Background: Pulmonary vasodilator therapy in Fontan patients can improve exercise tolerance. We aimed to assess the potential for non-invasive testing of acute vasodilator response using four... Show moreBackground: Pulmonary vasodilator therapy in Fontan patients can improve exercise tolerance. We aimed to assess the potential for non-invasive testing of acute vasodilator response using four-dimensional (D) flow MRI during oxygen inhalation. Materials and Methods: Six patients with well-functioning Fontan circulations were prospectively recruited and underwent cardiac MRI. Ventricular anatomical imaging and 4D Flow MRI were acquired at baseline and during inhalation of oxygen. Data were compared with six age-matched healthy volunteers with 4D Flow MRI scans acquired at baseline. Results: All six patients tolerated the MRI scan well. The dominant ventricle had a left ventricular morphology in all cases. On 4D Flow MRI assessment, two patients (Patients 2 and 6) showed improved cardiac filling with improved preload during oxygen administration, increased mitral inflow, increased maximum E-wave kinetic energy, and decreased systolic peak kinetic energy. Patient 1 showed improved preload only. Patient 5 showed no change, and patient 3 had equivocal results. Patient 4, however, showed a decrease in preload and cardiac filling/function with oxygen. Discussion: Using oxygen as a pulmonary vasodilator to assess increased pulmonary venous return as a marker for positive acute vasodilator response would provide pre-treatment assessment in a more physiological state - the awake patient. This proof-of-concept study showed that it is well tolerated and has shown changes in some stable patients with a Fontan circulation. Show less
Identification of flow patterns within the heart has long been recognized as a potential contribution to the understanding of physiological and pathophysiological processes of cardiovascular... Show moreIdentification of flow patterns within the heart has long been recognized as a potential contribution to the understanding of physiological and pathophysiological processes of cardiovascular diseases. Although the pulsatile flow itself is multi-dimensional and multi-directional, current available non-invasive imaging modalities in clinical practice provide calculation of flow in only 1-direction and lack 3-dimensional volumetric velocity information. Four-dimensional flow cardiovascular magnetic resonance imaging (4D flow CMR) has emerged as a novel tool that enables comprehensive and critical assessment of flow through encoding velocity in all 3 directions in a volume of interest resolved over time. Following technical developments, 4D flow CMR is not only capable of visualization and quantification of conventional flow parameters such as mean/peak velocity and stroke volume but also provides new hemodynamic parameters such as kinetic energy. As a result, 4D flow CMR is being extensively exploited in clinical research aiming to improve understanding of the impact of cardiovascular disease on flow and vice versa. Of note, the analysis of 4D flow data is still complex and accurate analysis tools that deliver comparable quantification of 4D flow values are a necessity for a more widespread adoption in clinic. In this article, the acquisition and analysis processes are summarized and clinical applications of 4D flow CMR on the heart including conventional and novel hemodynamic parameters are discussed. Finally, clinical potential of other emerging intra-cardiac 4D flow imaging modalities is explored and a near-future perspective on 4D flow CMR is provided. Show less
The purpose of this study was to directly assess (patho)physiology of intraventricular hemodynamic interplay between fourdimensional flow cardiovascular magnetic resonance imaging (4D Flow MRI)... Show moreThe purpose of this study was to directly assess (patho)physiology of intraventricular hemodynamic interplay between fourdimensional flow cardiovascular magnetic resonance imaging (4D Flow MRI)-derived vorticity with kinetic energy (KE) and viscous energy loss (EL) over the cardiac cycle and their association to ejection fraction (EF) and stroke volume (SV). Fifteen healthy subjects and thirty Fontan patients underwent whole heart 4D Flow MRI. Ventricular vorticity, KE, and EL were computed over systole (vorticity_volavg systole, KEavg systole, and ELavg systole) and diastole (vorticity_volavg diastole, KEavg diastole, and ELavg diastole). The association between vorticity_vol and KE and EL was tested by Spearman correlation. Fontan patients were grouped to normal and impaired EF groups. A significant correlation was found between SV and vorticity in healthy subjects (systolic: r = 0.84, P < 0.001; diastolic: r = 0.81, P < 0.001) and in Fontan patients (systolic: r = 0.61, P < 0.001; diastolic: r = 0.54, P = 0.002). Healthy subjects showed positive correlation between vorticity_vol versus KE (systole: r = 0.96, P < 0.001; diastole: r = 0.90, P < 0.001) and EL (systole: r = 0.85, P < 0.001; diastole: r = 0.84, P < 0.001). Fontan patients showed significantly elevated vorticity_vol compared with healthy subjects (vorticity_volavg systole: 3.1 [2.3-3.9] vs. 1.7 [1.3-2.4] L/s, P < 0.001; vorticity_volavg diastole: 3.1 [2.03.7] vs. 2.1 [1.6-2.8] L/s, P = 0.002). This elevated vorticity in Fontan patients showed strong association with KE (systole: r = 0.91, P < 0.001; diastole: r = 0.85, P < 0.001) and EL (systole: r = 0.82, P < 0.001; diastole: r = 0.89, P < 0.001). Fontan patients with normal EF showed significantly higher vorticity_volavg systole and ELavg systole, but significantly decreased KE avg diastole, in the presence of normal SV, compared with healthy subjects. Healthy subjects show strong physiological hemodynamic interplay between vorticity with KE and EL. Fontan patients demonstrate a pathophysiological hemodynamic interplay characterized by correlation of elevated vorticity with KE and EL in the presence of maintained normal stroke volume. Altered vorticity and energetic hemodynamics are found in the presence of normal EF in Fontan patients.NEW & NOTEWORTHY Physiologic intraventricular hemodynamic interplay/coupling is present in the healthy left ventricle between vorticity versus viscous energy loss and kinetic energy from four-dimensional flow cardiovascular magnetic resonance imaging (4D Flow MRI). Conversely, Fontan patients present compensatory pathophysiologic hemodynamic coupling by an increase in intraventricular vorticity that positively correlates to viscous energy loss and kinetic energy levels in the presence of maintained normal stroke volume. Altered vorticity and energetics are found in the presence of normal ejection fraction in Fontan patients. Show less
Kamphuis, V.P.; Elbaz, M.S.M.; Boogaard, P.J. van den; Kroft, L.J.M.; Geest, R.J. van der; Roos, A. de; ... ; Roest, A.A.W. 2019
Aims To non-invasively assess intraventricular viscous energy loss (EL) and proportionality to kinetic energy (KE) in Fontan patients using 4D flow magnetic resonance imaging (MRI) and compare to... Show moreAims To non-invasively assess intraventricular viscous energy loss (EL) and proportionality to kinetic energy (KE) in Fontan patients using 4D flow magnetic resonance imaging (MRI) and compare to healthy controls.Methods and results Thirty Fontan patients and 15 controls underwent 4D flow MRI. Ventricular EL was computed and normalized by end-diastolic volume (EDV). EL over the cardiac cycle (ELcycle) relative to the average kinetic energy (KEcycle) was quantified using a dimensionless index, ELindex (ELcycle/KEcycle). EL was significantly elevated in Fontan patients compared to controls (ELcycle/EDV: 3.7 vs. 2.6J/m(3), P=0.001). Fontan patients with inflow of blood entering a ventricle, which leaves that ventricle through a ventricular septal defect to the aorta, defined as discordant inflow-to-outflow showed significantly higher EL compared to patients with inflow of blood into the same ventricle from which the blood is ejected into the aorta, defined as concordant inflow-to-outflow (ELcycle/EDV: 6.8 vs. 3.2J/m(3), P=0.001). EL was not significantly different in Fontan patients with a systemic left vs. a systemic right ventricle (ELcycle/EDV: 3.5 vs. 3.6J/m(3), P=0.91). ELindex was significantly elevated in Fontan patients compared to controls (ELindex: 0.4 vs. 0.2, P<0.001). Highest ELindex was found in Fontan patients with discordant inflow-to-outflow compared to concordant inflow-to-outflow (0.5 vs. 0.3, P=0.01).Conclusion Fontan patients show disproportionate intraventricular EL relative to KE. Intraventricular EL is elevated in these patients compared to healthy controls, and highest EL is found in patients with discordant inflow-to-outflow. Show less
