardial ASL: Impact of physiological and acquisition parameters

PURPOSE

To investigate and mitigate the influence of physiological and acquisition-related parameters on myocardial blood flow (MBF) measurements obtained with myocardial Arterial Spin Labeling (myoASL).

METHODS

A Flow-sensitive Alternating Inversion Recovery (FAIR) myoASL sequence with bSSFP and spoiled GRE (spGRE) readout is investigated for MBF quantification. Bloch-equation simulations and phantom experiments were performed to evaluate how variations in acquisition flip angle (FA), acquisition matrix size (AMS), heart rate (HR) and bloodT 1 $$ {\mathrm{T}}_1 $$ relaxation time (T 1 , B $$ {\mathrm{T}}_{1,B} $$ ) affect quantification of myoASL-MBF. In vivo myoASL-images were acquired in nine healthy subjects. A corrected MBF quantification approach was proposed based on subject-specificT 1 , B $$ {\mathrm{T}}_{1,B} $$ values and, for spGRE imaging, subtracting an additional saturation-prepared baseline from the original baseline signal.

RESULTS

Simulated and phantom experiments showed a strong dependence on AMS and FA (R 2 $$ {R}^2 $$ >0.73), which was eliminated in simulations and alleviated in phantom experiments using the proposed saturation-baseline correction in spGRE. Only a very mild HR dependence (R 2 $$ {R}^2 $$ >0.59) was observed which was reduced when calculating MBF with individualT 1 , B $$ {\mathrm{T}}_{1,B} $$ . For corrected spGRE, in vivo mean global spGRE-MBF ranged from 0.54 to 2.59 mL/g/min and was in agreement with previously reported values. Compared to uncorrected spGRE, the intra-subject variability within a measurement (0.60 mL/g/min), between measurements (0.45 mL/g/min), as well as the inter-subject variability (1.29 mL/g/min) were improved by up to 40% and were comparable with conventional bSSFP.

CONCLUSION

Our results show that physiological and acquisition-related factors can lead to spurious changes in myoASL-MBF if not accounted for. Using individualT 1 , B $$ {\mathrm{T}}_{1,B} $$ and a saturation-baseline can reduce these variations in spGRE and improve reproducibility of FAIR-myoASL against acquisition parameters.

Quantitative myocardial perfusion should be interpreted in the light of sex and comorbidities in patients with suspected chronic coronary syndrome: A cardiac positron emission tomography study

Diagnosis and treatment of patients with suspected chronic coronary syndrome (CCS) currently relies on the degree of coronary artery stenosis and its significance for myocardial perfusion. However, myocardial perfusion can be affected by factors other than coronary stenosis. The aim of this study was to investigate to what extent sex, age, diabetes, hypertension and smoking affect quantitative myocardial perfusion, beyond the degree of coronary artery stenosis, in patients with suspected or established CCS. Eighty-six patients [median age 69 (range 46-86) years, 24 females] planned for elective coronary angiography due to suspected or established CCS were included. All patients underwent cardiac 13 N-NH3 positron emission tomography to quantify myocardial perfusion at rest and stress. Lowest myocardial perfusion (perfusionmin ) at stress and rest and lowest myocardial perfusion reserve (MPRmin ) for all vessel territories was used as dependent variables in a linear mixed model. Independent variables were vessel territory, degree of coronary artery stenosis (as a continuous variable of 0%-100% stenosis), sex, age, diabetes, hypertension and smoking habits. Degree of coronary artery stenosis (p < 0.001), male sex (1.8 ± 0.6 vs. 2.3 ± 0.6 mL/min/g, p < 0.001), increasing age (p = 0.025), diabetes (1.6 ± 0.5 vs. 2.0 ± 0.6 mL/min/g, p = 0.023) and smoking (1.9 ± 0.6 vs. 2.1 ± 0.6 mL/min/g, p = 0.052) were independently associated with myocardial perfusionmin at stress. Degree of coronary artery stenosis (p < 0.001), age (p = 0.040), diabetes (1.8 ± 0.6 vs. 2.3 ± 0.7, p = 0.046) and hypertension (2.2 ± 0.7 vs. 2.5 ± 0.6, p = 0.033) were independently associated with MPRmin . Sex, increasing age, diabetes, hypertension and smoking affect myocardial perfusion independent of coronary artery stenosis in patients with suspected or established CCS. Thus, these factors need to be considered when assessing the significance of reduced quantitative myocardial perfusion of patients with suspected or established CCS.

Reduced stress perfusion in myocardial infarction with nonobstructive coronary arteries

Myocardial infarction with nonobstructive coronary arteries (MINOCA) has several possible underlying causes, including coronary microvascular dysfunction (CMD). Early cardiovascular magnetic resonance imaging (CMR) is recommended, however cannot provide a diagnosis in 25% of cases. Quantitative stress CMR perfusion mapping can identify CMD, however it is unknown if CMD is present during long-term follow-up of MINOCA patients. Therefore, this study aimed to evaluate presence of CMD during long-term follow-up in MINOCA patients with an initial normal CMR scan. MINOCA patients from the second Stockholm myocardial infarction with normal coronaries study (SMINC-2), with a normal CMR scan at median 3 days after hospitalization were investigated with comprehensive CMR including stress perfusion mapping a median of 5 years after the index event, together with age- and sex-matched volunteers without symptomatic ischemic heart disease. Cardiovascular risk factors, medication and symptoms of myocardial ischemia measured by the Seattle Angina Questionnaire 7 (SAQ-7), were registered. In total, 15 patients with MINOCA and an initial normal CMR scan (59 ± 7 years old, 60% female), and 15 age- and sex-matched volunteers, underwent CMR. Patients with MINOCA and an initial normal CMR scan had lower global stress perfusion compared to volunteers (2.83 ± 1.8 vs 3.53 ± 0.7 ml/min/g, p = 0.02). There were no differences in other CMR parameters, hemodynamic parameters, or cardiovascular risk factors, except for more frequent use of statins in the MINOCA patient group compared to volunteers. In conclusion, global stress perfusion is lower in MINOCA patients during follow-up, compared to age- and sex-matched volunteers, suggesting that CMD may be a possible pathophysiological mechanism in MINOCA.Clinical Trial Registration: Clinicaltrials.gov identifier NCT02318498. Registered 2014-12-17.

Myocardial Perfusion Imaging by Cardiovascular Magnetic Resonance: Research Progress and Current Implementation

Cardiovascular diseases pose a significant health and economic burden worldwide, with coronary artery disease still recognized as a major problem. It is closely associated with hypertension, diabetes, obesity, smoking, lack of exercise, poor diet, and excessive alcohol consumption, which may lead to macro- and microvascular abnormalities in the heart. Coronary artery stenosis reduces the local supply of oxygen and nutrients to the myocardium and results in reduced levels of myocardial perfusion, which can lead to more severe conditions and irreversible damage to myocardial tissues. Therefore, accurate evaluation of myocardial perfusion abnormalities in patients with these risk factors is critical. As technology advances, magnetic resonance myocardial perfusion imaging has become more accurate at evaluating the myocardial microcirculation and has shown a powerful ability to detect myocardial ischemia. The purpose of this review is to summarize the principle, research progress of acquisition and analysis, and clinical implementation of cardiovascular magnetic resonance (CMR) myocardial perfusion imaging.