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1.
Comput Methods Biomech Biomed Engin ; 22(15): 1229-1238, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31437018

RESUMO

Vortex structures, as one of the most important features of cardiac flow, have a crucial impact on the left ventricle function and pathological conditions. These swirling flows are closely related to the presence of turbulence in left ventricle which is investigated in the current study. Using an extended model of the left heart, including a fluid-structure interaction (FSI) model of the mitral valve with a realistic geometry, the effect of using two numerical turbulent models, k-ε and Spalart-Allmaras (SA), on diastolic flow patterns is studied and compared with results from laminar flow model. As a result of the higher dissipation rate in turbulent models (k-ε and SA), vortices are larger and stronger in the laminar flow model. Comparing E/A ratio in the three models (Laminar, k-ε, and SA) with experimental data from healthy subjects, it is concluded that the results from k-ε model are more accurate.


Assuntos
Simulação por Computador , Circulação Coronária/fisiologia , Modelos Cardiovasculares , Função Ventricular/fisiologia , Velocidade do Fluxo Sanguíneo , Humanos , Valva Mitral/fisiologia , Análise Numérica Assistida por Computador , Pressão , Estresse Mecânico
2.
Artigo em Inglês | MEDLINE | ID: mdl-29993542

RESUMO

Echocardiography is widely used to provide critical left ventricular indices describing myocardial motion and blood inflow velocity. Tissue motion and blood flow are strongly connected and interdependent in the ventricle. During cardiac relaxation, rapid filling leads to the formation of a vortical blood flow pattern. In this paper, we introduce a high-frame-rate method to track vortex dynamics alongside myocardium motion, in a single heartbeat. Cardiac triplex imaging (B-mode + tissue Doppler + color Doppler) was obtained by insonating the left ventricle with diverging waves. We used coherent compounding with integrated motion compensation to obtain high-quality B-mode images. Tissue Doppler was retrieved and the septal and lateral velocities of the mitral annulus were deduced. A rate of ~80 triplex images/s was obtained. Vortex dynamics was analyzed by Doppler vortography. Blood vortex signature maps were used to track the vortex and compute core vorticities. The sequence was implemented in a Verasonics scanner with a 2.5-MHz phased array and tested in vivo in 12 healthy volunteers. Two main peaks appeared on the vorticity curves. These peaks were synchronized with the mitral inflow velocities with a small delay. We observed a relationship between the tissue and vortex waveforms, though also with a delay, which denoted the lag between the wall and the flow motion. Clinical diastolic indices combining basal and mitral inflow velocities (E/A ratio and E/ e' ratio) were determined and compared with those measured using a conventional ultrasound scanner; a good correlation was obtained ( r2 = 0.96 ). High-frame-rate Doppler echocardiography enabled us to retrieve time-resolved dynamics of the myocardium and vortex flow within the same cardiac cycle. Coupling wall-flow analysis could be of clinical relevance for early diagnosis of filling impairment.


Assuntos
Velocidade do Fluxo Sanguíneo/fisiologia , Ecocardiografia Doppler/métodos , Coração/diagnóstico por imagem , Coração/fisiologia , Interpretação de Imagem Assistida por Computador/métodos , Humanos , Valva Mitral/diagnóstico por imagem , Valva Mitral/fisiologia
3.
Ultrasound Obstet Gynecol ; 54(2): 225-231, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30251286

RESUMO

OBJECTIVE: Maternal hemodynamics in pregnancy is associated with fetal growth and birth weight, which in turn are associated with offspring cardiovascular disease later in life. The aim of this study was to quantify the extent to which birth weight is associated with cardiac structure and function in adolescence. METHODS: A subset of offspring (n = 1964; 55% female) of the Avon Longitudinal Study of Parents and Children were examined with echocardiography at a mean age of 17.7 (SD, 0.3) years. The associations of birth-weight Z-score for sex and gestational age with cardiac structure (assessed by relative wall thickness, left ventricular mass index (LVMI) and left atrial diameter index), systolic function (assessed by ejection fraction and left ventricular wall velocity) and diastolic function (assessed by early/late mitral inflow velocity (E/A) and early mitral inflow velocity/mitral annular early diastolic velocity (E/e')) were evaluated. Linear regression models were adjusted for several potential confounders, including maternal prepregnancy body mass index, age, level of education and smoking during pregnancy. RESULTS: Higher birth-weight Z-score was associated with lower E/A (mean difference, -0.024; 95% CI, -0.043 to -0.005) and E/e' (mean difference, -0.05; 95% CI, -0.10 to -0.001) and higher LVMI (mean difference, 0.38 g/m2.7 ; 95% CI, 0.09 to 0.67). There was no or inconsistent evidence of associations of birth-weight Z-score with relative wall thickness, left atrial diameter and measurements of systolic function. Further analyses suggested that the association between birth-weight Z-score and LVMI was driven mainly by an association observed in participants born small-for-gestational age and it did not persist when risk factors in adolescence were accounted for. CONCLUSIONS: Higher birth weight adjusted for sex and gestational age was associated with differences in measures of diastolic function in adolescence, but the observed associations were small. It remains to be determined the extent to which these associations translate into increased susceptibility to cardiovascular disease later in life. © 2018 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.


Assuntos
Peso ao Nascer/fisiologia , Ecocardiografia/métodos , Desenvolvimento Fetal/fisiologia , Ventrículos do Coração/diagnóstico por imagem , Adolescente , Fenômenos Fisiológicos Cardiovasculares , Diástole/fisiologia , Feminino , Retardo do Crescimento Fetal/diagnóstico por imagem , Retardo do Crescimento Fetal/epidemiologia , Retardo do Crescimento Fetal/fisiopatologia , Idade Gestacional , Hemodinâmica , Humanos , Estudos Longitudinais , Masculino , Valva Mitral/diagnóstico por imagem , Valva Mitral/fisiologia , Pais , Gravidez , Fatores de Risco , Fatores Sexuais , Volume Sistólico/fisiologia
4.
NMR Biomed ; 32(1): e4022, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30403426

RESUMO

Intracardiac blood flow patterns are affected by the morphology of cardiac structures and are set up to support the heart's pump function. Exercise affects contractility and chamber size as well as pre- and afterload. The aim of this study was to test the feasibility of four-dimensional phase contrast cardiovascular MRI under pharmacological stress and to study left ventricular blood flow under stress. 4D flow data were successfully acquired and analysed in 12 animals. During dobutamine infusion, heart rate and ejection fraction increased (82 ± 5 bpm versus 124 ± 3 bpm/46 ± 9% versus 65 ± 7%; both p < 0.05). A decrease in left ventricular end-diastolic volume (72 ± 14 mL versus 55 ± 8 mL; p < 0.05) and end-systolic volume (40 ± 15 mL versus 19 ± 6 mL; p < 0.05) but no change in stroke volume were observed. Trans-mitral diastolic inflow velocity increased under dobutamine and the trajectory of inflowing blood was directed towards the anterior septum with increased inflow angle (26 ± 5°) when compared with controls (15 ± 2°). In 5/6 animals undergoing stress diastolic vortices developed later, and in 3/6 animals vortices collapsed earlier with significantly smaller cross-sectional area during diastole. The vorticity index was not affected. Under the stress condition direct flow (% ejection within the next heart beat) increased from 43 ± 6% to 53 ± 8%. 4D MRI blood flow acquisition and analysis are feasible in pig hearts under dobutamine-induced stress. Flow patterns characterized by high blood velocity and antero-septally oriented diastolic inflow as well as decreased ventricular volumes are unfavourable conditions for diastolic vortex development under pharmacological stress, and cardiac output is increased by a rise in heart rate and directly ejected left ventricular blood volume.


Assuntos
Circulação Coronária/efeitos dos fármacos , Dobutamina/farmacologia , Ventrículos do Coração/efeitos dos fármacos , Descanso , Estresse Fisiológico/efeitos dos fármacos , Animais , Diástole/efeitos dos fármacos , Imagem Tridimensional , Valva Mitral/efeitos dos fármacos , Valva Mitral/fisiologia , Suínos
5.
Acta Biomater ; 85: 241-252, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30579963

RESUMO

BACKGROUND: Healthy function of tricuspid valve (TV) structures is essential to avoid tricuspid regurgitation (TR) and may significantly improve disease prognosis. Mitral valve (MV) structures have been extensively studied, but little is known about the TV and right-sided heart diseases. Therefore, clinical decisions and finite element (FE) simulations often rely heavily on MV data for TV applications, despite fundamentally different mechanical and physiological environments. METHOD/RESULTS: To bridge this gap, we performed a rigorous mechanical, morphological, and microstructural characterization of the MV and TV leaflets and chordae in a porcine model. Planar biaxial testing, uniaxial testing, second harmonic generation imaging and Verhoeff Van Gieson staining were performed. Morphological parameters, tissue moduli, extensibility, and anisotropy were quantified and compared. No major differences in leaflet mechanics or structure were found between TV and MV; chordal mechanics, morphology, and structure were found to compensate for anatomical and physiological loading differences between the valves. No differences in chordal mechanics were observed by insertion point within a leaflet; the septal tricuspid leaflet (STL) and posterior mitral leaflet (PML) did not have distinguishable strut chords, and the STL had the shortest chords. Within a valve, chords from septally-located leaflets were more extensible. MV chords were stiffer. CONCLUSIONS: This study presents the first rigorous comparative mechanical and structural dataset of MV and TV structures. Valve type and anatomical location may be stronger predictors of chordal mechanics. Chords from septally-located leaflets differ from each other and from their intravalvular counterparts; they merit special consideration in surgical and computational applications. STATEMENT OF SIGNIFICANCE: A better understanding of the tricuspid valve (TV) and its associated structures is important for making advancements towards the repair of tricuspid regurgitation. Mitral valve structures have been extensively studied, but little is known about the TV and right-sided heart diseases. Clinical decisions and computational simulations often rely heavily on MV data for TV applications, despite fundamentally different environments. We therefore performed a rigorous mechanical, morphological, and microstructural characterization of atrioventricular leaflets and chordae tendineae in a porcine model. Finding that valve type and anatomical location may be strong predictors of chordal mechanics, chords from septally-located leaflets differ from each other and from their intravalvular counterparts; they merit special consideration in surgical and computational applications.


Assuntos
Cordas Tendinosas/anatomia & histologia , Cordas Tendinosas/fisiologia , Valva Mitral/anatomia & histologia , Valva Mitral/fisiologia , Valva Tricúspide/anatomia & histologia , Valva Tricúspide/fisiologia , Animais , Fenômenos Biomecânicos , Modelos Biológicos , Suínos
6.
Orv Hetil ; 159(50): 2129-2135, 2018 Dec.
Artigo em Húngaro | MEDLINE | ID: mdl-30545264

RESUMO

INTRODUCTION: Morphology and function of the mitral annulus (MA) shows alterations in different valvular (for instance in mitral regurgitation) and non-valvular disorders (for instance in certain cardiomyopathies, cardiac amyloidosis). AIM: The aim of the present study was to examine the relationship between MA morphologic and functional properties and three-dimensional speckle-tracking echocardiography- (3DSTE) derived left ventricular (LV) ejection fraction (EF) in subjects with normal versus borderline LV-EF. METHOD: The present study comprised 146 volunteers (mean age: 32.0 ± 11.4 years; 74 males) in whom complete two-dimensional Doppler echocardiography was performed with a negative result extended with 3DSTE. The population was further divided into two groups according to their 3DSTE-derived LV-EF (borderline 50-54% versus ≥55%). RESULTS: In cases with borderline LV-EF, higher LV end-systolic LV volumes and lower LV longitudinal strain could be measured. All end-systolic and end-diastolic MA diameter, area and perimeter data proved to be higher in cases with borderline LV-EF. In these subjects, MA functional parameters proved to be lower as well. In contrast, LV-EF showed correlations neither with end-systolic and end-diastolic MA dimensions nor with MA functional parameters. CONCLUSIONS: 3DSTE-derived borderline LV-EF is associated with MA dilatation and functional impairment. Orv Hetil. 2018; 159(50): 2129-2135.


Assuntos
Ecocardiografia Doppler/métodos , Átrios do Coração/diagnóstico por imagem , Valva Mitral/diagnóstico por imagem , Adulto , Função Atrial/fisiologia , Ecocardiografia Tridimensional/métodos , Feminino , Ventrículos do Coração/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-Idade , Valva Mitral/fisiologia , Tamanho do Órgão
7.
J Vis Exp ; (141)2018 11 28.
Artigo em Inglês | MEDLINE | ID: mdl-30582607

RESUMO

Trans-mitral blood flow produces a three-dimensional rotational body of fluid, known as a vortex ring, that enhances the efficiency of left ventricular (LV) filling compared with a continuous linear jet. Vortex ring development is most often quantified with vortex formation time (VFT), a dimensionless parameter based on fluid ejection from a rigid tube. Our group is interested in factors that affect LV filling efficiency during cardiac surgery. In this report, we describe how to use standard two-dimensional (2D) and Doppler transesophageal echocardiography (TEE) to noninvasively derive the variables needed to calculate VFT. We calculate atrial filling fraction (ß) from velocity-time integrals of trans-mitral early LV filling and atrial systole blood flow velocity waveforms measured in the mid-esophageal four-chamber TEE view. Stroke volume (SV) is calculated as the product of the diameter of the LV outflow track measured in the mid-esophageal long axis TEE view and the velocity-time integral of blood flow through the outflow track determined in the deep transgastric view using pulse-wave Doppler. Finally, mitral valve diameter (D) is determined as the average of major and minor axis lengths measured in orthogonal mid-esophageal bicommissural and long axis imaging planes, respectively. VFT is then calculated as 4 × (1-ß) × SV/(πD3). We have used this technique to analyze VFT in several groups of patients with differing cardiac abnormalities. We discuss our application of this technique and its potential limitations and also review our results to date. Noninvasive measurement of VFT using TEE is straightforward in anesthetized patients undergoing cardiac surgery. The technique may allow cardiac anesthesiologists and surgeons to assess the impact of pathological conditions and surgical interventions on LV filling efficiency in real time.


Assuntos
Procedimentos Cirúrgicos Cardíacos/métodos , Ecocardiografia Doppler/métodos , Ecocardiografia Transesofagiana/métodos , Cardiopatias/diagnóstico por imagem , Cardiopatias/cirurgia , Monitorização Intraoperatória/métodos , Idoso , Velocidade do Fluxo Sanguíneo/fisiologia , Feminino , Frequência Cardíaca/fisiologia , Ventrículos do Coração/diagnóstico por imagem , Ventrículos do Coração/fisiopatologia , Hemodinâmica/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Valva Mitral/fisiologia , Volume Sistólico/fisiologia , Fatores de Tempo , Função Ventricular Esquerda/fisiologia
8.
J Heart Valve Dis ; 27(1): 32-37, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30560597

RESUMO

BACKGROUND: Currently, several different flexible mitral annuloplasty rings are available, and their efficacy for surgical repair of the mitral valve is, in general, considered equal. However, clinical experience indicates differences in remodeling capacity that have not yet been quantitatively assessed. The study aim was to compare the biomechanical properties of two commonly used flexible mitral annuloplasty rings in an acute pig model. METHODS: Medtronic Simulus Flex (n = 5) and Medtronic Duran AnCore (n = 7) flexible mitral annuloplasty rings were implanted in pigs (bodyweight 80 kg). The native mitral valve was used as a reference (n = 7). Mitral annular dynamics and dimensions were assessed using 11 sonomicrometry crystals placed in the mitral apparatus. A dedicated force transducer was used to detect deformational force transmission between the annuloplasty ring and the mitral annulus. RESULTS: Cyclic changes in mitral annular circumference and commissure-commissure distance were significantly reduced in the Simulus Flex group compared to the Duran AnCore group (p = 0.025 and p <0.01, respectively). In the Simulus Flex group, smaller deformational forces were recorded compared to the Duran AnCore group, but the difference was not statistically significant (p = 0.52 and p = 0.06 for the septal-lateral and the commissure-commissure force measurements, respectively). CONCLUSIONS: The Simulus Flex ring showed significantly more remodeling capacity than the Duran AnCore ring, but the latter ring preserved the natural dynamics of the mitral valve to a greater degree. Insights into these biomechanical differences may facilitate strategies for surgical reconstruction in degenerative mitral valve disease, especially in patients with excessive amounts of tissue and who are at risk of systolic anterior motion of the mitral valve.


Assuntos
Próteses Valvulares Cardíacas , Anuloplastia da Valva Mitral/instrumentação , Valva Mitral/cirurgia , Animais , Fenômenos Biomecânicos , Modelos Animais de Doenças , Valva Mitral/fisiologia , Desenho de Prótese , Suínos
9.
Gen Thorac Cardiovasc Surg ; 66(11): 648-652, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30046977

RESUMO

OBJECTIVES: This study aimed to elucidate the surgical outcome of aortic valve neocuspidization (AVNeo) in patients with aortic stenosis (AS). METHODS: From December 2010 to June 2017, we performed AVNeo for aortic valve pathologies in 144 patients. Of them, we evaluated 57 patients with AS who underwent AVNeo. Their mean age was 77.5 ± 8.8 years. Fifty-five patients had AS from degenerative changes, 1 from pericardium endocarditis, and 1 from prosthetic valve endocarditis. Forty patients had a tricuspid aortic valve, 1 had a unicuspid valve, 14 had a bicuspid valve, 1 had a quadricuspid valve, and 1 had postoperative aortic valve replacement (AVR). Preoperative echocardiography revealed an average peak pressure gradient of 89 ± 32.9 mmHg and a mean pressure gradient of 52 ± 18.8 mmHg. The surgical procedure complies with the 3 cuspid suturing to the aortic annulus with the glutaraldehyde-treated pericardium. RESULTS: There were no conversions to AVR. There were 2 noncardiac-related deaths owing to liver failure and sepsis. Postoperative echocardiography showed an average peak pressure gradient of 22 ± 10.7 mmHg 1 week after the procedure and 19.2 ± 9.7 mmHg 20 months after the procedure. Two patients underwent reoperation owing to infective endocarditis and recurrent aortic regurgitation. The mean follow-up period was 30.4 ± 20.8 months. The freedom from reoperation rates was 98.1 and 95.3% at 12 and 81 months of follow-up, respectively. CONCLUSIONS: AVNeo is suitable for patients with AS considering its early and mid-term outcomes. Verification of long-term outcomes and reliability is necessary.


Assuntos
Insuficiência da Valva Aórtica/cirurgia , Estenose da Valva Aórtica/cirurgia , Valva Aórtica/cirurgia , Pericárdio/transplante , Adulto , Idoso , Idoso de 80 Anos ou mais , Valva Aórtica/diagnóstico por imagem , Valva Aórtica/fisiopatologia , Insuficiência da Valva Aórtica/diagnóstico por imagem , Insuficiência da Valva Aórtica/fisiopatologia , Estenose da Valva Aórtica/diagnóstico por imagem , Estenose da Valva Aórtica/fisiopatologia , Procedimentos Cirúrgicos Cardíacos , Ecocardiografia , Feminino , Seguimentos , Próteses Valvulares Cardíacas , Hemodinâmica , Humanos , Masculino , Pessoa de Meia-Idade , Valva Mitral/fisiologia , Período Pós-Operatório , Reoperação , Reprodutibilidade dos Testes , Estudos Retrospectivos , Fatores de Tempo
10.
Indian Heart J ; 70(3): 368-372, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29961452

RESUMO

BACKGROUND: The mitral annulus (MA) is a crucial structure that is in constant motion throughout the cardiac cycle. The main purpose of this study was to determine if M-mode evaluation of the longitudinal motion of the MA could be useful to examine atrio-ventricular interactions. METHODS: Echocardiographic data obtained from 150 patients (mean age 56 ±â€¯16; 82 males) from the University of Cincinnati College of Medicine was evaluated to examine if any relationship exists between MA motion and measures of atrio-ventricular interactions. RESULTS: Even though left atrial size, left ventricular (LV) mass index, LV ejection fraction (LVEF) and degree of LV diastolic dysfunction (LVDD) were significant echocardiographic variables affecting MA motion; LVEF and the degree of LVDD were the main determinants of MA excursion during systole (MAPSE) and after atrial contraction (MAa). Our results confirm the surrogate value of MAPSE with regards to LVEF and also show that the extent of MA excursion during systole is the main determinant of MAa. The effect of LV diastolic function applies more strongly to MAPSE than to MAa. However, the maximal MAa amplitude varies in accordance to the type of LVDD. CONCLUSIONS: We have shown for the first time that M-mode interrogation of the MA longitudinal motion appears useful to assess atrio-ventricular interactions. Since LV systolic and diastolic functions are so closely related; additional studies are now required to examine how this longitudinal measure correlates with known circumferential rotational data obtained with other imaging modalities.


Assuntos
Função do Átrio Esquerdo/fisiologia , Átrios do Coração/diagnóstico por imagem , Ventrículos do Coração/diagnóstico por imagem , Valva Mitral/diagnóstico por imagem , Disfunção Ventricular Esquerda/fisiopatologia , Função Ventricular Esquerda/fisiologia , Diástole , Ecocardiografia Doppler em Cores , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Valva Mitral/fisiologia , Estudos Retrospectivos , Volume Sistólico , Sístole , Disfunção Ventricular Esquerda/diagnóstico
11.
PLoS One ; 13(5): e0196614, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29746603

RESUMO

BACKGROUND: Mitral annular plane systolic excursion (MAPSE) is an increasingly used echocardiography technique to assess left ventricular (LV) function. However, reproducibility and dependence on echocardiographic image quality for MAPSE in pediatric patients have not been studied to date. METHODS: We analyzed 284 transthoracic echocardiograms performed on consecutive normotensive children without structural heart disease (mean age 12.6±3.1 years, 50.4% female). B-mode and M-mode derived MAPSE measurements were performed and analyzed regarding inter- and intraobserver reliability and the influence of echocardiographic image quality. RESULTS: Overall, MAPSE measurements were highly reproducible with only minor bias. Both inter- and intraobserver reliability were significantly better for M-mode derived MAPSE (p<0.001). Echocardiographic image quality did not significantly influence M-mode MAPSE reproducibility (p>0.235). In contrast, B-mode lateral MAPSE was significantly better reproducible in optimal image quality (-0.07±1.04) when compared to suboptimal echocardiographic images (0.42±1.59, p<0.001). Moreover, poor quality images yielded significantly lower M-mode MAPSE values (14.3±2 mm) than near-optimal (15.2±1.9 mm, p<0.001) or optimal images (15.1±2.2 mm, p = 0.006). CONCLUSION: Echocardiographic image quality essentially has a negligible effect on MAPSE reproducibility and measurements. Consequently, MAPSE is a robust echocardiographic parameter with convincing reproducibility for the assessment of LV function in children-even in patients with substandard imaging conditions.


Assuntos
Valva Mitral/fisiologia , Sístole/fisiologia , Função Ventricular Esquerda/fisiologia , Adolescente , Criança , Ecocardiografia/métodos , Feminino , Humanos , Masculino , Reprodutibilidade dos Testes , Disfunção Ventricular Esquerda/fisiopatologia
12.
Sci Rep ; 8(1): 7625, 2018 05 16.
Artigo em Inglês | MEDLINE | ID: mdl-29769664

RESUMO

The olfactory bulb (OB) transforms sensory input into spatially and temporally organized patterns of activity in principal mitral (MC) and middle tufted (mTC) cells. Thus far, the mechanisms underlying odor representations in the OB have been mainly investigated in MCs. However, experimental findings suggest that MC and mTC may encode parallel and complementary odor representations. We have analyzed the functional roles of these pathways by using a morphologically and physiologically realistic three-dimensional model to explore the MC and mTC microcircuits in the glomerular layer and deeper plexiform layer. The model makes several predictions. MCs and mTCs are controlled by similar computations in the glomerular layer but are differentially modulated in deeper layers. The intrinsic properties of mTCs promote their synchronization through a common granule cell input. Finally, the MC and mTC pathways can be coordinated through the deep short-axon cells in providing input to the olfactory cortex. The results suggest how these mechanisms can dynamically select the functional network connectivity to create the overall output of the OB and promote the dynamic synchronization of glomerular units for any given odor stimulus.


Assuntos
Interneurônios/fisiologia , Valva Mitral/fisiologia , Odorantes , Bulbo Olfatório/fisiologia , Condutos Olfatórios/fisiologia , Olfato/fisiologia , Potenciais de Ação , Animais , Camundongos , Camundongos Endogâmicos C57BL , Bulbo Olfatório/citologia
13.
Sci Rep ; 8(1): 6187, 2018 04 18.
Artigo em Inglês | MEDLINE | ID: mdl-29670148

RESUMO

Highly resolved three-dimensional (3D) fluid structure interaction (FSI) simulation using patient-specific echocardiographic data can be a powerful tool for accurately and thoroughly elucidating the biomechanics of mitral valve (MV) function and left ventricular (LV) fluid dynamics. We developed and validated a strongly coupled FSI algorithm to fully characterize the LV flow field during diastolic MV opening under physiologic conditions. Our model revealed that distinct MV deformation and LV flow patterns developed during different diastolic stages. A vortex ring that strongly depended on MV deformation formed during early diastole. At peak E wave, the MV fully opened, with a local Reynolds number of ~5500, indicating that the flow was in the laminar-turbulent transitional regime. Our results  showed that during diastasis, the vortex structures caused the MV leaflets to converge, thus increasing mitral jet's velocity. The vortex ring became asymmetrical, with the vortex structures on the anterior side being larger than on the posterior side. During the late diastolic stages, the flow structures advected toward the LV outflow tract, enhancing fluid transport to the aorta. This 3D-FSI study demonstrated the importance of leaflet dynamics, their effect on the vortex ring, and their influence on MV function and fluid transport within the LV during diastole.


Assuntos
Diástole , Hemodinâmica , Valva Mitral/fisiologia , Modelos Cardiovasculares , Sístole , Algoritmos , Função Atrial , Velocidade do Fluxo Sanguíneo , Átrios do Coração/diagnóstico por imagem , Ventrículos do Coração/diagnóstico por imagem , Humanos , Imagem Tridimensional , Imagem por Ressonância Magnética/métodos , Valva Mitral/diagnóstico por imagem , Função Ventricular
14.
Eur Phys J E Soft Matter ; 41(2): 27, 2018 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-29488031

RESUMO

In this paper a computational model for the ventricular flow with a mitral valve and modeled chordae tendineae is presented. The results are compared with an analogous case in which the chordae are not included and their presence is replaced by kinematic boundary conditions. The problem is studied using direct numerical simulation of the Navier-Stokes equations, two-way coupled with a structural solver for the ventricle and mitral valve dynamics. An experimental validation of the model is performed by a comparison of the results with a companion dedicated experiment. It is found that the inclusion of the chordae tendineae makes the model self-consistent thus avoiding the use of ad hoc kinematic constraints to mimic their effect. In this way it is possible to simulate the correct system dynamics without user-defined parameters. More in detail, the results have shown that the mitral valve dynamics can be described also without chordae with the help of ad hoc kinematic constrains, whereas the changes produced in the intra-ventricular flow need the explicit consideration of the chordae in the model. On the other hand, the computational load increases owing to the presence of additional structures that, being thin filaments, are also demanding for the spatial resolution requirements. Since the presence of the chordae tendineae produces only specific differences in the overall flow structure, we conclude that their explicit modeling should be limited to those cases in which their presence is unavoidable.


Assuntos
Cordas Tendinosas/fisiologia , Valva Mitral/fisiologia , Modelos Cardiovasculares , Função Ventricular Esquerda , Fenômenos Biomecânicos , Débito Cardíaco , Humanos
15.
Int Heart J ; 59(1): 149-153, 2018 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-29332921

RESUMO

Tissue Doppler velocity during early diastole (e') is one of the most feasible and reproducible echocardiographic assessments to reflect active relaxation of the left ventricle. Although several reports have described the mechanisms of temporal diastolic dysfunction in the early neonatal period, factors influencing diastolic function have not been determined. The purpose of this study was to elucidate factors significantly influencing e' in the early neonatal period.A total of 179 consecutive normal neonates underwent echocardiographic studies performed at 0 days and 5-10 days after birth. The statistical relationships between e' and age, body weight, mean blood pressure, heart rate, shortening fraction of the left ventricle, peak systolic motion velocity (s'), early diastolic transmitral flow velocity over annulus velocity, Tei index, and diastolic wall strain (DWS) were analyzed.Between the 0 days and 5-10-days-after birth groups, significant differences were shown in mean blood pressure, shortening fraction of left ventricle, e', and Tei index. Age, body weight, mean blood pressure, s', and DWS showed significant correlations with e'. In multivariate regression analysis within these parameters, s' (ß = 0.6119, P < 0.0001) and DWS (ß = 0.1216, P = 0.0321) showed positive correlations with e'.Longitudinal systolic motion velocity and ventricular wall stiffness of the left ventricle influence diastolic relaxation in normal neonates. Age, body weight, and circumferential systolic function are not significant factors.


Assuntos
Velocidade do Fluxo Sanguíneo/fisiologia , Diagnóstico Precoce , Ventrículos do Coração/fisiopatologia , Disfunção Ventricular Esquerda/diagnóstico , Função Ventricular Esquerda/fisiologia , Diástole , Ecocardiografia Doppler , Estudos de Viabilidade , Feminino , Ventrículos do Coração/diagnóstico por imagem , Humanos , Recém-Nascido , Masculino , Valva Mitral/diagnóstico por imagem , Valva Mitral/fisiologia , Fluxo Sanguíneo Regional/fisiologia , Reprodutibilidade dos Testes , Sístole , Disfunção Ventricular Esquerda/fisiopatologia
16.
Clin Physiol Funct Imaging ; 38(3): 341-350, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-28402044

RESUMO

Pulsed Doppler (PW) and tissue Doppler imaging (TDI) measurements are part of every echocardiography examination for evaluation of left ventricular (LV) diastolic function and filling pressure. The purpose of this study was to summarize published data on normal values for PW and TDI measurements. A PubMed search was performed on the 10th of October 2016 to identify relevant articles. Studies were considered relevant if they included more than 200 healthy individuals. A total of 13 studies were identified. Of these, 13 studies with 7777 subjects reported PW measurement over the mitral valve, six studies with 4082 subjects reported PW measurement in the pulmonary vein and 10 studies with 5988 subjects reported TDI. We also report weighted mean values for 14 different variables. As expected, measurements varied with age. There were no major differences between men and women. In contrast, there was a large difference in reported values between studies, in corresponding age groups. This review therefore raises caution about relying on normal values from just one study.


Assuntos
Ecocardiografia Doppler de Pulso/normas , Ecocardiografia Doppler/normas , Valva Mitral/diagnóstico por imagem , Veias Pulmonares/diagnóstico por imagem , Função Ventricular Esquerda , Pressão Ventricular , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Valva Mitral/fisiologia , Valor Preditivo dos Testes , Veias Pulmonares/fisiologia , Valores de Referência , Reprodutibilidade dos Testes , Fatores Sexuais , Adulto Jovem
18.
Artigo em Inglês | MEDLINE | ID: mdl-28776326

RESUMO

Multiple studies have demonstrated that the pathological geometries unique to each patient can affect the durability of mitral valve (MV) repairs. While computational modeling of the MV is a promising approach to improve the surgical outcomes, the complex MV geometry precludes use of simplified models. Moreover, the lack of complete in vivo geometric information presents significant challenges in the development of patient-specific computational models. There is thus a need to determine the level of detail necessary for predictive MV models. To address this issue, we have developed a novel pipeline for building attribute-rich computational models of MV with varying fidelity directly from the in vitro imaging data. The approach combines high-resolution geometric information from loaded and unloaded states to achieve a high level of anatomic detail, followed by mapping and parametric embedding of tissue attributes to build a high-resolution, attribute-rich computational models. Subsequent lower resolution models were then developed and evaluated by comparing the displacements and surface strains to those extracted from the imaging data. We then identified the critical levels of fidelity for building predictive MV models in the dilated and repaired states. We demonstrated that a model with a feature size of about 5 mm and mesh size of about 1 mm was sufficient to predict the overall MV shape, stress, and strain distributions with high accuracy. However, we also noted that more detailed models were found to be needed to simulate microstructural events. We conclude that the developed pipeline enables sufficiently complex models for biomechanical simulations of MV in normal, dilated, repaired states.


Assuntos
Valva Mitral/fisiologia , Modelos Cardiovasculares , Animais , Simulação por Computador , Hemodinâmica , Interpretação de Imagem Assistida por Computador , Valva Mitral/diagnóstico por imagem , Ovinos , Microtomografia por Raio-X
19.
Heart ; 104(9): 725-731, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29175978

RESUMO

Constrictive pericarditis (CP) is a form of diastolic heart failure that arises because an inelastic pericardium inhibits cardiac filling. This disorder must be considered in the differential diagnosis for unexplained heart failure, particularly when the left ventricular ejection fraction is preserved. Risk factors for the development of CP include prior cardiac surgery and radiation therapy, but most cases are still deemed to be idiopathic. Making the diagnosis may be challenging and requires meticulous echocardiographic assessment, often supplemented by cross-sectional cardiac imaging and haemodynamic catheterisation. The key pathophysiological concepts, which serve as the basis for many of the diagnostic criteria, remain: (1) dissociation of intrathoracic and intracardiac pressures and (2) enhanced ventricular interaction. Complete surgical pericardiectomy is the only effective treatment for chronic CP. A subset of patients with subacute inflammatory CP, often identified by cardiac MRI, may respond to anti-inflammatory treatments.


Assuntos
Pericardite Constritiva/terapia , Velocidade do Fluxo Sanguíneo/fisiologia , Angiografia por Tomografia Computadorizada/métodos , Diagnóstico Diferencial , Ecocardiografia/métodos , Eletrocardiografia , Hemodinâmica/fisiologia , Veias Hepáticas/fisiologia , Humanos , Angiografia por Ressonância Magnética/métodos , Anamnese/métodos , Valva Mitral/fisiologia , Contração Miocárdica/fisiologia , Pericardite Constritiva/diagnóstico , Pericardite Constritiva/fisiopatologia , Exame Físico/métodos , Resultado do Tratamento
20.
J Biomech ; 66: 51-56, 2018 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-29169632

RESUMO

Using in vitro models, the mechanics as well as surgical techniques for mitral valves (MV) and MV devices can be studied in a more controlled environment with minimal monetary investment and risk. However, these current models rely on certain simplifications, one being that the MV has a static, rigid annulus. In order to study more complex issues of imaging diagnostics and implanted device function, it would be more advantageous to verify their use for a dynamic environment in a dynamic simulator. This study provides the novel design and development of a dynamically contracting annulus (DCA) within an in vitro simulator, and its subsequent use to study MV biomechanics. Experiments were performed to study the ability of the DCA to reproduce the MV leaflet mechanics in vitro, as seen in vivo, as well as investigate how rigid annuloplasties affect MV leaflet mechanics. Experiments used healthy, excised MVs and normal hemodynamics; contractile waveforms were derived from human in vivo data. Stereophotogrammetry and echocardiography were used to measure anterior leaflet strain and the change in MV geometry. In pursuit of the first in vitro MV simulator that more completely represents the dynamic motion of the full valvular apparatus, this study demonstrated the successful operation of a dynamically contracting mitral annulus. It was seen that the diseased contractile state increased anterior leaflet strain compared to the healthy contractile state. In addition, it was also shown in vitro that simulated rigid annuloplasty increased mitral anterior leaflet strain compared to a healthy contraction.


Assuntos
Valva Mitral/cirurgia , Animais , Ecocardiografia , Humanos , Valva Mitral/fisiologia , Insuficiência da Valva Mitral/fisiopatologia , Fotogrametria , Ovinos , Suínos
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