Journal of Cardiovascular Magnetic Resonance最新文献

Background: Normal reference ranges in cardiovascular imaging studies are typically established as the mean value plus and minus twice the standard deviation (SD) of a healthy reference cohort ("2 SD-method"). Although widely used for cardiac magnetic resonance (CMR), this approach has not been previously validated. The purpose of this study was to use longitudinal cohort data to assess the clinical predictive validity of normal reference values for cardiac CMR.

Methods: Normal reference ranges for left- and right ventricular (LV and RV) CMR parameters were derived from baseline exam data of 1518 participants (age 45-84years) in the Multi-Ethnic Study of Atherosclerosis (MESA) study without known CV disease and without established CV risk factors. Cut-off values at 1 and 2 SDs were obtained for the following LV and RV parameters indexed to body surface area: end-diastolic volume (LVEDVi, RVEDVi), end-systolic volume (LVESVi, RVESVi), mass (LVMi, RVMi), as well as for LVED diameter (LVEDD), LVED wall thickness, and ejection fraction (LVEF, RVEF). The relationship of reference values to CV events was then evaluated in the entire MESA cohort with CMR data (n=4915), including individuals with CV risk factors at the baseline exam. Cox proportional hazard models were calculated for major adverse and all CV events (MACE and ACE, respectively) at 5 and 10 years of follow-up.

Results: At 5 years of follow-up, LVEDVi, LVESVi, and LVEF beyond the 2SD-threshold of the mean reference values were predictors of MACE and ACE in men and women (HR 2.1-4.3; P<.001-.029). In men, LVMi and LVED wall thickness above the 1 SD-threshold were associated with CV events (HR 1.6-2.1; P<.001-.002). For women, LVED wall thickness above the 1 SD-threshold significantly increased risk of adverse events (HR 1.6-2.3; P.034-.002) while LVMi was associated with events only for values above the 2SD-threshold (HR 2.7-4.1; P<.001). Notably, LVEDD, RVMi, RVESVi, and RVEF were not associated with CV events in men or women. CV events over 10 years showed similar trends.

Conclusion: Our results support the clinical relevance of CMR normal reference ranges for LV parameters. Most LV CMR parameters beyond the normal reference range (2SD-threshold) were associated with elevated CV risk at 5 and 10 years. Elevated LVEDDi, RVMi, RVESVi, and RVEF, however, were not associated with CV events.

Background: Despite its potential to improve the assessment of cardiovascular diseases, four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) is hampered by long scan times. 4D flow CMR is conventionally acquired with three motion encodings and one reference encoding, as the three-dimensional velocity data are obtained by subtracting the phase of the reference from the phase of the motion encodings. In this study, we aim to use deep learning to predict the reference encoding from the three motion encodings for cardiovascular 4D flow.

Methods: A U-Net was trained with adversarial learning (U-Net_ADV) and with a velocity frequency-weighted loss function (U-Net_VEL) to predict the reference encoding from the three motion encodings obtained with a non-symmetric velocity-encoding scheme. Whole-heart 4D flow datasets from 126 patients with different types of cardiomyopathies were retrospectively included. The models were trained on 113 patients with a 5-fold cross-validation, and tested on 13 patients. Flow volumes in the aorta and pulmonary artery, mean and maximum velocity, total and maximum turbulent kinetic energy at peak systole in the cardiac chambers and main vessels were assessed.

Results: Three-dimensional velocity data reconstructed with the reference encoding predicted by deep learning agreed well with the velocities obtained with the reference encoding acquired at the scanner for both models. U-Net_ADV performed more consistently throughout the cardiac cycle and across the test subjects, while U-Net_VEL performed better for systolic velocities. Comprehensively, the largest error for flow volumes, maximum and mean velocities was -6.031% for maximum velocities in the right ventricle for the U-Net_ADV, and -6.92% for mean velocities in the right ventricle for U-Net_VEL. For total turbulent kinetic energy, the highest errors were in the left ventricle (-77.17%) for the U-Net_ADV, and in the right ventricle (24.96%) for the U-Net_VEL, while for maximum turbulent kinetic energy were in the pulmonary artery for both models, with a value of -15.5% for U-Net_ADV and 15.38% for the U-Net_VEL.

Conclusion: Deep learning-enabled referenceless 4D flow CMR permits velocities and flow volumes quantification comparable to conventional 4D flow. Omitting the reference encoding reduces the amount of acquired data by 25%, thus allowing shorter scan times or improved resolution, which is valuable for utilization in the clinical routine.

Background: Atrial fibrillation (AF) ablation may induce reverse left atrial (LA) remodeling, yet few studies have prospectively evaluated its short- and long-term effects. This study assessed LA volumetric and functional remodeling using cardiovascular magnetic resonance (CMR) imaging early and late after pulmonary vein isolation (PVI) in AF patients.

Methods: This study involved 61 AF patients undergoing radiofrequency PVI. CMR scans were performed pre-PVI, within 72 h and 3months post-PVI. LA volumes and strain were assessed using two- and four-chamber cine images. Early AF recurrence was monitored during 3months follow-up.

Results: LAVImin significantly increased early post-PVI (22.5±8.7 mL/m² to 25.8±9.9 mL/m², p<0.01). At 3months, both LAVImin and LAVImax significantly reduced compared to early post-PVI (25.4±8.87 mL/m² to 19.4±7.7 mL/m², p<0.001; 48.2±12.7 mL/m² to 38.7±10.6 mL/m², p<0.001, respectively), as well as compared to baseline (22.5±8.7 mL/m² to 20.1±8.5 mL/m², p=0.04; 45.6±11.8 mL/m² to 39.3±11.2 mL/m², p<0.001, respectively). Early post-PVI, LA emptying fraction (LA EF), LA reservoir, and contractile strain significantly reduced compared to baseline (from 51.6±10.8% to 47.1±8.9%, p<0.01; 18.3±4.4% to 15.4±2.9%, p<0.001; 8.3±3.1% to 5.4±1.8%, p<0.001, respectively). At 3months, LA EF, LA reservoir, and contractile strain significantly increased as compared to early post-PVI (from 47.1±8.9% to 50.5±8.6%, p<0.01; 15.4±2.9% to 16.8±3.1%, p<0.01; 5.4±1.8% to 6.9±2.3%, p<0.001, respectively). However, LA reservoir and contractile strain remained significantly lower compared to baseline (18.3±4.4% to 16.8±3.1%, p=0.02; 8.3±3.1% to 6.9±2.3%, p<0.01, respectively). In patients with early AF recurrence 27.9% (17/61), LA volume reduction and partial functional recovery were not observed during 3months post-PVI.

Conclusion: LA volumes significantly reduced 3months post-PVI. While LA function initially declined, it showed partial recovery at 3months. However, LA reservoir and contractile strain remained reduced compared to pre-PVI. LA reverse remodeling and partial LA functional recovery only occurred in patients without early AF recurrence.

Background: Accumulation of progressive extracardiac disease is nearly universal for patients with single ventricle heart disease palliated to a Fontan circulation; however, etiologies are poorly understood. Limited flow reserve in the Fontan circulation may underlie extracardiac disease found in Fontan physiology through reduced oxygen and nutrient delivery to the tissues. This study aimed to determine regional flow volumes and oxygen delivery to key organ systems in children and adolescents with a Fontan circulation.

Methods: In 17 Fontan subjects and 14 biventricular controls, regional arterial flow volumes to the carotid, celiac, superior mesenteric, renal, and iliac arteries were quantified with magnetic resonance imaging. Arterial oxygen content was calculated using subject hemoglobin level and pulse oximetry, and regional oxygen delivery was calculated using regional flow volume and oxygen content for the above-listed arteries. Cardiac output was measured from ascending aorta flow, systemic blood flow from the caval veins, and aorto-pulmonary collateral flow was calculated as the difference between the two. Flows were compared between groups (t-test) and associations were analyzed between flows and with maximal exercise performance on clinical cardiopulmonary exercise testing (Pearson correlation).

Results: On average, renal and iliac arterial flows were lower in the Fontan group, compared to controls. Carotid, celiac, and superior mesenteric arterial flows were preserved in the Fontan group. Arterial oxygen content was equivalent between groups, and thus, regional oxygen delivery followed the same pattern as regional flows. Cardiac output was no different between groups, but systemic blood flow was lower in Fontans due to loss of flow to aorto-pulmonary collaterals. Systemic blood flow correlated with iliac flow such that those with the lowest systemic flow had the least amount of iliac flow. Celiac arterial flow correlated with percent-predicted peak oxygen consumption on exercise testing.

Conclusion: Our results are consistent with a limited flow reserve in the Fontan circulation with sacrifice of iliac arterial flow as global systemic blood flow decreases. Importantly, these data were measured with subjects supine and at rest. Future work requires the addition of exercise to determine how flow to specific organs is affected by increasing metabolic demand from the extremities.

Background: Impaired right atrial (RA) function is strongly predictive of adverse outcomes in adults with pulmonary arterial hypertension (PAH) but remains incompletely understood in pediatric PAH. In this pediatric multi-center retrospective cohort study using cardiovascular magnetic resonance imaging (CMR), we analyzed RA size and phasic function and its associations with PAH severity.

Methods: PAH and control pediatric patients from two centers who underwent CMR from 2010 to 2023 were identified. RA volumes were measured throughout the cardiac cycle using the single-plane, area-length method on a standard 4-chamber cine sequence. Total, conduit phase, and active phase stroke volume (SVi; indexed to BSA) and ejection fraction (EF) were calculated. A novel marker, the A/C ratio, was calculated as active/conduit SVi. RA size and phasic function measurements were correlated with clinical, hemodynamic, and non-RA CMR metrics of PAH severity and were associated with adverse events (Potts shunt, lung transplant listing/surgery, and/or death) using univariate and bivariate Cox proportional-hazards regression analyses. Intra- and inter-rater reliability was analyzed using intra-class correlation coefficients (ICC).

Results: Compared to controls (n=36), children with PAH (n=72) had higher RA volumes, lower conduit phasic function, and higher active phasic function. In PAH patients, minimum RA volume, active SVi, and A/C ratio directly correlated with NT-proBNP and right ventricular (RV) size, filling pressures, and afterload, while they were inversely correlated with exercise capacity and RVEF. RA conduit EF (cEF) correlations were reversed. During median follow-up of 3.2 years [IQR 1.0, 5.9], RA cEF and A/C ratio remained independent predictors of adverse events after adjustment for common metrics of PAH severity on bivariate analysis, including RVEF (RA cEF aHR 0.91 [95% CI: 0.83-0.99]; A/C ratio aHR 1.58 [95% CI: 1.09-2.29]) and indexed pulmonary vascular resistance (RA cEF aHR 0.83 [95% CI: 0.74-0.93]; A/C ratio aHR 1.79 [95% CI: 1.34-2.41]). RA volume measurements had excellent reliability (ICC >0.97).

Conclusion: Correlating with disease severity, impaired RA physiology in pediatric PAH is characterized by RA dilation, reduced conduit phasic function, and compensatory augmentation of active phasic function. Assessment of RA size and phasic function is feasible and highly reproducible using standard CMR sequences.

Background: Current myocardial arterial spin labeling (ASL) methods are sensitive to noise (background and physiology), which limits the accuracy of myocardial blood flow (MBF) measurement. In this study, we demonstrated a new deep learning-enabled myocardial ASL approach (DeepMASL) and evaluated its accuracy to quantify MBF in a canine model of coronary arterial disease in vivo. The reference method was invasive microsphere measurements.

Methods: Eighteen mongrel dogs were divided into two groups: healthy (n = 9) and coronary stenosis (n = 9). The latter was induced in an open-chest model with 3 types of stenosis: 50% (n= 3), 70% (n = 3), and 90% (n = 3). Each dog received pharmaceutically induced hyperemia, by the infusion of either dipyridamole or dobutamine to induce different levels of MBF. Microsphere measurements were performed at rest and during the hyperemia. A cardiac ASL sequence was employed to acquire ASL signals at the mid-section of the heart, at rest and during the hyperemia. A physics-based deep learning network (DeepMASL) was developed using synthetic ASL signals with different levels of background noise. Segmented MBF values produced by both non-DeepMASL and DeepMASL methods were measured in all dogs to compare with segmented microsphere MBF values.

Results: While the non-DeepMASL method severely underestimated hyperemic MBF by 33-49%, the DeepMASL approach dramatically improved the accuracy to obtain error less than 10%. There were strong correlations (r = 0.85 - 0.86) in segmented MBF values between measurements by DeepMASL and microsphere methods in either normal or ischemic dogs with varying degrees of coronary artery stenosis. The Bland-Altman analysis revealed mild to moderate variations of DeepMASL (95% confident interval: -1.3 to 1.5 ml/min/g in normal dogs and -1.8 to 1.3 ml/min/g in stenotic dogs) and almost zero bias.

Conclusion: The novel DeepMASL demonstrates much improved accuracy in the quantification of regional MBF at varying levels of coronary artery stenosis, which is correlated strongly with microsphere MBF values. The validated data indicates the potential for this DeepMASL technique to be translated for noncontrast diagnosis of myocardial perfusion deficit in a clinical setting.

Background: Aortic stenosis is a debilitating disease characterized by pressure overload and development of myocardial fibrosis. Animal models that mimic this disease are crucial for translational research. Aortic constriction in rats is commonly used to induce pressure overload, but the precise disease progression in the O-ring induced model of ascending aortic constriction has not been thoroughly evaluated. Additionally, identifying early imaging biomarkers that can predict fibrosis could enhance the model's translational relevance. This study aims to evaluate a rat model of progressive pressure overload using cardiovascular magnetic resonance imaging (CMR) by investigating the degree of constriction at different time points and identifying early imaging biomarkers predicting myocardial fibrosis at later stages.

Methods: Sprague Dawley rats (n=14) underwent aortic banding with O-rings (inner diameter of 1.5 mm or 1.3 mm). Sham-operated rats (n=8) served as controls. CMR was performed every fourth week until 20 weeks post-surgery, followed by tissue harvesting and measurements of fibrosis with histology.

Results: All banding groups gradually developed left ventricular (LV) hypertrophy, impaired LV diastolic function (increased E/SRe), increased left atrial (LA) size, and impaired LA function (reduced LA ejection fraction and peak LA strain), but preserved LV ejection fraction during the course of study. The tightest constriction exhibited increased LV fibrosis at 20 weeks. LA diameter at 4 weeks independently predicted LV myocardial fibrosis.

Conclusion: This animal model mimics the gradual progression of stenosis seen in humans, highlighting its translational potential. Early LA diameter predicted myocardial fibrosis. These findings underscore the model's relevance for studying disease progression in LV pressure overload.

Background: Three-dimensional (3D) cardiovascular magnetic resonance angiography produces detailed images of the heart and its vascular surroundings. However, the technique is challenged in clinical settings for pediatric patients primarily due to the uncooperative nature of pediatric patients, especially those at young age. This work is to propose and assess a 1-minute 3D whole-heart cardiovascular magnetic resonance (CMR) imaging technique for pediatric patients with congenital heart diseases (CHD) based on a non-Cartesian gradient echo-based ultrashort echo time (UTE) sequence together with the ferumoxytol contrast.

Methods: Both the 3D fast whole-heart MRI sequence and the clinical 3D balanced steady-state free precession (bSSFP) whole-heart sequence were used for acquiring the whole-heart imaging post ferumoxytol contrast. Image quality assessment in reformatted angiograms was performed between the 3D bSSFP and 3D UTE sequence by two readers independently. Statistical analysis was also performed using the paired t-test to assess the statistical significance of image quality. The p-value <0.05 was considered indicative of a statistically significant difference. Case studies were provided to visually compare images from the proposed technique and the clinical 3D bSSFP sequence.

Results: Thirty-eight studies were performed in 38 consecutive children with a mean age of 10 years [range 5 months to 24 years]. The 3D UTE sequence achieved higher scores in 7 of 10 cardiac structures chosen for comparison. Through statistical analysis, it was determined that the 3D UTE sequence offers superior image quality for all pulmonary veins and maintains comparable quality for the superior vena cava, left atrium, and pulmonary arteries compared to the 3D bSSFP sequence. While for left atrial appendage and ventricular anatomy, the 3D bSSFP sequence was found to yield better image quality compared to the 3D UTE sequence.

Conclusion: The ferumoxytol-enhanced 3D UTE sequence enables whole-heart imaging in less than 1 minute with clinically acceptable image quality and hence can be used as a supplemental tool for the 3D bSSFP sequence in clinical practice.

Aims: Anomalous aortic origin of a coronary artery (AAOCA) can result in sudden cardiac death in the young and risk stratification is challenging. Though dobutamine stress cardiovascular magnetic resonance (DS-CMR) is feasible in pediatric patients, exercise stress CMR (ES-CMR) may have lower rates of adverse events, higher diagnostic accuracy, and the ability to better reflect the physiologic changes occurring with exercise. We aimed to describe our institution's experience with ES-CMR using supine bicycle ergometry in pediatric and young adult patients with AAOCA.

Methods and results: We retrospectively reviewed the medical records of AAOCA patients who underwent ES-CMR at our institution between 2011 and 2024 for demographic, clinical presentation, cardiopulmonary exercise test (CPET), and ES-CMR data. The exercise-based portion of the CMR consisted of supine cycle ergometry utilizing a ramp protocol, immediately after which ES perfusion imaging was performed. Fifteen minutes after stress imaging, rest perfusion imaging was acquired. Of 38 patients who underwent ES-CMR, the median age was 16 years (range 13-24) and 68% were male. Diagnoses included anomalous right coronary artery (n=28), anomalous left coronary artery (n=8), and single coronary artery (n=1 single right, n=1 single left). Median maximal heart rate (HR) during ES-CMR was 160 bpm (range 130-190, median 80% predicted) compared to a median maximal HR during patients' most recent CPET of 187 bpm (range 160-203, median 97% predicted). No patients had perfusion defects at rest or with exercise stress, or evidence of myocardial scarring CONCLUSION: We demonstrate for the first time the use of ES-CMR in a cohort of pediatric and young adult patients with AAOCA. ES-CMR is a unique modality to assess for ischemia at rest and stress to assist with risk stratification by simulating physiologic changes with exercise stress. Although maximum heart rates during supine cycle ergometry are lower than those reached during CPET, they are similar to those reached during DS-CMR. ES-CMR is a valuable diagnostic tool and may be useful in the risk stratification of patients with AAOCA.