| 1. |
- Eriksson, Jonatan, et al.
(författare)
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Left ventricular hemodynamic forces as a marker of mechanical dyssynchrony in heart failure patients with left bundle branch block
- 2017
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Left bundle branch block (LBBB) causes left ventricular (LV) dyssynchrony which is often associated with heart failure. A significant proportion of heart failure patients do not demonstrate clinical improvement despite cardiac resynchronization therapy (CRT). How LBBB-related effects on LV diastolic function may contribute to those therapeutic failures has not been clarified. We hypothesized that LV hemodynamic forces calculated from 4D flow MRI could serve as a marker of diastolic mechanical dyssynchrony in LBBB hearts. MRI data were acquired in heart failure patients with LBBB or matched patients without LBBB. LV pressure gradients were calculated from the Navier-Stokes equations. Integration of the pressure gradients over the LV volume rendered the hemodynamic forces. The findings demonstrate that the LV filling forces are more orthogonal to the main LV flow direction in heart failure patients with LBBB compared to those without LBBB during early but not late diastole. The greater the conduction abnormality the greater the discordance of LV filling force with the predominant LV flow direction (r(2) = 0.49). Such unique flow-specific measures of mechanical dyssynchrony may serve as an additional tool for considering the risks imposed by conduction abnormalities in heart failure patients and prove to be useful in predicting response to CRT.
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| 2. |
- Fredriksson, Alexandru G, et al.
(författare)
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4-D blood flow in the human right ventricle
- 2011
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Ingår i: American Journal of Physiology. Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 301:6, s. H2344-H2350
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Tidskriftsartikel (refereegranskat)abstract
- Right ventricular (RV) function is a powerful prognostic indicator in many forms of heart disease, but its assessment remains challenging and inexact. RV dysfunction may alter the normal patterns of RV blood flow, but those patterns have been incompletely characterized. We hypothesized that, based on anatomic differences, the proportions and energetics of RV flow components would differ from those identified in the left ventricle (LV) and that the portion of the RV inflow passing directly to outflow (Direct Flow) would be prepared for effective systolic ejection as a result of preserved kinetic energy (KE) compared with other RV flow components. Three-dimensional, time-resolved phase-contrast velocity, and balanced steady-state free-precession morphological data were acquired in 10 healthy subjects using MRI. A previously validated method was used to separate the RV and LV end-diastolic volumes into four flow components and measure their volume and KE over the cardiac cycle. The RV Direct Flow: 1) followed a smoothly curving route that did not extend into the apical region of the ventricle; 2) had a larger volume and possessed a larger presystolic KE (0.4 +/- 0.3 mJ) than the other flow components (P andlt; 0.001 and P andlt; 0.01, respectively); and 3) represented a larger part of the end-diastolic blood volume compared with the LV Direct Flow (P andlt; 0.01). These findings suggest that diastolic flow patterns distinct to the normal RV create favorable conditions for ensuing systolic ejection of the Direct Flow component. These flow-specific aspects of RV diastolic-systolic coupling provide novel perspectives on RV physiology and may add to the understanding of RV pathophysiology.
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| 3. |
- Zajac, Jakub
(författare)
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Assessment of Ventricular Function in Normal and Failing Hearts Using 4D Flow CMR
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heart failure is a common disorder and a major cause of illness and death in the population, creating an enormous health-care burden. It is a complex condition, representing the end-point of many cardiovascular diseases. In general heart failure progresses slowly over time and once it is diagnosed it has a poor prognosis which is comparable with that of many types of cancer.The heart has an ability to adapt in response to long lasting increases in hemodynamic demand; the heart conforms its shape and size in order to maintain adequate cardiac output. This process is called remodeling and can be triggered by pathologies such as hypertension or valvular disease. When the myocardial remodeling is maintained chronically it becomes maladaptive and is associated with an increased risk of heart failure.In many cases, heart failure is associated with left bundle branch block (LBBB). This electrical disturbance leads to dyssynchronous left ventricular (LV) contraction and relaxation which may contribute to cardiac dysfunction and ultimately heart failure. Mechanical dyssynchrony can be treated with cardiac resynchronization therapy (CRT). However, many heart failure patients do not demonstrate clinical improvement despite CRT.Blood flow plays an important role in the normal development of the fetal heart. However, flow-induced forces may also induce changes in the heart cells that could lead to pathological remodeling in the adult heart. Until recently, measurement tools have been inadequate in describing the complex three-dimensional and time-varying characteristics of blood flow within the beating heart.4D (3D + time) flow cardiovascular magnetic resonance (CMR) enables acquisition of three-dimensional, three-directional, time-resolved velocity data from which visualization and quantification of the blood flow patterns over a complete cardiac cycle can be performed. In this thesis, novel 4D Flow CMR based methods are used to study the intraventricular blood flow in healthy subjects and heart failure patients with and without ventricular dyssynchrony in order to gain new knowledge of the ventricular function.Different flow components were assessed in normal heart ventricles. It was found that inflowing blood that passes directly to outflow during the same heartbeat (the Direct Flow component) was larger and possessed more kinetic energy (KE) than other flow components. Diastolic flow through the normal heart appears to create favorable conditions for effective systolic ejection. This organized blood flow pattern within the normal LV is altered in heart failure patients and is associated with decreased preservation of KE which might be unfavorable for efficient LV ejection. Inefficient flow of blood through the heart may influence diastolic wall stress, and thus contribute to pathological myocardial remodeling.In dyssynchronous LVs of heart failure patients with LBBB, Direct Flow showed even more reduced preservation of KE compared to similarly remodeled LVs without LBBB. Furthermore, in LBBB patients, LV filling hemodynamic forces, acting on the myocardium, were more orthogonal to the main flow direction compared to patients without LBBB. Deviation of LV flow forces and reduction of KE preservation and may reflect impairment of LV diastolic function and less efficient ensuing ejection related to dyssynchrony in these failing ventricles.Blood flow patterns were also studied with respect to fluctuations of the velocity of the flow (turbulent flow) in normal and failing LVs. In failing hearts, turbulent kinetic energy (TKE) was higher during diastole than in healthy subjects. TKE is a cause of energy loss and can thus be seen as a measure of flow inefficiency.Elucidating the transit of multidimensional blood flow through the heart chambers is fundamental in understanding the physiology of the heart and to detect abnormalities in cardiac function. The 4D Flow CMR parameters presented in this thesis can be utilized to detect altered intracardiac blood flow and may be used as markers of deteriorating cardiac function, pathological remodeling and mechanical dyssynchrony in heart failure.
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| 4. |
- Zajac, Jakub, et al.
(författare)
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Mechanical dyssynchrony alters left ventricular flow energetics in failing hearts with LBBB : a 4D flow CMR pilot study.
- 2018
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Ingår i: The International Journal of Cardiovascular Imaging. - : Springer. - 1569-5794 .- 1875-8312 .- 1573-0743. ; 34:4, s. 587-596
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Tidskriftsartikel (refereegranskat)abstract
- The impact of left bundle branch block (LBBB) related mechanical dyssynchrony on left ventricular (LV) diastolic function remains unclear. 4D flow cardiovascular magnetic resonance (CMR) has provided reliable markers of LV dysfunction: reduced volume and kinetic energy (KE) of the portion of LV inflow which passes directly to outflow (Direct Flow) has been demonstrated in failing hearts compared to normal hearts. We sought to investigate the impact of mechanical dyssynchrony on diastolic function by comparing 4D flow in myopathic LVs with and without LBBB. CMR data were acquired at 3 T in 22 heart failure patients; 11 with LBBB and 11 without LBBB matched according to several demographic and clinical parameters. An established 4D flow analysis method was used to separate the LV end-diastolic (ED) volume into functional flow components based on the blood's timing and route through the heart cavities. While the Direct Flow volume was not different between the groups, the KE possessed at ED was lower in LBBB patients (P = 0.018). Direct Flow entering the LV during early diastolic filling possessed less KE at ED in LBBB patients compared to non-LBBB patients, whereas no intergroup difference was observed during late filling. Pre-systolic KE of LV Direct Flow was reduced in patients with LBBB compared to matched patients with normal conduction. These intriguing findings propose that 4D flow specific measures can serve as markers of LV mechanical dyssynchrony in heart failure patients, and could possibly be investigated as predictors of response to cardiac resynchronization therapy.
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