Impact of training data composition on the generalizability of convolutional neural network aortic cross-section segmentation in four-dimensional magnetic resonance flow imaging.

BACKGROUND: Four-dimensional cardiovascular magnetic resonance flow imaging (4D flow CMR) plays an important role in assessing cardiovascular diseases. However, the manual or semi-automatic segmentation of aortic vessel boundaries in 4D flow data introduces variability and limits the reproducibility of aortic hemodynamics visualization and quantitative flow-related parameter computation. This paper explores the potential of deep learning to improve 4D flow CMR segmentation by developing models for automatic segmentation and analyzes the impact of the training data on the generalization of the model across different sites, scanner vendors, sequences, and pathologies. METHODS: The study population consists of 260 4D flow CMR datasets, including subjects without known aortic pathology, healthy volunteers, and patients with bicuspid aortic valve (BAV) examined at different hospitals. The dataset was split to train segmentation models on subsets with different representations of characteristics, such as pathology, gender, age, scanner model, vendor, and field strength. An enhanced three-dimensional U-net convolutional neural network (CNN) architecture with residual units was trained for time-resolved two-dimensional aortic cross-sectional segmentation. Model performance was evaluated using Dice score, Hausdorff distance, and average symmetric surface distance on test data, datasets with characteristics not represented in the training set (model-specific), and an overall evaluation set. Standard diagnostic flow parameters were computed and compared with manual segmentation results using Bland-Altman analysis and interclass correlation. RESULTS: The representation of technical factors, such as scanner vendor and field strength, in the training dataset had the strongest influence on the overall segmentation performance. Age had a greater impact than gender. Models solely trained on BAV patients' datasets performed well on datasets of healthy subjects but not vice versa. CONCLUSION: This study highlights the importance of considering a heterogeneous dataset for the training of widely applicable automatic CNN segmentations in 4D flow CMR, with a particular focus on the inclusion of different pathologies and technical aspects of data acquisition.

Ambulatory sedation for children under 6 years with CHD in MRI and CT.

INTRODUCTION: In infants and young children, good image quality in MRI and CT requires sedation or general anesthesia to prevent motion artefacts. This study aims to determine the safety of ambulatory sedation for children with CHD in an outpatient setting as a feasible alternative to in-hospital management. METHODS: We recorded 91 consecutive MRI and CT examinations of patients with CHD younger than 6 years with ambulatory sedation. CHD diagnoses, vital signs, applied sedatives, and adverse events during or after ambulatory sedation were investigated. RESULTS: We analysed 91 patients under 72 months (6 years) of age (median 26.0, range 1-70 months; 36% female). Sixty-eight per cent were classified as ASA IV, 25% as ASA III, and 7% as ASA II (American Society of Anesthesiologists Physical Status Classification). Ambulatory sedation was performed by using midazolam, propofol, and/or S-ketamine. The median sedation time for MRI was 90 minutes (range 35-235 minutes) and 65 minutes for CT (range 40-280 minutes). Two male patients (age 1.5 months, ASA II, and age 17 months, ASA IV) were admitted for in-hospital observation due to unexpected severe airway obstruction. The patients were discharged without sequelae after 1 and 3 days, respectively. All other patients were sent home on the day of examination. CONCLUSION: In infants and young children with CHD, MRI or CT imaging can be performed under sedation in an outpatient setting by a well-experienced team. In-hospital backup should be available for unexpected events.

Surgical outcome of the borderline hypoplastic left ventricle: impact of the left ventricle rehabilitation strategy.

OBJECTIVE: This study aims to assess the surgical outcome of borderline hypoplastic left ventricle before and after the induction of the left ventricle rehabilitation strategy. METHODS: A retrospective review investigated patients with borderline hypoplastic left ventricle who underwent surgical intervention between 2012 and 2022. The patient cohort was stratified into two groups based on the initiation of left ventricle rehabilitation: an early-era group (E group, 2012-2017) and a late-era group (L group, 2018-2022). Left ventricle rehabilitation was defined as palliation combined with other procedures aimed at promoting left ventricular growth such as restriction of atrial septal defect, relief of inflow/outflow obstructive lesions, and resection of endocardial fibroelastosis. RESULTS: A total of 58 patients were included. Primary diagnosis included 12 hypoplastic left heart syndromes, 11 critical aortic valve stenosis, and others. A total of 9 patients underwent left ventricle rehabilitation, 8 of whom underwent restriction of atrial septal defect. As for clinical outcomes, 9 of 23 patients achieved biventricular repair in the E group, whereas in the L group, 27 of 35 patients achieved biventricular repair (39% vs. 77%, p = 0.004). Mortality did not differ statistically between the two groups (log-rank test p = 0.182). As for the changes after left ventricle rehabilitation, left ventricular growth was observed in 8 of 9 patients. The left ventricular end-diastolic volume index (from 11.4 to 30.1 ml/m2, p = 0.017) and left ventricular apex-to-right ventricular apex ratio (from 86 to 106 %, p = 0.014) significantly increased after left ventricle rehabilitation. CONCLUSIONS: The introduction of the left ventricle rehabilitation strategy resulted in an increased proportion of patients achieving biventricular repair without a concomitant increase in mortality. Left ventricle rehabilitation was associated with enhanced left ventricular growth and the formation of a well-defined left ventricle apex. Our study underscores the significance of left ventricle rehabilitation strategies facilitating successful biventricular repair. The data suggest establishing restrictive atrial communication may be a key factor in promoting left ventricular growth.

Bioelectrical Impedance Analysis as a Contemporary Biomarker of Obesity in Adults with Marfan- or Loeys-Dietz-Syndrome.

Background: It is clinically widely overlooked that many patients with Marfan- (MFS) or Loeys-Dietz-Syndrome (LDS) are obese. While anthropometric routine parameters are not very suitable, the modern Bioelectrical Impedance Analysis (BIA) seems superior for the acquisition of reliable noninvasive assessment of body composition of patients. The aim of the study was to assess the body composition of patients with MFS/LDS by BIA in order to detect occult obesity, which may be a risk marker for aortic or vascular complications. Methods: In this exploratory cross-sectional study, 50 patients (66% female; mean age: 37.7 ± 11.7 [range: 17-64] years) with a molecular genetic (n = 45; 90%) or clinical (n = 5; 10%) proven diagnosis of MFS or LDS were enrolled between June 2020 and February 2022. All BIA-measurements were performed with the Multifrequence-Impedance-Analyzer Nutriguard-MS (Data Input, Poecking, Germany). Results: The MFS/LDS collective was significantly different from an age-, sex-, and BMI-adjusted control in terms of body fat, percent cellularity, body cell mass, extra cellular mass/body cell mass index, and phase angle (all p < 0.05). The mean BIA-measured bodyfat was 31.7 ± 8.7% [range: 9.5-53.5%], while the mean calculated BMI of the included patients was 23.0 ± 4.8 kg/ m 2 [range: 15.2-41.9 kg/ m 2 ]. Therefore, using the obesity cut-off values for the body fat percentage of 25% in men and 35% in women, the BIA classifies as many as 28 patients (56.0%) as obese. In contrast only 12 patients (24.0%) were pre-obese, respectively 3 (6.0%) obese by BMI. The significant difference (p < 0.001) had an accordance of 42.7%. Overall, 15 patients (13 MFS; 2 LDS) had previous aortic surgery (n = 14) and/or interventional treatment (n = 2) for aortic complications (aneurysm, aortic dissection). 11 out of these 15 (73.3%) were currently classified as obese by BIA. Conclusions: The fact that many patients with MFS or LDS are obese is widely unknown, although obesity may be associated with impaired vascular endothelial function and an increased risk of cardiovascular complications. Also, in patients with MFS/LDS, BIA allows a reliable assessment of the body composition beyond the normal anthropometric parameters, such as BMI. In the future, BIA-data possibly may be of particular importance for the assessment of the vascular risk of MFS/LDS patients, besides the aortic diameters.

Improved Tricuspid Valve Function, Preload Recruitment and Ventricular Efficiency During Submaximal Exercise in Patients with Unoperated Ebstein's Anomaly: An MRI Study.

BACKGROUND: Adolescents and adults with native Ebstein's anomaly (EA) are at the benign part of the Ebstein spectrum, having survived infancy without surgery. In this population, surgical indication and timing remain objects of controversy and depend, among other factors, on exercise capacity. PURPOSE: To better understand the pathophysiology of exercise adaptation in native EA. STUDY TYPE: Retrospective. POPULATION: Ten patients with unoperated EA (age range 18-61 years) and 13 healthy subjects as controls. FIELD STRENGTH/SEQUENCE: Balanced steady-state free precession cine and phase contrast flow sequences at 1.5 T. ASSESSMENT: We measured volumes and flows at rest and during submaximal exercise. Hemodynamic parameters including stroke volume (SV), cardiac index (CI), ejection fraction (EF), and tricuspid regurgitation (TR) were calculated. STATISTICAL TESTS: We used nonparametric Mann-Whitney U-test and Wilcoxon signed-rank test. A P-value of <0.05 was considered statistically significant. RESULTS: Rest CI and SV were significantly higher in controls; rest heart rate (HR) was similar in the two groups (median 71 bpm by patients and 65 bpm by controls, P = 0.448). During exercise, CI increased significantly in both groups: from 2.40 to 3.35 L/min/m2 in the patient group and from 3.60 to 4.20 L/min/m2 in controls; HR increased significantly in both groups. SV increased significantly in the patient group, whereas it remained stable in controls (P = 0.5284). Patients' median TR decreased significantly: median 42% at rest and 30% during exercise; concomitantly, left ventricular (LV) preload increased significantly (+3% indexed LV end-diastolic volume) as did LVEF (median 59% at rest vs. 65% during exercise). DATA CONCLUSION: During submaximal exercise, patients with mild to moderate EA improved their cardiovascular system's total efficiency by increasing CI; this was obtained by an increase in HR and by the recruitment of volume, as shown by an increased LV end-diastolic volume and SV, with simultaneous decrease in TR. This was different from healthy subjects in which CI increased only due to HR increase. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 3.

Transcatheter implantation of covered stents serving as extravascular conduits-Proof of a CT-based approach in three cases.

BACKGROUND: Covered stents perform similar to surgically implanted conduits, although the stents work inside of vessels. We present a computed tomography (CT)-based workflow for the implantation of covered stents as extravascular conduits. METHODS: We selected three different use cases: 1. Connecting a left-sided partially anomalous drainage of a pulmonary vein to the left atrium. 2. Bypassing an outgrown Dacron conduit in aortic recoarctation. 3. Re-directing hepatic venous blood to the left lung in a Fontan patient with heterotaxy, connecting the innominate vein to the right pulmonary artery like a right-sided cavopulmonary connection. By postprocessing and analyzing CT scans for planning and by the use of long needles under biplane fluoroscopy for the realization of the procedure, we projected and performed the exit of a long needle out of a vessel, the re-entering of a target vessel, and the bridging of the extravascular distance by implantation of covered stents. RESULTS: In all three cases, the covered stents were placed successfully, connecting vessels of 15-50 mm distance from each other with very good hemodynamic results. In one case, two stents were placed consecutively, overlapping each other to accomplish an exact fitting at the connection sites to the native vessels.

Magnetic Resonance Imaging Risk Factors for Ventricular Arrhythmias in Tetralogy of Fallot.

Sudden cardiac death (SCD) is the most common cause of late mortality in tetralogy of Fallot (TOF). Pulmonary regurgitation (PR) was previously found to be the most common hemodynamic abnormality associated with ventricular arrhythmias (VA), but cardiovascular magnetic resonance (CMR)-based studies did not show this association. The aim of this study is to investigate the risk factors for VA in TOF using CMR. Electronic records of TOF patients and their CMR studies between July 2006 and October 2018 in one center were retrospectively reviewed. Demographic, clinical and CMR data of patients were collected. Outcome was defined as sustained ventricular tachycardia (VT), aborted SCD and SCD. From a total of 434 TOF patients with complete CMR studies, 19 (4.4%) patients developed a positive outcome (12 sustained VT, 4 aborted SCD, 3 SCD) at a median age of 24 years. The number of surgical interventions was significantly greater in patients who developed VA. Right ventricular volumes were significantly larger in patients who suffered a positive outcome. Odds ratio for developing VA was 6.905 for RVEDVI ≥ 160 ml/m2 and 6.141 for RVESVI ≥ 80 ml/m2 (P = 0.0014 and 0.0012, respectively). Event-free survival was longer in patients with smaller right ventricular volumes. In conclusion, right ventricular dimensions are the most significant factors associated with the development of VA in TOF. The number of surgical interventions is also related to an increased risk.

Different CMR Imaging Modalities for Native and Patch-Repaired Right Ventricular Outflow Tract Sizing: Impact on Percutaneous Pulmonary Valve Replacement Planning.

Percutaneous pulmonary valve replacement (PPVI) in native or patched right ventricular outflow tract (RVOT) has proven to be feasible. The procedure is highly dependent on the size of the RVOT. Several methods exist to evaluate the size of the RVOT by cardiovascular magnetic resonance (CMR). We evaluated different CMR modalities for measuring RVOT diameters. Thirty-one consecutive patients with native or patched RVOT were retrospectively evaluated. CMR was part of follow-up of patients with corrected Tetralogy of Fallot or pulmonary stenosis with significant pulmonary regurgitation (PR). CMR included 3D-SSFP whole-heart in systole, diastole, and contrast-enhanced MR angiography (ceMRA). Diameters of the RVOT were assessed by the three sequences. Additionally, in patients who underwent cardiac catheterization (n = 11) for PPVI, vessel diameters assessed by cine-angiography were compared to CMR. Systolic diameters of RVOT were significantly larger compared to the diameters taken in diastole and ceMRA (median difference 5.0 mm and 3.8 mm). Diastolic and ceMRA diameters did not differ significantly. CMR diameters taken in systole showed no statistical difference to systolic diameters taken by cine-angiography, while diastolic and ceMRA diameters were significantly smaller. PPVI was feasible to a maximal CMR diameter of 31 mm measured by SSFP whole-heart sequence in systole. Absolute diameters of native RVOT differ depending on the CMR sequence and timing of acquisition (systolic vs diastolic gating). Diameters taken during heart catheterization by cine-angiography best correlate to systolic CMR values. Data may help to select RVOTs suitable for PPVI.

Elevated diastolic wall shear stress in regurgitant semilunar valvular lesions.

BACKGROUND: Alterations in wall shear stress (WSS) assessed using 4D flow MRI have been shown to play a role in various vascular pathologies, such as bicuspid aortic valve aortopathy. Most studies have focused on systolic WSS, whereas altered diastolic hemodynamics in regurgitant semilunar valvular lesions have not so far been well characterized. PURPOSE: To investigate diastolic WSS in aortic and pulmonary regurgitation. STUDY TYPE: Retrospective data analysis. POPULATION: Thirty tetralogy of Fallot patients, 19 bicuspid aortic valve patients, 11 healthy volunteers. FIELD STRENGTH/SEQUENCE: 5 T, 3D time-resolved phase-contrast MRI with 3D velocity encoding. ASSESSMENT: Estimation of WSS and its axial and circumferential vector components along cardiac cycle timeframes in the proximal main pulmonary artery in pulmonary regurgitation (PR) and in the proximal ascending aorta in aortic regurgitation (AR) as well as in healthy volunteers. STATISTICAL TESTS: Wilcoxon matched pairs test was used for intra-group comparisons and Mann-Whitney test for intergroup comparisons. Correlations were assessed using Spearman correlation. RESULTS: WSS along the entire cardiac cycle was higher in PR and AR in comparison with controls (mean WSS 0.381 ± 0.070 vs. 0.220 ± 0.018, P < 0.0001; 0.361 ± 0.099 vs. 0.212 ± 0.030, P < 0.0001; respectively). Peak diastolic WSS was significantly higher than the mean WSS in AR and PR (P < 0.0001-0.005). The severity of PR correlated with the peak diastolic axial WSS (Spearman's r s = 0.454, P = 0.018), whereas the severity of AR correlated with both peak systolic and diastolic tangential WSS (Spearman's r s = 0.458, P = 0.049; r s = 0.539, P = 0.017, respectively). DATA CONCLUSION: Elevated diastolic WSS is a component of the altered flow hemodynamics in AR and PR. This may give more insight into the pathophysiologic role of WSS in vascular remodeling in AR and PR. LEVEL OF EVIDENCE: 4 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019;50:763-770.

Non-invasive Hemodynamic CMR Parameters Predicting Maximal Exercise Capacity in 54 Patients with Ebstein's Anomaly.

BACKGROUND: Exercise capacity is a well-defined marker of outcome in congenital heart disease. We analyzed seventeen cardiovascular magnetic resonance (CMR) derived parameters and their correlation to exercise capacity in patients with Ebstein's anomaly (EA). METHODS: Fifty-four surgery free patients, age 5 to 69 years (median 30 years) prospectively underwent CMR examination and cardiopulmonary exercise testing (CPET). The following volume/flow parameters were compared with peak oxygen uptake as the percentage of normal (peakVO2%) using univariate and multivariate analysis: right and left ventricular ejection fraction (RVEF and LVEF), the indexed end-diastolic and end-systolic volumes (RVEDVi, RVESVi, LVEDVi, and LVESVi), the indexed stroke volumes (RVSVi and LVSVi), the total normalized right and left heart volumes; the total right to left heart volume ratio (R/L-ratio). The indexed antegrade flow (ante), indexed net flow (net) as well as cardiac index (CI) in the aorta (Ao) and pulmonary artery (PA) were used. RESULTS: RVEF (R2 0.2788), indexed flow PA net (R2 0.2330), and PA ante (R2 0.1912) showed the best correlation with peakVO2% (all p < 0.001) in the univariate model. Further significant correlation could also be demonstrated with CI-PA, LVEF, LVSVi, Aorta net, RVESVi, and Aorta ante. Multivariate analysis for RVEF and indexed net flow PA revealed a R2 of 0.4350. CONCLUSION: Functional CMR parameters as RVEF and LVEF and flow data of cardiac forward flow correlate to peakVO2%. Evaluation of the indexed net flow in the pulmonary artery and the overall function of the right ventricle best predicts the maximal exercise capacity in patients with EA.

Wall shear stress estimation in the aorta: Impact of wall motion, spatiotemporal resolution, and phase noise.

BACKGROUND: Wall shear stress (WSS) presents an important parameter for assessing blood flow characteristics and evaluating flow-mediated lesions in the aorta. PURPOSE: To investigate the robustness of WSS and oscillatory shear index (OSI) estimation based on 4D flow MRI against vessel wall motion, spatiotemporal resolution, and velocity encoding (VENC). STUDY TYPE: Simulated and prospective. POPULATION: Synthetic 4D flow MRI data of the aorta, simulated using the Lattice-Boltzmann method; in vivo 4D flow MRI data of the aorta from healthy volunteers (n = 11) and patients with congenital heart defects (n = 17). FIELD STRENGTH/SEQUENCE: 1.5T; 4D flow MRI with PEAK-GRAPPA acceleration and prospective electrocardiogram triggering. ASSESSMENT: Predicated upon 3D cubic B-splines interpolation of the image velocity field, WSS was estimated in mid-systole, early-diastole, and late-diastole and OSI was derived. We assessed the impact of spatiotemporal resolution and phase noise, and compared results based on tracked-using deformable registration-and static vessel wall location. STATISTICAL TESTS: Bland-Altman analysis to assess WSS/OSI differences; Hausdorff distance (HD) to assess wall motion; and Pearson's correlation coefficient (PCC) to assess correlation of HD with WSS. RESULTS: Synthetic data results show systematic over-/underestimation of WSS when different spatial resolution (mean ± 1.96 SD up to -0.24 ± 0.40 N/m2 and 0.5 ± 1.38 N/m2 for 8-fold and 27-fold voxel size, respectively) and VENC-depending phase noise (mean ± 1.96 SD up to 0.31 ± 0.12 N/m2 and 0.94 ± 0.28 N/m2 for 2-fold and 4-fold VENC increase, respectively) are given. Neglecting wall motion when defining the vessel wall perturbs WSS estimates to a considerable extent (1.96 SD up to 1.21 N/m2 ) without systematic over-/underestimation (Bland-Altman mean range -0.06 to 0.05). DATA CONCLUSION: In addition to sufficient spatial resolution and velocity to noise ratio, accurate tracking of the vessel wall is essential for reliable image-based WSS estimation and should not be neglected if wall motion is present. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.

Aortopulmonary collateral flow quantification by MR at rest and during continuous submaximal exercise in patients with total cavopulmonary connection.

BACKGROUND: Aortopulmonary collateral flow is considered to have significant impact on the outcome of patients with single ventricle circulation and total cavopulmonary connection (TCPC). There is little information on collateral flow during exercise. PURPOSE: To quantify aortopulmonary collateral flow at rest and during continuous submaximal exercise in clinical patients doing well with TCPC. STUDY TYPE: Prospective, case controlled. POPULATION: Thirteen patients with TCPC (17 (11-37) years) and 13 age and sex-matched healthy controls (18 (11-38) years). FIELD STRENGTH: 1.5T; free breathing; phase sensitive gradient echo sequence. ASSESSMENT: Blood flow in the ascending and descending aorta and superior vena cava were measured at rest and during continuous submaximal physical exercise in patients and controls. Systemic blood flow (Qs ) was assumed to be represented by the sum of flow in the superior caval vein (Qsvc ) and the descending aorta (QAoD ) at the diaphragm level. Aortopulmonary collateral flow (Qcoll ) was calculated by subtracting Qs from flow in the ascending aorta (QAoA ). STATISTICS: Mann-Whitney U-test and Wilcoxon test for comparison between groups and between rest and exercise. RESULTS: Absolute collateral flow in TCPC patients at rest was 0.4 l/min/m2 (-0.1-1.2), corresponding to 14% (-2-42) of Qs . Collateral flow did not change during exercise (difference -0.01 (-0.7-1.0) l/min/m2 , P = 0.97). TCPC patients had significantly lower Qs at rest (2.5 (1.6-4.1) vs. 3.5 (2.6-4.8) l/min/m2 , P = 0.001) and during submaximal exercise (3.2 (2.0-6.0) vs. 4.8 (3.3-6.9) l/min/m2 , P = 0.001), compared to healthy controls. The increase in Qs with exercise was also significantly lower in patients than in healthy controls (median 0.6 vs. 1.2 l/min/m2 , P < 0.02). DATA CONCLUSION: Clinical patients doing well with TCPC have significant aortopulmonary collateral flow at rest (14% of Qs ) compared to healthy controls, which does not change during submaximal exercise. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1509-1516.

Long-Standing Cyanosis in Congenital Heart Disease Does not Cause Diffuse Myocardial Fibrosis.

The assumption of the presence of diffuse myocardial fibrosis in long-standing cyanotic congenital heart disease (CHD) inspired us to noninvasively determine the myocardial extracellular volume (ECV) using contrast CMR. T1 maps were measured pre and 10 min after the injection of 0.15 mmol/kg of gadolinium in 25 subjects. Seven patients with long-standing cyanotic CHD and no previous cardiac surgery (aged 16-53 years and oxygen saturations of 69-90%), nine normal subjects (aged 14-49 years), and nine patients with previously cyanotic CHD, who had been corrected by open heart surgery (aged 2 months-58 years, mean 9 years). Late gadolinium enhancement was performed to exclude scar areas. The T1 values were measured in the interventricular septum and in the left lateral or inferior ventricular wall, such that same areas were assessed in every patient in the pre- and post-contrast T1 scan. ECV was calculated according to ΔR1myocardium/ΔR1blood * (1 - hematocrit). Cyanotic patients had significantly lower ECV percentage than the previous cyanotic patients (septum: 22 ± 2.7% vs 35 ± 4.6%, p = 0.002; LV wall: 22 ± 2.2% vs 30 ± 3.7%, p = 0.01, respectively). No significant differences were found between cyanotic patients and normal controls (septum: 22 ± 2.7% vs 24 ± 1.4%, p = 0.44; LV wall: 22 ± 2.2% vs 24 ± 2%, p = 0.57, respectively). Long-standing cyanosis in CHD without cardiac surgery does not cause diffuse myocardial fibrosis or expansion of the myocardial ECV.

Comparison of MR flow quantification in peripheral and main pulmonary arteries in patients after right ventricular outflow tract surgery: A retrospective study.

PURPOSE: To compare the quantification of pulmonary stroke volume (SV) by phase contrast magnetic resonance (PC-MR) in the main pulmonary artery (MPA) to the sum of SVs in both peripheral pulmonary arteries (PPA) in different right ventricular (RV) outflow pathologies. MATERIALS AND METHODS: Pulmonary SV was determined by PC-MR in the MPA and the PPA in healthy individuals (H, n = 54), patients after correction for tetralogy of Fallot with significant pulmonary regurgitation and without pulmonary or RV outflow tract stenosis (PR, n = 50), and in patients with RV outflow tract or pulmonary valve stenosis (PS, n = 50). Resulting SVs were compared to aortic SV in the ascending aorta. RESULTS: Mean age was similar between the groups: H 28 ± 17 vs. PR 24 ± 11 vs. PS 22 ± 10 years. Bland-Altman analyses revealed in all groups a relatively small systemic (bias) but large random error (limits of agreement) for pulmonary SV determined in the MPA as compared to summed SVs in the PPA. The largest limits of agreement were present in PS patients: H: MPA 3.9% (-11, + 19) vs. PPA 0.4% (-15, + 15); PR: MPA 5.2% (-25, + 36) vs. PPA 0.6% (-24, + 26); PS: MPA 5% (-36; + 46), PPA -0.03% (-34, + 35). CONCLUSION: The accuracy of PC-MR in the MPA is reasonable; however, a large random error (precision) is observed that is most pronounced in PS patients. This potential error should be taken into consideration when interpreting MPA flow measurements. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1839-1845.

Importance of Non-invasive Right and Left Ventricular Variables on Exercise Capacity in Patients with Tetralogy of Fallot Hemodynamics.

Good quality of life correlates with a good exercise capacity in daily life in patients with tetralogy of Fallot (ToF). Patients after correction of ToF usually develop residual defects such as pulmonary regurgitation or stenosis of variable severity. However, the importance of different hemodynamic parameters and their impact on exercise capacity is unclear. We investigated several hemodynamic parameters measured by cardiovascular magnetic resonance (CMR) and echocardiography and evaluated which parameter has the most pronounced effect on maximal exercise capacity determined by cardiopulmonary exercise testing (CPET). 132 patients with ToF-like hemodynamics were tested during routine follow-up with CMR, echocardiography and CPET. Right and left ventricular volume data, ventricular ejection fraction and pulmonary regurgitation were evaluated by CMR. Echocardiographic pressure gradients in the right ventricular outflow tract and through the tricuspid valve were measured. All data were classified and correlated with the results of CPET evaluations of these patients. The analysis was performed using the Random Forest model. In this way, we calculated the importance of the different hemodynamic variables related to the maximal oxygen uptake in CPET (VO2%predicted). Right ventricular pressure showed the most important influence on maximal oxygen uptake, whereas pulmonary regurgitation and right ventricular enddiastolic volume were not important hemodynamic variables to predict maximal oxygen uptake in CPET. Maximal exercise capacity was only very weakly influenced by right ventricular enddiastolic volume and not at all by pulmonary regurgitation in patients with ToF. The variable with the most pronounced influence was the right ventricular pressure.

Myocardial blood flow in patients with transposition of the great arteries ­ risk factor for dysfunction of the morphologic systemic right ventricle late after atrial repair.

BACKGROUND: Dysfunction of the morphologic systemic right ventricle (RV) is a sequela in long-term survivors with transposition of the great arteries (TGA) after atrial switch operation (AtSO). Impairment of myocardial blood flow (MBF) and coronary flow reserve (CFR) are hypothesized as predisposing factors. METHODS AND RESULTS: The study group comprised 20 patients after AtSO (22.7 ± 5.03 years) and 15 individuals with congenitally corrected transposition (ccTGA) (30.6 ± 19.4 years). MBF was quantified by positron emission tomography; controls for coronary flow were 11 healthy volunteers (26.2 ± 5.1 years). Exercise capacity, ventricular mass, function and end-diastolic volume assessed by coronary magnetic resonance (CMR), hemodynamic parameters assessed by cardiac catheterization and echocardiography, and B-type natriuretic peptide levels correlated with MBF. At rest, MBF did not differ between patients and healthy volunteers (MBFrestml·100 g(-1)·min(-1); ccTGA: 75 ± 14 vs. AtSO: 73 ± 16 vs. controls: 77 ± 15; NS). After vasodilatation, MBF increased significantly, but was significantly lower in ccTGA and AtSO groups compared with controls (MBFstressml·100 g(-1)·min(-1); ccTGA: 198 ± 38 vs. AtSO: 167 ± 46 vs. controls 310 ± 74; P<0.001). In ccTGA, CFR correlated significantly with clinical, CMR, echocardiographic and hemodynamic parameters, but for AtSO patients no significant correlation could be calculated. CONCLUSIONS: In patients with ccTGA, maximal coronary blood flow is attenuated and significantly correlated with ventricular function, whereas dysfunction of the morphologic systemic RV after AtSO is a multifactorial problem.

Long-Term Survival Is Superior in Patients With Pulsatile Pulmonary Flow After the Björk Procedure.

Background: This study aims to evaluate clinical outcomes and hemodynamic variables late after the Björk procedure, regarding the pulmonary flow pattern. Methods: Patients who survived more than 15 years after the Björk procedure were included and then divided into two groups according to their pulmonary flow pattern by pulsed-wave Doppler assessment of echocardiography: patients with pulsatile systolic pulmonary flow (Group P) and those without (Group N). Results: A total of 43 patients were identified, of whom 13 patients were divided into Group P and 30 in Group N. Median age at the Björk procedure was 5.7 (2.1-7.3) years, and median follow-up was 32 (28-36) years. Survival after 15 years was higher in Group P, compared with Group N (100% vs 76% at 30 years, P = .045). Cardiac catheterization data demonstrated higher cardiac index in Group P patients compared with Group N patients (3.5 vs 2.8 L/m2, P = .014). Cardiac magnetic resonance imaging study revealed that Group P patients had higher right ventricular end-diastolic volume index (96 vs 57 mL/m2, P = .005), higher end-systolic volume index (49 vs 30 mL/m2, P = .013) and higher right ventricular stroke volume index (48 vs 25 mL/m2, P < .001), compared with Group N patients. Exercise capacity tests demonstrated that Group P patients showed a higher percent predicted peak oxygen consumption, compared with Group N patients (73 vs 58%, P < .001). Conclusions: Late after the Björk procedure, patients with a pulsatile systolic pulmonary flow had a larger right ventricle and better exercise capacity compared with those without pulsatile systolic pulmonary flow.

Quantifying aortic valve regurgitation in patients with congenital aortic valve disease by 2D and 4D flow magnetic resonance analysis.

BACKGROUND: In congenital aortic valve disease, quantifying aortic regurgitation (AR) varies by the measurement site. Our study aimed to identify the optimal site for AR assessment using 2D and 4D MR flow measurements, with a focus on vortices. METHODS: We retrospectively analysed 31 patients with congenital aortic valve disease, performing 2D and 4D MR flow measurements at the aortic valve, sinotubular junction (STJ), ascending aorta (AAo), and using midpulmonary artery measurements as a reference. We assessed percentage AR and net forward volumes, calculated linear correlations, and plotted Bland-Altman plots. Net forward flow at all aortic sites were correlated with the main pulmonary artery. Differences in AR between 2D and 4D flows were linked to vortices detected by 4D streamlines. RESULTS: The best agreement in % AR between 2D and 4D flows was at the aortic valve (mean difference 4D2D -2.9%, limits of agreement 8.7% to -14.3%; r2 = 0.7). Correlations weakened at STJ and AAo. Vortices in the ascending aorta led to AR overestimation in 2D measurements. Net forward flow at the aortic valve by 4D flow correlated closer with main pulmonary artery than did 2D flow. (Mean difference for 2D and 4D MR flow 7.5 ml and 4.2 ml, respectively). CONCLUSIONS: For congenital aortic valve disease, the most accurate AR quantification occurs at the aortic valve using 2D and 4D MR flow. Notably, vortices in the ascending aorta can result in AR overestimation with 2D MR flow.

Myocardial Scarring and Sudden Cardiac Death in Young Patients With Hypertrophic Cardiomyopathy: A Multicenter Cohort Study.

Importance: The ability to predict sudden cardiac death (SCD) in children and adolescents with hypertrophic cardiomyopathy (HCM) is currently inadequate. Late gadolinium enhancement (LGE) by cardiovascular magnetic resonance (CMR) imaging is associated with SCD events in adults with HCM. Objective: To examine the prognostic significance of LGE in patients with HCM who are younger than 21 years. Design, Setting, and Participants: This multicenter, retrospective cohort study was conducted from April 8, 2015, to September 12, 2022, in patients with HCM who were younger than 21 years and had undergone CMR imaging across multiple sites in the US, Europe, and South America. Observers of CMR studies were masked toward outcomes and demographic characteristics. Exposure: Natural history of HCM. Main Outcome and Measures: The primary outcome was SCD and surrogate events, including resuscitated cardiac arrest and appropriate discharges from an implantable defibrillator. Continuous and categorical data are expressed as mean (SD), median (IQR), or number (percentage), respectively. Survivor curves comparing patients with and without LGE were constructed by the Kaplan-Meier method, and likelihood of subsequent clinical events was further evaluated using univariate and multivariable Cox proportional hazards models. Results: Among 700 patients from 37 international centers, median (IQR) age was 14.8 (11.9-17.4) years, and 518 participants (74.0%) were male. During a median (IQR) [range] follow-up period of 1.9 (0.5-4.1) [0.1-14.8] years, 35 patients (5.0%) experienced SCD or equivalent events. LGE was present in 230 patients (32.9%), which constituted an mean (SD) burden of 5.9% (7.3%) of left ventricular myocardium. The LGE amount was higher in older patients and those with greater left ventricular mass and maximal wall thickness; patients with LGE had lower left ventricular ejection fractions and larger left atrial diameters. The presence and burden of LGE was associated with SCD, even after correcting for existing risk stratification tools. Patients with 10% or more LGE, relative to total myocardium, had a higher risk of SCD (unadjusted hazard ratio [HR], 2.19; 95% CI, 1.59-3.02; P < .001). Furthermore, the addition of LGE burden improved the performance of the HCM Risk-Kids score (before LGE addition: 0.66; 95% CI, 0.58-0.75; after LGE addition: 0.73; 95% CI, 0.66-0.81) and Precision Medicine in Cardiomyopathy score (before LGE addition: 0.68; 95% CI, 0.49-0.77; after LGE addition: 0.73; 95% CI, 0.64-0.82) SCD predictive models. Conclusions and Relevance: In this retrospective cohort study, quantitative LGE was a risk factor for SCD in patients younger than 21 years with HCM and improved risk stratification.

Demonstration of value of optimizing ECG triggering for cardiovascular magnetic resonance in patients with congenital heart disease.

BACKGROUND: Optimal ECG triggering is of paramount importance for correct blood flow quantification during cardiovascular magnetic resonance (CMR). However, optimal ECG triggering and therefore blood flow quantification is impaired in many patients with congenital heart disease (CHD) due to complex QRS patterns. Therefore, a new ECG-trigger algorithm was developed to address triggering problems due to complex QRS patterns.The aim of this study was to test this new ECG-trigger algorithm in routine patients with CHD and its impact on blood flow quantification. METHODS: 35 consecutive routine patients with CHD undergoing CMR were included in the study. (40% Fallot's Tetralogy, 20% aortic arch pathology, 14% transposition of the great arteries, 26% others; age 26+/-11 yrs).In all patients, blood flow in the ascending aorta was quantified using the old ECG-trigger algorithm and the new ECG-trigger algorithm in random order. Blood flow quantified using the old or new ECG-trigger algorithm was compared by Bland-Altman analysis.Three blinded investigators evaluated the vector clouds and trigger points of both ECG-trigger methods. Evaluation criteria were false positive and false negative triggered QRS complexes (specificity and sensitivity), and accuracy of detection. Accuracy of detection was defined as time scatter of the trigger around the correct trigger point. RESULTS: Specificity, sensitivity, and accuracy of detection significantly increased using the new ECG-trigger algorithm compared to the old ECG-trigger algorithm.Blood flow quantification using the old or new ECG-trigger algorithm differed more than 5% in 31% of the cases. CONCLUSIONS: Our results suggest that optimizing ECG triggering during CMR using our new algorithm can avoid errors of >5% in approximately 1/3 of routine patients with congenital heart disease (CHD). We furthermore suggest that incorrect ECG triggering appears to be problematic for blood flow quantification of many patients with CHD undergoing routine CMR.