Mitochondrial oxidative phosphorylation capacity in skeletal muscle measured by ultrafast Z-spectroscopy (UFZ) MRI at 3T.

PURPOSE: To investigate the feasibility of rapid CEST MRI acquisition for evaluating oxidative phosphorylation (OXPHOS) in human skeletal muscle at 3T, utilizing ultrafast Z-spectroscopy (UFZ) combined with MRI and the Polynomial and Lorentzian line-shape Fitting (PLOF) technique. METHODS: UFZ MRI on muscle was evaluated with turbo spin echo (TSE) and 3D EPI readouts. Five healthy subjects performed in-magnet plantar flexion exercise (PFE) and subsequent changes of amide, PCr, and partial PCr mixed Cr (Cr+) CEST dynamic signals post-exercise were enabled by PLOF fitting. PCr/Cr CEST signal was further refined through pH correction by using the ratios between PCr/Cr and amide signals, named PCAR/CAR, respectively. RESULTS: UFZ MRI with TSE readout significantly reduces acquisition time, achieving a temporal resolution of <50 s for collecting high-resolution Z-spectra. Following PFE, the recovery/decay times (τ) for both PCr and Cr in the gastrocnemius muscle of the calf were notably longer when determined using PCr/Cr CEST compared to those after pH correction with amideCEST, namely τ Cr + $$ {\tau}_{Cr^{+}} $$ = 87.1 ± 15.8 s and τ PCr $$ {\tau}_{PCr} $$ = 98.1 ± 20.4 s versus τ CAR $$ {\tau}_{CAR} $$ = 32.9 ± 19.7 s and τ PCAR $$ {\tau}_{PCAR} $$ = 43.0 ± 13.0 s, respectively. τ PCr $$ {\tau}_{PCr} $$ obtained via 31P MRS ( τ PCr $$ {\tau}_{PCr} $$ = 50.3 ± 6.2 s) closely resemble those obtained from pH-corrected PCr/Cr CEST signals. CONCLUSION: The outcomes suggest potential of UFZ MRI as a robust tool for non-invasive assessment of mitochondrial function in skeletal muscles. pH correction is critical for the reliable OXPHOS measurement by CEST.

Simultaneous creatine and phosphocreatine mapping of skeletal muscle by CEST MRI at 3T.

PURPOSE: To confirm that CrCEST in muscle exhibits a slow-exchanging process, and to obtain high-resolution amide, creatine (Cr), and phosphocreatine (PCr) maps of skeletal muscle using a POlynomial and Lorentzian Line-shape Fitting (PLOF) CEST at 3T. METHODS: We used dynamic changes in PCr/CrCEST of mouse hindlimb before and after euthanasia to assign the Cr and PCr CEST peaks in the Z-spectrum at 3T and to obtain the optimum saturation parameters. Segmented 3D EPI was employed to obtain multi-slice amide, PCr, and Cr CEST maps of human skeletal muscle. Subsequently, the PCrCEST maps were calibrated using the PCr concentrations determined by 31 P MRS. RESULTS: A comparison of the Z-spectra in mouse hindlimb before and after euthanasia indicated that CrCEST is a slow-exchanging process in muscle (<150.7 s-1 ). This allowed us to simultaneously extract PCr/CrCEST signals at 3T using the PLOF method. We determined optimal B1 values ranging from 0.3 to 0.6 µT for CrCEST in muscle and 0.3-1.2 µT for PCrCEST. For the study on human calf muscle, we determined an optimum saturation time of 2 s for both PCr/CrCEST (B1 = 0.6 µT). The PCr/CrCEST using 3D EPI were found to be comparable to those obtained using turbo spin echo (TSE). (3D EPI/TSE PCr: (2.6 ± 0.3) %/(2.3 ± 0.1) %; Cr: (1.3 ± 0.1) %/(1.4 ± 0.07) %). CONCLUSIONS: Our study showed that in vivo CrCEST is a slow-exchanging process. Hence, amide, Cr, and PCr CEST in the skeletal muscle can be mapped simultaneously at 3T by PLOF CEST.

Creatine mapping of the brain at 3T by CEST MRI.

PURPOSE: To assess the feasibility of CEST-based creatine (Cr) mapping in brain at 3T using the guanidino (Guan) proton resonance. METHODS: Wild type and knockout mice with guanidinoacetate N-methyltransferase deficiency and low Cr and phosphocreatine (PCr) concentrations in the brain were used to assign the Cr and protein-based arginine contributions to the GuanCEST signal at 2.0 ppm. To quantify the Cr proton exchange rate, two-step Bloch-McConnell fitting was used to fit the extracted CrCEST line-shape and multi-B1 Z-spectral data. The pH response of GuanCEST was simulated to demonstrate its potential for pH mapping. RESULTS: Brain Z-spectra of wild type and guanidinoacetate N-methyltransferase deficiency mice show a clear Guan proton peak at 2.0 ppm at 3T. The CrCEST signal contributes ∼23% to the GuanCEST signal at B1 = 0.8 µT, where a maximum CrCEST effect of 0.007 was detected. An exchange rate range of 200-300 s-1 was estimated for the Cr Guan protons. As revealed by the simulation, an elevated GuanCEST in the brain is observed when B1 is less than 0.4 µT at 3T, when intracellular pH reduces by 0.2. Conversely, the GuanCEST decreases when B1 is greater than 0.4 µT with the same pH drop. CONCLUSIONS: CrCEST mapping is possible at 3T, which has potential for detecting intracellular pH and Cr concentration in brain.

Coronary artery endothelial function and aging in people with HIV and HIV-negative individuals.

Coronary artery disease (CAD) is a common comorbidity in people with human immunodeficiency virus (HIV) (PWH) and impaired coronary endothelial function (CEF) plays a central role in the pathogenesis of CAD. Age-related impaired CEF among PWH, however, is not well characterized. We investigated the association between CEF and age in males and females with and without HIV using 3-T magnetic resonance imaging (MRI). We measured the changes in coronary cross-sectional area (CSA) and coronary blood flow during isometric handgrip exercise (IHE), an established endothelial-dependent stressor with smaller increases in CSA and coronary blood flow indicative of impaired CEF. We included 106 PWH and 82 individuals without HIV. Differences in demographic and clinical characteristics between PWH and individuals without HIV were explored using Pearson's χ2 test for categorical variables and Welch's t test for continuous variables. Linear regression models were used to examine the association between CEF and age. CEF was significantly lower in PWH as compared with individuals without HIV. Coronary endothelial dysfunction was also present at younger ages in PWH than in the individuals without HIV and there were significant differences in CEF between the PWH and individuals without HIV across age groups. Among the individuals without HIV, the percent changes in CSA were inversely related to age in unadjusted and adjusted models. There was no significant association between CEF and age in PWH. To the best of our knowledge, this is the first study to examine the relationship between age and CEF in PWH, and our results suggest that factors other than age significantly impair CEF in PWH across the life span.NEW & NOTEWORTHY This is the first study to examine the relationship between age and coronary endothelial function (CEF) in people with human immunodeficiency virus (HIV) (PWH). CEF was assessed using magnetic resonance imaging (MRI) in people with and without HIV. Although age and CEF were significantly inversely related in individuals without HIV, there was no association between age and CEF in PWH.

Association of Soluble Markers of Inflammation With Peri-coronary Artery Inflammation in People With and Without HIV Infection and Without Cardiovascular Disease.

Background: Inflammation is linked to elevated cardiovascular disease (CVD) risk in people with HIV (PWH) on antiretroviral therapy (ART). Fat attenuation index (FAI) is a measure of peri-coronary inflammation that independently predicts CVD risk in HIV-uninfected persons. Whether FAI is associated with soluble inflammatory markers is unknown. Methods: Plasma levels of inflammatory markers were measured in 58 PWH and 16 controls without current symptoms or prior known CVD who underwent coronary computed tomography angiography and had FAI measurements. A cross-sectional analysis was performed, and associations of markers with FAI values of the right coronary artery (RCA) and left anterior descending artery (LAD) were assessed using multivariable regression models adjusted for the potential confounders age, sex, race, low-density lipoprotein cholesterol, body mass index, and use of lipid-lowering medication. Results: Several inflammatory markers had significant associations with RCA or LAD FAI in adjusted models, including sCD14, sCD163, TNFR-I, and TNFR-II, CCL5, CX3CL1, IP-10. Conclusions: The associations between indices of systemic and peri-coronary inflammation are novel and suggest that these systemic markers and FAI together are promising noninvasive biomarkers that can be applied to assess asymptomatic CVD in people with and without HIV; they also may be useful tools to evaluate effects of anti-inflammatory interventions.

The exchange rate of creatine CEST in mouse brain.

PURPOSE: To estimate the exchange rate of creatine (Cr) CEST and to evaluate the pH sensitivity of guanidinium (Guan) CEST in the mouse brain. METHODS: Polynomial and Lorentzian line-shape fitting (PLOF) were implemented to extract the amine, amide, and Guan CEST signals from the brain Z-spectrum at 11.7T. Wild-type (WT) and knockout mice with the guanidinoacetate N-methyltransferase deficiency (GAMT-/- ) that have low Cr and phosphocreatine (PCr) concentrations in the brain were used to extract the CrCEST signal. To quantify the CrCEST exchange rate, a two-step Bloch-McConnell (BM) fitting was used to fit the CrCEST line-shape, B1 -dependent CrCEST, and the pH response with different B1 values. The pH in the brain cells was altered by hypercapnia to measure the pH sensitivity of GuanCEST. RESULTS: Comparison between the Z-spectra of WT and GAMT-/- mice suggest that the CrCEST is between 20% and 25% of the GuanCEST in the Z-spectrum at 1.95 ppm between B1 = 0.8 and 2 µT. The CrCEST exchange rate was found to be around 240-480 s-1 in the mouse brain, which is significantly lower than that in solutions (∼1000 s-1 ). The hypercapnia study on the mouse brain revealed that CrCEST at B1 = 2 µT and amineCEST at B1 = 0.8 µT are highly sensitive to pH change in the WT mouse brain. CONCLUSIONS: The in vivo CrCEST exchange rate is slow, and the acquisition parameters for the CrCEST should be adjusted accordingly. CrCEST is the major contribution to the opposite pH-dependence of GuanCEST signal under different conditions of B1 in the brain.

Contribution of skeletal muscle-specific microRNA-133b to insulin resistance in heart failure.

Insulin resistance (IR) is one of the hallmarks of heart failure (HF). Abnormalities in skeletal muscle (SM) metabolism have been identified in patients with HF. However, the underlying mechanisms of IR development in SM in HF are poorly understood. Herein, we hypothesize that HF upregulates miR-133b in SM and in turn alters glucose metabolism and the propensity toward IR. Mitochondria isolated from SM of mice with HF induced by transverse aortic constriction (TAC) showed lower respiration and downregulation of muscle-specific components of the tricarboxylic acid (TCA) cycle, AMP deaminase 1 (AMPD1), and fumarate compared with those from control animals. RNA-Seq and subsequent qPCR validation confirmed upregulation of SM-specific microRNA (miRNA), miR-133b, in TAC versus sham animals. miR-133b overexpression alone resulted in significantly lower mitochondrial respiration, cellular glucose uptake, and glycolysis along with lower ATP production and cellular energy reserve compared with the scramble (Scr) in C2C12 cells. miR-133b binds to the 3'-untranslated region (UTR) of KLF15, the transcription factor for the insulin-sensitive glucose transporter, GLUT4. Overexpression of miR-133b lowers GLUT4 and lowers pAkt in presence of insulin in C2C12 cells. Finally, lowering miR-133b in primary skeletal myocytes isolated from TAC mice using antagomir-133b reversed the changes in KLF15, GLUT4, and AMPD1 compared with the scramble-transfected myocytes. Taken together, these data demonstrate a role for SM miR-133b in altered glucose metabolism in HF and suggest the therapeutic potential in HF to improve glucose uptake and glycolysis by restoring GLUT4 abundance. The data uncover a novel mechanism for IR and ultimately SM metabolic abnormalities in patients with HF.NEW & NOTEWORTHY Heart failure is associated with systemic insulin resistance and abnormalities in glucose metabolism but the underlying mechanisms are poorly understood. In the skeletal muscle, the major peripheral site of glucose utilization, we observe an increase in miR-133b in heart failure mice, which reduces the insulin-sensitive glucose transporter (GLUT4), glucose uptake, and metabolism in C2C12 and in myocytes. The antagomir for miR-133b restores GLUT4 protein and markers of metabolism in skeletal myocytes from heart failure mice demonstrating that miR-133b is an exciting target for systemic insulin resistance in heart failure and an important player in the cross talk between the heart and the periphery in the heart failure syndrome.

The Relationship Between Impaired Coronary Endothelial Function and Systemic Markers of Inflammation in People Living With HIV.

BACKGROUND: People with HIV (PWH) are at an increased risk of cardiovascular disease, partially believed to be related to chronically elevated systemic inflammation. Abnormal systemic endothelial function (SEF) and coronary endothelial function (CEF) develop early in atherogenesis and predict adverse events. It is unknown whether abnormal CEF is related to systemic inflammation in PWH. METHODS: In this substudy of a prior randomized controlled trial in PWH without prior clinical coronary artery disease suppressed on antiretroviral therapy with CEF as a primary end point (N = 82), we investigated the associations between baseline serum markers of inflammation and adhesion and baseline CEF, assessed by noninvasive MRI measures of percentage changes in coronary blood flow and cross-sectional area during isometric handgrip exercise, and SEF using brachial ultrasound for flow-mediated dilation. We also evaluated whether baseline marker levels were associated with CEF after 8 weeks in the placebo group (N = 40). RESULTS: CEF measures were abnormal at baseline, based on trial entry criteria. A higher value of CEF was directly associated with levels of interleukin 10, whereas CEF at baseline was inversely associated with E-selectin. Worse CEF at 8 weeks was directly associated with baseline tumor necrosis factor alpha, intercellular adhesion molecule 1, C-reactive protein, interferon gamma and sICAM-3. SEF at baseline or 8 weeks was not associated with any baseline markers. CONCLUSION: Coronary but not systemic endothelial dysfunction was significantly associated with select markers of inflammation and adhesion in PWH. Furthermore, CEF but not SEF at 8 weeks was associated with baseline levels of inflammation. Our findings suggest that abnormal CEF and systemic markers of inflammation are linked in PWH.

The Association of Clustered Ventricular Arrhythmia and Cycle Length With Scar Burden in Cardiomyopathy.

BACKGROUND: Patients with ≥2 ventricular arrhythmia (VA) events within 3 months (clustered VA) have increased risk for mortality. OBJECTIVES: The aim of this study was to examine the association of risk factors including scar characteristics on cardiovascular magnetic resonance imaging with clustered VA and VA cycle length in nonischemic cardiomyopathy (NICM) and ischemic cardiomyopathy (ICM). METHODS: Data from 329 primary prevention implantable cardioverter-defibrillator recipients (mean age 57 years, 26% women) were analyzed from the Left Ventricular Structural Predictors of Sudden Cardiac Death study. RESULTS: Twenty-one patients developed clustered VA (median time 2.7 years after implantable cardioverter-defibrillator placement). Men had the greatest risk for recurrent VA. Patients with NICM and scar had the highest incidence rate of clustered VA. In patients with NICM, each 1-g increase in core scar correlated with greater clustered VA risk (HR: 1.19; 95% CI: 1.07-1.32). Gray scar was similar among subgroups. Patients with NICM with clustered VA had the longest mean VA cycle length (297 ± 40 milliseconds). Higher core scar burden correlated with longer VA cycle length in patients with NICM (P = 0.002), and higher body mass index correlated with shorter VA cycle length in those with ICM (P = 0.02). Type of VA was similar between cardiomyopathy subgroups, and no scar pattern predominated. CONCLUSIONS: Clustered VA was most common in patients with NICM and scar, with greatest risk among those with larger core scar. Core scar correlated with slower VA in patients with NICM, and higher body mass index correlated with faster VA in those with ICM. Type of VA was similar by cardiomyopathy etiology, and no dominant scar pattern was associated with clustered VA.

Myocardial ATP depletion detected noninvasively predicts sudden cardiac death risk in patients with heart failure.

BACKGROUNDSudden cardiac death (SCD) remains a worldwide public health problem in need of better noninvasive predictive tools. Current guidelines for primary preventive SCD therapies, such as implantable cardioverter defibrillators (ICDs), are based on left ventricular ejection fraction (LVEF), but these guidelines are imprecise: fewer than 5% of ICDs deliver lifesaving therapy per year. Impaired cardiac metabolism and ATP depletion cause arrhythmias in experimental models, but to our knowledge a link between arrhythmias and cardiac energetic abnormalities in people has not been explored, nor has the potential for metabolically predicting clinical SCD risk.METHODSWe prospectively measured myocardial energy metabolism noninvasively with phosphorus magnetic resonance spectroscopy in patients with no history of significant arrhythmias prior to scheduled ICD implantation for primary prevention in the setting of reduced LVEF (≤35%).RESULTSBy 2 different analyses, low myocardial ATP significantly predicted the composite of subsequent appropriate ICD firings for life-threatening arrhythmias and cardiac death over approximately 10 years. Life-threatening arrhythmia risk was approximately 3-fold higher in patients with low ATP and independent of established risk factors, including LVEF. In patients with normal ATP, rates of appropriate ICD firings were several-fold lower than reported rates of ICD complications and inappropriate firings.CONCLUSIONTo the best of our knowledge, these are the first data linking in vivo myocardial ATP depletion and subsequent significant arrhythmic events in people, suggesting an energetic component to clinical life-threatening ventricular arrhythmogenesis. The findings support investigation of metabolic strategies that limit ATP loss to treat or prevent life-threatening cardiac arrhythmias and herald noninvasive metabolic imaging as a complementary SCD risk stratification tool.TRIAL REGISTRATIONClinicalTrials.gov NCT00181233.FUNDINGThis work was supported by the DW Reynolds Foundation, the NIH (grants HL61912, HL056882, HL103812, HL132181, HL140034), and Russell H. Morgan and Clarence Doodeman endowments at Johns Hopkins.

Mitochondrial Creatine Kinase Attenuates Pathologic Remodeling in Heart Failure.

BACKGROUND: Abnormalities in cardiac energy metabolism occur in heart failure (HF) and contribute to contractile dysfunction, but their role, if any, in HF-related pathologic remodeling is much less established. CK (creatine kinase), the primary muscle energy reserve reaction which rapidly provides ATP at the myofibrils and regenerates mitochondrial ADP, is down-regulated in experimental and human HF. We tested the hypotheses that pathologic remodeling in human HF is related to impaired cardiac CK energy metabolism and that rescuing CK attenuates maladaptive hypertrophy in experimental HF. METHODS: First, in 27 HF patients and 14 healthy subjects, we measured cardiac energetics and left ventricular remodeling using noninvasive magnetic resonance 31P spectroscopy and magnetic resonance imaging, respectively. Second, we tested the impact of metabolic rescue with cardiac-specific overexpression of either Ckmyofib (myofibrillar CK) or Ckmito (mitochondrial CK) on HF-related maladaptive hypertrophy in mice. RESULTS: In people, pathologic left ventricular hypertrophy and dilatation correlate closely with reduced myocardial ATP levels and rates of ATP synthesis through CK. In mice, transverse aortic constriction-induced left ventricular hypertrophy and dilatation are attenuated by overexpression of CKmito, but not by overexpression of CKmyofib. CKmito overexpression also attenuates hypertrophy after chronic isoproterenol stimulation. CKmito lowers mitochondrial reactive oxygen species, tissue reactive oxygen species levels, and upregulates antioxidants and their promoters. When the CK capacity of CKmito-overexpressing mice is limited by creatine substrate depletion, the protection against pathologic remodeling is lost, suggesting the ADP regenerating capacity of the CKmito reaction rather than CK protein per se is critical in limiting adverse HF remodeling. CONCLUSIONS: In the failing human heart, pathologic hypertrophy and adverse remodeling are closely related to deficits in ATP levels and in the CK energy reserve reaction. CKmito, sitting at the intersection of cardiac energetics and redox balance, plays a crucial role in attenuating pathologic remodeling in HF. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT00181259.

Coronary Endothelial Dysfunction in People Living With HIV Is Related to Body Fat Distribution.

BACKGROUND: People living with HIV (PLWH) on antiretroviral therapy (ART) are at increased risk of atherosclerotic disease. Abnormal adipose distribution is common in PLWH and may contribute to atherosclerosis. Because coronary artery endothelial function (CEF) is impaired in early atherosclerosis, predicts future cardiovascular events, and is reduced in PLWH, we investigated associations between body fat distribution and CEF in PLWH. SETTING: Prospective cohort study. METHODS: PLWH on stable ART underwent MRI to quantify CEF, measured as change in coronary cross-sectional area from rest to that during isometric handgrip exercise, an endothelial-dependent stressor. Abdominal visceral and subcutaneous fat area (axial L4 level) and liver fat fraction were quantified using MRI. Linear regression was used to determine associations between CEF and independent variables. RESULTS: Among 84 PLWH (52 ± 11 years; 33% women), mean cross-sectional area change was 0.74 ± 11.7%, indicating impaired CEF. On univariable regression analysis, CEF was inversely related to waist circumference (R = -0.31, P = 0.014), hip circumference (R = -0.27, P = 0.037), and subcutaneous fat area (R = -0.25, P = 0.031). We did not observe significant relationships between CEF and liver fat fraction, waist/hip ratio, or visceral fat area. On multivariable regression adjusted for age, sex, and race, CEF was associated with waist circumference, hip circumference, subcutaneous fat, and liver fat fraction. CONCLUSION: Waist and hip circumference and subcutaneous fat area are associated with impaired CEF, an established metric of abnormal vascular health in PLWH on stable ART, and may contribute to the increased rate of heart disease in this population.

Assessment of coronary inflammation in antiretroviral treated people with HIV infection and active HIV/hepatitis C virus co-infection.

OBJECTIVE: People with HIV (PWH) and co-infected with hepatitis C virus (PWH + HCV) have increased risk of cardiovascular disease (CVD). Peri-coronary inflammation, measured by fat attenuation index (FAI) on coronary computed tomography angiography (CCTA), independently predicts cardiovascular risk in the general population but has not been studied in the PWH + HCV population. We tested whether peri-coronary inflammation is increased in PWH or PWH + HCV, and whether inflammation changes over time. DESIGN: Cross-sectional analysis to determine FAI differences among groups. Longitudinal analysis in PWH to assess changes in inflammation over time. METHODS: Age-matched and sex-matched seropositive groups (PWH and PWH + HCV) virologically suppressed on antiretroviral therapy, HCV viremic, and without prior CVD and matched controls underwent CCTA. Peri-coronary FAI was measured around the proximal right coronary artery (RCA) and left anterior descending artery (LAD). Follow-up CCTA was performed in 22 PWH after 20.6-27.4 months. RESULTS: A total of 101 participants (48 women) were studied (60 PWH, 19 PWH + HCV and 22 controls). In adjusted analyses, peri-coronary FAI did not differ between seropositive groups and controls. Low attenuation coronary plaque was significantly less common in seropositive groups compared with controls (LAD, P = 0.035; and RCA, P = 0.017, respectively). Peri-coronary FAI values significantly progressed between baseline and follow-up in PWH (RCA: P = 0.001, LAD: P = <0.001). CONCLUSION: PWH and PWH + HCV without history of CVD do not have significantly worse peri-coronary inflammation, assessed by FAI, compared with matched controls. However, peri-coronary inflammation in mono-infected PWH significantly increased over approximately 22 months. FAI measures may be an important imaging biomarker for tracking asymptomatic CVD progression in PWH.

3D Attention M-net for Short-axis Left Ventricular Myocardium Segmentation in Mice MR cardiac Images.

Small rodent cardiac magnetic resonance imaging (MRI) plays an important role in preclinical models of cardiac disease. Accurate myocardial boundaries delineation is crucial to most morphological and functional analysis in rodent cardiac MRIs. However, rodent cardiac MRIs, due to animal's small cardiac volume and high heart rate, are usually acquired with sub-optimal resolution and low signal-to-noise ratio (SNR). These rodent cardiac MRIs can also suffer from signal loss due to the intra-voxel dephasing. These factors make automatic myocardial segmentation challenging. Manual contouring could be applied to label myocardial boundaries but it is usually laborious, time consuming, and not systematically objective. In this study, we present a deep learning approach based on 3D attention M-net to perform automatic segmentation of left ventricular myocardium. In the deep learning architecture, we use dual spatial-channel attention gates between encoder and decoder along with multi-scale feature fusion path after decoder. Attention gates enable networks to focus on relevant spatial information and channel features to improve segmentation performance. A distance derived loss term, besides general dice loss and binary cross entropy loss, was also introduced to our hybrid loss functions to refine segmentation contours. The proposed model outperforms other generic models, like U-Net and FCN, in major segmentation metrics including the dice score (0.9072), Jaccard index (0.8307) and Hausdorff distance (3.1754 pixels), which are comparable to the results achieved by state-of-the-art models on human cardiac ACDC17 datasets.Clinical relevance Small rodent cardiac MRI is routinely used to probe the effect of individual genes or groups of genes on the etiology of a large number of cardiovascular diseases. An automatic myocardium segmentation algorithm specifically designed for these data can enhance accuracy and reproducibility of cardiac structure and function analysis.

Randomized Trial of Anti-inflammatory Medications and Coronary Endothelial Dysfunction in Patients With Stable Coronary Disease.

Aims: Inflammation plays a critical role in the pathogenesis of coronary artery disease (CAD), however the impact of anti-inflammatory therapies to reduce those processes which promote atherosclerosis in CAD patients is unknown. We aimed to test the hypothesis that anti-inflammatory approaches improve impaired coronary endothelial function (CEF), a driver of coronary atherosclerosis, in stable CAD patients. Methods and Results: We performed a single-center, randomized, placebo-controlled, double-blinded trial to assess whether low dose methotrexate (MTX), low dose colchicine (LDC), and/or their combination (MTX+LDC), improves CEF using non-invasive MRI measures in patients with stable CAD (N = 94). The primary endpoint was the MRI-detected change in coronary cross-sectional area from rest to isometric handgrip exercise (IHE), a predominantly nitric oxide-dependent endothelial dependent stressor. Coronary and systemic endothelial endpoints, and serum inflammatory markers, were collected at baseline, 8 and 24 weeks. Anti-inflammatory study drugs were well-tolerated. There were no significant differences in any of the CEF parameters among the four groups (MTX, LDC, MTX+LDC, placebo) at 8 or 24 weeks. Serum markers of inflammation and systemic endothelial function measures were also not significantly different among the groups. Conclusion: This is the first study to examine the effects of the anti-inflammatory approaches using MTX, LDC, and/or the combination in stable CAD patients on CEF, a marker of vascular health and the primary endpoint of the study. Although these anti-inflammatory approaches were relatively well-tolerated, they did not improve coronary endothelial function in patients with stable CAD. Clinical Trial Registration: www.clinicaltrials.gov, identifier: NCT02366091.

CinE caRdiac magneTic resonAnce to predIct veNTricular arrhYthmia (CERTAINTY).

Better models to identify individuals at low risk of ventricular arrhythmia (VA) are needed for implantable cardioverter-defibrillator (ICD) candidates to mitigate the risk of ICD-related complications. We designed the CERTAINTY study (CinE caRdiac magneTic resonAnce to predIct veNTricular arrhYthmia) with deep learning for VA risk prediction from cine cardiac magnetic resonance (CMR). Using a training cohort of primary prevention ICD recipients (n = 350, 97 women, median age 59 years, 178 ischemic cardiomyopathy) who underwent CMR immediately prior to ICD implantation, we developed two neural networks: Cine Fingerprint Extractor and Risk Predictor. The former extracts cardiac structure and function features from cine CMR in a form of cine fingerprint in a fully unsupervised fashion, and the latter takes in the cine fingerprint and outputs disease outcomes as a cine risk score. Patients with VA (n = 96) had a significantly higher cine risk score than those without VA. Multivariate analysis showed that the cine risk score was significantly associated with VA after adjusting for clinical characteristics, cardiac structure and function including CMR-derived scar extent. These findings indicate that non-contrast, cine CMR inherently contains features to improve VA risk prediction in primary prevention ICD candidates. We solicit participation from multiple centers for external validation.

Volumetric coronary endothelial function assessment: a feasibility study exploiting stack-of-stars 3D cine MRI and image-based respiratory self-gating.

Abnormal coronary endothelial function (CEF), manifesting as depressed vasoreactive responses to endothelial-specific stressors, occurs early in atherosclerosis, independently predicts cardiovascular events, and responds to cardioprotective interventions. CEF is spatially heterogeneous along a coronary artery in patients with atherosclerosis, and thus recently developed and tested non-invasive 2D MRI techniques to measure CEF may not capture the extent of changes in CEF in a given coronary artery. The purpose of this study was to develop and test the first volumetric coronary 3D MRI cine method for assessing CEF along the proximal and mid-coronary arteries with isotropic spatial resolution and in free-breathing. This approach, called 3D-Stars, combines a 6 min continuous, untriggered golden-angle stack-of-stars acquisition with a novel image-based respiratory self-gating method and cardiac and respiratory motion-resolved reconstruction. The proposed respiratory self-gating method agreed well with respiratory bellows and center-of-k-space methods. In healthy subjects, 3D-Stars vessel sharpness was non-significantly different from that by conventional 2D radial in proximal segments, albeit lower in mid-portions. Importantly, 3D-Stars detected normal vasodilatation of the right coronary artery in response to endothelial-dependent isometric handgrip stress in healthy subjects. Coronary artery cross-sectional areas measured using 3D-Stars were similar to those from 2D radial MRI when similar thresholding was used. In conclusion, 3D-Stars offers good image quality and shows feasibility for non-invasively studying vasoreactivity-related lumen area changes along the proximal coronary artery in 3D during free-breathing.