Evaluation of atrial septal defects with 4D flow MRI-multilevel and inter-reader reproducibility for quantification of shunt severity

4D flow cardiac MRI to assess pulmonary blood flow in patients with pulmonary arterial hypertension associated with congenital heart disease

PURPOSE

The purpose of this study was to evaluate the accuracy of four-dimensional flow cardiac magnetic resonance imaging (4D flow MRI) compared to right heart catheterization in measuring pulmonary flow (Qp), systemic flow (Qs) and pulmonary-to-systemic flow ratio (Qp/Qs) in patients with pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD).

MATERIALS AND METHODS

The study was registered on Clinical-trial.gov (NCT03928002). Sixty-four patients with PAH-CHD who underwent 4D flow MRI were included. There were 16 men and 48 women with a mean age of 45.3 ± 13.7 (standard deviation [SD]) years (age range: 21-77 years). Fifty patients (50/64; 78%) presented with pre-tricuspid shunt. Qp (L/min), Qs (L/min) and Qp/Qs were measured invasively using direct Fick method during right heart catheterization and compared with measurements assessed by 4D flow MRI within a 24-48-hour window.

RESULTS

The average mean pulmonary artery pressure was 51 ± 17 (SD) mm Hg with median pulmonary vascular resistance of 8.8 Wood units (Q1, Q3: 5.3, 11.7). A strong linear correlation was found between Qp measurements obtained with 4D flow MRI and those obtained with the Fick method (r = 0.96; P < 0.001). Bland Altman analysis indicated a mean difference of 0.15 ± 0.48 (SD) L/min between Qp estimated by 4D flow MRI and by right heart catheterization. A strong correlation was found between Qs and Qp/Qs measured by 4D flow MRI and those obtained with the direct Fick method (r = 0.85 and r = 0.92; P < 0.001 for both).

CONCLUSION

Qp as measured by 4D flow MRI shows a strong correlation with measurements derived from the direct Fick method. Further investigation is needed to develop less complex and standardized methods for measuring essential PAH parameters, such as pulmonary arterial pressures and pulmonary vascular resistance.

Technical recommendations for computed tomography guidance of intervention in the right ventricular outflow tract: Native RVOT, conduits and bioprosthetic valves:: A white paper of the Society of Cardiovascular Computed Tomography (SCCT), Congenital Heart Surgeons' Society (CHSS), and Society for Cardiovascular Angiography & Interventions (SCAI)

This consensus document for the performance of Cardiovascular Computed Tomography (CCT) to guide intervention in the right ventricular outflow tract (RVOT) in patients with congenital disease (CHD) was developed collaboratively by pediatric and adult interventionalists, surgeons and cardiac imagers with expertise specific to this patient subset. The document summarizes definitions of RVOT dysfunction as assessed by multi-modality imaging techniques and reviews existing consensus statements and guideline documents pertaining to indications for intervention. In the context of this background information, recommendations for CCT scan acquisition and a standardized approach for reporting prior to surgical or transcatheter pulmonary valve replacement are proposed and presented. It is the first Imaging for Intervention collaboration for CHD patients and encompasses imaging and reporting recommendations prior to both surgical and percutaneous pulmonary valve replacement.

Technical Recommendations for Computed Tomography Guidance of Intervention in the Right Ventricular Outflow Tract: Native RVOT, Conduits, and Bioprosthetic Valves

This consensus document for the performance of cardiovascular computed tomography (CCT) to guide intervention in the right ventricular outflow tract (RVOT) in patients with congenital heart disease (CHD) was developed collaboratively by pediatric and adult interventionalists, surgeons, and cardiac imagers with expertise specific to this patient subset. The document summarizes definitions of RVOT dysfunction as assessed by multimodality imaging techniques and reviews existing consensus statements and guideline documents pertaining to indications for intervention. In the context of this background information, recommendations for CCT scan acquisition and a standardized approach for reporting prior to surgical or transcatheter pulmonary valve replacement are proposed and presented. It is the first Imaging for Intervention collaboration for CHD patients and encompasses imaging and reporting recommendations prior to both surgical and percutaneous pulmonary valve replacement.

Postoperative Complications, Readmissions, Lengths of Stay, and Cost Analyses of Patients Who Have Atrial Septal Defects After Total Joint Arthroplasty

BACKGROUND

Atrial septal defects (ASDs) are a common congenital heart defect. This study aimed to determine whether patients diagnosed with ASDs undergoing total joint arthroplasty have differences in 1) medical complications, 2) readmissions, 3) lengths of stay (LOS), and 4) costs.

METHODS

Using an administrative claims data set, a retrospective query from 2010 to 2020 was performed. The ASD patients were 1:5 ratio matched with controls, yielding a total of 45,695 total knee arthroplasty (TKA) (ASD = 7,635, control = 38,060) and 18,407 total hip arthroplasty (THA) (ASD = 3,084, control = 15,323) patients. Outcomes included medical complications, readmissions, LOS, and costs. Logistical regressions were used to calculate odds ratios (ORs) and P values. P values < 0.001 were significant.

RESULTS

The ASD patients had higher odds of medical complications after TKA (38.8 versus 21.0%; OR 2.09; P < .001) and THA (45.2 versus 23.5%; OR 2.1; P < .001), noticeably deep vein thromboses, strokes, and other thromboembolic complications. The ASD patients were not significantly more likely to be readmitted after TKA (5.3 versus 4.7%; OR 1.13; P = .033) or THA (6.0 versus 5.7%; OR 1.05; P = .531). Patient LOS was not significantly greater in ASD patients undergoing TKA (3.2 versus 3.2 days; P = .805) but was greater after THA (5.3 versus 3.76 days; P < .001). Same-day surgery costs were not significantly increased in ASD patients after TKA ($23,892.53 versus $23,453.40; P = .066) but were after THA ($23,981.93 versus $23,579.18; P < .001). Costs within 90 days were similar between cohorts.

CONCLUSION

The ASD patients have greater 90-day complications following primary total joint arthroplasty. Providers may consider preoperative cardiac clearance or adjusting anticoagulation in this population to mitigate these risks.

LEVEL OF EVIDENCE

III.

Resolution of Trifascicular Heart Block with Effective Closure of Congenital Atrial Septal Defect Followed by Later Coronavirus Disease 2019-associated Cardiac Strain

Heart block (HB) is one of the most serious arrhythmias. Higher degrees of HB-for example, trifascicular HB-result in a more intense patient condition. Atrial septal defects (ASDs) represent the most common congenital heart disease in adults. All ASDs generally result in a left-to-right shunt, commonly causing right-side enlargement and dilation and, to a lesser extent, left atrial enlargement. A 26-year-old woman presented to the physician outpatient clinic with a complicated ASD with trifascicular HB and severe mitral and tricuspid regurgitations. The trifascicular HB with valvular regurgitations resolved with congenital ASD closure; however, she was diagnosed with coronavirus disease 2019 (COVID-19)-associated cardiac strain 3 years later. Interventions included electrocardiography, oxygenation, echocardiography, and cardiovascular surgical repair. A dramatic electrocardiographic response and better clinical outcomes despite dilations of both atria were observed. Trifascicular HB is a newly recorded association after congenital ASDs in adults. The disappearance of trifascicular HB after surgical closure of the congenital ASD is an indicator of effective surgical repair. The occurrence of COVID-19 pneumonia later, with atrial dilations continuing after the infection, may be a constellation of risk factors for the observed cardiac strain.

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.

The current state and potential innovation of fetal cardiac MRI

Fetal cardiac MRI is a rapidly evolving form of diagnostic testing with utility as a complementary imaging modality for the diagnosis of congenital heart disease and assessment of the fetal cardiovascular system. Previous technical limitations without cardiac gating for the fetal heart rate has been overcome with recent technology. There is potential utility of fetal electrocardiography for direct cardiac gating. In addition to anatomic assessment, innovative technology has allowed for assessment of blood flow, 3D datasets, and 4D flow, providing important insight into fetal cardiovascular physiology. Despite remaining technical barriers, with increased use of fCMR worldwide, it will become an important clinical tool to improve the prenatal care of fetuses with CHD.

Repeatability and reproducibility of various 4D Flow MRI postprocessing software programs in a multi-software and multi-vendor cross-over comparison study

BACKGROUND

Different software programs are available for the evaluation of 4D Flow cardiovascular magnetic resonance (CMR). A good agreement of the results between programs is a prerequisite for the acceptance of the method. Therefore, the goal was to compare quantitative results from a cross-over comparison in individuals examined on two scanners of different vendors analyzed with four postprocessing software packages.

METHODS

Eight healthy subjects (27 ± 3 years, 3 women) were each examined on two 3T CMR systems (Ingenia, Philips Healthcare; MAGNETOM Skyra, Siemens Healthineers) with a standardized 4D Flow CMR sequence. Six manually placed aortic contours were evaluated with Caas (Pie Medical Imaging, SW-A), cvi42 (Circle Cardiovascular Imaging, SW-B), GTFlow (GyroTools, SW-C), and MevisFlow (Fraunhofer Institute MEVIS, SW-D) to analyze seven clinically used parameters including stroke volume, peak flow, peak velocity, and area as well as typically scientifically used wall shear stress values. Statistical analysis of inter- and intrareader variability, inter-software and inter-scanner comparison included calculation of absolute and relative error (ER), intraclass correlation coefficient (ICC), Bland-Altman analysis, and equivalence testing based on the assumption that inter-software differences needed to be within 80% of the range of intrareader differences.

RESULTS

SW-A and SW-C were the only software programs showing agreement for stroke volume (ICC = 0.96; ER = 3 ± 8%), peak flow (ICC: 0.97; ER = -1 ± 7%), and area (ICC = 0.81; ER = 2 ± 22%). Results from SW-A/D and SW-C/D were equivalent only for area and peak flow. Other software pairs did not yield equivalent results for routinely used clinical parameters. Especially peak maximum velocity yielded poor agreement (ICC ≤ 0.4) between all software packages except SW-A/D that showed good agreement (ICC = 0.80). Inter- and intrareader consistency for clinically used parameters was best for SW-A and SW-D (ICC = 0.56-97) and worst for SW-B (ICC = -0.01-0.71). Of note, inter-scanner differences per individual tended to be smaller than inter-software differences.

CONCLUSIONS

Of all tested software programs, only SW-A and SW-C can be used equivalently for determination of stroke volume, peak flow, and vessel area. Irrespective of the applied software and scanner, high intra- and interreader variability for all parameters have to be taken into account before introducing 4D Flow CMR in clinical routine. Especially in multicenter clinical trials a single image evaluation software should be applied.

Impact of ferumoxytol vs gadolinium on 4D flow cardiovascular magnetic resonance measurements in small children with congenital heart disease

BACKGROUND

Cardiovascular magnetic resonance (CMR) allows for time-resolved three-dimensional phase-contrast (4D Flow) analysis of congenital heart disease (CHD). Higher spatial resolution in small infants requires thinner slices, which can degrade the signal. Particularly in infants, the choice of contrast agent (ferumoxytol vs. gadolinium) may influence 4D Flow CMR accuracy. Thus, we investigated the accuracy of 4D Flow CMR measurements compared to gold standard 2D flow phase contrast (PC) measurements in ferumoxytol vs. gadolinium-enhanced CMR of small CHD patients with shunt lesions.

METHODS

This was a retrospective study consisting of CMR studies from complex CHD patients less than 20 kg who had ferumoxytol or gadolinium-enhanced 4D Flow and standard two-dimensional phase contrast (2D-PC) flow collected. 4D Flow clinical software (Arterys) was used to measure flow in great vessels, systemic veins, and pulmonary veins. 4D Flow accuracy was defined as percent difference or correlation against conventional measurements (2D-PC) from the same vessels. Subgroup analysis was performed on two-ventricular vs single-ventricular CHD, arterial vs venous flow, as well as low flows (defined as < 1.5 L/min) in 1V CHD.

RESULTS

Twenty-one ferumoxytol-enhanced and 23 gadolinium-enhanced CMR studies were included, with no difference in age (2.1 ± 1.6 vs. 2.3 ± 1.9 years, p = 0.70), patient body surface area (0.50 ± 0.2 vs. 0.52 ± 0.2 m2, p = 0.67), or vessel diameter (11.4 ± 5.2 vs. 12.4 ± 5.6 mm, p = 0.22). Ten CMR studies with single ventricular CHD were included. Overall, ferumoxytol-enhanced 4D flow CMR measurements demonstrated less percent difference to 2D-PC when compared to gadolinium-enhanced 4D Flow CMR studies. In subgroup analyses of arterial vs. venous flows (high velocity vs. low velocity) and low flow in single ventricle CHD, ferumoxytol-enhanced 4D Flow CMR measurements had stronger correlation to 2D-PC CMR. The contrast-to-noise ratio (CNR) in ferumoxytol-enhanced studies was higher than the CNR in gadolinium-enhanced studies.

CONCLUSIONS

Ferumoxytol-enhanced 4D Flow CMR has improved accuracy when compared to gadolinium 4D Flow CMR, particularly for infants with small vessels in CHD.

Kat-ARC accelerated 4D flow CMR: clinical validation for transvalvular flow and peak velocity assessment

BACKGROUND

To validate the k-adaptive-t autocalibrating reconstruction for Cartesian sampling (kat-ARC), an exclusive sparse reconstruction technique for four-dimensional (4D) flow cardiac magnetic resonance (CMR) using conservation of mass principle applied to transvalvular flow.

METHODS

This observational retrospective study (2020/21-075) was approved by the local ethics committee at the University of East Anglia. Consent was waived. Thirty-five patients who had a clinical CMR scan were included. CMR protocol included cine and 4D flow using Kat-ARC acceleration factor 6. No respiratory navigation was applied. For validation, the agreement between mitral net flow (MNF) and the aortic net flow (ANF) was investigated. Additionally, we checked the agreement between peak aortic valve velocity derived by 4D flow and that derived by continuous-wave Doppler echocardiography in 20 patients.

RESULTS

The median age of our patient population was 63 years (interquartile range [IQR] 54-73), and 18/35 (51%) were male. Seventeen (49%) patients had mitral regurgitation, and seven (20%) patients had aortic regurgitation. Mean acquisition time was 8 ± 4 min. MNF and ANF were comparable: 60 mL (51-78) versus 63 mL (57-77), p = 0.310). There was an association between MNF and ANF (rho = 0.58, p < 0.001). Peak aortic valve velocity by Doppler and 4D flow were comparable (1.40 m/s, [1.30-1.75] versus 1.46 m/s [1.25-2.11], p = 0.602) and also correlated with each other (rho = 0.77, p < 0.001).

CONCLUSIONS

Kat-ARC accelerated 4D flow CMR quantified transvalvular flow in accordance with the conservation of mass principle and is primed for clinical translation.

Usefulness of a Pulse Oximeter and Multimodality Imaging for Diagnosing Platypnea-orthodeoxia Syndrome

Platypnea-orthodeoxia syndrome (POS) is a rare disease characterized by dyspnea and hypoxemia in orthostatism that improves in the recumbent position. We herein report an 81-year-old woman with dyspnea in the upright position following thoracic vertebral compression fractures. After the patient's daughter brought a recording showing decreasing SpO₂ (peripheral capillary oxygen saturation) in the upright position as measured by a portable pulse oximeter outside the hospital, a small atrial septal defect (ASD) was detected. A contrast echocardiogram and four-dimensional flow magnetic resonance imaging demonstrated a right-to-left shunt. The patient's symptoms dramatically improved after percutaneous ASD closure. In conclusion, such new technologies are useful for diagnosing POS.

Pathology and Advanced Imaging—Characterization of a Congenital Cardiac Defect and Complex Hemodynamics in a Pig: A Case Report

Domestic pigs are widely used in cardiovascular research as the porcine circulatory system bears a remarkable resemblance to that of humans. In order to reduce variability, only clinically healthy animals enter the study as their health status is assessed in entry examination. Like humans, pigs can also suffer from congenital heart disease, such as an atrial septal defect (ASD), which often remains undetected. Due to the malformation of the endocardial cushion during organ development, mitral valve defects (e.g., mitral clefts) are sometimes associated with ASDs, further contributing to hemodynamic instability. In this work, we report an incidental finding of a hemodynamically highly relevant ASD in the presence of incompetent mitral and tricuspid valves, in an asymptomatic, otherwise healthy juvenile pig. In-depth characterization of the cardiac blood flow by four-dimensional (4D) flow magnetic resonance imaging (MRI) revealed a prominent diastolic left-to-right and discrete systolic right-to-left shunt, resulting in a pulmonary-to-systemic flow ratio of 1.8. Severe mitral (15 mL/stroke) and tricuspid (22 mL/stroke) regurgitation further reduced cardiac output. Pathological examination confirmed the presence of an ostium primum ASD and found a serous cyst of lymphatic origin that was filled with clear fluid partially occluding the ASD. A large mitral cleft was identified as the most likely cause of severe regurgitation, and histology showed mild to moderate endocardiosis in the coaptation area of both atrio-ventricular valves. In summary, although not common, congenital heart defects could play a role as a cause of experimental variability or even intra-experimental mortality when working with apparently heathy, juvenile pigs.

The role of 4D flow MRI for clinical applications in cardiovascular disease: current status and future perspectives

Magnetic resonance imaging (MRI) four-dimensional (4D) flow is a type of phase-contrast (PC) MRI that uses blood flow encoded in 3 directions, which is resolved relative to 3 spatial and temporal dimensions of cardiac circulation. It can be used to simultaneously quantify and visualize hemodynamics or morphology disorders. 4D flow MRI is more comprehensive and accurate than two-dimensional (2D) PC MRI and echocardiography. 4D flow MRI provides numerous hemodynamic parameters that are not limited to the basic 2D parameters, including wall shear stress (WSS), pulse wave velocity (PWV), kinetic energy, turbulent kinetic energy (TKE), pressure gradient, and flow component analysis. 4D flow MRI is widely used to image many parts of the body, such as the neck, brain, and liver, and has a wide application spectrum to cardiac diseases and large vessels. This present review aims to summarize the hemodynamic parameters of 4D flow MRI technology and generalize their usefulness in clinical practice in relation to the cardiovascular system. In addition, we note the improvements that have been made to 4D flow MRI with the application of new technologies. The application of new technologies can improve the speed of 4D flow, which would benefit clinical applications.

Structural Heart 4D Flow MRI for Hemodynamic Assessment: How We Do It

MRI is an essential diagnostic tool in the anatomic and functional evaluation of cardiovascular disease. In many practices, 2D phase-contrast (2D-PC) has been used for blood flow quantification. 4D Flow MRI is a time-resolved volumetric acquisition that captures the vector field of blood flow along with anatomic images. 4D Flow MRI provides a simpler acquisition compared to 2D-PC and facilitates a more accurate and comprehensive hemodynamic assessment. Advancements in accelerated imaging have significantly shortened scan times of 4D Flow MRI while preserving image quality, enabling this technology to transition from the research arena to routine clinical practice. In this article, we review technical optimization based on our clinical experience of over 10 years with 4D Flow MRI. We also present pearls and pitfalls in the practical application of 4D Flow MRI, including how to quantify cardiovascular shunts, valvular or vascular stenosis, and valvular regurgitation. As experience increases, and as 4D Flow sequences and post-processing software become more broadly available, 4D Flow MRI will likely become an essential component of cardiac imaging for practices involved in the management of congenital and acquired structural heart disease.

A prediction model of simple echocardiographic variables to screen for potentially correctable shunts in adult patients with pulmonary arterial hypertension associated with atrial septal defects: a cross-sectional study

During the routine follow-up of adult patients with pulmonary arterial hypertension associated with atrial septal defects (ASD-PAH), the suitability of shunt closure depends on the invasive right heart catheterization (RHC). It is difficult to grasp the timing of RHC shunt closure for moderate-severe PAH. This retrospective cross-sectional study was designed to investigate which echocardiographic variables are related to pulmonary vascular resistance (PVR) in adult ASD-PAH patients and propose a method using echocardiographic variables to screen for patients where shunt closure is suitable. A total of 139 adult ASD-PAH patients with a PASP ≥ 60 mmHg measured by transthoracic echocardiogram (TTE) were included in this study. All RHCs were performed within a week after TTE. The Correctable shunt was defined as PVR ≤ 4.6 wood units (WU). Multivariate regressions were performed with echocardiographic variables. The nomogram of prediction model was constructed by the predictors of PVR ≤ 4.6 WU by multivariate logistic regression analysis. Multivariate linear regression revealed that TAPSE (tricuspid annular plane systolic excursion)/pulmonary artery systolic pressure (PASP) measured by TTE was negatively associated with PVR (β per SD: - 1.84, 95%CI - 2.62, - 1.06). Multivariate logistic regression showed that TAPSE/PASP and pulmonary valve (PV) peak velocity were positively associated with a potentially correctable shunt (PVR ≤ 4.6 WU) (OR per SD: 2.38, 95%CI 1.34, 4.25, and OR per SD: 2.67, 95%CI 1.26, 5.64, respectively). In receiver operating characteristic analysis, the TAPSE/PASP + PV peak velocity combined model achieved the best performance (AUC: 0.8584, sensitivity: 83.33%, specificity: 72.16%). Internal verification showed stable performance (AUC: 0.8591, sensitivity: 88.10%, specificity: 68.04%). The net benefit of this model was greater than other models when it came to a wide range probability threshold in decision curve analysis. TAPSE/PASP + PV the peak velocity model may have great value in predicting adult ASD-PAH patients with operability potential, which could help clinicians make the treatment decision for follow-up patients.

4D Flow MRI Quantification of Congenital Shunts: Comparison to Invasive Catheterization

PURPOSE

To compare invasive right heart catheterization with four-dimensional (4D) flow MRI for estimating shunt fraction in patients with intracardiac and extracardiac shunts.

MATERIALS AND METHODS

In this retrospective study, patients who underwent 4D flow MRI and invasive right heart catheterization with a shunt run between August 2015 and November 2018 were included. The primary objective was comparison of estimated shunt fraction (ratio of pulmonary-to-systemic flow, Q_p/Q_s) at 4D flow and catheterization. Secondary objectives included comparison of the right ventricular-to-left ventricular stroke volume ratio (RVSV/LVSV) to shunt fraction (for those with applicable shunts) and comparison of cardiac output between 4D flow and catheterization. Statistical analysis included Pearson correlation and Bland-Altman plots.

RESULTS

A total of 33 patients met inclusion criteria (mean age, 49 years ± 16 [standard deviation]; 24 women). 4D flow measurements of Q_p/Q_s strongly correlated with those at catheterization (r = 0.938), and there was no bias. RVSV/LVSV correlated strongly with Q_p/Q_s from 4D flow (r = 0.852) and catheterization (r = 0.842). Measurements of left ventricle (Q_s) and right ventricle (Q_P) cardiac output from 4D flow and catheterization (Fick) correlated moderately overall (r = 0.673 [Q_p] and r = 0.750 [Q_s]).

CONCLUSION

Shunt fraction measurement using 4D flow MRI compares well with that using invasive cardiac catheterization.Supplemental material is available for this article.© RSNA, 2021.

[Assessment of intracardiac flows by Magnetic Resonance Imaging: The 4D Flow imaging]

2D flow cardiac MRI is a well-established technique but has some current limitations in routine practice. New 4D flow MRI may overcome these limitations, providing dramatic dynamic imaging, easily understandable, allowing robust quantification of flows. 4D flow imaging should become soon the reference technic for valvular regurgitations and congenital heart disease.

Left ventricular global longitudinal strain in bicupsid aortic valve patients: head-to-head comparison between computed tomography, 4D flow cardiovascular magnetic resonance and speckle-tracking echocardiography

Left ventricular global longitudinal strain (LVGLS) analysis is a sensitive measurement of myocardial deformation most often done using speckle-tracking transthoracic echocardiography (TTE). We propose a novel approach to measure LVGLS using feature-tracking software on the magnitude dataset of 4D flow cardiovascular magnetic resonance (CMR) and compare it to dynamic computed tomography (CT) and speckle tracking TTE derived measurements. In this prospective cohort study 59 consecutive adult patients with a bicuspid aortic valve (BAV) were included. The study protocol consisted of TTE, CT, and CMR on the same day. Image analysis was done using dedicated feature-tracking (4D flow CMR and CT) and speckle-tracking (TTE) software, on apical 2-, 3-, and 4-chamber long-axis multiplanar reconstructions (4D flow CMR and CT) or standard apical 2-, 3-, and 4-chamber acquisitions (TTE). CMR and CT GLS analysis was feasible in all patients. Good correlations were observed for GLS measured by CMR (− 21 ± 3%) and CT (− 20 ± 3%) versus TTE (− 20 ± 3%, Pearson’s r: 0.67 and 0.65, p < 0.001). CMR also correlated well with CT (Pearson’s r 0.62, p < 0.001). The inter-observer analysis showed moderate to good reproducibility of GLS measurement by CMR, CT and TTE (Pearsons’s r: 0.51, 0.77, 0.70 respectively; p < 0.05). Additionally, ejection fraction (EF), end-diastolic and end-systolic volume measurements (EDV and ESV) correlated well between all modalities (Pearson’s r > 0.61, p < 0.001). Feature-tracking GLS analysis is feasible using the magnitude images acquired with 4D flow CMR. GLS measurement by CMR correlates well with CT and speckle-tracking 2D TTE. GLS analysis on 4D flow CMR allows for an integrative approach, integrating flow and functional data in a single sequence. Not applicable, observational study.

4-Dimensional Flow by Cardiac Magnetic Resonance Informs Surgical Planning in Partial Anomalous Pulmonary Venous Return

Four-dimensional flow cardiac magnetic resonance enhances the visualization of blood flow in a 3-dimensional volume throughout the cardiac cycle, thus dramatically improving visualization of pulmonary venous anatomy by cardiac magnetic resonance. We demonstrate the impact of 4-dimensional flow on diagnosis and surgical planning for partial anomalous pulmonary venous return. (Level of Difficulty: Beginner.).

4D Flow Vorticity Visualization Predicts Regions of Quantitative Flow Inconsistency for Optimal Blood Flow Measurement

PURPOSE

To evaluate whether automated vorticity mapping four-dimensional (4D) flow MRI can identify regions of quantitative flow inconsistency.

MATERIALS AND METHODS

In this retrospective study, 35 consecutive patients who underwent MR angiography with 4D flow MRI at 3.0 T from December 2017 to October 2018 were analyzed using a λ 2-based technique for vorticity visualization and quantification. The patients were aged 58.6 years ± 14.4 (standard deviation), 12 were women, 18 had ascending aortic aneurysms (maximal diameter > 4.0 cm), and 10 had bicuspid aortic valves. Flow measurements were made in the ascending aorta (aAo), mid-descending aorta, main pulmonary artery, and superior vena cava. Statistical tests included t tests and F tests with a type I error threshold (α) of .05.

RESULTS

The 35 patients were visually classified as having no (n = 9), mild (n = 8), moderate (n = 11), or severe vorticity (n = 7). Across all patients, standard deviation of cardiac output in the aAo (0.58 L/min ± 0.45) was significantly (P < .001) higher than in the pulmonary arteries (0.15 L/min ± 0.10) and descending aorta and superior vena cava (0.14 L/min ± 0.12). The standard deviation of cardiac output observed in the aAo was significantly greater (P < .01) in patients with moderate or severe vorticity (0.73 L/min ± 0.55) than in those with none or mild vorticity (0.44 L/min ± 0.26).

CONCLUSION

Cardiac output and blood flow are essential MRI measurements in the evaluation of structural heart disease. Vorticity visualization may be used to help guide optimal location for flow quantification.© RSNA, 2020See also the commentary by Markl in this issue.

Role of Doppler echocardiography for assessing right ventricular cardiac output in patients with atrial septal defect

BACKGROUND

Although Doppler echocardiography is routinely used to assess left ventricle cardiac output, there are limited data about the feasibility of Doppler echocardiography for right ventricular (RV) cardiac output assessment in patients with left-to-right shunt. The purpose of the study was to determine the correlation between Doppler-derived and Fick-derived RV cardiac index (CI), and the interobserver correlation in Doppler-derived RV CI assessment.

METHODS

Retrospective study of patients (age ≥18 years) with unrepaired atrial septal defect who underwent cardiac catheterization and echocardiography (within 3 days), 2004-2017. RV CI was calculated using the hydraulic orifice formula: [.785 × (right ventricle outflow tract diameter)²  × right ventricular outflow tract (RVOT) time velocity integral × heart rate]/body surface area.

RESULTS

A total of 128 patients (age 52 ± 17 years; female 88 [69%]) met the inclusion criteria. There was a modest correlation between Doppler-derived and Fick-derived RV CI (r = .57, P < .001), and the mean difference between Doppler-derived and Fick-derived RV CI was -.3 (95% confidence interval of agreement, -.8 to +.9) L/min/m² . There was also a modest correlation between Doppler-derived RV CI from observer #1 and observer #2 (r = .62, P < .001), and the mean difference between Doppler-derived RV CI from observer #1 and observer #2 was -.2 (95% confidence interval of agreement, -.9 to +.6).

CONCLUSIONS

The current study demonstrated a modest correlation between Doppler-derived and Fick-derived RV cardiac output, and a modest interobserver correlation in Doppler-derived RV cardiac output assessment. Further studies are required to validate these results and to explore other potential applications such as in patients with chronic pulmonary regurgitation.

Validation of 4D flow CMR against simultaneous invasive hemodynamic measurements: a swine study

The purpose of this study was to compare invasively measured aorta flow with 2D phase contrast flow and 4D flow measurements by cardiovascular magnetic resonance (CMR) imaging in a large animal model. Nine swine (mean weight 63 ± 4 kg) were included in the study. 4D flow CMR exams were performed on a 1.5T MRI scanner. Flow measurements were performed on 4D flow images at the aortic valve level, in the ascending aorta, and main pulmonary artery. Simultaneously, flow was measured using an invasive flow probe, placed around the ascending aorta. Additionally, standard 2D phase contrast flow and 2D left ventricular (LV) volumetric data were used for comparison. The correlations of cardiac output (CO) between the invasive flow probe, and CMR modalities were strong to very strong. CO measured by 4D flow CMR correlated better with the CO measured by the invasive flow probe than 2D flow CMR flow and volumetric LV data (4D flow CMR: Spearman’s rho = 0.86 at the aortic valve level and 0.90 at the ascending aorta level; 2D flow CMR: 0.67 at aortic valve level; LV measurements: 0.77). In addition, there tended to be a correlation between mean pulmonary artery flow and aorta flow with 4D flow (Spearman’s rho = 0.65, P = 0.07), which was absent in measurements obtained with 2D flow CMR (Spearman’s rho = 0.40, P = 0.33). This study shows that aorta flow can be accurately measured by 4D flow CMR compared to simultaneously measured invasive flow. This helps to further validate the quantitative reliability of this technique.