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      Mechanical dyssynchrony alters left ventricular flow energetics in failing hearts with LBBB: a 4D flow CMR pilot study

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          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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          The online version of this article (doi:10.1007/s10554-017-1261-5) contains supplementary material, which is available to authorized users.

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          Asymmetric redirection of flow through the heart.

          Through cardiac looping during embryonic development, paths of flow through the mature heart have direction changes and asymmetries whose topology and functional significance remain relatively unexplored. Here we show, using magnetic resonance velocity mapping, the asymmetric redirection of streaming blood in atrial and ventricular cavities of the adult human heart, with sinuous, chirally asymmetric paths of flow through the whole. On the basis of mapped flow fields and drawings that illustrate spatial relations between flow paths, we propose that asymmetries and curvatures of the looped heart have potential fluidic and dynamic advantages. Patterns of atrial filling seem to be asymmetric in a manner that allows the momentum of inflowing streams to be redirected towards atrio-ventricular valves, and the change in direction at ventricular level is such that recoil away from ejected blood is in a direction that can enhance rather than inhibit ventriculo-atrial coupling. Chiral asymmetry might help to minimize dissipative interaction between entering, recirculating and outflowing streams. These factors might combine to allow a reciprocating, sling-like, 'morphodynamic' mode of action to come into effect when heart rate and output increase during exercise.
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            AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society: endorsed by the International Society for Computerized Electrocardiology.

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              Significance of QRS complex duration in patients with heart failure.

              Prolongation of QRS (> or =120 ms) occurs in 14% to 47% of heart failure (HF) patients. Left bundle branch block is far more common than right bundle branch block. Left-sided intraventricular conduction delay is associated with more advanced myocardial disease, worse left ventricular (LV) function, poorer prognosis, and a higher all-cause mortality rate compared with narrow QRS complex. It also predisposes heart failure patients to an increased risk of ventricular tachyarrhythmias, but the incidence of cardiac or sudden death remains unclear because of limited observations. A progressive increase in QRS duration worsens the prognosis. No electrocardiographic measure is specific enough to provide subgroup risk categorization for excluding or selecting HF patients for prophylactic implantable cardioverter-defibrillator (ICD) therapy. In ICD patients with HF, a wide underlying QRS complex more than doubles the cardiac mortality compared with a narrow QRS complex. There is a high incidence of an elevated defibrillation threshold at the time of ICD implantation in patients with QRS > or =200 ms. Mechanical LV dyssynchrony potentially treatable by ventricular resynchronization occurs in about 70% of HF patients with left-sided intraventricular conduction delay, a fact that would explain the lack of therapeutic response in about 30% of patients subjected to ventricular resynchronization according to standard criteria relying on QRS duration. The duration of the basal QRS complex does not reliably predict the clinical response to ventricular resynchronization, and QRS narrowing after cardiac resynchronization therapy does not correlate with hemodynamic and clinical improvement. Mechanical LV dyssynchrony is best shown by evolving echocardiographic techniques (predominantly tissue Doppler imaging) currently in the process of standardization.
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                Author and article information

                Contributors
                +46 101030000 , jakubzajac@gmail.com
                Journal
                Int J Cardiovasc Imaging
                Int J Cardiovasc Imaging
                The International Journal of Cardiovascular Imaging
                Springer Netherlands (Dordrecht )
                1569-5794
                1875-8312
                2 November 2017
                2 November 2017
                2018
                : 34
                : 4
                : 587-596
                Affiliations
                [1 ]ISNI 0000 0001 2162 9922, GRID grid.5640.7, Division of Cardiovascular Medicine, Department of Medical and Health Sciences, , Linköping University, ; 581 85 Linköping, Sweden
                [2 ]ISNI 0000 0001 2162 9922, GRID grid.5640.7, Center for Medical Image Science and Visualization (CMIV), , Linköping University, ; Linköping, Sweden
                [3 ]ISNI 0000 0001 2162 9922, GRID grid.5640.7, Department of Clinical Physiology, Department of Medical and Health Sciences, , Linköping University, ; Linköping, Sweden
                [4 ]ISNI 0000 0001 2162 9922, GRID grid.5640.7, Department of Cardiology, Department of Medical and Health Sciences, , Linköping University, ; Linköping, Sweden
                [5 ]ISNI 0000 0001 2297 6811, GRID grid.266102.1, Department of Medicine, , University of California San Francisco, ; San Francisco, CA USA
                Article
                1261
                10.1007/s10554-017-1261-5
                5859696
                29098524
                8b450437-a908-4a87-a10d-4ff1995f1d48
                © The Author(s) 2017

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

                History
                : 5 July 2017
                : 19 October 2017
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/501100003793, Hjärt-Lungfonden;
                Award ID: 20140398
                Award Recipient :
                Funded by: Vetenskapsrådet (SE)
                Award ID: 621-2014-6191
                Award Recipient :
                Funded by: European Research Council (BE)
                Award ID: 310612
                Award Recipient :
                Categories
                Original Paper
                Custom metadata
                © Springer Science+Business Media B.V., part of Springer Nature 2018

                Cardiovascular Medicine
                heart failure,left bundle branch block,left ventricular mechanical dyssynchrony,4d flow cmr

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