Cine MRI-derived radiomics features indicate hemodynamic changes in the pulmonary artery

Although cine MRI-derived radiomics features in the cardiac blood pool have been used to represent cardiac function and motion, the clinical relevance of radiomics features in the great vessels is still unknown. The aim of the present study was to test the hypothesis that cine MRI-derived radiomics features of the pulmonary artery (PA) can represent hemodynamic abnormalities in pulmonary hypertension (PH). With the approval of the institutional review board (IRB), 50 PH patients (21 males, 36-89 years old, diagnosed with right heart catheterization [RHC]) and 23 healthy volunteers (14 males, 26-80 years old) were retrospectively enrolled in this study. All participants underwent cardiac 4D flow and cine MRI (25 retrospective phases) at the right ventricular (RV) outflow tract (RVOT). A total of 93 radiomics features were extracted from RVOT cine images through a fixed size region of interest (ROI) at the proximal part of the PA. The peak values of the 6 first order features were different between the PH patients and controls. 4D flow-derived mean velocity in PA was related to 'Kurtosis' (r = 0.452,), 'Range' (r = 0.426), 'Autocorrelation' (r = 0.407), 'Joint Average' (r = 0.459), 'Sum Average' (r = 0.459), 'High Gray Level Emphasis' (r = 0.41), 'Large Dependence High Gray Level Emphasis' (r = 0.44), 'High Gray Level Run Emphasis' (r = 0.422), 'Gray Level Variance' (r = 0.419), 'High Gray Level Zone Emphasis' (r = 0.451), and 'Small Area High Gray Level Emphasis' (r = 0.415). Mean RV pressure was related to 'Inverse Variance' (r = 0.43) and 'Run Percentage' (r = 0.403). All p values < 0.05. Cine MRI-derived PA radiomics features have the potential to serve as novel imaging biomarkers for representing hemodynamic changes in pulmonary circulation.

Ultra-rapid, Free-breathing, Real-time Cardiac Cine MRI Using GRASP Amplified with View Sharing and KWIC Filtering

Purpose To achieve ultra-high temporal resolution (approximately 20 msec) in free-breathing, real-time cardiac cine MRI using golden-angle radial sparse parallel (GRASP) reconstruction amplified with view sharing (VS) and k-space-weighted image contrast (KWIC) filtering. Materials and Methods Fourteen pediatric patients with congenital heart disease (mean age [SD], 9 years ± 2; 13 male) and 10 adult patients with arrhythmia (mean age, 62 years ± 8; nine male) who underwent both standard breath-hold cine and free-breathing real-time cine using GRASP were retrospectively identified. To achieve high temporal resolution, each time frame was reconstructed using six radial spokes, corresponding to acceleration factors ranging from 24 to 32. To compensate for loss in spatial resolution resulting from over-regularization in GRASP, VS and KWIC filtering were incorporated. The blur metric, visual image quality scores, and biventricular parameters were compared between clinical and real-time cine images. Results In pediatric patients, the incorporation of VS and KWIC into GRASP (ie, GRASP + VS + KWIC) produced significantly (P < .05) sharper x-y-t (blur metric: 0.36 ± 0.03, 0.41 ± 0.03, 0.48 ± 0.03, respectively) and x-y-f (blur metric: 0.28 ± 0.02, 0.31 ± 0.03, 0.37 ± 0.03, respectively) component images compared with GRASP + VS and conventional GRASP. Only the noise score differed significantly between GRASP + VS + KWIC and clinical cine; all visual scores were above the clinically acceptable (3.0) cutoff point. Biventricular volumetric parameters strongly correlated (R2 > 0.85) between clinical and real-time cine images reconstructed with GRASP + VS + KWIC and were in good agreement (relative error < 6% for all parameters). In adult patients, the visual scores of all categories were significantly lower (P < .05) for clinical cine compared with real-time cine with GRASP + VS + KWIC, except for noise (P = .08). Conclusion Incorporating VS and KWIC filtering into GRASP reconstruction enables ultra-high temporal resolution (approximately 20 msec) without significant loss in spatial resolution. Keywords: Cine, View Sharing, k-Space-weighted Image Contrast Filtering, Radial k-Space, Pediatrics, Arrhythmia, GRASP, Compressed Sensing, Real-Time, Free-Breathing Supplemental material is available for this article. © RSNA, 2024.

Cine MRI-Derived Radiomics Features of the Cardiac Blood Pool: Periodicity, Specificity, and Reproducibility

BACKGROUND

Although radiomics features of the left ventricular wall have been used to assess cardiac diseases, radiomics features of the cardiac blood pool have been relatively ignored.

PURPOSE

To test the hypothesis that cine MRI-derived radiomics features of the cardiac blood pool are associated with cardiac function and motion.

STUDY TYPE

Retrospective.

POPULATION

A total of 26 healthy volunteers (51.2 ± 15.6 years; 17 males).

FIELD STRENGTH/SEQUENCE

A 1.5 T/balanced steady-state free precession (bSSFP).

ASSESSMENT

The radiomics features (107 features in seven classes) of the blood pool of the left/right ventricle/atrium (LV/RV/LA/RA) were extracted on four-chamber cine images (25 phases). Conventional cardiac function parameters (volumes, ejection fraction [EF] and longitudinal strain) were assessed in each cardiac chamber. Intraobserver- and interobserver agreements of radiomics features of all chambers acquired at all phases were assessed, as well as scan-rescan agreement in a subset of 13 volunteers.

STATISTICAL TESTS

Pearson correlation coefficients (r) were used to assess the associations between peak values of radiomics features and end-diastolic (or maximal) volume, end-systolic (or minimal) volume, EF, and longitudinal strain of corresponding chambers. Good intraobserver, interobserver, and scan-rescan agreements for radiomics features acquired were defined as intraclass correlation coefficient (ICC) > 0.7 or coefficient of variation (CoV) < 20%.

RESULTS

Most radiomics features of the blood pool varied periodically throughout the cardiac cycle. Peak values of chamber-specific blood pool radiomics features were correlated with traditional cardiac function and motion indices of corresponding chambers (r: 0.4-0.87). Ninety-three (87%), 86 (80%), and 73 (68%) radiomics features demonstrated good intraobserver, interobserver, and scan-rescan reproducibility, respectively.

CONCLUSION

Cine MRI-derived radiomics features within LV/RV/LA/RA are associated with traditional cardiac function and motion indices of corresponding chambers and may have the potential to become novel quantitative imaging biomarkers in cardiovascular medicine.

EVIDENCE LEVEL

3.

TECHNICAL EFFICACY

1.

Clinical Applications of Four-Dimensional Flow MRI

Four-dimensional flow MRI is a powerful phase contrast technique used for assessing three-dimensional (3D) blood flow dynamics. By acquiring a time-resolved velocity field, it enables flexible retrospective analysis of blood flow that can include qualitative 3D visualization of complex flow patterns, comprehensive assessment of multiple vessels, reliable placement of analysis planes, and calculation of advanced hemodynamic parameters. This technique provides several advantages over routine two-dimensional flow imaging techniques, allowing it to become part of clinical practice at major academic medical centers. In this review, we present the current state-of-the-art cardiovascular, neurovascular, and abdominal applications.

Alirocumab and plaque volume, calf muscle blood flow, and walking performance in peripheral artery disease: A randomized clinical trial

BACKGROUND

The distal superficial femoral artery (SFA) is most commonly affected in peripheral artery disease (PAD). The effects of the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor alirocumab added to statin therapy on SFA atherosclerosis, downstream flow, and walking performance are unknown.

METHODS

Thirty-five patients with PAD on maximally tolerated statin therapy were recruited. Patients were randomized to alirocumab 150 mg subcutaneously (n = 18) or matching placebo (n = 17) therapy every 2 weeks for 1 year. The primary outcome was change in SFA plaque volume by black blood magnetic resonance imaging (MRI). Secondary outcomes were changes in calf muscle perfusion by cuff/occlusion hyperemia arterial spin labeling MRI, 6-minute walk distance (6MWD), low-density lipoprotein (LDL) cholesterol, and other biomarkers.

RESULTS

Age (mean ± SD) was 64 ± 8 years, 20 (57%) patients were women, 17 (49%) were Black individuals, LDL was 107 ± 36 mg/dL, and the ankle-brachial index 0.71 ± 0.20. The LDL fell more with alirocumab than placebo (mean [95% CI]) (-49.8 [-66.1 to -33.6] vs -7.7 [-19.7 to 4.3] mg/dL; p < 0.0001). Changes in SFA plaque volume and calf perfusion showed no difference between groups when adjusted for baseline (+0.25 [-0.29 to 0.79] vs -0.04 [-0.47 to 0.38] cm3; p = 0.37 and 0.22 [-8.67 to 9.11] vs 3.81 [-1.45 to 9.08] mL/min/100 g; p = 0.46, respectively), nor did 6MWD.

CONCLUSION

In this exploratory study, the addition of alirocumab therapy to statins did not alter SFA plaque volume, calf perfusion or 6MWD despite significant LDL lowering. Larger studies with longer follow up that include plaque characterization may improve understanding of the effects of intensive LDL-lowering therapy in PAD (ClinicalTrials.gov Identifier: NCT02959047).

Cine magnetic resonance imaging detects shorter cardiac rest periods in postcapillary pulmonary hypertension

AIMS

A shorter cardiac rest period within a cardiac cycle is usually thought to be a result of a fast heart rate, and its clinical relevance has long been ignored. The aim of the present study was to test the hypothesis that the length of cardiac rest periods is altered in postcapillary pulmonary hypertension (PH).

METHODS AND RESULTS

Twenty-six patients with postcapillary PH and 20 healthy controls were recruited for cardiac magnetic resonance imaging (MRI) scans. All participants had a heart rate no higher than 80 beats/minute. Cine magnetic resonance imaging (MRI, acquired at a four-chamber view) was analyzed to determine the length of cardiac rest periods at end-systole and mid-to-late diastole. PH patients had a shorter rest period at mid-to-late diastole than controls (17.5 ± 8.7% vs. 24.2 ± 4.2%, P = 0.003). Receiver operating characteristic (ROC) curves showed that the proportion of the rest period in diastole (defined as the length of diastasis/diastole) can discriminate PH patients from controls [area under the curve (AUC) = 0.83, 95% confidence interval (CI): 0.71-0.96]. The existence of postcapillary PH was a significant contributor (β = -5.537, P = 0.023) to shorter cardiac rest periods at mid-to-late diastole after adjusting for potential confounders, including age, sex, heart rate, and blood pressure.

CONCLUSIONS

Postcapillary PH is independently associated with shorter cardiac rest periods at mid-to-late diastole. The length of cardiac rest periods has the potential to become a novel quantitative imaging biomarker for indicating cardiovascular health.

Potential Prognostic Value of Native T1 in Pulmonary Hypertension Patients

Native T1, extracellular volume fraction (ECV), and late gadolinium enhancement (LGE) characterize myocardial tissue and relate to patient prognosis in a variety of diseases, including pulmonary hypertension. The purpose of this study was to evaluate if left ventricle (LV) fibrosis measurements have prognostic value for cardiac outcomes in pulmonary hypertension subgroups. 54 patients with suspected pulmonary hypertension underwent right-heart catheterization and were classified into pulmonary hypertension subgroups: pre-capillary component (PreCompPH) and isolated post-capillary (IpcPH). Cardiac magnetic resonance imaging (MRI) scans were performed with the acquisition of balanced cine steady-state free precession, native T1, and LGE pulse sequences to measure cardiac volumes and myocardial fibrosis. Associations between cardiac events and cardiac MRI measurements were analyzed within PreCompPH and IpcPH patients. IpcPH: LV native T1 was higher in patients who experienced a cardiac event within two years vs. those who did not. In patients with LV native T1 > 1050 ms, the rate of cardiac events was higher. ECV and quantitative LGE did not differ between groups. PreCompPH: native T1, ECV, and quantitative/qualitative LGE did not differ between patients who experienced a cardiac event within two years vs. those who did not. LV native T1 may have potential value for forecasting cardiac events in IpcPH, but not in PreCompPH, patients.

Pilot Tone-Triggered MRI for Quantitative Assessment of Cardiac Function, Motion, and Structure

OBJECTIVE

The aim of this study was to test the hypothesis that there are good agreements between cardiac functional and structural indices derived from magnetic resonance imaging (MRI) sequences triggered with pilot tone (PT) and electrocardiogram (ECG).

MATERIALS AND METHODS

Sixteen healthy volunteers (11 male, age 21-76 years) underwent a cardiac MRI scan. Cine MRI, T1, and T2 mapping were acquired by using PT and ECG triggering. Quantitative measurements, including left and right ventricular end-diastolic volume, end-systolic volume, stroke volume, ejection fraction, longitudinal strain, left ventricular T1 and T2 values, left and right atrial longitudinal strain, and maximal/minimal volumes, were measured. The interclass correlation coefficient, coefficient of variation, and Bland-Altman plots were used to evaluate the agreements between measurements derived by MRI sequences triggered with 2 methods.

RESULTS

There were no significant differences among end-diastolic volume, end-systolic volume, stroke volume, ejection fraction, left ventricle mass, T1 and T2 values, or longitudinal strains acquired using PT and ECG. There were good agreements and low variations between the levels of these indices acquired with PT and ECG. Interclass correlation coefficients mainly ranged from 0.73 to 0.98. The coefficients of variation ranged from 1.4% to 22.6%.

CONCLUSIONS

Pilot tone-triggered MRI provides comparable measurements of cardiac function, motion, and structure as ECG-triggered MRI. Pilot tone has the potential to become a backup of ECG gating in cardiovascular imaging.

Quantitative Assessment of Regional Pulmonary Transit Times in Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) contributes to restricted flow through the pulmonary circulation characterized by elevated mean pulmonary artery pressure acquired from invasive right heart catheterization (RHC). MRI may provide a noninvasive alternative for diagnosis and characterization of PH.

PURPOSE

To characterize PH via quantification of regional pulmonary transit times (rPTT).

STUDY TYPE

Retrospective.

POPULATION

A total of 43 patients (58% female); 24 controls (33% female). RHC-confirmed patients classified as World Health Organization (WHO) subgroups 1-4.

FIELD STRENGTH/SEQUENCE

A 1.5 T/time-resolved contrast-enhanced MR Angiography (CE-MRA).

ASSESSMENT

CE-MRA data volumes were combined into a 4D matrix (3D resolution + time). Contrast agent arrival time was defined as the peak in the signal-intensity curve generated for each voxel. Average arrival times within a vessel region of interest (ROI) were normalized to the main pulmonary artery ROI (t₀ ) for eight regions to define rPTT for all subjects. Subgroup analysis included grouping the four arterial and four venous regions. Intraclass correlation analysis completed for reproducibility.

STATISTICAL TESTS

Analysis of covariance with age as covariate. A priori Student's t-tests or Wilcoxon rank-sum test; α = 0.05. Results compared to controls unless noted. Significant without listing P value. ICC ran as two-way absolute agreement model with two observers.

RESULTS

PH patients demonstrated elevated rPTT in all vascular regions; average rPTT increase in arterial and venous branches was 0.85 ± 0.15 seconds (47.7%) and 1.0 ± 0.18 seconds (16.9%), respectively. Arterial rPTT was increased for all WHO subgroups; venous regions were elevated for subgroups 2 and 4 (group 1, P = 0.86; group 3, P = 0.32). No significant rPTT differences were found between subgroups (P = 0.094-0.94). Individual vessel ICC values ranged from 0.58 to 0.97.

DATA CONCLUSION

Noninvasive assessment of PH using standard-of-care time-resolved CE-MRA can detect increased rPTT in PH patients of varying phenotypes compared to controls.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 3.

A Left ventricle remodeling in patients with bicuspid aortic valve

PURPOSE

We assessed the impact of bicuspid aortic valve (BAV), aortic stenosis (AS), and regurgitation (AR) on the metrics of left ventricular (LV) remodeling, as measured by electrocardiogram (ECG), transthoracic echocardiography (TTE), and cardiac magnetic resonance (CMR).

METHODS

This retrospective CMR study included 11 patients with both AS and AR (BAV-ASR), 30 with AS (BAV-AS), 28 with AR (BAV-AR), 47 with neither AS nor AR (BAV-no_AS/AR), and 40 with trileaflet aortic valve (TAV-no_AS/AR). CMR analysis included the LV end-diastolic volume index (LVEDVi), mass index (LVMi), and extracellular volume fraction (ECV). The Sokolow-Lyon and Cornell products by ECG and TTE-derived E/e' were measured.

RESULTS

There were no differences in the ECG, TTE, and CMR parameters between BAV-no_AS/AR and TAV-no_AS/AR. However, the presence of aortic valve dysfunction resulted in an elevated Sokolow-Lyon product for BAV-ASR (p = 0.017) and BAV-AR (p = 0.001), as well as increased Cornell product (p = 0.04) and E/e' (p < 0.001) for BAV-AS compared with BAV-no_AS/AR. LVEDVi and LVMi were elevated in patients with BAV-ASR and BAV-AR compared with those with BAV-no_AS/AR (LVEDVi: 101 ± 29 ml/m² and 112 ± 32 ml/m² vs. 74 ± 15 ml/m², p = 0.005 and p < 0.001, LVMi: 75 ± 7 g/m² and 64 ± 14 g/m² vs. 47 ± 9 g/m², respectively; p < 0.001). There was no difference in ECV between the BAV and TAV-no_AS/AR subgroups.

CONCLUSION

Normally functioning BAV did not result in LV remodeling. However, concomitant AV dysfunction was associated with statistically significant morphological remodeling.

Systolic reverse flow derived from 4D flow cardiovascular magnetic resonance in bicuspid aortic valve is associated with aortic dilation and aortic valve stenosis: a cross sectional study in 655 subjects

BACKGROUND

Bicuspid aortic valve (BAV) disease is associated with increased risk of aortopathy. In addition to current intervention guidelines, BAV mediated changes in aortic 3D hemodynamics have been considered as risk stratification measures. We aimed to evaluate the association of 4D flow cardiovascular magnetic resonance (CMR) derived voxel-wise aortic reverse flow with aortic dilation and to investigate the role of aortic valve regurgitation (AR) and stenosis (AS) on reverse flow in systole and diastole.

METHODS

510 patients with BAV (52 ± 14 years) and 120 patients with trileaflet aortic valve (TAV) (61 ± 11 years) and mid-ascending aorta diameter (MAAD) > 35 mm who underwent CMR including 4D flow CMR were retrospectively included. An age and sex-matched healthy control cohort (n = 25, 49 ± 12 years) was selected. Voxel-wise reverse flow was calculated in the aorta and quantified by the mean reverse flow in the ascending aorta (AAo) during systole and diastole.

RESULTS

BAV patients without AS and AR demonstrated significantly increased systolic and diastolic reverse flow (222% and 13% increases respectively, p < 0.01) compared to healthy controls and also had significantly increased systolic reverse flow compared to TAV patients with aortic dilation (79% increase, p < 0.01). In patients with isolated AR, systolic and diastolic AAo reverse flow increased significantly with AR severity (c = - 83.2 and c = - 205.6, p < 0.001). In patients with isolated AS, AS severity was associated with an increase in both systolic (c = - 253.1, p < 0.001) and diastolic (c = - 87.0, p = 0.02) AAo reverse flow. Right and left/right and non-coronary fusion phenotype showed elevated systolic reverse flow (> 17% increase, p < 0.01). Right and non-coronary fusion phenotype showed decreased diastolic reverse flow (> 27% decrease, p < 0.01). MAAD was an independent predictor of systolic (p < 0.001), but not diastolic, reverse flow (p > 0.1).

CONCLUSION

4D flow CMR derived reverse flow associated with BAV was successfully captured even in the absence of AR or AS and in comparison to TAV patients with aortic dilation. Diastolic AAo reverse flow increased with AR severity while AS severity strongly correlated with increased systolic reverse flow in the AAo. Additionally, increasing MAAD was independently associated with increasing systolic AAo reverse flow. Thus, systolic AAo reverse flow may be a valuable metric for evaluating disease severity in future longitudinal outcome studies.

Left Ventricular Fibrosis Assessment by Native T1, ECV, and LGE in Pulmonary Hypertension Patients

Cardiac magnetic resonance imaging (MRI) is emerging as an alternative to right heart catheterization for the evaluation of pulmonary hypertension (PH) patients. The aim of this study was to compare cardiac MRI-derived left ventricle fibrosis indices between pre-capillary PH (PrePH) and isolated post-capillary PH (IpcPH) patients and assess their associations with measures of ventricle function. Global and segmental late gadolinium enhancement (LGE), longitudinal relaxation time (native T1) maps, and extracellular volume fraction (ECV) were compared among healthy controls (N = 25; 37% female; 52 ± 13 years), PH patients (N = 48; 60% female; 60 ± 14 years), and PH subgroups (PrePH: N = 29; 65% female; 55 ± 12 years, IpcPH: N = 19; 53% female; 66 ± 13 years). Cardiac cine measured ejection fraction, end diastolic, and end systolic volumes and were assessed for correlations with fibrosis. LGE mural location was qualitatively assessed on a segmental basis for all subjects. PrePH patients had elevated (apical-, mid-antero-, and mid-infero) septal left ventricle native T1 values (1080 ± 74 ms, 1077 ± 39 ms, and 1082 ± 47 ms) compared to IpcPH patients (1028 ± 53 ms, 1046 ± 36 ms, 1051 ± 44 ms) (p < 0.05). PrePH had a higher amount of insertional point LGE (69%) and LGE patterns characteristic of non-vascular fibrosis (77%) compared to IpcPH (37% and 46%, respectively) (p < 0.05; p < 0.05). Assessment of global LGE, native T1, and ECV burdens did not show a statistically significant difference between PrePH (1.9 ± 2.7%, 1056.2 ± 36.3 ms, 31.2 ± 3.7%) and IpcPH (2.7 ± 2.7%, 1042.4 ± 28.1 ms, 30.7 ± 4.7%) (p = 0.102; p = 0.229 p = 0.756). Global native T1 and ECV were higher in patients (1050.9 ± 33.8 and 31.0 ± 4.1%) than controls (28.2 ± 3.7% and 1012.9 ± 29.4 ms) (p < 0.05). Cardiac MRI-based tissue characterization may augment understanding of cardiac involvement and become a tool to facilitate PH patient classification.

Team Approach to Improving Radiologist Wellness: A Case-Based Methodology

Radiologist wellness is important on an individual and group/institutional level and helps to promote a strong and healthy working environment, which can improve radiologist retention and engagement. This paper will discuss case examples of radiologist wellness improvements in a single academic institution over a 3-year period using the DMAIC (Define, Measure, Analyze, Improve, and Control) model. Leveraging this framework led to the implementation of reading room assistants, reduction in work-related injuries by improvements in ergonomics, and the formation of a faculty mentorship program.

Combined modality PET/MR for the detection of severe large vessel vasculitis

Background

Large vessel vasculitis (LVV) can be characterized based on symptom severity, and this characterization helps clinicians decide upon treatment approach. Our aim was to compare the imaging findings of combined modality positron emission tomography/magnetic resonance (PET/MR) and inflammatory markers between severe and non-severe LVV. A retrospective query was performed to identify all patients with LVV who underwent PET/MR at our institution between January 2015 and January 2021.

Results

Eleven patients (nine females; age 62.2 ± 16.4 years) underwent 15 PET/MR scans. Positivity was defined by findings indicative of active LVV on each modality: PET positive if vessel metabolic activity > liver metabolic activity; MR positive if wall thickening or contrast enhancement. When positive PET or positive MR findings were considered a positive scan, LVV patients with severe disease (n = 9 scans) showed a higher number of positive scans (n = 9) compared to the number of positive scans in non-severe patients (n = 3) (p < 0.05). The sensitivity and specificity for the detection of severe LVV were 1.00 and 0.50, respectively. When only the presence of both positive PET and positive MR findings were considered a positive scan, inflammatory marker levels were not significantly different between severe and non-severe LVV groups (severe: erythrocyte sedimentation rate (ESR) = 9.8 ± 10.6 mm/h; C-reactive protein (CRP) = 0.6 ± 0.4 mg/dL) (non-severe: ESR = 14.3 ± 22.4 mm/h; CRP = 0.5 ± 0.6 mg/dL). Blood- and liver-normalized maximum standardized uptake values were not significantly different between severe and non-severe patients (1.4 ± 0.3 vs 1.5 ± 0.4; 1.1 ± 0.4 vs 1.0 ± 0.3, respectively).

Conclusions

Because of the differences observed, PET/MR appears to be better suited to facilitate the characterization of LVV as severe or non-severe compared to inflammatory marker measurements and quantitative measurements of metabolic activity. Qualitative assessment of PET and MR positivity by 18F-fluorodeoxyglucose PET/MR may be able to supplement clinical symptoms-based LVV classification decisions and may be helpful when clinical symptoms overlap with other disease processes.

Aortic Pulse Wave Velocity Evaluated by 4D Flow MRI Across the Adult Lifespan

BACKGROUND

Evaluation of aortic stiffness by pulse wave velocity (PWV) across the adult lifespan is needed to better understand normal aging in women and men.

PURPOSE

To characterize PWV in the thoracic aorta using 4D flow MRI in an age- and sex-stratified cohort of healthy adults.

STUDY TYPE

Retrospective.

POPULATION

Ninety nine healthy participants (age: 46 ± 15 [19-79] years, 50% female), divided into young adults (<45 years) (N = 48), midlife (45-65 years) (N = 37), and later life (>65 years) (N = 14) groups.

FIELD STRENGTH/SEQUENCE

1.5 T or 3 T, 2D cine bSSFP, 4D flow MRI.

ASSESSMENT

Cardiac functional parameters of end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and myocardial mass were assessed by 2D cine bSSFP. PWV and aortic blood flow velocity were assessed by 4D flow MRI. Reproducibility of PWV was evaluated in a subset of nine participants.

STATISTICAL TESTS

Analysis of variance, Pearson's correlation coefficient (r), linear regression, intraclass correlation coefficient (ICC). A P value < 0.05 was considered statistically significant.

RESULTS

PWV increased significantly with age (young adults: 5.4 ± 0.9 m/sec, midlife: 7.2 ± 1.1 m/sec, and later life: 9.4 ± 1.8 m/sec) (r = 0.79, slope = 0.09 m/sec/year). PWV did not differ in women and men in entire sample (P = 0.40) or within age groups (young adults: P = 0.83, midlife: P = 0.17, and later life: P = 0.96). PWV was significantly correlated with EDV (r = -0.29), ESV (r = -0.23), SV (r = -0.28), myocardial mass (r = 0.21), and mean aortic blood flow velocity (r = -0.62). In the test-retest subgroup (N = 9), PWV was 6.7 ± 1.5 [4.4-9.3] m/sec and ICC = 0.75.

DATA CONCLUSION

4D flow MRI quantified higher aortic PWV with age, by approximately 1 m/sec per decade, and significant differences between young adults, midlife and later life. Reproducibility analysis showed good test-retest agreement. Increased PWV was associated with decline in cardiac function and reduced aortic blood flow velocity. This study demonstrates the utility of 4D flow MRI-derived aortic PWV for studying aging.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 2.

Baseline 4D Flow-Derived in vivo Hemodynamic Parameters Stratify Descending Aortic Dissection Patients With Enlarging Aortas

Purpose

The purpose of our study was to assess the value of true lumen and false lumen hemodynamics compared to aortic morphological measurements for predicting adverse-aorta related outcomes (AARO) and aortic growth in patients with type B aortic dissection (TBAD).

Materials and Methods

Using an IRB approved protocol, we retrospectively identified patients with descending aorta (DAo) dissection at a large tertiary center. Inclusion criteria includes known TBAD with ≥ 6 months of clinical follow-up after initial presentation for TBAD or after ascending aorta intervention for patients with repaired type A dissection with residual type B aortic dissection (rTAAD). Patients with prior descending aorta intervention were excluded. The FL and TL of each patient were manually segmented from 4D flow MRI data, and 3D parametric maps of aortic hemodynamics were generated. Groups were divided based on (1) presence vs. absence of AARO and (2) growth rate ≥ vs. < 3 mm/year. True and false lumen kinetic energy (KE), stasis, peak velocity (PV), reverse/forward flow (RF/FF), FL to TL KE ratio, as well as index aortic diameter were compared between groups using the Mann–Whitney U or independent t-test.

Results

A total of n = 51 patients (age: 58.4 ± 15.0 years, M/F: 31/20) were included for analysis of AARO. This group contained n = 26 patients with TBAD and n = 25 patients with rTAAD. In the overall cohort, AARO patients had larger baseline diameters, lower FL-RF, FL stasis, TL-KE, TL-FF and TL-PV. Among patients with de novo TBAD, those with AAROs had larger baseline diameter, lower FL stasis and TL-PV. In both the overall cohort and in the subgroup of de novo TBAD, subjects with aortic growth ≥ 3mm/year, patients had a higher KE ratio.

Conclusion

Our study suggests that 4D flow MRI is a promising tool for TBAD evaluation that can provide information beyond traditional MRA or CTA. 4D flow has the potential to become an integral aspect of TBAD work-up, as hemodynamic assessment may allow earlier identification of at-risk patients who could benefit from earlier intervention.

Optimal saturation recovery time for minimizing the underestimation of arterial input function in quantitative cardiac perfusion MRI

Purpose

The purpose of this study was to determine an optimal saturation‐recovery time (TS) for minimizing the underestimation of arterial input function (AIF) in quantitative cardiac perfusion MRI without multiple gadolinium injections per subject.

Methods

We scanned 18 subjects (mean age = 59 ± 14 years, 9/9 males/females) to acquire resting perfusion data and 1 additional subject (age = 38 years, male) to obtain stress‐rest perfusion data using a 5‐fold accelerated pulse sequence with radial k‐space sampling and applied k‐space weighted image contrast (KWIC) filters on the same k‐space data to retrospectively reconstruct five AIF images with effective TS ranging from 10 to 21.2 ms (2.8 ms steps). Undersampled images were reconstructed using a compressed sensing framework with temporal‐total‐variation and temporal‐principal‐component as 2 orthogonal sparsifying transforms. The image processing steps included, same motion correction across five different AIF images, signal normalization by the proton‐density‐weighted‐image, signal‐to‐T₁ conversion using a Bloch equation, T₁‐to‐gadolinium‐concentration conversion assuming fast water exchange, T₂* correction to the AIF, and gadolinium‐concentration to myocardial blood flow (MBF) conversion based on a Fermi model.

Results

Among five TS values, the shortest TS (10 ms) produced significantly (P < 0.05) higher peak AIF and lower resting MBF (13.73 mM, 0.73 mL g⁻¹ min⁻¹) than 12.8 ms (11.24 mM, 0.89 mL g⁻¹ min⁻¹), 15.6 ms (9.56 mM, 1.05 mL g⁻¹ min⁻¹), 18.4 ms (8.55 mM, 1.17 mL g⁻¹ min⁻¹), and 21.2 ms (7.95 mM, 1.27 mL g⁻¹ min⁻¹). Similarly, shorter TS reduced underestimation of AIF (or overestimation of MBF) for both during stress and at rest, but this effect was canceled in myocardial‐perfusion‐reserve (MPR).

Conclusion

This study demonstrates that TS of 10 ms reduces the underestimation of AIF and, hence, the overestimation of MBF compared with longer TS values (12.8‐21.2 ms).

Multiparametric Cardiac Magnetic Resonance Imaging Detects Altered Myocardial Tissue and Function in Heart Transplantation Recipients Monitored for Cardiac Allograft Vasculopathy

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a complication beyond the first-year post-heart transplantation (HTx). We aimed to test the utility of cardiac magnetic resonance (CMR) to detect functional/structural changes in HTx recipients with CAV.

METHODS

Seventy-seven prospectively recruited HTx recipients beyond the first-year post-HTx and 18 healthy controls underwent CMR, including cine imaging of ventricular function and T1- and T2-mapping to assess myocardial tissue changes. Data analysis included quantification of global cardiac function and regional T2, T1 and extracellular volume based on the 16-segment model. International Society for Heart and Lung Transplantation criteria was used to adjudicate CAV grade (0–3) based on coronary angiography.

RESULTS

The majority of HTx recipients (73%) presented with CAV (1: n = 42, 2/3: n = 14, 0: n = 21). Global and segmental T2 (49.5 ± 3.4 ms vs 50.6 ± 3.4 ms, p < 0.001;16/16 segments) were significantly elevated in CAV-0 compared to controls. When comparing CAV-2/3 to CAV-1, global and segmental T2 were significantly increased (53.6 ± 3.2 ms vs. 50.6 ± 2.9 ms, p < 0.001; 16/16 segments) and left ventricular ejection fraction was significantly decreased (54 ± 9% vs. 59 ± 9%, p < 0.05). No global, structural, or functional differences were seen between CAV-0 and CAV-1.

CONCLUSIONS

Transplanted hearts display functional and structural alteration compared to native hearts, even in those without evidence of macrovasculopathy (CAV-0). In addition, CMR tissue parameters were sensitive to changes in CAV-1 vs. 2/3 (mild vs. moderate/severe). Further studies are warranted to evaluate the diagnostic value of CMR for the detection and classification of CAV.

MRA of the Supraaortic Vasculature: Comparison of Gadobutrol and Gadoterate Meglumine at 1.5 T

BACKGROUND

Gadobutrol (GB) and gadoterate meglumine (GM) are contrast agents used for contrast-enhanced magnetic resonance angiography (CEMRA). Supraaortic vasculature (SAV) CEMRAs are used to evaluate stroke risk and neurologic symptoms. There is a need to compare the SAV CEMRA image quality obtained with GB and GM.

PURPOSE

To intra-individually compare MRA images obtained with equimolar GB and GM at 1.5 T in the SAV.

STUDY TYPE

Prospective, crossover.

POPULATION

Twenty-eight subjects (54 ± 13 years; 17 female).

FIELD STRENGTH/SEQUENCE

1.5 T; three-dimensional (3D) gradient recalled echo.

ASSESSMENT

Quantitative image quality was measured by normalized signal intensity (SI_n ) [SI_n  = SI blood/SD blood] and contrast ratio (CR) [CR = SI blood/SI muscle], determined by an observer (JWC) with 1 year of vascular imaging experience. Three radiologists (AS, PA, and MU) with (5, 5, and 6 years of) vascular imaging experience evaluated image quality by Likert-scale ratings (of image impression, wall conspicuity, and artifact absence).

STATISTICAL TESTS

SI_n and CR were compared with paired t-tests or Wilcoxon signed-rank tests and Bland-Altman plots. Qualitative ratings were compared with Wilcoxon signed-rank test.

RESULTS

No significant difference in SI_n was found between GB and GM. CRs with GB were significantly higher than GM at the right common carotid (6.9 ± 2.5 vs. 4.8 ± 1), left internal carotid (7.3 ± 2 vs. 4.4 ± 1.2), right internal carotid (7.7 ± 2.2 vs. 5 ± 1.1), and left vertebral (6.6 ± 2.2 vs. 4.5 ± 1.1) arteries. Bland-Altman plots showed relatively greater differences between GB and GM at higher CRs and SI_n s. GM showed significantly higher artifact than GB (3.56 ± 0.52 vs. 3.36 ± 0.46) and significantly lower overall image quality (10.73 ± 1.45 vs. 11.26 ± 1.58) at the left vertebral artery.

DATA CONCLUSION

At 1.5 T and equimolar demonstration, GB (0.1 mL/kg, i.e., 0.1 mmol/kg) showed higher CRs in the SAV compared to GM (0.2 mL/kg, i.e., 0.1 mmol/kg) at most vessels. Subjective image quality was not significantly different between the two agents for most vessels.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

Role of Ergonomic Improvements in Decreasing Repetitive Stress Injuries and Promoting Well-Being in a Radiology Department

RATIONALE AND OBJECTIVES

To determine if ergonomic improvements in a radiology department can decrease repetitive stress injuries (RSIs), advance ergonomics knowledge, and improve well-being.

MATERIALS AND METHODS

Radiologists in an academic institution were surveyed regarding physician wellness, workstations, RSIs, and ergonomics knowledge before and after interventions over 1 year. Interventions included committee formation, education, wrist pads and wireless mice, broken table and chair replacement, and cord organization. Mann-Whitney U test was used for analysis.

RESULTS

Survey response was 40% preinterventions (59/147), and 42% (66/157) postinterventions. Preinterventions, of radiologists with RSI history, 17/40 (42%) reported the RSI caused symptoms which can lead to burnout, and 15/40 (37%) responded their RSI made them think about leaving their job. Twenty-three of 59 (39%) radiologists had an active RSI preinterventions. Postinterventions, 9/25 (36%) RSI resolved, 13/25 (52%) RSI improved, and 3/25 (12%) RSI did not improve. RSI improvements were attributed to ergonomic interventions in 19/25 (76%) and therapy in 2/25 (8%). Radiologists who thought their workstation was designed with well-being in mind increased from 9/59 (15%) to 52/64 (81%). The percentage of radiologists knowing little or nothing about ergonomics decreased from 15/59 (25%) to 5/64 (8%). After ergonomics interventions, more radiologists thought the administration cared about safety and ergonomics, equipment was distributed fairly, and radiologists had the ability to ask for equipment (p < .01). Fifty-three of 64 (83%) of radiologists after interventions said improving workstation ergonomic design contributed to well-being.

CONCLUSION

Ergonomic improvements in radiology can decrease RSIs, advance ergonomics knowledge, and improve well-being.

Automated segmentation of biventricular contours in tissue phase mapping using deep learning

Tissue phase mapping (TPM) is an MRI technique for quantification of regional biventricular myocardial velocities. Despite its potential, clinical use is limited due to the requisite labor-intensive manual segmentation of cardiac contours for all time frames. The purpose of this study was to develop a deep learning (DL) network for automated segmentation of TPM images, without significant loss in segmentation and myocardial velocity quantification accuracy compared with manual segmentation. We implemented a multi-channel 3D (three dimensional; 2D + time) dense U-Net that trained on magnitude and phase images and combined cross-entropy, Dice, and Hausdorff distance loss terms to improve the segmentation accuracy and suppress unnatural boundaries. The dense U-Net was trained and tested with 150 multi-slice, multi-phase TPM scans (114 scans for training, 36 for testing) from 99 heart transplant patients (44 females, 1-4 scans/patient), where the magnitude and velocity-encoded (V_x , V_y , V_z ) images were used as input and the corresponding manual segmentation masks were used as reference. The accuracy of DL segmentation was evaluated using quantitative metrics (Dice scores, Hausdorff distance) and linear regression and Bland-Altman analyses on the resulting peak radial and longitudinal velocities (V_r and V_z ). The mean segmentation time was about 2 h per patient for manual and 1.9 ± 0.3 s for DL. Our network produced good accuracy (median Dice = 0.85 for left ventricle (LV), 0.64 for right ventricle (RV), Hausdorff distance = 3.17 pixels) compared with manual segmentation. Peak V_r and V_z measured from manual and DL segmentations were strongly correlated (R ≥ 0.88) and in good agreement with manual analysis (mean difference and limits of agreement for V_z and V_r were -0.05 ± 0.98 cm/s and -0.06 ± 1.18 cm/s for LV, and -0.21 ± 2.33 cm/s and 0.46 ± 4.00 cm/s for RV, respectively). The proposed multi-channel 3D dense U-Net was capable of reducing the segmentation time by 3,600-fold, without significant loss in accuracy in tissue velocity measurements.

Evaluation of Pulmonary Hypertension Using 4D Flow MRI

BACKGROUND

Cardiac magnetic resonance imaging (MRI) is becoming an alternative to right heart catheterization (RHC) for evaluating pulmonary hypertension (PH). A need exists to further evaluate cardiac MRI's ability to characterize PH.

PURPOSE

To evaluate the potential for four-dimensional (4D) flow MRI-derived pulmonary artery velocities to characterize PH.

STUDY TYPE

Prospective case-control.

POPULATION

Fifty-four PH patients (56% female); 25 controls (36% female).

FIELD STRENGTH/SEQUENCE

1.5 T; gradient recalled echo 4D flow and balanced steady-state free precession cardiac cine.

ASSESSMENT

RHC was used to derive patients' pulmonary vascular resistance (PVR). 4D flow measured blood velocities at the main, left, and right pulmonary arteries (MPA, LPA, and RPA); cine measured ejection fraction, end diastolic, and end systolic volumes (EF, EDV, and ESV). EDV and ESV were normalized (indexed) to body surface area (ESVI and EDVI). Parameters were evaluated between, and within, PH subgroups: pulmonary arterial hypertension (PAH); PH due to left heart disease (PH-LHD)/chronic lung disease (PH-CLD)/or chronic thrombo-emboli (CTE-PH).

STATISTICAL TESTS

Analysis of variance and Kruskal-Wallis tests compared parameters between subgroups. Pearson's r assessed velocity, PVR, and volume correlations. Significance definition: P < 0.05.

RESULTS

PAH peak and mean velocities were significantly lower than in controls at the LPA (36 ± 12 cm/second and 20 ± 4 cm/second vs. 59 ± 15 cm/second and 32 ± 9 cm/second). At the RPA, mean velocities were significantly lower in PAH vs. controls (27 ± 6 cm/second vs. 40 ± 9 cm/second). Peak velocities significantly correlated with right ventricular EF at the MPA (r = 0.286), RPA (r = 0.400), and LPA (r = 0.401). Peak velocity significantly correlated with right ventricular ESVI at the RPA (r = -0.355) and LPA (r = -0.316). Significant correlations between peak velocities and PVR were moderate at the LPA in PAH (r = -0.641) and in PH-LHD (r = -0.606) patients, and at the MPA in PH-CLD (r = -0.728). CTE-PH showed non-significant correlations between peak velocity and PVR at all locations.

DATA CONCLUSION

Preliminary findings suggest 4D flow can identify PAH and track PVR changes.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 5.

Erratum: 5D Flow MRI: A Fully Self-gated, Free-running Framework for Cardiac and Respiratory Motion-resolved 3D Hemodynamics

[This corrects the article DOI: 10.1148/ryct.2020200219.].

Identification of Cardiac Fibrosis in Young Adults With a Homozygous Frameshift Variant in SERPINE1

Importance

Cardiac fibrosis is exceedingly rare in young adults. Identification of genetic variants that cause early-onset cardiomyopathy may inform novel biological pathways. Experimental models and a single case report have linked genetic deficiency of plasminogen activator inhibitor-1 (PAI-1), a downstream target of cardiac transforming growth factor β, with cardiac fibrosis.

Objective

To perform detailed cardiovascular phenotyping and genotyping in young adults from an Amish family with a frameshift variant (c.699_700dupTA) in SERPINE1, the gene that codes for PAI-1.

Design, Setting, and Participants

This observational study included participants from 3 related nuclear families from an Amish community in the primary analysis and participants from the extended family in the secondary analysis. Participants were recruited from May 2015 to December 2016, and analysis took place from June 2015 to June 2020.

Main Outcomes and Measures

(1) Multimodality cardiovascular imaging (transthoracic echocardiography and cardiac magnetic resonance imaging), (2) whole-exome sequencing, and (3) induced pluripotent stem cell-derived cardiomyocytes.

Results

Among 17 participants included in the primary analysis, the mean (interquartile range) age was 23.7 (20.9-29.9) years and 9 individuals (52.9%) were confirmed to be homozygous for the SERPINE1 c.699_700dupTA variant. Late gadolinium enhancement was present in 6 of 9 homozygous participants (67%) with absolute PAI-1 deficiency vs 0 of 8 in the control group (P = .001). Late gadolinium enhancement patterns tended to be dense and linear, usually subepicardial but also midmyocardial and transmural with noncoronary distributions. Targeted whole-exome sequencing analysis identified that homozygosity for c.699_700dupTA SERPINE1 was the only shared pathogenic variant or variant of uncertain significance after examination of cardiomyopathy genes among those with late gadolinium enhancement. Induced pluripotent stem cell-derived cardiomyocytes from participants homozygous for the SERPINE1 c.699_700dupTA variant exhibited susceptibility to cardiomyocyte injury in response to angiotensin II (increased transforming growth factor β1 secretion and release of lactate dehydrogenase) compared with control induced pluripotent stem cell-derived cardiomyocytes. In a secondary analysis based on echocardiography in 155 individuals across 3 generations in the extended family, no difference in global longitudinal strain was observed in carriers for the SERPINE1 c.699_700dupTA variant compared with wild-type participants, supporting an autosomal recessive inheritance pattern.

Conclusions and Relevance

In this study, a highly penetrant, autosomal recessive, cardiac fibrosis phenotype among young adults with homozygous frameshift variant for SERPINE1 was identified, suggesting an optimal range of PAI-1 levels are needed for cardiac homeostasis.

Updates in Magnetic Resonance Venous Imaging

For years, magnetic resonance angiography (MRA) has been a leading imaging modality in the assessment of venous disease involving the pelvis and lower extremities. Current advancement in noncontrast MRA techniques enables imaging of a larger subset of patients previously excluded due to allergy or renal insufficiency, allowing for preintervention assessment and planning. In this article, the current status of MR venography, with a focus on current advancements, will be presented. Protocols and parameters for MR venographic imaging of the pelvis and lower extremities, including contrast and noncontrast enhanced techniques, will be reviewed based on a recent literature review of applied MR venographic techniques. Finally, several disease-specific entities, including pelvic congestion and compression syndromes, will be discussed with a focus on imaging parameters that may best characterize these disease processes and optimize anatomical planning prior to intervention.

Fibrosis in Hypertrophic Cardiomyopathy Patients With and Without Sarcomere Gene Mutations

BACKGROUND

Patients with hypertrophic cardiomyopathy (HCM) and an identified sarcomere mutation have worse outcomes than those without though the underlying mechanism is incompletely understood. The presence of replacement fibrosis measured by late gadolinium enhancement (LGE) and diffuse fibrosis measured by extracellular volume (ECV) using cardiac magnetic resonance imaging (CMR) are associated with ventricular arrhythmias and cardiac mortality. We aimed to associate these two forms of fibrosis with identified sarcomere mutations.

METHODS AND RESULTS

Three hundred and thirty-six (336) patients with HCM underwent CMR at a single quaternary referral centre between January 2012 and February 2017. Genetic testing was performed in 73 of these patients, yielding an identified sarcomeric mutation in 29 (G+), no mutation in 39 (G-), and a variant of unknown significance (VUS) in five. LGE was more prevalent in G+ compared to G- patients (86 vs. 56%, OR 4.3, p=0.01) and was more extensive (7.5±5.5% of left ventricular [LV] mass vs. 3.0±3.0%, p<0.001). Global ECV from myocardial segments excluding LGE was similar among both groups (26.9±2.9 vs. 25.6±2.8%, p=0.46). However, in G+ patients ECV was greater in the hypertrophied regions of the basal anteroseptum (30.2±7.0 vs. 26.8±3.6%, p=0.004) and basal inferoseptum (28.1±4.3 vs. 26.2±2.9%, p=0.005).

CONCLUSIONS

Genotyped HCM patients with an identified sarcomere mutation have greater LGE and greater regional, but not global, ECV than HCM patients without an identified mutation. This difference in fibrosis may contribute to worse outcomes in patients with an identified HCM mutation.

Association of Pro-B-Type Natriuretic Peptide With Cardiac Magnetic Resonance-Measured Global and Regional Cardiac Function and Structure Over 10 Years: The MESA Study

Background

NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) is widely used to diagnose and manage patients with heart failure. We aimed to investigate associations between NT‐proBNP levels and development of global and regional myocardial impairment, dyssynchrony, and risk of developing myocardial scar over time.

Methods and Results

We included 2416 adults (45–84 years) without baseline clinical cardiovascular disease from MESA (Multi‐Ethnic Study of Atherosclerosis). NT‐proBNP was assessed at baseline (2000–2002). Cardiac magnetic resonance–measured left ventricular parameters were assessed at baseline and year 10 (2010–2012). Tagged cardiac magnetic resonance and myocardial dyssynchrony were assessed. We used linear and logistic regression models to study the relationships between quartiles of NT‐proBNP levels and outcome variables. Left ventricular parameters decreased over time. After 10‐year follow‐up and adjusting for cardiovascular disease risk factors, people in the highest quartile had significantly greater decline in left ventricular ejection fraction (−1.60%; 95% CI, −2.26 to −0.94; P<0.01) and smaller decline in left ventricular end systolic volume index (−0.47 mL/m²; 95% CI, −1.18 to 0.23; P<0.01) compared with those in the lowest quartile. Individuals in the highest quartile had more severe risk factor adjusted global, mid, and apical regional dyssynchrony compared with those in the lowest, second, and third quartiles (all P‐trend<0.05). Compared with the lowest‐quartile group, the adjusted odds ratios for having myocardial scar was 1.3 (95% CI, 0.7–2.2) for quartile 2; 1.2 (95% CI, 0.6–2.3) for quartile 3; and 2.7 (95% CI, 1.4–5.5) for quartile 4 (P‐trend=0.012) for the total sample.

Conclusions

Among participants without baseline clinical cardiovascular disease, higher baseline NT‐proBNP concentration was significantly associated with subclinical changes in developing myocardial dysfunction, more severe cardiac dyssynchrony, and higher odds of having myocardial scar over a 10‐year period independent of traditional cardiovascular disease risk factors.

A theoretical framework for retrospective T 2 ∗ correction to the arterial input function in quantitative myocardial perfusion MRI

PURPOSE

To develop and evaluate a flexible, Bloch-equation based framework for retrospective T 2 ∗ correction to the arterial input function (AIF) obtained with quantitative cardiac perfusion pulse sequences.

METHODS

Our framework initially calculates the gadolinium concentration [Gd] based on T₁ measurements alone. Next, T 2 ∗ is estimated from this initial calculation of [Gd] while assuming fast water exchange and using the literature native T₂ and static magnetic field variation (ΔB₀ ) values. Finally, the [Gd] is recalculated after performing T 2 ∗ correction to the Bloch equation signal model. Using this approach, we performed T 2 ∗ correction to historical phantom and in vivo, dual-imaging perfusion data sets from 3 different patient groups obtained using different pulse sequences and imaging parameters. Images were processed to quantify both the AIF and resting myocardial blood flow (MBF). We also performed a sensitivity analysis of our T 2 ∗ correction to ±20% variations in native T₂ and ΔB₀ .

RESULTS

Compared with the ground truth [Gd] of phantom, the normalized root-means-square-error (NRMSE) in measured [Gd] was 5.1%, 1.3%, and 0.6% for uncorrected, our corrected, and Kellman's corrected, respectively. For in vivo data, both the peak AIF (7.0 ± 3.0 mM vs. 8.6 ± 7.1 mM, 7.2 ± 0.9 mM vs. 8.6 ± 1.7 mM, 7.7 ± 1.8 mM vs. 10.3 ± 5.1 mM, P < .001) and resting MBF (1.3 ± 0.1 mL/g/min vs. 1.1 ± 0.1 mL/g/min, 1.3 ± 0.1 mL/g/min vs. 1.1 ± 0.1 mL/g/min, 1.2 ± 0.1 mL/g/min vs. 0.9 ± 0.1 mL/g/min, P < .001) values were significantly different between uncorrected and corrected for all 3 patient groups. Both the peak AIF and resting MBF values varied by <5% over the said variations in native T₂ and ΔB₀ .

CONCLUSION

Our theoretical framework enables retrospective T 2 ∗ correction to the AIF obtained with dual-imaging, cardiac perfusion pulse sequences.

Cine MRI detects elevated left heart pressure in pulmonary hypertension

Cine magnetic resonance imaging (MRI) is an emerging modality for evaluating left ventricular (LV) motion/deformation patterns, which may have potential to identify LV dysfunctions underlying postcapillary pulmonary hypertension (PH). The aim of this study was to test the hypothesis that cine MRI-derived LV motion/deformation indices can be used to identify an elevated left heart pressure in PH. This was a retrospective study, which included 26 precapillary and 28 postcapillary PH patients (23 males, 58.9 ± 13.5 years old). All patients underwent right heart catheterization (the "reference standard") and cardiac MRI. Balanced steady-state free precession cine sequence acquired at 1.5 T was used. Cine MRI datasets were analyzed by using heart deformation analysis. LV motion/deformation indices were measured through 25 phases within a cardiac cycle. Peak LV displacement, velocity, strain, and strain rates at systole, early and late diastole were compared between the two patient groups using t-tests. The Pearson correlation coefficient (r) was used to investigate the association between cine MRI-derived indices and pulmonary capillary wedge pressure (PCWP). Multivariable linear and logistic regression models were applied to assess the ability of MRI-derived parameters to predict PCWP and postcapillary PH. Compared to 26 precapillary PH patients, the 28 postcapillary PH patients had lower peak late radial diastolic displacement (0.43 ± 0.19 cm vs. 0.64 ± 0.18 cm) and velocity (12.2 ± 5.8 mm/s vs. 18.9 ± 5.6 mm/s) and peak late radial (52.1 ± 32.7%/s vs. 97.1 ± 38%/s) and circumferential (38 ± 19.8%/s vs. 63.1 ± 22.9%/s) strain rates. PCWP was correlated with peak late radial diastolic displacement (r = -0.54) and velocity (r = -0.57) and peak late radial (r = -0.63) and circumferential diastolic (r = -0.63) strain rates. Peak late radial strain rate could predict PCWP (β = -0.09) and postcapillary PH (β = -0.036). All p < 0.05. Cine MRI-derived LV late diastolic motion/deformation properties can be used to estimate elevated left heart pressure in PH. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 1.

5D Flow MRI: A Fully Self-gated, Free-running Framework for Cardiac and Respiratory Motion-resolved 3D Hemodynamics

PURPOSE

To implement, validate, and apply a self-gated free-running whole-heart five-dimensional (5D) flow MRI framework to evaluate respiration-driven effects on three-dimensional (3D) hemodynamics in a clinical setting.

MATERIALS AND METHODS

In this prospective study, a free-running five-dimensional (5D) flow sequence was implemented with 3D radial sampling, self-gating, and a compressed-sensing reconstruction. The 5D flow was evaluated in a pulsatile phantom and adult participants with aortic and/or valvular disease who were enrolled between May and August 2019. Conventional twofold-accelerated four-dimensional (4D) flow of the thoracic aorta with navigator gating was performed as a reference comparison. Continuous parameters were evaluated for parameter normality and were compared between conventional 4D flow and 5D flow using a signed-rank or two-tailed paired t test. Differences between respiratory states were evaluated using a repeated-measure analysis of variance or a nonparametric Friedman test.

RESULTS

A total of 20 adult participants (mean age, 49 years ± 17 [standard deviation]; 18 men and two women) were included. In vitro 5D flow results showed excellent agreement with conventional 4D flow-derived values (peak and net flow, <7% difference over all quantified planes). Whole-heart 5D flow data were collected in all participants in 7.65 minutes ± 0.35 (acceleration rate = 36.0-76.9) versus 9.88 minutes ± 3.17 for conventional aortic 4D flow. In vivo, 5D flow demonstrated moderate agreement with conventional 4D flow but demonstrated overestimation in net flow and peak velocity (up to 26% and 12%, respectively) in the ascending aorta and underestimation (<12%) in the arch and descending aorta. Respiratory-resolved analyses of caval veins showed significantly increased net and peak flow in the inferior vena cava in end inspiration compared with end expiration, and the opposite trend was shown in the superior vena cava.

CONCLUSION

A free-running 5D flow MRI framework consistently captured cardiac and respiratory motion-resolved 3D hemodynamics in less than 8 minutes. Supplemental material is available for this article. © RSNA, 2020.

Cardiac MRI Reveals Late Diastolic Changes in Left Ventricular Relaxation Patterns During Healthy Aging

BACKGROUND

Cardiac MRI is an emerging modality for evaluating left ventricular (LV) diastolic dysfunction (LVDD), a pathological condition that is prevalent in aging populations. However, there is a lack of reports of MRI-derived LV diastolic properties in late diastole.

PURPOSE

To test the hypothesis that cine MRI-derived motion/deformation indices can be used to characterize age-related changes on LV relaxation patterns in late diastole.

STUDY TYPE

Retrospective.

POPULATION

In all, 412 participants (72.5 ± 4.6 years old, range 65-84) without a documented history of cardiovascular diseases.

FIELD STRENGTH/SEQUENCE

Balanced steady-state free precession(bSSFP) acquired at 1.5T.

ASSESSMENT

Participants were divided into younger (65-74 years old, n = 275) and older (75-84 years old, n = 137) groups. Status of diabetes mellitus (DM), hypertension (HTN), and lipid disorders were recorded for each participant. Cine MRI datasets were analyzed by using heart deformation analysis (HDA). LV motion/deformation indices (displacement, velocity, strain, and strain rate) were measured through 22 phases within a cardiac cycle.

STATISTICAL TESTS

The prevalence of traditional cardiovascular risk conditions, LV ejection fraction (LVEF), peak LV regional displacement, velocity, and strain rates at early and late diastole were compared between two participant groups using chi-square tests or t-tests.

RESULTS

Older participants had a significantly lower peak early radial displacement (0.797 ± 0.249 cm vs. 0.876 ± 0.286 cm), radial velocity (19.3 ± 6.3 mm/s vs. 17.5 ± 5.2 mm/s), and circumferential strain rate (64.6 ± 15.7%/s vs. 70.1 ± 17%/s) but a higher peak late circumferential strain rate (69.8 ± 16.3 %/s vs. 66 ± 15.8 %/s) than their younger counterparts.

DATA CONCLUSION

Cine MRI can be used to characterize age-related LV relaxation patterns in late diastole.

LEVEL OF EVIDENCE

3.

TECHNICAL EFFICACY STAGE

1.

Relation of Late Gadolinium Enhancement and Extracellular Volume Fraction to Ventricular Arrhythmias in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HC) represents a major cause of sudden cardiac death in young adults. Late gadolinium enhancement (LGE) and extracellular volume (ECV) by T1 mapping are cardiac magnetic resonance (CMR) techniques to quantify fibrosis in HC. The relationships of LGE and ECV with ventricular arrhythmia, left ventricular (LV) diastolic function, and risk factors for sudden cardiac death (SCD) in HC are unclear. We studied 103 HC patients (mean age 51 ± 14, 42% women) who underwent CMR from 2012 to 2014. Global LGE and mean ECV were evaluated in relation to history of nonsustained ventricular tachycardia (NSVT), diastolic function by echocardiography, and SCD risk factors. LGE was present in 71 (69%) subjects. Wide variation was demonstrated in LGE (0.5% to 45.9%) and mean ECV (17.6% to 47.4%). Prevalence of NSVT increased continuously with LGE and was greater in subjects with ECV above the study population mean (27%). Increased LGE was associated with LV diastolic dysfunction and LV wall thickness. In conclusion, while ECV appears to have a threshold (27%) above which it is associated with NSVT, LGE demonstrates a more robust relationship with NSVT and measures of diastolic dysfunction.

Cardiac MRI Myocardial Functional and Tissue Characterization Detects Early Cardiac Dysfunction in a Mouse Model of Chemotherapy-Induced Cardiotoxicity

BACKGROUND

Doxorubicin and doxorubicin-trastuzumab combination chemotherapy have been associated with cardiotoxicity that eventually leads to heart failure and may limit dose-effective cancer treatment. Current diagnostic strategies rely on decreased ejection fraction (EF) to diagnose cardiotoxicity.

PURPOSE

The aim of this study is to explore the potential of cardiac MR (CMR) imaging to identify imaging biomarkers in a mouse model of chemotherapy-induced cardiotoxicity.

METHODS

A cumulative dose of 25 mg/kg doxorubicin was administered over three weeks using subcutaneous pellets (n = 9, Dox). Another group (n = 9) received same dose of Dox and a total of 10 mg/kg trastuzumab (DT). Mice were imaged at baseline, 5/6 weeks and 10 weeks post-treatment on a 7T MRI system. The protocol included short-axis cine MRI covering the left ventricle (LV) and mid-ventricular short-axis tissue phase mapping (TPM), pre- and post-contrast T1 mapping, T2 mapping and Displacement Encoding with Stimulated Echoes (DENSE) strain encoded MRI. EF, peak myocardial velocities, native T1, T2, extracellular volume (ECV), and myocardial strain were quantified. N = 7 mice were sacrificed for histopathologic assessment of apoptosis at 5/6 weeks.

RESULTS

Global peak systolic longitudinal velocity was reduced at 5/6 weeks in Dox (0.6 ± 0.3 vs 0.9 ± 0.3, p = 0.02). In the Dox group, native T1 was reduced at 5/6 weeks (1.3 ± 0.2 ms vs 1.6 ± 0.2 ms, p = 0.02), and relatively normalized at week 10 (1.4 ± 0.1 ms vs 1.6 ± 0.2 ms, p > 0.99). There was no change in EF and other MRI parameters and histopathologic results demonstrated minimal apoptosis in all mice (~1-2 apoptotic cell/high power field), suggesting early-stage cardiotoxicity.

CONCLUSIONS

In a mouse model of chemotherapy-induced cardiotoxicity using doxorubicin and trastuzumab, advanced CMR shows promise in identifying treatment-related decrease in myocardial velocity and native T1 prior to the onset of cardiomyocyte apoptosis and reduction of EF.

Society for Cardiovascular Magnetic Resonance (SCMR) guidance for re-activation of cardiovascular magnetic resonance practice after peak phase of the COVID-19 pandemic

During the peak phase of the COVID-19 pandemic, alterations of standard operating procedures were necessary for health systems to protect patients and healthcare workers and ensure access to vital hospital resources. As the peak phase passes, re-activation plans are required to safely manage increasing clinical volumes. In the context of cardiovascular magnetic resonance (CMR), re-activation objectives include continued performance of urgent CMR studies and resumption of CMR in patients with semi-urgent and elective indications in an environment that is safe for both patients and health care workers.

Slow-Release Doxorubicin Pellets Generate Myocardial Cardiotoxic Changes in Mice Without Significant Systemic Toxicity

An increasing volume of pre-clinical and clinical-translational research is attempting to identify novel biomarkers for improved diagnosis and risk-stratification of chemotherapy-induced cardiotoxicity. Most published animal models have employed weekly intraperitoneal injections of doxorubicin to reach a desired cumulative dose. This approach can be associated with severe systemic toxicity which limits the animal model usefulness, particularly for advanced imaging. In the current study, slow-release subcutaneous doxorubicin pellets demonstrated histopathologic evidence of cardiotoxicity at doses similar to standard human dose-equivalents without limiting animal survival or ability to participate in advanced imaging studies. This approach may provide a more robust cardiotoxicity animal model.

Rapid dealiasing of undersampled, non-Cartesian cardiac perfusion images using U-net

Compressed sensing (CS) is a promising method for accelerating cardiac perfusion MRI to achieve clinically acceptable image quality with high spatial resolution (1.6 × 1.6 × 8 mm³ ) and extensive myocardial coverage (6-8 slices per heartbeat). A major disadvantage of CS is its relatively lengthy processing time (~8 min per slice with 64 frames using a graphics processing unit), thereby making it impractical for clinical translation. The purpose of this study was to implement and test whether an image reconstruction pipeline including a neural network is capable of reconstructing 6.4-fold accelerated, non-Cartesian (radial) cardiac perfusion k-space data at least 10 times faster than CS, without significant loss in image quality. We implemented a 3D (2D + time) U-Net and trained it with 132 2D + time datasets (coil combined, zero filled as input; CS reconstruction as reference) with 64 time frames from 28 patients (8448 2D images in total). For testing, we used 56 2D + time coil-combined, zero-filled datasets (3584 2D images in total) from 12 different patients as input to our trained U-Net, and compared the resulting images with CS reconstructed images using quantitative metrics of image quality and visual scores (conspicuity of wall enhancement, noise, artifacts; each score ranging from 1 (worst) to 5 (best), with 3 defined as clinically acceptable) evaluated by readers. Including pre- and post-processing steps, compared with CS, U-Net significantly reduced the reconstruction time by 14.4-fold (32.1 ± 1.4 s for U-Net versus 461.3 ± 16.9 s for CS, p < 0.001), while maintaining high data fidelity (structural similarity index = 0.914 ± 0.023, normalized root mean square error = 1.7 ± 0.3%, identical mean edge sharpness of 1.2 mm). The median visual summed score was not significantly different (p = 0.053) between CS (14; interquartile range (IQR) = 0.5) and U-Net (12; IQR = 0.5). This study shows that the proposed pipeline with a U-Net is capable of reconstructing 6.4-fold accelerated, non-Cartesian cardiac perfusion k-space data 14.4 times faster than CS, without significant loss in data fidelity or image quality.

Left Ventricular Extracellular Volume Expansion Is Not Associated with Atrial Fibrillation or Atrial Fibrillation-mediated Left Ventricular Systolic Dysfunction

PURPOSE

To determine whether left ventricular (LV) extracellular volume (ECV) expansion is associated with atrial fibrillation (AF) or AF-mediated LV systolic dysfunction (LVSD) while minimizing the influence of biologic and imaging methodologic confounders.

MATERIALS AND METHODS

This study examined the prevalence of LV ECV expansion in 137 patients with AF (mean age, 62 years ± 11 [standard deviation]; 92 male patients and 45 female patients; 83 paroxysmal and 54 persistent) who underwent preablation cardiovascular MRI. Biologic confounders were minimized by measuring the ECV fraction and excluding patients with severe LV hypertrophy, defined as wall thickness greater than 1.5 cm. Imaging confounders were minimized by using an arrhythmia-insensitive-rapid (AIR) cardiac T1 mapping pulse sequence. Other cardiac functional parameters, including LV ejection fraction (LVEF) and left atrial end-diastolic volume indexed to body surface area, were assessed using cine cardiovascular MRI. A substudy was conducted in 32 patients with no AF (mean age, 54 years ± 16) in sinus rhythm to establish control values and convert these values between the AIR sequence and literature-based modified Look-Locker inversion recovery (MOLLI) values.

RESULTS

The mean ECV was not significantly different (P > .05) between patients with AF with a normal LVEF (24.5% ± 2.8; n = 107), patients with AF with LVSD (24.5% ± 2.5; n = 30), and patients with no AF (24.4% ± 3.8; n = 32), but there was a significant interaction between ECV and CHA₂DS₂-VASc score (P = .045). Compared with the literature data obtained from healthy control patients scanned using MOLLI, 99.3% of patients with AF had ECV below the fibrosis cutoff point (32.8% when converted from MOLLI T1 mapping to AIR T1 mapping), including a subset of patients with AF (n = 28) with low CHA₂DS₂-VASc score (0/1 for men/women).

CONCLUSION

Study results suggest that an LV ECV expansion is not associated with AF or AF-mediated LVSD. Supplemental material is available for this article. © RSNA, 2020See also the commentary by Stillman in this issue.

Hypertrophic Cardiomyopathy Is Associated with Altered Left Ventricular 3D Blood Flow Dynamics

Purpose

To employ four-dimensional (4D) flow MRI to investigate associations between hemodynamic parameters with systolic anterior motion (SAM), mitral regurgitation (MR), stroke volume, and cardiac mass in patients with hypertrophic cardiomyopathy (HCM).

Materials and Methods

A total of 13 patients with HCM (51 years ± 16 [standard deviation]; 10 men) and 11 age-matched healthy control subjects (54 years ± 15; eight men) underwent cardiac 4D flow MRI data analysis including calculation of peak systolic and diastolic control-averaged left ventricular (LV) velocity maps to quantify volumes of elevated velocity (EVV) in the left ventricle. Standard-of-care cine imaging was performed in short-axis, LV outflow tract (LVOT), and two-, three-, and four-chamber views on which the presence of SAM, presence of MR, total stroke volume, and cardiac mass were assessed.

Results

Systolic EVV in patients with HCM was 7 mL ± 5, which was significantly associated with elevated aortic peak velocity (R = 0.87; P < .001), decreased LVOT diameter (R = 0.68; P = .01), and increased cardiac mass (R = 0.62; P = .02). In addition, EVV differed significantly between patients with and those without SAM (10 mL ± 4.7 vs 3 mL ± 2.3; P = .03) and those with and those without MR (9.9 mL ± 4.8 vs 4.0 mL ± 3.2; P < .05). In the atrial systolic phase, peak diastolic velocity in the LV correlated with septal thickness (R = 0.66; P = .01).

Conclusion

Quantification and visualization of EVV in the LV is feasible and may provide further insight into the clinical manifestations of altered hemodynamics in HCM.© RSNA, 2020.

Evaluating Biventricular Myocardial Velocity and Interventricular Dyssynchrony in Adult Patients During the First Year After Heart Transplantation

BACKGROUND

Magnetic resonance tissue phase mapping (TPM) measures three-directional myocardial velocities of the left and right ventricle (LV, RV). This noninvasive technique may supplement endomyocardial biopsy (EMB) in monitoring grafts post-heart transplantation (HTx).

PURPOSE

To assess biventricular myocardial velocity alterations in grafts and investigate the relationship between velocities and acute cellular rejection (ACR) episodes.

STUDY TYPE

Prospective.

SUBJECTS

Twenty-seven patients within 1 year post-HTx (49 ± 13 years, 19 M) and 18 age-matched controls (49 ± 15 years, 12 M).

FIELD STRENGTH/SEQUENCE

1.5T, 2D balanced steady-state free precession, and TPM.

ASSESSMENT

Ventricular function: end-diastolic and end-systolic volumes, stroke volumes, ejection fraction (EF), and myocardial mass. TPM velocities: peak-systolic and peak-diastolic velocities, cardiac twist, and interventricular dyssynchrony. ACR rejection episodes: International Society for Heart and Lung Transplantation grading of EMB specimens.

STATISTICAL TESTS

The Lilliefors test for normality, unpaired t-tests, and Wilcoxon rank-sum tests for normally and nonnormally distributed data, respectively, were used, as well as multivariate regression for confounding variables and Pearson's correlation for associations between TPM velocities and global function.

RESULTS

Compared to controls, HTx patients demonstrated reduced biventricular systolic longitudinal velocities (LV: 5.2 ± 2.1 vs. 4.0 ± 1.5 cm/s, P < 0.05; RV: 4.2 ± 1.3 vs. 3.1 ± 1.2 cm/s, P < 0.01). Correlation analysis revealed significant positive relationships for biventricular EF with radial peak velocities of the same ventricle in both systole and diastole (LV systole: r = 0.48, P < 0.01; LV diastole: r = 0.28, P < 0.05; RV systole: r = 0.35, P < 0.01; RV diastole: r = 0.36, P < 0.01). Segmentally, longitudinal velocities were impaired in 7/16 LV segments and 5/10 RV segments in systole and 7/10 RV segments in diastole. TPM analysis in studies with >4 preceding ACR episodes showed globally reduced RV and LV systolic radial velocity, and segmentally reduced radial and longitudinal systolic velocities.

DATA CONCLUSION

Biventricular global and segmental velocities were reduced in HTx patients. Patients with >4 rejection episodes showed reduced myocardial velocities. The TPM sequence may add functional information for monitoring graft dysfunction.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 2 J. Magn. Reson. Imaging 2020;52:920-929.

Left ventricular extracellular volume expansion does not predict recurrence of atrial fibrillation following catheter ablation

INTRODUCTION

A recent study reported that diffuse left ventricular (LV) fibrosis is a predictor of atrial fibrillation (AF) recurrence following catheter ablation, by measuring postcontrast cardiac T1 (an error prone metric as per the 2017 Society for Cardiovascular Magnetic Resonance consensus statement) using an inversion-recovery pulse sequence (an error prone method in arrhythmia) in AF ablation candidates. The purpose of this study was to verify the prior study, by measuring extracellular volume (ECV) fraction (an accurate metric) using a saturation-recovery pulse sequence (accurate method in arrhythmia).

METHODS AND RESULTS

This study examined 100 AF patients (mean age = 62 ± 11 years, 69 males and 31 females, 67 paroxysmal [pAF] and 33 persistent [peAF]) who underwent a preablation cardiovascular magnetic resonance (CMR) exam. LV ECV and left atrial (LA) and LV functional parameters were quantified using standard analysis methods. During an average follow-up period of 457 ± 261 days with 4 ± 3 rhythm checks per patient, 72 patients maintained sinus rhythm. Between those who maintained sinus rhythm (n = 72) and those who reverted to AF (n = 28), the only clinical characteristic that was significantly different was age (60 ± 12 years vs 66 ± 9 years); for CMR metrics, neither mean LV ECV (25.1 ± 3.3% vs 24.7 ± 3.7%), native LV T1 (1093.8 ± 73.5 ms vs 1070.2 ± 115.9 ms), left ventricular ejection fraction (54.1 ± 11.2% vs 55.7 ± 7.1%), nor LA end diastolic volume/body surface area (42.4 ± 14.8 mL/m2 vs 43.4 ± 19.6 mL/m2 ) were significantly different (P ≥ .23). According to Cox regression tests, none of the clinical and imaging variables predict AF recurrence.

CONCLUSION

Neither LV ECV nor other CMR metrics predict recurrence of AF following catheter ablation.

Diffuse right ventricular fibrosis in heart failure with preserved ejection fraction and pulmonary hypertension

Aims

While right ventricular (RV) dysfunction is associated with worse prognosis in co‐morbid pulmonary hypertension and heart failure with preserved ejection fraction (PH‐HFpEF), the mechanisms driving RV dysfunction are unclear. We evaluated the extent and clinical correlates of diffuse RV myocardial fibrosis in PH‐HFpEF, as measured by cardiovascular magnetic resonance‐derived extracellular volume (ECV).

Methods and results

We prospectively enrolled participants with PH‐HFpEF (n = 14), pulmonary arterial hypertension (PAH; n = 13), and controls (n = 8). All participants underwent high‐resolution cardiovascular magnetic resonance, and case subjects (PH‐HFpEF and PAH) additionally underwent right heart catheterization. T1 mapping was performed using high‐resolution modified look‐locker inversion recovery with a 1 × 1 mm² in‐plane resolution. RV free wall T1 values were quantified, and ECV was calculated. Participants with PH‐HFpEF were older and carried higher rates of hypertension and obstructive sleep apnoea than those with PAH. While RV ECV was similar between PH‐HFpEF and PAH (33.1 ± 8.0 vs. 34.0 ± 4.5%; P = 0.57), total pulmonary resistance was lower in PH‐HFpEF compared with PAH [PH‐HFpEF: 5.68 WU (4.70, 7.66 WU) vs. PAH: 8.59 WU (8.14, 12.57 WU); P = 0.01]. RV ECV in PH‐HFpEF was associated with worse indices of RV structure (RV end‐diastolic volume: r = 0.67, P = 0.01) and RV function (RV free wall strain: r = 0.59, P = 0.03) but was not associated with RV afterload (total pulmonary resistance: r = 0.08, P = 0.79). Conversely, there was a strong correlation between RV ECV and RV afterload in PAH (r = 0.57, P = 0.04).

Conclusions

Diffuse RV fibrosis, as measured by ECV, is present in PH‐HFpEF and is associated with adverse RV structural and functional remodelling but not degree of pulmonary vasculopathy. In PH‐HFpEF, diffuse RV fibrosis may occur out of proportion to the degree of RV afterload.

Semi-quantitative myocardial perfusion MRI in heart transplant recipients at rest: repeatability in healthy controls and assessment of cardiac allograft vasculopathy

BACKGROUND

Cardiac Allograft Vasculopathy (CAV) is a major cause of chronic cardiac allograft failure. Invasive coronary angiography (ICA) and intravascular ultrasound (IVUS) are the current diagnostic methods. Myocardial perfusion MRI has become a promising non-invasive method to evaluate myocardial ischemia, but has not been thoroughly validated in CAV. Our objective was to assess the repeatability of myocardial rest-perfusion MRI in healthy volunteers and its feasibility in detecting CAV in transplant patients (Tx).

METHODS

Twelve healthy volunteers and twenty transplant patients beyond the first year post- transplant underwent cardiac MRI at 1.5 T at rest including first-pass perfusion imaging in short axis (base, mid, apex) after injection of gadolinium. Volunteers underwent repeated cardiac MRI on different days (interval = 15.6 ± 2.4 days) to assess repeatability. Data analysis included semi-automatic contouring of endocardial and epicardial borders of the left ventricle (LV) and quantification of peak perfusion, time-to-peak (TTP) perfusion, and upslope of the perfusion curve.

RESULTS

Between scans and re-scans in healthy volunteers, peak signal intensity, slope, and TTP demonstrated moderate agreement (ICC = 0.53, 0.48, and 0.59, respectively; all, p < .001). Peak signal intensity, slope, and TTP were moderately variable with COV values of 23%, 42%, and 35%, respectively. Peak perfusion was significantly reduced in CAV positive (n = 9 Tx patients) compared to CAV negative (n = 11 Tx patients) groups (90.7 ± 27.0 vs 139.5 ± 30.2, p < .001).

CONCLUSION

Cardiac MRI is a moderately repeatable method for the semi-quantitative assessment of first-pass myocardial perfusion at rest. Semi-quantitative surrogate markers of LV perfusion could play a role in CAV detection.