Left Ventricular Diastolic Function in Children with Atrial Septal Defects Improves After Closure by Means of Increased Hydraulic Force.

Hydraulic force aids diastolic filling of the left ventricle (LV) by facilitating basal movement of the atrioventricular plane. The short-axis atrioventricular area difference (AVAD) determines direction and magnitude of this force. Patients with atrial septal defect (ASD) have reduced LV filling due to the left-to-right shunt across the atrial septum and thus potentially altered hydraulic force. The aims were therefore to use cardiac magnetic resonance images to assess whether AVAD and thus the hydraulic force differ in children with ASD compared to healthy children, and if it improves after ASD closure. Twenty-two children with ASD underwent cardiac magnetic resonance before ASD closure. Of these 22 children, 17 of them repeated their examination also after ASD closure. Twelve controls were included. Left atrial and ventricular areas were delineated in short-axis images, and AVAD was defined as the largest ventricular area minus the largest atrial area at each time frame and normalized to body height (AVADi). At end diastole AVADi was positive in all participants, suggesting a force acting towards the atrium assisting the diastolic movement of the atrioventricular plane; however, lower in children both before (6.3 cm2/m [5.2-8.0]; p < 0.0001) and after ASD closure (8.7 cm2/m [6.6-8.5]; p = 0.0003) compared to controls (12.2 cm2/m [11.3-13.9]). Left ventricular diastolic function improves after ASD closure in children by means of improved hydraulic force assessed by AVAD. Although AVADi improved after ASD closure, it was still lower than in controls, indicating diastolic abnormality even after ASD closure. In patients where AVADi is low, ASD closure may help avoid diastolic function deterioration and improve outcome. This could likely be important also in patients with small shunt volumes, especially if they are younger, who currently do not undergo ASD closure. Changes in clinical routine may be considered pending larger outcome studies.

Atrioventricular Area Difference Aids Diastolic Filling in Patients with Repaired Tetralogy of Fallot.

A hydraulic force aids diastolic filling of the left ventricle (LV) and is proportional to the difference in short-axis area between the left ventricle and atrium; the atrioventricular area difference (AVAD). Patients with repaired Tetralogy of Fallot (rToF) and pulmonary regurgitation (PR) have reduced LV filling which could lead to a negative AVAD and a hydraulic force impeding diastolic filling. The aim was to assess AVAD and to determine whether the hydraulic force aids or impedes diastolic filling in patients with rToF and PR, compared to controls. Twelve children with rToF (11.5 [9-13] years), 12 pediatric controls (10.5 [9-13] years), 12 adults with rToF (21.5 [19-27] years) and 12 adult controls (24 [21-29] years) were retrospectively included. Cine short-axis images were acquired using cardiac magnetic resonance imaging. Atrioventricular area difference was calculated as the largest left ventricular short-axis area minus the largest left atrial short-axis area at beginning of diastole and end diastole and indexed to height (AVADi). Children and adults with rToF and PR had higher AVADi (0.3 cm2/m [- 1.3 to 0.8] and - 0.6 [- 1.5 to - 0.2]) at beginning of diastole compared to controls (- 2.7 cm2/m [- 4.9 to - 1.7], p = 0.015) and - 3.3 cm2/m [- 3.8 to - 2.8], p = 0.017). At end diastole AVADi did not differ between patients and controls. Children and adults with rToF and pulmonary regurgitation have an atrioventricular area difference that do not differ from controls and thus a net hydraulic force that contributes to left ventricular diastolic filling, despite a small underfilled left ventricle due to pulmonary regurgitation.

Comparison of 2D and 4D Flow MRI in Neonates Without General Anesthesia.

BACKGROUND: Neonates with critical congenital heart disease require early intervention. Four-dimensional (4D) flow may facilitate surgical planning and improve outcome, but accuracy and precision in neonates are unknown. PURPOSE: To 1) validate two-dimensional (2D) and 4D flow MRI in a phantom and investigate the effect of spatial and temporal resolution; 2) investigate accuracy and precision of 4D flow and internal consistency of 2D and 4D flow in neonates; and 3) compare scan time of 4D flow to multiple 2D flows. STUDY TYPE: Phantom and prospective patients. POPULATION: A total of 17 neonates with surgically corrected aortic coarctation (age 18 days [IQR 11-20]) and a three-dimensional printed neonatal aorta phantom. FIELD STRENGTH/SEQUENCE: 1.5T, 2D flow and 4D flow. ASSESSMENT: In the phantom, 2D and 4D flow volumes (ascending and descending aorta, and aortic arch vessels) with different resolutions were compared to high-resolution reference 2D flow. In neonates, 4D flow was compared to 2D flow volumes at each vessel. Internal consistency was computed as the flow volume in the ascending aorta minus the sum of flow volumes in the aortic arch vessels and descending aorta, divided by ascending aortic flow. STATISTICAL TESTS: Bland-Altman plots, Pearson correlation coefficient (r), and Student's t-tests. RESULTS: In the phantom, 2D flow differed by 0.01 ± 0.02 liter/min with 1.5 mm spatial resolution and -0.01 ± 0.02 liter/min with 0.8 mm resolution; 4D flow differed by -0.05 ± 0.02 liter/min with 2.4 mm spatial and 42 msec temporal resolution, -0.01 ± 0.02 liter/min with 1.5 mm, 42 msec resolution and -0.01 ± 0.02 liter/min with 1.5 mm, 21 msec resolution. In patients, 4D flow and 2D flow differed by -0.06 ± 0.08 liter/min. Internal consistency in patients was -11% ± 17% for 2D flow and 5% ± 13% for 4D flow. Scan time was 17.1 minutes [IQR 15.5-18.5] for 2D flow and 6.2 minutes [IQR 5.3-6.9] for 4D flow, P < 0.0001. DATA CONCLUSION: Neonatal 4D flow MRI is time efficient and can be acquired with good internal consistency without contrast agents or general anesthesia, thus potentially expanding 4D flow use to the youngest and smallest patients. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 2.

Higher blood pressure in adolescent boys after very preterm birth and fetal growth restriction.

BACKGROUND: Although preterm birth predisposes for cardiovascular disease, recent studies in children indicate normal blood pressure and arterial stiffness. This prospective cohort study therefore assessed blood pressure and arterial stiffness in adolescents born very preterm due to verified fetal growth restriction (FGR). METHODS: Adolescents (14 (13-17) years; 52% girls) born very preterm with FGR (preterm FGR; n = 24) and two control groups born with appropriate birth weight (AGA), one in similar gestation (preterm AGA; n = 27) and one at term (term AGA; n = 28) were included. 24-hour ambulatory blood pressure and aortic pulse wave velocity (PWV) and distensibility by magnetic resonance imaging were acquired. RESULTS: There were no group differences in prevalence of hypertension or in arterial stiffness (all p ≥ 0.1). In boys, diastolic and mean arterial blood pressures increased from term AGA to preterm AGA to preterm FGR with higher daytime and 24-hour mean arterial blood pressures in the preterm FGR as compared to the term AGA group. In girls, no group differences were observed (all p ≥ 0.1). CONCLUSIONS: Very preterm birth due to FGR is associated with higher, yet normal blood pressure in adolescent boys, suggesting an existing but limited impact of very preterm birth on cardiovascular risk in adolescence, enhanced by male sex and FGR. IMPACT: Very preterm birth due to fetal growth restriction was associated with higher, yet normal blood pressure in adolescent boys. In adolescence, very preterm birth due to fetal growth restriction was not associated with increased thoracic aortic stiffness. In adolescence, very preterm birth in itself showed an existing but limited effect on blood pressure and thoracic aortic stiffness. Male sex and fetal growth restriction enhanced the effect of preterm birth on blood pressure in adolescence. Male sex and fetal growth restriction should be considered as additional risk factors to that of preterm birth in cardiovascular risk stratification.

Non-invasive quantification of pressure-volume loops in patients with Fontan circulation.

BACKGROUND: Pressure-volume (PV) loops provide comprehensive information of cardiac function, but commonly implies an invasive procedure under general anesthesia. A novel technique has made it possible to non-invasively estimate PV loops with cardiac magnetic resonance (CMR) and brachial pressure which would enable good volume estimation of often anatomically complex ventricles without the need of anesthesia in most cases. In this study we aimed to compare how hemodynamic parameters derived from PV loops in patients with Fontan circulation differ to controls. METHODS: Patients with Fontan circulation (n = 17, median age 12 years, IQR 6-15) and healthy controls (n = 17, 14 years, IQR 13-22) were examined with CMR. Short axis balanced steady-state free-precession cine images covering the entire heart were acquired. PV loops were derived from left ventricular volumes in all timeframes and brachial blood pressure from cuff sphygmomanometry. RESULTS: Fontan patients had lower stroke work, ventricular mechanical efficiency and external power compared to controls. Fontan patients with dominant right ventricle had higher potential energy indexed to body surface area but lower contractility (Ees) compared to controls. Fontan patients had higher arterial elastance (Ea) and Ea/Ees ratio than controls. Contractility showed no correlation with ejection fraction (EF) in Fontan patients irrespective of ventricular morphology. No difference was seen in energy per ejected volume between Fontan patients and controls. CONCLUSIONS: This non-invasive PV-loop method could be used in future studies to show the potential prognostic value of these measures and if changes in ventricular function over time can be detected earlier by this method compared to changes in ventricular volumes and EF. In contrast to patients with acquired heart failure, Fontan patients had similar energy per ejected volume as controls which suggests similar ventricular oxygen consumption to deliver the same volume in Fontan patients as in controls.

Changes in left and right ventricular longitudinal function after pulmonary valve replacement in patients with Tetralogy of Fallot.

Timing and indication for pulmonary valve replacement (PVR) in patients with repaired Tetralogy of Fallot (rToF) and pulmonary regurgitation (PR) are uncertain. To improve understanding of pumping mechanics, we investigated atrioventricular coupling before and after surgical PVR. Cardiovascular magnetic resonance was performed in patients (n = 12) with rToF and PR > 35% before and after PVR and in healthy controls (n = 15). Atrioventricular plane displacement (AVPD), global longitudinal peak systolic strain (GLS), atrial and ventricular volumes, and caval blood flows were analyzed. Right ventricular (RV) AVPD and RV free wall GLS were lower in patients before PVR compared with controls (P < 0.0001; P < 0.01) and decreased after PVR (P < 0.0001 for both). Left ventricular AVPD was lower in patients before PVR compared with controls (P < 0.05) and decreased after PVR (P < 0.01). Left ventricular GLS did not differ between patients and controls (P > 0.05). Right atrial reservoir volume and RV stroke volume generated by AVPD correlated in controls (r = 0.93; P < 0.0001) and patients before PVR (r = 0.88; P < 0.001) but not after PVR. In conclusion, there is a clear atrioventricular coupling in patients before PVR that is lost after PVR, possibly because of loss of pericardial integrity. Impaired atrioventricular coupling complicates assessment of ventricular function after surgery using measurements of longitudinal function. Changes in atrioventricular coupling seen in patients with rToF may be energetically unfavorable, and long-term effects of surgery on atrioventricular coupling is therefore of interest. Also, AVPD and GLS cannot be used interchangeably to assess longitudinal function in rToF.NEW & NOTEWORTHY There is a clear atrioventricular coupling in patients with Tetralogy of Fallot (ToF) and pulmonary regurgitation before surgical pulmonary valve replacement (PVR) that is lost after operation, possibly because of loss of pericardial integrity. The impaired atrioventricular coupling complicates assessment of ventricular function after surgery when using measurements of longitudinal function. Left ventricular atrioventricular plane displacement (AVPD) found differences between patients and controls and changes after PVR that longitudinal strain could not detect. This indicates that AVPD and strain cannot be used interchangeably to assess longitudinal function in repaired ToF.

Altered biventricular hemodynamic forces in patients with repaired tetralogy of Fallot and right ventricular volume overload because of pulmonary regurgitation.

Intracardiac hemodynamic forces have been proposed to influence remodeling and be a marker of ventricular dysfunction. We aimed to quantify the hemodynamic forces in patients with repaired tetralogy of Fallot (rToF) to further understand the pathophysiological mechanisms as this could be a potential marker for pulmonary valve replacement (PVR) in these patients. Patients with rToF and pulmonary regurgitation (PR) > 20% ( n = 18) and healthy control subjects ( n = 15) underwent MRI, including four-dimensional flow. A subset of patients ( n = 8) underwent PVR and MRI after surgery. Time-resolved hemodynamic forces were quantified using 4D-flow data and indexed to ventricular volume. Patients had higher systolic and diastolic left ventricular (LV) hemodynamic forces compared with control subjects in the lateral-septal/LV outflow tract ( P = 0.011 and P = 0.0031) and inferior-anterior ( P < 0.0001 and P < 0.0001) directions, which are forces not aligned with blood flow. Forces did not change after PVR. Patients had higher RV diastolic forces compared with control subjects in the diaphragm-right ventricular (RV) outflow tract (RVOT; P < 0.001) and apical-basal ( P = 0.0017) directions. After PVR, RV systolic forces in the diaphragm-RVOT direction decreased ( P = 0.039) to lower levels than in control subjects ( P = 0.0064). RV diastolic forces decreased in all directions ( P = 0.0078, P = 0.0078, and P = 0.039) but were still higher than in control subjects in the diaphragm-RVOT direction ( P = 0.046). In conclusion, patients with rToF and PR had LV hemodynamic forces less aligned with intraventricular blood flow compared with control subjects and higher diastolic RV forces along the regurgitant flow direction in the RVOT and that of tricuspid inflow. Remaining force differences in the LV and RV after PVR suggest that biventricular pumping does not normalize after surgery. NEW & NOTEWORTHY Biventricular hemodynamic forces in patients with repaired tetralogy of Fallot and pulmonary regurgitation were quantified for the first time. Left ventricular hemodynamic forces were less aligned to the main blood flow direction in patients compared with control subjects. Higher right ventricular forces were seen along the pulmonary regurgitant and tricuspid inflow directions. Differences in forces versus control subjects remain after pulmonary valve replacement, suggesting that altered biventricular pumping does not normalize after surgery.

Disturbed left and right ventricular kinetic energy in patients with repaired tetralogy of Fallot: pathophysiological insights using 4D-flow MRI.

OBJECTIVES: Indications for pulmonary valve replacement (PVR) in patients with pulmonary regurgitation (PR) after repaired tetralogy of Fallot (rToF) are debated. We aimed to compare right (RV) and left ventricular (LV) kinetic energy (KE) measured by 4D-flow magnetic resonance imaging (MRI) in patients to controls, to further understand the pathophysiological effects of PR. METHODS: Fifteen patients with rToF with PR > 20% and 14 controls underwent MRI. Ventricular volumes and KE were quantified from cine MRI and 4D-flow, respectively. Lagrangian coherent structures were used to discriminate KE in the PR. Restrictive RV physiology was defined as end-diastolic forward flow. RESULTS: LV systolic peak KE was lower in rToF, 2.8 ± 1.1 mJ, compared to healthy volunteers, 4.8 ± 1.1 mJ, p < 0.0001. RV diastolic peak KE was higher in rToF (7.7 ± 4.3 mJ vs 3.1 ± 1.3 mJ, p = 0.0001) and the difference most pronounced in patients with non-restrictive RV physiology. KE was primarily located in the PR volume at the time of diastolic peak KE, 64 ± 17%. CONCLUSION: This is the first study showing disturbed KE in patients with rToF and PR, in both the RV and LV. The role of KE as a potential early marker of ventricular dysfunction to guide intervention needs to be addressed in future studies. KEY POINTS: • Kinetic energy (KE) reflects ventricular performance • KE is a potential marker of ventricular dysfunction in Fallot patients • KE is disturbed in both ventricles in patients with tetralogy of Fallot • KE contributes to the understanding of the pathophysiology of pulmonary regurgitation • Lagrangian coherent structures enable differentiation of ventricular inflows.

Decreased Diastolic Ventricular Kinetic Energy in Young Patients with Fontan Circulation Demonstrated by Four-Dimensional Cardiac Magnetic Resonance Imaging.

Four-dimensional (4D) flow magnetic resonance imaging (MRI) enables quantification of kinetic energy (KE) in intraventricular blood flow. This provides a novel way to understand the cardiovascular physiology of the Fontan circulation. In this study, we aimed to quantify the KE in functional single ventricles. 4D flow MRI was acquired in eleven patients with Fontan circulation (median age 12 years, range 3-29) and eight healthy volunteers (median age 26 years, range 23-36). Follow-up MRI after surgical or percutaneous intervention was performed in 3 patients. Intraventricular KE was calculated throughout the cardiac cycle and indexed to stroke volume (SV). The systolic/diastolic ratio of KE in Fontan patients was similar to the ratio of the controls' left ventricle (LV) or right ventricle (RV) depending on the patients' ventricular morphology (Cohen´s κ = 1.0). Peak systolic KE/SV did not differ in patients compared to the LV in controls (0.016 ± 0.006 mJ/ml vs 0.020 ± 0.004 mJ/ml, p = 0.09). Peak diastolic KE/SV in Fontan patients was lower than in the LV of the control group (0.028 ± 0.010 mJ/ml vs 0.057 ± 0.011 mJ/ml, p < 0.0001). The KE during diastole showed a plateau in patients with aortopulmonary collaterals. This is to our knowledge the first study that quantifies the intraventricular KE of Fontan patients. KE is dependent on the morphology of the ventricle, and diastolic KE indexed to SV in patients is decreased compared to controls. The lower KE in Fontan patients may be a result of impaired ventricular filling.

In vivo hepatic flow distribution by computational fluid dynamics can predict pulmonary flow distribution in patients with Fontan circulation.

In Fontan patients, a lung deprived of hepatic blood may develop pulmonary arterio-venous malformations (PAVMs) resulting in shunting, reduced pulmonary vascular resistance (PVR) and decreased oxygenation. To provide guidance for corrective invasive interventions, we aimed to non-invasively determine how the hepatic to pulmonary blood flow balance correlates with pulmonary flow, PVR, and with oxygen saturation. Magnetic resonance imaging (MRI) data from eighteen Fontan patients (eight females, age 3-14 years) was used to construct patient-specific computational fluid dynamics (CFD) models to calculate the hepatic to pulmonary blood flow. This was correlated with pulmonary vein flow, simulated PVR and oxygen saturation. Clinical applicability of the findings was demonstrated with an interventional patient case. The hepatic to pulmonary blood flow balance correlated with right/left pulmonary vein flow (R2 = 0.50), left/right simulated PVR (R2 = 0.47), and oxygen saturation at rest (R2 = 0.56). In the interventional patient, CFD predictions agreed with post-interventional MRI measurements and with regressions in the cohort. The balance of hepatic blood to the lungs has a continuous effect on PVR and oxygen saturation, even without PAVM diagnosis. MRI combined with CFD may help in planning of surgical and interventional designs affecting the hepatic to pulmonary blood flow balance in Fontan patients.

Patients with volume-loaded right ventricle - quantification of left ventricular hemodynamic response to intervention measured by noninvasive pressure-volume loops.

Volume loading of the right ventricle (RV) in patients with atrial septal defect (ASD) and patients with repaired Tetralogy of Fallot (rToF) affects the pumping mechanics of the left ventricle (LV). Intervention of the lesion will relieve the RV volume load however quantifiable impact on exercise capacity, arrhytmias or death are limited. A possible explanation could be remaining effects on the function of the LV. The aim of this study was therefore to investigate if hemodynamics of the LV differs between patients with RV volume load due to ASD or rToF and healthy controls and if they change after intervention. Eighteen patients with ASD, 17 patients with rToF and 16 healthy controls underwent cardiac magnetic resonance imaging (CMR) and maximal exercise test with continuous gas analysis. Reexamination was performed 13 ± 2 months after closure of the ASD in 13 of the patients and 10 ± 4 months after pulmonary valve replacement (PVR) in 9 of the patients with rToF. Non-invasive PV-loops from CMR and brachial pressures were analyzed. Stroke work (SW) and potential energy (PE) increased after ASD closure but not in ToF patients after valve repair. Patients with ASD or rToF had higher contractility and arterial elastance than controls. No major effects were seen in LV energetics or in peak VO2 after ASD closure or PVR. Peak VO2 correlated positively with SW and PE in patients with ASD (r = 0.54, p < 0.05; r = 0.61, p < 0.01) and controls (r = 0.72, p < 0.01; r = 0.53, p < 0.05) to approximately the same degree as peak VO2 and end-diastolic volume (EDV) or end-systolic volume (ESV). In ToF patients there was no correlation between PV loop parameters and peak VO2 even if correlation was found between peak VO2 and EDV or ESV. In conclusion, the LV seems to adapt its pumping according to anatomic circumstances without losing efficiency, however there are indications of persistent vascular dysfunction, expressed as high arterial elastance, which might have impact on exercise performance and prognosis. Future studies might elucidate if the duration of RV volume load and decreased LV filling have any impact on the ability of the vascular function to normalize after ASD closure or PVR.

Central venous stenosis after subclavian versus internal jugular dialysis catheter insertion (CITES) in adults in need of a temporary central dialysis catheter: study protocol for a two-arm, parallel-group, non-inferiority randomised controlled trial.

BACKGROUND: The right internal jugular vein is currently recommended for temporary central dialysis catheters (tCDC) based on results from previous studies showing a lower incidence of central vein stenosis compared to the subclavian vein. Data is however conflicting, and there are several advantages when the subclavian route is used for tCDCs. This prospective, controlled, randomised, non-inferiority study aims to compare the incidence of post-catheterisation central vein stenosis between the right subclavian and the right internal jugular routes. METHODS: Adult patients needing a tCDC will be included from several hospitals and randomised to either subclavian or internal jugular vein catheterisation with a silicone tCDC. Inclusion continues until 50 patients in each group have undergone a follow-up CT venography. The primary outcome is the incidence of post-catheterisation central vein stenosis detected by a CT venography performed 1.5 to 3 months after removal of the tCDC. Secondary outcomes include between-group comparisons of (I) the patients' experience of discomfort and pain, (II) any dysfunction of the tCDC during use, (III) catheterisation success rate and (IV) the number of mechanical complications. Furthermore, the ability to detect central vein stenosis by a focused ultrasound examination will be evaluated using the CT venography as golden standard. DISCUSSION: The use of the subclavian route for tCDC placement has largely been abandoned due to older studies with various methodological issues. However, the subclavian route offers several advantages for the patient. This trial is designed to provide robust data on the incidence of central vein stenosis after silicone tCDC insertion in the era of ultrasound-guided catheterisations. TRIAL REGISTRATION: Clinicaltrials.gov; NCT04871568. Prospectively registered on May 4, 2021.

Haemodynamic left-ventricular changes during dobutamine stress in patients with atrial septal defect assessed with magnetic resonance imaging-based pressure-volume loops.

BACKGROUND: Atrial septal defect (ASD) results in a left-to-right shunt causing right-ventricular (RV) volume overload and decreased cardiac output from the left ventricle. Pressure-volume (PV) loops enable comprehensive assessment of ventricular function and might increase understanding of the pathophysiology of ASD. The aim of this study was to investigate if left-ventricular (LV) haemodynamic response to stress in patients with ASD differs from controls. MATERIAL AND METHODS: Patients with ASD (n = 18, age 51 ± 18) and healthy controls (n = 16, age 35 ± 13) underwent cardiac magnetic resonance (CMR) and brachial cuff pressure measurements at rest and during dobutamine stress. An in-house, validated method was used to compute PV loops. RESULTS: Patients had lower stroke work, potential energy and external power at rest than controls (p < 0.001; p < 0.05; p < 0.05). Stroke work and external power increased and potential energy decreased during stress in patients (p < 0.05; p < 0.0001; p < 0.01) and controls (p < 0.0001; p < 0.001; p < 0.01). Contractility and arterial elastance at rest were higher in patients than controls (p < 0.01; p < 0.01). Contractility increased during stress in both groups (p < 0.0001; p < 0.001). There was no difference between patients and controls in arterio-ventricular coupling. CONCLUSION: LV haemodynamic response to stress can be assessed using noninvasive PV loops derived from CMR and brachial blood pressure. Patients with ASD had normal LV energy efficiency, in contrast to other patient groups with decreased cardiac output. Data suggest that patients with ASD had an increased inotropic level at rest with high contractility and heart rate but were able to respond with a further increase during stress, albeit to not as high a cardiac output as controls.

Computational Fluid Dynamics Support for Fontan Planning in Minutes, Not Hours: The Next Step in Clinical Pre-Interventional Simulations.

Computational fluid dynamics (CFD) modeling may aid in planning of invasive interventions in Fontan patients. Clinical application of current CFD techniques is however limited by complexity and long computation times. Therefore, we validated a "lean" CFD method to magnetic resonance imaging (MRI) and an "established" CFD method, ultimately aiming to reduce complexity to enable predictive CFD during ongoing interventions. Fifteen Fontan patients underwent MRI for CFD modeling. The differences between lean and established approach, in hepatic and total flow percentage to the left pulmonary artery (%LPA), power loss and relative wall shear stress area were 1.5 ± 4.0%, -0.17 ± 1.1%, -0.055 ± 0.092 mW and 1.1 ± 1.4%. Compared with MRI, the lean and established method showed a bias in %LPA of -1.9 ± 3.4% and -1.8 ± 3.1%. Computation time was for the lean and established approach 3.0 ± 2.0 min and 7.0 ± 3.4 h, respectively. We conclude that the proposed lean method provides fast and reliable results for future CFD support during interventions.

Non-invasive quantification of pressure-volume loops from cardiovascular magnetic resonance at rest and during dobutamine stress.

Non-invasive quantification of pressure-volume (PV) loops from brachial pressure and cardiovascular magnetic resonance is a validated method but its application has been limited to resting heart rates. The aim of this study was to improve the previous method and validate it against invasive left-ventricular pressure measurements in an experimental porcine model, and further apply it to 16 healthy humans at rest and during dobutamine stress. In addition, the improved method calculates the arterial elastance which provides the computation of the ratio of effective arterial (Ea ) to maximal ventricular elastance (Emax ) representing the ventricular-arterial coupling. In the porcine model, the differences between the improved non-invasively derived PV loops and invasively measured PV loops were for stroke work (mean ± SD) 0.00 ± 0.03 J, ventricular efficiency -1.1 ± 0.4%, and contractility 1.1 ± 0.1 mmHg/ml. In human subjects during dobutamine stress, stroke work increased from 1.3 ± 0.3 to 1.7 ± 0.4 J, ventricular efficiency from 71 ± 4 to 82 ± 4%, contractility from 1.3 ± 0.2 to 2.3 ± 0.6 mmHg/ml, and the ratio of arterial to ventricular elastance decreased from 0.96 to 0.56. The improved method for non-invasive PV loops constitutes a more robust diagnostic tool for cardiac disease states in a wider range of study cohorts at both rest and during stress.

Right ventricular remodeling after conduit replacement in patients with corrected tetralogy of Fallot - evaluation by cardiac magnetic resonance.

PURPOSE: To evaluate the potential for right ventricular reverse remodelling after pulmonary valve replacement using cardiac magnetic resonance imaging, in adults with corrected tetralogy of Fallot and severe pulmonary insufficiency. MATERIAL AND METHODS: Ten patients with previous correction of tetralogy of Fallot with severe pulmonary insufficiency accepted for pulmonary valve replacement were evaluated prospectively with cardiac magnetic resonance imaging preoperatively and re-evaluated 10 ± 5 months postoperatively. Follow up for survival was 100% complete with mean of 37 ± 12 months. RESULTS: The preoperative mean indexed right ventricular end-diastolic volume was reduced from 161 ± 33 ml/m2 to 120 ± 23 ml/m2 postoperatively, p < 0.001. The preoperative mean indexed right ventricular stroke volume was reduced from 72 ± 20 ml/m2 to 50 ± 6 ml/m2 postoperatively, p = 0.002. After pulmonary valve replacement, the right ventricular ejection fraction did not change significantly (46% versus 42%, p = 0.337). Pulmonary insufficiency fraction decreased from 49% ± 11 to 1% ± 1 postoperatively, p < 0.001. CONCLUSIONS: Pulmonary valve replacement leads to a favourable early reverse remodelling with a reduction in RV volumes and improved function in all patients regardless of their preoperative indexed right ventricular volume.

Simulation of aortopulmonary collateral flow in Fontan patients for use in prediction of interventional outcomes.

PURPOSE: Patients with complex congenital heart disease may need to be converted to a Fontan circulation with systemic venous return surgically connected to the pulmonary circulation. These patients frequently form aortopulmonary collaterals (APC), that is arterial inflows to the pulmonary artery vascular tree. The aim of this study was to develop a method to calculate the effect of APC on the pulmonary flow distribution based on magnetic resonance imaging (MRI) measurements and computational fluid dynamics simulations in order to enable prediction of interventional outcomes in Fontan patients. METHODS: Patient-specific models of 11 patients were constructed in a 3D-design software based on MRI segmentations. APC flow was quantified as the difference between pulmonary venous flow and pulmonary artery flow, measured by MRI. A method was developed to include the modulating effect of the APC flow by calculating the patient-specific relative pulmonary vascular resistance. Simulations, including interventions with a Y-graft replacement and a stent dilatation, were validated against MRI results. RESULTS: The bias between simulated and MRI-measured fraction of blood to the left lung was 2·9 ± 5·3%. Including the effects of the APC flow in the simulation (n = 6) reduced simulation error from 9·8 ± 7·0% to 5·2 ± 6·3%. Preliminary findings in two patients show that the effect of surgical and catheter interventions could be predicted using the demonstrated methods. CONCLUSIONS: The work demonstrates a novel method to include APC flow in predictive simulations of Fontan hemodynamics. APC flow was found to have a significant contribution to the pulmonary flow distribution in Fontan patients.