Assessment of viscous energy loss and the association with three-dimensional vortex ring formation in left ventricular inflow: In vivo evaluation using four-dimensional flow MRI.

PURPOSE: To evaluate viscous energy loss and the association with three-dimensional (3D) vortex ring formation in left ventricular (LV) blood flow during diastolic filling. THEORY AND METHODS: Thirty healthy volunteers were compared with 32 patients with corrected atrioventricular septal defect as unnatural mitral valve morphology and inflow are common in these patients. 4DFlow MRI was acquired from which 3D vortex ring formation was identified in LV blood flow at peak early (E)-filling and late (A)-filling and characterized by its presence/absence, orientation, and position from the lateral wall. Viscous energy loss was computed over E-filling, A-filling, and complete diastole using the Navier-Stokes energy equations. RESULTS: Compared with healthy volunteers, viscous energy loss was significantly elevated in patients with disturbed vortex ring formation as characterized by a significantly inclined orientation and/or position closer to the lateral wall. Highest viscous energy loss was found in patients without a ring-shaped vortex during E-filling (on average more than double compared with patients with ring-shape vortex, P < 0.003). Altered A-filling vortex ring formation was associated with significant increase in total viscous energy loss over diastole even in the presence of normal E-filling vortex ring. CONCLUSION: Altered vortex ring formation during LV filling is associated with increased viscous energy loss. Magn Reson Med 77:794-805, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Comparative Evaluation of Flow Quantification across the Atrioventricular Valve in Patients with Functional Univentricular Heart after Fontan's Surgery and Healthy Controls: Measurement by 4D Flow Magnetic Resonance Imaging and Streamline Visualization.

PURPOSE: To evaluate the inflow pattern and flow quantification in patients with functional univentricular heart after Fontan's operation using 4D flow magnetic resonance imaging (MRI) with streamline visualization when compared with the conventional 2D flow approach. METHOD: Seven patients with functional univentricular heart after Fontan's operation and twenty-three healthy controls underwent 4D flow MRI. In two orthogonal two-chamber planes, streamline visualization was applied, and inflow angles with peak inflow velocity (PIV) were measured. Transatrioventricular flow quantification was assessed using conventional 2D multiplanar reformation (MPR) and 4D MPR tracking the annulus and perpendicular to the streamline inflow at PIV, and they were validated with net forward aortic flow. RESULTS: Inflow angles at PIV in the patient group demonstrated wide variation of angles and directions when compared with the control group (P < .01). The use of 4D flow MRI with streamlines visualization in quantification of the transatrioventricular flow had smaller limits of agreement (2.2 ± 4.1 mL; 95% limit of agreement -5.9-10.3 mL) when compared with the static plane assessment from 2DFlow MRI (-2.2 ± 18.5 mL; 95% limit of agreement agreement -38.5-34.1 mL). Stronger correlation was present in the 4D flow between the aortic and trans-atrioventricular flow (R2 correlation in 4D flow: 0.893; in 2D flow: 0.786). CONCLUSIONS: Streamline visualization in 4D flow MRI confirmed variable atrioventricular inflow directions in patients with functional univentricular heart with previous Fontan's procedure. 4D flow aided generation of measurement planes according to the blood flood dynamics and has proven to be more accurate than the fixed plane 2D flow measurements when calculating flow quantifications.

Atrioventricular septal defect: From embryonic development to long-term follow-up.

Atrioventricular septal defect (AVSD) covers a spectrum of heart anomalies with a common atrioventricular connection and has an incidence of 4-5.3 per 10.000 live births. About half of the AVSDs occur in patient with Down syndrome. This review provides a bench to bedside overview of AVSD. Developmental aspects, nomenclature, anatomy, and classification of AVSD are discussed. Furthermore an overview of genetic and maternal risk factors for AVSD is provided, and available literature on (fetal) diagnosis, surgical techniques and follow-up is presented. Special attention is given to differences in developmental, anatomical and prognostic factors of AVSD between non-syndromic and Down syndrome patients.

Altered left ventricular vortex ring formation by 4-dimensional flow magnetic resonance imaging after repair of atrioventricular septal defects.

OBJECTIVES: During normal left ventricular (LV) filling, a vortex ring structure is formed distal to the left atrioventricular valve (LAVV). Vortex structures contribute to efficient flow organization. We aimed to investigate whether LAVV abnormality in patients with a corrected atrioventricular septal defect (AVSD) has an impact on vortex ring formation. METHODS: Whole-heart 4D flow MRI was performed in 32 patients (age: 26 ± 12 years), and 30 healthy subjects (age: 25 ± 14 years). Vortex ring cores were detected at peak early (E-peak) and peak late filling (A-peak). When present, the 3-dimensional position and orientation of the vortex ring was defined, and the circularity index was calculated. Through-plane flow over the LAVV, and the vortex formation time (VFT), were quantified to analyze the relationship of vortex flow with the inflow jet. RESULTS: Absence of a vortex ring during E-peak (healthy subjects 0%, vs patients 19%; P = .015), and A-peak (healthy subjects 10% vs patients 44%; P = .008) was more frequent in patients. In 4 patients, this was accompanied by a high VFT (5.1-7.8 vs 2.4 ± 0.6 in healthy subjects), and in another 2 patients with abnormal valve anatomy. In patients compared with controls, the vortex cores had a more-anterior and apical position, closer to the ventricular wall, with a more-elliptical shape and oblique orientation. The shape of the vortex core closely resembled the valve shape, and its orientation was related to the LV inflow direction. CONCLUSIONS: This study quantitatively shows the influence of abnormal LAVV and LV inflow on 3D vortex ring formation during LV inflow in patients with corrected AVSD, compared with healthy subjects.

Disturbed Intracardiac Flow Organization After Atrioventricular Septal Defect Correction as Assessed With 4D Flow Magnetic Resonance Imaging and Quantitative Particle Tracing.

OBJECTIVES: Four-dimensional (3 spatial directions and time) velocity-encoded flow magnetic resonance imaging with quantitative particle tracing analysis allows assessment of left ventricular (LV) blood flow organization. Corrected atrioventricular septal defect (AVSD) patients have an abnormal left atrioventricular valve shape. We aimed to analyze flow organization in corrected AVSD patients and healthy controls. METHODS: A total of 32 patients (age, 25 ± 14 years), 21 after partial AVSD correction and 11 after complete/intermediate AVSD correction, and 30 healthy volunteers (26 ± 12 years) underwent whole-heart four-dimensional velocity-encoded flow magnetic resonance imaging. Particle tracing in the 16-segment LV cavity model was used to quantitatively evaluate blood flow organization discriminating multiple components. RESULTS: Patients showed a smaller percentage of direct flow compared with controls (30% ± 9% vs 44% ± 11%; P < 0.001). In patients, more inflow was observed in the basal inferior segment (22% ± 11% vs controls, 17% ± 5%; P = 0.005), with less direct but more retained inflow (ie, part of inflow that is not ejected from LV in subsequent systole). In patients, more inflow reached the midventricular level (68% ± 13% vs controls, 58% ± 9%; P < 0.001), most notably as retained inflow in the lateral segments. Subsequently, in patients, more (mostly retained) inflow reached the apex (23% ± 13% vs 14% ± 7%; P < 0.001), which correlated with early peak filling velocity (r = 0.637, P < 0.001). Patients with a corrected complete or intermediate AVSD presented with less direct flow (24% ± 8% vs 33% ± 8%; P = 0.003) and more apical inflow (30% ± 14% vs 18% ± 12%; P = 0.014) compared with a corrected partial AVSD. CONCLUSION: Multicomponent particle tracing combined with 16-segment analysis quantitatively demonstrated altered LV flow organization after AVSD correction, with less direct and more retained inflow in apical and lateral LV cavity segments, which may contribute to decreased cardiac pumping efficiency.

High-temporal velocity-encoded MRI for the assessment of left ventricular inflow propagation velocity: Comparison with color M-mode echocardiography.

PURPOSE: To develop an alternative method for Vp-assessment using high-temporal velocity-encoded magnetic resonance imaging (VE-MRI). Left ventricular (LV) inflow propagation velocity (Vp) is considered a useful parameter in the complex assessment of LV diastolic function and is measured by Color M-mode echocardiography. MATERIALS AND METHODS: A total of 43 patients diagnosed with ischemic heart failure (61 ± 11 years) and 22 healthy volunteers (29 ± 13 years) underwent Color M-mode echocardiography and VE-MRI to assess the inflow velocity through the mitral valve (mean interexamination time 14 days). Temporal resolution of VE-MRI was 10.8-11.8 msec. Local LV inflow velocity was sampled along a 4-cm line starting from the tip of the mitral leaflets and for consecutive sample points the point-in-time was assessed when local velocity exceeded 30 cm/s. From the position-time relation, Vp was calculated by both the difference quotient (Vp-MRI-DQ) as well as from linear regression (Vp-MRI-LR). RESULTS: Good correlation was found between Vp-echo and both Vp-MRI-DQ (r = 0.83, P < 0.001) and Vp-MRI-LR (r = 0.84, P < 0.001). Vp-MRI showed a significant but small underestimation as compared to Vp measured by echocardiography (Vp-MRI-DQ: 5.5 ± 16.2 cm/s, P = 0.008; Vp-MRI-LR: 9.9 ± 15.2 cm/s, P < 0.001). Applying age-related cutoff values for Vp to identify LV impaired relaxation, kappa-agreement with echocardiography was 0.72 (P < 0.001) for Vp-MRI-DQ and 0.69 (P < 0.001) for Vp-MRI-LR. CONCLUSION: High temporal VE-MRI represents a novel approach to assess Vp, showing good correlation with Color M-mode echocardiography. In healthy subjects and patients with ischemic heart failure, this new method demonstrated good agreement with echocardiography to identify LV impaired relaxation.

Characterization and quantification of dynamic eccentric regurgitation of the left atrioventricular valve after atrioventricular septal defect correction with 4D Flow cardiovascular magnetic resonance and retrospective valve tracking.

BACKGROUND: To characterize and directly quantify regurgitant jets of left atrioventricular valve (LAVV) in patients with corrected atrioventricular septal defect (AVSD) by four-dimensional (4D)Flow Cardiovascular Magnetic Resonance (CMR), streamline visualization and retrospective valve tracking. METHODS: Medical ethical committee approval and informed consent from all patients or their parents were obtained. In 32 corrected AVSD patients (age 26 ± 12 years), echocardiography and whole-heart 4DFlow CMR were performed. Using streamline visualization on 2- and 4-chamber views, the angle between regurgitation and annulus was followed throughout systole. On through-plane velocity-encoded images reformatted perpendicular to the regurgitation jet the cross-sectional jet circularity index was assessed and regurgitant volume and fraction were calculated. Correlation and agreement between different techniques was performed with Pearson's r and Spearman's rho correlation and Bland-Altman analysis. RESULTS: In 8 patients, multiple regurgitant jets over the LAVV were identified. Median variation in regurgitant jet angle within patients was 36°(IQR 18-64°) on the 2-chamber and 30°(IQR 20-40°) on the 4-chamber. Regurgitant jets had a circularity index of 0.61 ± 0.16. Quantification of the regurgitation volume was feasible with 4DFlow CMR with excellent correlation between LAVV effective forward flow and aortic flow (r = 0.97, p < 0.001) for internal validation and moderate correlation with planimetry derived regurgitant volume (r = 0.65, p < 0.001) and echocardiographic grading (rho = 0.51, p = 0.003). CONCLUSIONS: 4DFlow CMR with streamline visualization revealed multiple, dynamic and eccentric regurgitant jets with non-circular cross-sectional shape in patients after AVSD correction. 4DFlow with retrospective valve tracking allows direct and accurate quantification of the regurgitation of these complex jets.

Abnormal sinoatrial node development resulting from disturbed vascular endothelial growth factor signaling.

BACKGROUND: Sinus node dysfunction is frequently observed in patients with congenital heart disease (CHD). Variants in the Vascular Endothelial Growth Factor-A (VEGF) pathway are associated with CHD. In Vegf(120/120) mice, over-expressing VEGF120, a reduced sinoatrial node (SAN) volume was suggested. Aim of the study is to assess the effect of VEGF over-expression on SAN development and function. METHODS: Heart rate was measured in Vegf(120/120) and wildtype (WT) embryos during high frequency ultrasound studies at embryonic day (E)12.5, 14.5 and 17.5 and by optical mapping at E12.5. Morphology was studied with several antibodies. SAN volume estimations were performed, and qualitative-PCR was used to quantify expression of genes in SAN tissues of WT and Vegf(120/120) embryos. RESULTS: Heart rate was reduced in Vegf(120/120) compared with WT embryos during embryonic echocardiography (52 ± 17 versus 125 ± 31 beats per minute (bpm) at E12.5, p<0.001; 123 ± 37 vs 160 ± 29 bmp at E14.5, p=0.024; and 177 ± 30 vs 217 ± 34 bmp, at E17.5 p=0.017) and optical mapping (81 ± 5 vs 116 ± 8 bpm at E12.5; p=0.003). The SAN of mutant embryos was smaller and more vascularized, and showed increased expression of the fast conducting gap junction protein, Connexin43. CONCLUSIONS: Over-expression of VEGF120 results in reduced heart rate and a smaller, less compact and hypervascularized SAN with increased expression of Connexin43. This indicates that VEGF is necessary for normal SAN development and function.

Characterization and improved quantification of left ventricular inflow using streamline visualization with 4DFlow MRI in healthy controls and patients after atrioventricular septal defect correction.

PURPOSE: To evaluate trans-left atrioventricular valve (LAVV) blood flow and optimize left ventricular inflow quantification in healthy controls and patients after atrioventricular septal defect (AVSD) correction. MATERIALS AND METHODS: Twenty-five patients after AVSD correction and 25 controls underwent 4DFlow MRI. Using streamline visualization in four- and two-chamber views, inflow direction at early and late filling was defined at the annulus level and at the peak inflow velocity (PIV) level. Trans-LAVV flow volume and velocity were assessed from a static 2D-multiplanar-reformat (MPR), a 4D-MPR tracking LAVV annulus and a 4D-MPR tracking the PIV-level, angulated perpendicular to the inflow. RESULTS: In patients, on average 9° more laterally directed inflow was found at the PIV-level compared to controls. In controls, 4DFlow velocity mapping with LAVV annulus tracking resulted in lower absolute error with aortic flow (3 (1-8) mL) than with static 2D-MPR (7 (4-16) mL, P = 0.001). In patients, 4D-MPR tracking the PIV-level, resulted in lower absolute error with aortic flow (2 (1-4) mL) than with 4D-MPR LAVV annulus tracking (6 (2-10) mL, P = 0.003). CONCLUSION: Streamline visualization of 4DFlow MRI data revealed dynamic trans-LAVV inflow and more lateral flow after AVSD correction. Streamline visualization improved trans-LAVV flow quantification as the positioning and angulation of the measurement plane was optimized, allowing an accurate assessment of left ventricular inflow.

Morphogenesis and molecular considerations on congenital cardiac septal defects.

The primary unseptated heart tube undergoes extensive remodeling including septation at the atrial, atrioventricular, ventricular, and ventriculo-arterial level. Alignment and fusion of the septal components is required to ensure full septation of the heart. Deficiencies lead to septal defects at various levels. Addition of myocardium and mesenchymal tissues from the second heart field (SHF) to the primary heart tube, as well as a population of neural crest cells, provides the necessary cellular players. Surprisingly, the study of the molecular background of these defects does not show a great diversity of responsible transcription factors and downstream gene pathways. Epigenetic modulation and mutations high up in several transcription factor pathways (e.g. NODAL and GATA4) may lead to defects at all levels. Disturbance of modulating pathways, involving primarily the SHF-derived cell populations and the genes expressed therein, results at the arterial pole (e.g. TBX1) in a spectrum of ventricular septal defects located at the level of the outflow tract. At the venous pole (e.g. TBX5), it can explain a variety of atrial septal defects. The various defects can occur as isolated anomalies or within families. In this review developmental, morphological, genetic, as well as epigenetic aspects of septal defects are discussed.

Vortex flow during early and late left ventricular filling in normal subjects: quantitative characterization using retrospectively-gated 4D flow cardiovascular magnetic resonance and three-dimensional vortex core analysis.

BACKGROUND: LV diastolic vortex formation has been suggested to critically contribute to efficient blood pumping function, while altered vortex formation has been associated with LV pathologies. Therefore, quantitative characterization of vortex flow might provide a novel objective tool for evaluating LV function. The objectives of this study were 1) assess feasibility of vortex flow analysis during both early and late diastolic filling in vivo in normal subjects using 4D Flow cardiovascular magnetic resonance (CMR) with retrospective cardiac gating and 3D vortex core analysis 2) establish normal quantitative parameters characterizing 3D LV vortex flow during both early and late ventricular filling in normal subjects. METHODS: With full ethical approval, twenty-four healthy volunteers (mean age: 20±10 years) underwent whole-heart 4D Flow CMR. The Lambda2-method was used to extract 3D LV vortex ring cores from the blood flow velocity field during early (E) and late (A) diastolic filling. The 3D location of the center of vortex ring core was characterized using cylindrical cardiac coordinates (Circumferential, Longitudinal (L), Radial (R)). Comparison between E and A filling was done with a paired T-test. The orientation of the vortex ring core was measured and the ring shape was quantified by the circularity index (CI). Finally, the Spearman's correlation between the shapes of mitral inflow pattern and formed vortex ring cores was tested. RESULTS: Distinct E- and A-vortex ring cores were observed with centers of A-vortex rings significantly closer to the mitral valve annulus (E-vortex L=0.19±0.04 versus A-vortex L=0.15±0.05; p=0.0001), closer to the ventricle's long-axis (E-vortex: R=0.27±0.07, A-vortex: R=0.20±0.09, p=0.048) and more elliptical in shape (E-vortex: CI=0.79±0.09, A-vortex: CI=0.57±0.06; <0.001) compared to E-vortex. The circumferential location and orientation relative to LV long-axis for both E- and A-vortex ring cores were similar. Good to strong correlation was found between vortex shape and mitral inflow shape through both the annulus (r=0.66) and leaflet tips (r=0.83). CONCLUSIONS: Quantitative characterization and comparison of 3D vortex rings in LV inflow during both early and late diastolic phases is feasible in normal subjects using retrospectively-gated 4D Flow CMR, with distinct differences between early and late diastolic vortex rings.

Imaging the first trimester heart: ultrasound correlation with morphology.

First trimester sonography is a widely used technique to examine the foetus early in pregnancy. The desire to recognise complex anatomy already in early developmental stages stresses the need for a thorough knowledge of basic developmental processes as well as recognition of cardiac compartments based on their morphology. In this paper, we describe the possibilities and limitations of sonographic assessment of the foetal heart between 10 and 14 weeks of gestation and correlate this to morphology. Examples of the most commonly detected congenital anomalies are atrioventricular septal defects, transposition of the great arteries, and hypoplastic left heart, which are shown in this paper.

Echocardiographic assessment of embryonic and fetal mouse heart development: a focus on haemodynamics and morphology.

BACKGROUND: Heart development is a complex process, and abnormal development may result in congenital heart disease (CHD). Currently, studies on animal models mainly focus on cardiac morphology and the availability of hemodynamic data, especially of the right heart half, is limited. Here we aimed to assess the morphological and hemodynamic parameters of normal developing mouse embryos/fetuses by using a high-frequency ultrasound system. METHODS: A timed breeding program was initiated with a WT mouse line (Swiss/129Sv background). All recordings were performed transabdominally, in isoflurane sedated pregnant mice, in hearts of sequential developmental stages: 12.5, 14.5, and 17.5 days after conception (n = 105). RESULTS: Along development the heart rate increased significantly from 125 ± 9.5 to 219 ± 8.3 beats per minute. Reliable flow measurements could be performed across the developing mitral and tricuspid valves and outflow tract. M-mode measurements could be obtained of all cardiac compartments. An overall increase of cardiac systolic and diastolic function with embryonic/fetal development was observed. CONCLUSION: High-frequency echocardiography is a promising and useful imaging modality for structural and hemodynamic analysis of embryonic/fetal mouse hearts.

Cardiovascular function and flow by 4-dimensional magnetic resonance imaging techniques: new applications.

Acquisition techniques related to 4-dimensional (4D) flow magnetic resonance imaging (MRI) improved rapidly over the last 3 decades. Most importantly, a major improvement was the acceleration of the acquisition, which resulted in a clinically feasible scan duration and led to more comprehensive use of 4D flow MRI in clinical research. This resulted in several new applications of 4D flow MRI for the evaluation of various physiological and pathologic cardiovascular flow patterns. Visualization tools aim at displaying the direction and magnitude of blood flow velocity from 4D flow data, by using for instance a vector glyph or streamline representation or by constructing pathlines from particle tracing. Such tools are applied to provide insight in the temporal distribution of the 3D flow velocity and enable the quantification of hemodynamic markers. These hemodynamic markers play an important role in the quantitation of abnormalities in cardiovascular blood flow patterns and the characterization of vascular and myocardial remodelling, which can possibly be used to predict pathology such as heart failure, aortic dissection, or aneurysm or thrombus formation. This review focuses on the clinical use of 4D flow MRI and presents an overview of new applications of visualization and quantification tools to describe physiological and pathologic cardiovascular blood flow.

Aortopexy as treatment for tracheo-bronchomalacia in children: an 18-year single-center experience.

OBJECTIVES: To define the factors influencing the outcome of aortopexy as management of tracheo-bronchomalacia. DESIGN: A retrospective, single-center, observational, cohort study. SETTINGS: Surgical services in a tertiary care hospital. PATIENTS: One hundred five children who underwent an aortopexy for tracheo-bronchomalacia between 1990 and 2008. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Comorbidity (categorized into three groups), surgical approach, and location of malacia were reviewed and analyzed in relation to mortality, need for a second intervention, complications, time to extubation after surgery, intensive care unit stay, and clinical improvement. Median age at surgery was 24 wks (1 wk-541 wks). Two surgical approaches were used: median sternotomy (n = 46) and left anterior parasternal (n = 59). Long-term (>2 yrs) follow-up was available for 73 patients (median = 7.0 yrs [2-18 yrs]); 73% were asymptomatic, 18% had minor symptoms, and 9% needed either ventilation or tracheostomy. The overall mortality rate was 9%, of which one-third was airway-related. Multivariable analysis revealed that major comorbidities were a significant risk factor both for mortality and the need for further procedures (re-do surgery, tracheostomy, internal stents) in contrast to surgical approach and involvement of the bronchus. Intensive care unit stay and days of ventilation after surgery were also significantly higher in patients with major comorbidities. CONCLUSIONS: Aortopexy proved to be an effective treatment for most cases of tracheo-bronchomalacia, but major comorbidity was associated with an adverse outcome. Our data suggest that aortopexy should be considered in most cases of severe tracheo-bronchomalacia.

Aortopexy for persistent tracheal obstruction after double aortic arch repair.

Persistent respiratory symptoms often occur after double aortic arch (DAA) repair but rarely require a second operation. We report 4 children with severe respiratory problems (failure to extubate, 2; severe respiratory distress, 2) caused by severe tracheomalacia and tracheal compression after DAA repair, treated by anterior aortopexy. Aortopexy proved effective and safe in improving symptoms and provides a simple treatment option for children with severe malacia or tracheal compression after DAA repair.

Long segment congenital tracheal stenosis in twins successfully treated by slide tracheoplasty.

Long segment congenital tracheal stenosis (LSCTS), associated with complete tracheal rings, is a rare condition, difficult to manage and historically associated with high mortality rate. We report two pairs of identical twins all affected by LSCTS successfully treated by sliding tracheoplasty. All had severe respiratory distress. Three infants had left pulmonary artery (LPA) sling and one intra-cardiac malformation. Slide tracheoplasty was done under cardiopulmonary bypass, and cardiovascular malformations were corrected at the same time. One child needed plication of paralyzed right hemi-diaphragm and another distal tracheal Palmaz stent insertion due severe tracheobronchomalacia. All children are doing well during 6 months follow-up. Slide tracheoplasty seems to produce the same good early results in twins as for singletons with LSCTS.