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1.
Catheter Cardiovasc Interv ; 95(5): 1009-1016, 2020 04 01.
Artículo en Inglés | MEDLINE | ID: mdl-31287238

RESUMEN

OBJECTIVES: We investigated the impact of (transcatheter heart valve) THV expansion at the level of the native annulus and implant depth on valve performance and neo-sinus flow stasis. BACKGROUND: Flow stasis in the neo-sinus is one of the identified risk factors of THV thrombosis. METHODS: A 29 mm CoreValve and 26 mm SAPIEN 3 were deployed under different expansions (CoreValve, SAPIEN 3) and implant depths (CoreValve) within a patient-derived aortic root in a pulse duplicator. Fluorescent dye was injected during diastole into the neo-sinus and imaged over 20 cardiac cycles. Washout times were computed as a measure of flow stasis for each deployment. RESULTS: The 10% CoreValve under-expansion improved neo-sinus washout over full expansion by 8% (p < .001), and higher CoreValve implant depth improved neo-sinus washout (p < .001). The 10% SAPIEN 3 under-expansion improved neo-sinus washout by 23% (p < .001). Under-expansion of both valve types caused higher pressure gradients and smaller effective orifice areas than full expansion. CONCLUSIONS: Neo-sinus flow stasis is influenced by THV expansion and implant depth (CoreValve). The 10% valve under-deployment (oversizing) may facilitate reduced flow stasis in the neo-sinus with minimal increase in pressure gradients. This strategy may be helpful for patient anatomies, which are in-between transcatheter valve sizes.


Asunto(s)
Válvula Aórtica/cirugía , Prótesis Valvulares Cardíacas , Falla de Prótesis , Trombosis/etiología , Reemplazo de la Válvula Aórtica Transcatéter/efectos adversos , Reemplazo de la Válvula Aórtica Transcatéter/instrumentación , Válvula Aórtica/diagnóstico por imagen , Válvula Aórtica/fisiopatología , Velocidad del Flujo Sanguíneo , Análisis de Falla de Equipo , Hemodinámica , Humanos , Ensayo de Materiales , Modelos Cardiovasculares , Modelación Específica para el Paciente , Diseño de Prótesis , Trombosis/fisiopatología
2.
Arterioscler Thromb Vasc Biol ; 39(3): 467-481, 2019 03.
Artículo en Inglés | MEDLINE | ID: mdl-30602302

RESUMEN

Objective- Calcific aortic valve (AV) disease, characterized by AV sclerosis and calcification, is a major cause of death in the aging population; however, there are no effective medical therapies other than valve replacement. AV calcification preferentially occurs on the fibrosa side, exposed to disturbed flow (d-flow), whereas the ventricularis side exposed to predominantly stable flow remains protected by unclear mechanisms. Here, we tested the role of novel flow-sensitive UBE2C (ubiquitin E2 ligase C) and microRNA-483-3p (miR-483) in flow-dependent AV endothelial function and AV calcification. Approach and Results- Human AV endothelial cells and fresh porcine AV leaflets were exposed to stable flow or d-flow. We found that UBE2C was upregulated by d-flow in human AV endothelial cells in the miR-483-dependent manner. UBE2C mediated OS-induced endothelial inflammation and endothelial-mesenchymal transition by increasing the HIF-1α (hypoxia-inducible factor-1α) level. UBE2C increased HIF-1α by ubiquitinating and degrading its upstream regulator pVHL (von Hippel-Lindau protein). These in vitro findings were corroborated by immunostaining studies using diseased human AV leaflets. In addition, we found that reduction of miR-483 by d-flow led to increased UBE2C expression in human AV endothelial cells. The miR-483 mimic protected against endothelial inflammation and endothelial-mesenchymal transition in human AV endothelial cells and calcification of porcine AV leaflets by downregulating UBE2C. Moreover, treatment with the HIF-1α inhibitor (PX478) significantly reduced porcine AV calcification in static and d-flow conditions. Conclusions- These results suggest that miR-483 and UBE2C and pVHL are novel flow-sensitive anti- and pro-calcific AV disease molecules, respectively, that regulate the HIF-1α pathway in AV. The miR-483 mimic and HIF-1α pathway inhibitors may serve as potential therapeutics of calcific AV disease.


Asunto(s)
Estenosis de la Válvula Aórtica/etiología , Válvula Aórtica/patología , Calcinosis/etiología , Células Endoteliales/metabolismo , Hemorreología , Subunidad alfa del Factor 1 Inducible por Hipoxia/fisiología , MicroARNs/genética , Enzimas Ubiquitina-Conjugadoras/biosíntesis , Proteína Supresora de Tumores del Síndrome de Von Hippel-Lindau/metabolismo , Animales , Válvula Aórtica/metabolismo , Estenosis de la Válvula Aórtica/metabolismo , Estenosis de la Válvula Aórtica/patología , Calcinosis/metabolismo , Calcinosis/patología , Adhesión Celular , Transdiferenciación Celular , Células Cultivadas , Femenino , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia/antagonistas & inhibidores , Inflamación , MicroARNs/agonistas , Monocitos/fisiología , Compuestos de Mostaza/farmacología , Oligonucleótidos/farmacología , Técnicas de Cultivo de Órganos , Fenilpropionatos/farmacología , Procesamiento Proteico-Postraduccional , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/farmacología , Reología , Estrés Mecánico , Porcinos , Enzimas Ubiquitina-Conjugadoras/fisiología , Ubiquitinación
3.
Pediatr Cardiol ; 41(5): 1021-1030, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32377893

RESUMEN

Apicocaval juxtaposition (ACJ) is a rare form of viscerocardiac malpositions in association with single-ventricle congenital heart defects. The Fontan surgery is the common palliation, and possible surgical options include ipsilateral, contralateral, and intra-atrial conduits. Concerns include lower hemodynamic performances or risks of conduit compression by the cardiac mass. This study investigates the hemodynamics and clinical outcomes of ACJ patients and potential surgical improvements. Ten consecutive ACJ patients were included, along with a reference cohort of ten non-ACJ patients. Magnetic resonance images were acquired at 6 ± 0.6 year follow-up for anatomical analysis and hemodynamic assessments using computational fluid dynamics. Metrics of interest are deformation index (DI), indexed power loss (iPL), and hepatic flow distribution (HFDoff). A "virtual" surgery was performed to explore potential hemodynamic improvements using a straightened conduit. DI for ACJ patients fell within the DI range of non-ACJ patients. Contralateral conduits had insignificantly higher iPL (0.070 [0.032,0.137]) than ipsilateral conduits (0.041 [0.013,0.095]) and non-ACJ conduits (0.034 [0.011,0.061]). HFDoff was similar for the ipsilateral (21 [12,35]), contralateral (26 [7,41]), and non-ACJ Fontan conduits (17 [0,48]). Virtual surgery demonstrated that a straightened conduit reduced HFDoff and iPL for the contralateral and ipsilateral conduits, potentially leading to improved clinical outcomes. In this limited sample, the hemodynamic performance of ACJ patients was not significantly different from their non-ACJ counterparts. The use of a straightened conduit option could potentially improve patient outcomes. Additionally, the fear of significant compression of conduits for ACJ patients was unsupported.


Asunto(s)
Procedimiento de Fontan/métodos , Cardiopatías Congénitas/cirugía , Adolescente , Estudios de Casos y Controles , Niño , Femenino , Procedimiento de Fontan/efectos adversos , Cardiopatías Congénitas/diagnóstico por imagen , Cardiopatías Congénitas/fisiopatología , Ventrículos Cardíacos/anomalías , Ventrículos Cardíacos/cirugía , Hemodinámica , Humanos , Imagen por Resonancia Magnética , Masculino , Arteria Pulmonar/patología , Arteria Pulmonar/cirugía
4.
Circulation ; 137(4): 388-399, 2018 01 23.
Artículo en Inglés | MEDLINE | ID: mdl-29358344

RESUMEN

Bioprostheses are prone to structural valve degeneration, resulting in limited long-term durability. A significant challenge when comparing the durability of different types of bioprostheses is the lack of a standardized terminology for the definition of a degenerated valve. This issue becomes especially important when we try to compare the degeneration rate of surgically inserted and transcatheter bioprosthetic valves. This document, by the VIVID (Valve-in-Valve International Data), proposes practical and standardized definitions of valve degeneration and provides recommendations for the timing of clinical and imaging follow-up assessments accordingly. Its goal is to improve the quality of research and clinical care for patients with deteriorated bioprostheses by providing objective and strict criteria that can be utilized in future clinical trials. We hope that the adoption of these criteria by both the cardiological and surgical communities will lead to improved comparability and interpretation of durability analyses.


Asunto(s)
Bioprótesis/clasificación , Enfermedades de las Válvulas Cardíacas/cirugía , Implantación de Prótesis de Válvulas Cardíacas/instrumentación , Prótesis Valvulares Cardíacas/clasificación , Válvulas Cardíacas/cirugía , Falla de Prótesis , Terminología como Asunto , Reemplazo de la Válvula Aórtica Transcatéter/instrumentación , Remoción de Dispositivos , Enfermedades de las Válvulas Cardíacas/diagnóstico por imagen , Enfermedades de las Válvulas Cardíacas/fisiopatología , Implantación de Prótesis de Válvulas Cardíacas/efectos adversos , Válvulas Cardíacas/diagnóstico por imagen , Válvulas Cardíacas/fisiopatología , Humanos , Valor Predictivo de las Pruebas , Diseño de Prótesis , Factores de Tiempo , Reemplazo de la Válvula Aórtica Transcatéter/efectos adversos , Resultado del Tratamiento
5.
Catheter Cardiovasc Interv ; 93(1): 134-140, 2019 01 01.
Artículo en Inglés | MEDLINE | ID: mdl-30265436

RESUMEN

PURPOSE: The study aimed to characterize the geometry of the aortic root pre- and post-transcatheter aortic valve replacement (TAVR) and investigate differences in pre- and post-TAVR anatomy. BACKGROUND: A greater understanding of how aortic root geometry changes after TAVR is needed to facilitate further investigation into the hemodynamic profiles of the post-TAVR aortic root. METHODS: Anatomical measurements were conducted on de-identified, retrospective post-TAVR 4DCT scans of 109 patients with aortic stenosis obtained from the RESOLVE study. The diameter of the aortic root was measured at the level of the annulus, left ventricular outflow tract (LVOT), sinus of Valsalva, sinotubular junction (STJ) and ascending aorta. The heights of the STJ and coronary arteries were also measured. RESULTS: All aortic root dimensions were normally distributed across the cohort and changed significantly between pre- and post-TAVR conditions (P < 0.01). Post-TAVR dimensions changed significantly from peak systole to end diastole (P < 0.01). Regression models were obtained for all aortic root dimensions in terms of annulus diameter with excellent coefficient of determination (R2 > 0.95, P < 0.001). CONCLUSIONS: There are significant differences between pre- and post-TAVR as well as peak systolic and end diastolic aortic root anatomy. Appropriate anatomical dimensions should be selected for benchtop testing as the geometry varies greatly throughout the cardiac cycle.


Asunto(s)
Estenosis de la Válvula Aórtica/cirugía , Válvula Aórtica/cirugía , Tomografía Computarizada Cuatridimensional , Tomografía Computarizada Multidetector , Reemplazo de la Válvula Aórtica Transcatéter , Anciano , Anciano de 80 o más Años , Válvula Aórtica/diagnóstico por imagen , Válvula Aórtica/fisiopatología , Estenosis de la Válvula Aórtica/diagnóstico por imagen , Estenosis de la Válvula Aórtica/fisiopatología , Femenino , Humanos , Masculino , Valor Predictivo de las Pruebas , Estudios Retrospectivos , Resultado del Tratamiento , Estados Unidos
6.
Artif Organs ; 43(2): 181-188, 2019 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-30393925

RESUMEN

The current methodology of Fontan palliation results in a one "pump" circulatory system with passive flow to the lungs. Inherent hemodynamic differences exist between a biventricular circulatory system and this modified physiology, leading to a host of long-term complications. Mechanical circulatory support (MCS) is a potential option to combat these pathophysiological conditions. In this study, we examine the VentriFlo True Pulse Pump as a MCS option to support a failing Fontan patient. An in vitro circulatory loop was used to model a failing Fontan patient, reproducing pathophysiological pressures and flow rates. The VentriFlo True Pulse Pump was positioned as a right sided support, testing multiple cannulation and baffle restriction strategies, as well as various pumping parameters including flow rate, frequency, stroke volume and the ejection to filling time ratio. A 10 mm Hg decrease in IVC pressure and 0.75 L/min increase in cardiac output were achieved using a complete baffle restriction strategy. Additional cannulation and banding strategies were not as successful. Pump flow rate and frequency significantly impacted hemodynamics, while the ejection to filling time ratio did not. Though not ideal, complete baffle restriction was necessary to achieve successful support. The ability to tune individual pumping parameters for a given MCS device will have a substantial impact on the pressures and flow augmentation seen in a Fontan circulation. Both future pump design and off-label VADs for Fontan use should consider the pump configuration and parameter combinations presented here, which offered successful support.


Asunto(s)
Procedimiento de Fontan/instrumentación , Cardiopatías Congénitas/cirugía , Corazón Auxiliar , Modelos Cardiovasculares , Simulación por Computador , Hemodinámica/fisiología , Humanos
7.
Circulation ; 136(17): 1598-1609, 2017 Oct 24.
Artículo en Inglés | MEDLINE | ID: mdl-28724752

RESUMEN

BACKGROUND: Transcatheter heart valve (THV) thrombosis has been increasingly reported. In these studies, thrombus quantification has been based on a 2-dimensional assessment of a 3-dimensional phenomenon. METHODS: Postprocedural, 4-dimensional, volume-rendered CT data of patients with CoreValve, Evolut R, and SAPIEN 3 transcatheter aortic valve replacement enrolled in the RESOLVE study (Assessment of Transcatheter and Surgical Aortic Bioprosthetic Valve Dysfunction With Multimodality Imaging and Its Treatment with Anticoagulation) were included in this analysis. Patients on anticoagulation were excluded. SAPIEN 3 and CoreValve/Evolut R patients with and without hypoattenuated leaflet thickening were included to study differences between groups. Patients were classified as having THV thrombosis if there was any evidence of hypoattenuated leaflet thickening. Anatomic and THV deployment geometries were analyzed, and thrombus volumes were computed through manual 3-dimensional reconstruction. We aimed to identify and evaluate risk factors that contribute to THV thrombosis through the combination of retrospective clinical data analysis and in vitro imaging in the space between the native and THV leaflets (neosinus). RESULTS: SAPIEN 3 valves with leaflet thrombosis were on average 10% further expanded (by diameter) than those without (95.5±5.2% versus 85.4±3.9%; P<0.001). However, this relationship was not evident with the CoreValve/Evolut R. In CoreValve/Evolut Rs with thrombosis, the thrombus volume increased linearly with implant depth (R2=0.7, P<0.001). This finding was not seen in the SAPIEN 3. The in vitro analysis showed that a supraannular THV deployment resulted in a nearly 7-fold decrease in stagnation zone size (velocities <0.1 m/s) when compared with an intraannular deployment. In addition, the in vitro model indicated that the size of the stagnation zone increased as cardiac output decreased. CONCLUSIONS: Although transcatheter aortic valve replacement thrombosis is a multifactorial process involving foreign materials, patient-specific blood chemistry, and complex flow patterns, our study indicates that deployed THV geometry may have implications on the occurrence of thrombosis. In addition, a supraannular neosinus may reduce thrombosis risk because of reduced flow stasis. Although additional prospective studies are needed to further develop strategies for minimizing thrombus burden, these results may help identify patients at higher thrombosis risk and aid in the development of next-generation devices with reduced thrombosis risk.


Asunto(s)
Válvulas Cardíacas/cirugía , Hemodinámica , Modelos Cardiovasculares , Trombosis/fisiopatología , Reemplazo de la Válvula Aórtica Transcatéter/efectos adversos , Femenino , Humanos , Masculino , Trombosis/etiología
8.
J Magn Reson Imaging ; 47(1): 246-254, 2018 01.
Artículo en Inglés | MEDLINE | ID: mdl-28390180

RESUMEN

PURPOSE: Valve mediated hemodynamics have been postulated to contribute to pathology of the ascending aorta (AAo). The objective of this study is to assess the association of aortic valve morphology and hemodynamics with downstream AAo size in subjects with bicuspid aortic valve (BAV) disease. MATERIALS AND METHODS: Four-dimensional flow MRI at 1.5 or 3 Tesla was used to evaluate the hemodynamics in the proximal AAo of 52 subjects: size-matched controls with tricuspid aortic valves (n = 24, mid ascending aorta [MAA] diameter = 38.0 ± 4.9 mm) and BAV patients with aortic dilatation (n = 14 right and left coronary leaflet fusion [RL]-BAV, MAA diameter = 38.1 ± 5.3 mm; n = 14 right and noncoronary leaflet fusion [RN]-BAV, MAA diameter = 36.5 ± 6.6 mm). A validated semi-automated technique was used to evaluate hemodynamic metrics (flow angle, flow displacement, and jet quadrant) and valve morphology (orifice circularity) for all subjects. Regression analysis of these metrics to AAo diameter was performed. RESULTS: RN-BAV subjects displayed a stronger correlation between hemodynamic metrics in the proximal AAo with diameter in the distal AAo compared with size-matched tricuspid aortic valve (TAV) controls and RL-BAV subjects. The distal AAo diameter was found to be strongly correlated to the upstream flow displacement (R2adjusted = 0.75) and flow angle (R2adjusted = 0.66) measured at the sino-tubular junction (STJ). Orifice circularity was also strongly correlated (R2adjusted = 0.53) to the distal AAo diameter in RN-BAV subjects. For TAV controls and RL-BAV subjects, correlations were weaker (R2adjusted < 0.2). CONCLUSION: Hemodynamics in the STJ were strongly correlated to the distal AAo diameter for the RN-BAV subjects. Hemodynamic metrics were more strongly correlated to the downstream aortic size when compared with valve morphology metrics. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:246-254.


Asunto(s)
Aorta/diagnóstico por imagen , Enfermedades de la Aorta/diagnóstico por imagen , Válvula Aórtica/diagnóstico por imagen , Imagen por Resonancia Magnética , Adulto , Anciano , Válvula Aórtica/anomalías , Estenosis de la Válvula Aórtica/diagnóstico por imagen , Enfermedad de la Válvula Aórtica Bicúspide , Electrocardiografía/métodos , Femenino , Enfermedades de las Válvulas Cardíacas/diagnóstico por imagen , Hemodinámica , Humanos , Imagenología Tridimensional , Masculino , Persona de Mediana Edad , Estudios Retrospectivos
9.
Catheter Cardiovasc Interv ; 92(4): 797-807, 2018 10 01.
Artículo en Inglés | MEDLINE | ID: mdl-30091509

RESUMEN

OBJECTIVES: We aimed to evaluate diastolic leaflet tethering as a factor that may cause mitral stenosis (MS) after simulated MitraClip implantation, using an in vitro left heart simulator. BACKGROUND: Leaflet tethering commonly seen in functional mitral regurgitation may be a significant factor affecting the severity of MS after MitraClip implantation. METHODS: A left heart simulator with excised ovine mitral valves (N = 6), and custom edge-to-edge clip devices (GTclip) was used to mimic implantation of MitraClip in a variety of positions. Anterior mitral leaflet (AML) tethering severity was varied for each case (leaflet excursion of 75°, 60°, and 45°, consistent with mild, moderate and severe tethering), and the baseline mitral annular area (MAA) was varied across samples (3.6-4.8 cm2 ). The resulting mitral valve area (MVA), and peak/mean mitral valve gradient (MVG) were measured in each case. RESULTS: AML tethering severity was a highly significant factor increasing MVG and decreasing MVA (P < 0.001). When GTclip placement was simulated with severe AML tethering, mean MVG >5 mmHg resulted more frequently than with GTclip placement alone (46% vs. 4%, respectively). However, severe AML tethering alone significantly reduced baseline MVA to 3.6 ± 0.2 cm2 , and increased baseline MVG to 3.0 ± 0.4 mmHg. At MAA above 4.7 cm2 , severe AML tethering did not cause moderate MS, even with placement of two GTclips (95% confidence). CONCLUSIONS: Our results show that diastolic AML tethering may predispose to MS after clip placement, however, MS was not observed when baseline MVA was above 4.0 cm2 . Severity of AML tethering may be an important criterion in selecting patients for edge-to-edge repair.


Asunto(s)
Implantación de Prótesis de Válvulas Cardíacas/instrumentación , Prótesis Valvulares Cardíacas , Hemodinámica , Anuloplastia de la Válvula Mitral/instrumentación , Estenosis de la Válvula Mitral/etiología , Válvula Mitral/cirugía , Animales , Simulación por Computador , Implantación de Prótesis de Válvulas Cardíacas/efectos adversos , Humanos , Válvula Mitral/diagnóstico por imagen , Válvula Mitral/fisiopatología , Anuloplastia de la Válvula Mitral/efectos adversos , Estenosis de la Válvula Mitral/diagnóstico por imagen , Estenosis de la Válvula Mitral/fisiopatología , Modelos Cardiovasculares , Diseño de Prótesis , Factores de Riesgo , Índice de Severidad de la Enfermedad , Oveja Doméstica , Resultado del Tratamiento
10.
Cardiol Young ; 26(1): 116-26, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-25712430

RESUMEN

BACKGROUND: The physiological importance of the lateral tunnel stenosis in the Fontan pathway for children with single ventricle physiology can be difficult to determine. The impact of the stenosis and stent implantation on total cavopulmonary connection resistance has not been characterized, and there are no clear guidelines for intervention. Methods and results A computational framework for haemodynamic assessment of stent implantation in patients with lateral tunnel stenosis was developed. Cardiac magnetic resonances images were reconstructed to obtain total cavopulmonary connection anatomies before stent implantation. Stents with 2-mm diameter increments were virtually implanted in each patient to understand the impact of stent diameter. Numerical simulations were performed in all geometries with patient-specific flow rates. Exercise conditions were simulated by doubling and tripling the lateral tunnel flow rate. The resulting total cavopulmonary connection vascular resistances were computed. A total of six patients (age: 14.4 ± 3.1 years) with lateral tunnel stenosis were included for preliminary analysis. The mean baseline resistance was 1.54 ± 1.08 WU · m(2) and dependent on the stenosis diameter. It was further exacerbated during exercise. It was observed that utilising a stent with a larger diameter lowered the resistance, but the resistance reduction diminished at larger diameters. CONCLUSIONS: Using a computational framework to assess the severity of lateral tunnel stenosis and the haemodynamic impact of stent implantation, it was observed that stenosis in the lateral tunnel pathway was associated with higher total cavopulmonary connection resistance than unobstructed pathways, which was exacerbated during exercise. Stent implantation could reduce the resistance, but the improvement was specific to the minimum diameter.


Asunto(s)
Procedimiento de Fontan/métodos , Cardiopatías Congénitas/fisiopatología , Cardiopatías Congénitas/cirugía , Hemodinámica , Modelación Específica para el Paciente , Stents , Adolescente , Niño , Constricción Patológica , Humanos , Complicaciones Posoperatorias/cirugía , Arteria Pulmonar/cirugía , Estudios Retrospectivos , Adulto Joven
11.
J Cardiovasc Magn Reson ; 17: 51, 2015 Jun 26.
Artículo en Inglés | MEDLINE | ID: mdl-26112155

RESUMEN

BACKGROUND: The development of clinically applicable fluid-structure interaction (FSI) models of the left heart is inherently challenging when using in vivo cardiovascular magnetic resonance (CMR) data for validation, due to the lack of a well-controlled system where detailed measurements of the ventricular wall motion and flow field are available a priori. The purpose of this study was to (a) develop a clinically relevant, CMR-compatible left heart physical model; and (b) compare the left ventricular (LV) volume reconstructions and hemodynamic data obtained using CMR to laboratory-based experimental modalities. METHODS: The LV was constructed from optically clear flexible silicone rubber. The geometry was based off a healthy patient's LV geometry during peak systole. The LV phantom was attached to a left heart simulator consisting of an aorta, atrium, and systemic resistance and compliance elements. Experiments were conducted for heart rate of 70 bpm. Wall motion measurements were obtained using high speed stereo-photogrammetry (SP) and cine-CMR, while flow field measurements were obtained using digital particle image velocimetry (DPIV) and phase-contrast magnetic resonance (PC-CMR). RESULTS: The model reproduced physiologically accurate hemodynamics (aortic pressure = 120/80 mmHg; cardiac output = 3.5 L/min). DPIV and PC-CMR results of the center plane flow within the ventricle matched, both qualitatively and quantitatively, with flow from the atrium into the LV having a velocity of about 1.15 m/s for both modalities. The normalized LV volume through the cardiac cycle computed from CMR data matched closely to that from SP. The mean difference between CMR and SP was 5.5 ± 3.7%. CONCLUSIONS: The model presented here can thus be used for the purposes of: (a) acquiring CMR data for validation of FSI simulations, (b) determining accuracy of cine-CMR reconstruction methods, and


Asunto(s)
Ventrículos Cardíacos/anatomía & histología , Hemodinámica , Imagen por Resonancia Cinemagnética/instrumentación , Modelos Anatómicos , Modelos Cardiovasculares , Contracción Miocárdica , Fantasmas de Imagen , Función Ventricular Izquierda , Presión Arterial , Fenómenos Biomecánicos , Gasto Cardíaco , Frecuencia Cardíaca , Humanos , Fotogrametría , Valor Predictivo de las Pruebas , Reproducibilidad de los Resultados , Reología , Elastómeros de Silicona , Factores de Tiempo
12.
J Heart Valve Dis ; 24(1): 22-9, 2015 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26182616

RESUMEN

BACKGROUND AND AIM OF THE STUDY: Transcatheter aortic valve replacements (TAVRs) are performed using fluoroscopic guidance, which makes precise positioning challenging. The aim of the present study was to investigate the effect of TAV positioning on flow characteristics in the ascending aorta and sinuses. METHODS: A commonly used TAV design with a supra-annular support section was investigated using particle image velocimetry (PIV) under physiological flow and pressure conditions. A bioprosthetic valve served as a control and mimicked the native aortic valve. The valve assembly was mounted in a custom-designed chamber with an axisymmetric sinus, the design of which was based on anatomic dimensions. The TAV was deployed in the supra-annular (high) and sub- annular (low) implantation positions and studied at two cardiac outputs (5.0 and 2.5 l/min). RESULTS: The TAV showed good systolic flow characteristics with wide forward flow jets in the ascending aorta (V = 1.5 m/s at 5.0 1/min; V = 1.0 m/s at 2.5 1/min). In the high implantation, the physical spacing between the leaflet free edge and sinotubular junction was reduced (< 10 mm), causing a weaker sinus vortex and a lower washout. A larger region of low velocity (< 0.1 m/s) in the sinus was observed at high implantation at all time points, particularly at a cardiac output of 2.5 l/min. In the low implantation, good sinus washout was observed. CONCLUSION: For optimal sinus washout, sub- annular TAV deployment is recommended, particularly for patients with smaller sinuses. An impaired cardiac output may also require sub- annular deployment for adequate sinus washout. The study results confirmed the need for precise TAV deployment tailored to patient-specific annular and sinus dimensions, as sub-optimal positioning may inhibit coronary perfusion and cause potential regions of stasis near the aortic annulus.


Asunto(s)
Estenosis de la Válvula Aórtica/terapia , Cateterismo Cardíaco/instrumentación , Implantación de Prótesis de Válvulas Cardíacas/instrumentación , Prótesis Valvulares Cardíacas , Seno Aórtico/fisiopatología , Estenosis de la Válvula Aórtica/diagnóstico , Estenosis de la Válvula Aórtica/fisiopatología , Velocidad del Flujo Sanguíneo , Presión Sanguínea , Cateterismo Cardíaco/métodos , Gasto Cardíaco , Ecocardiografía Doppler en Color , Implantación de Prótesis de Válvulas Cardíacas/métodos , Humanos , Ensayo de Materiales , Diseño de Prótesis , Flujo Sanguíneo Regional , Seno Aórtico/diagnóstico por imagen , Estrés Mecánico , Resultado del Tratamiento
13.
J Biomech Eng ; 137(12): 121007, 2015 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-26502376

RESUMEN

The mitral valve (MV) is a bileaflet valve positioned between the left atrium and ventricle of the heart. The annulus of the MV has been observed to undergo geometric changes during the cardiac cycle, transforming from a saddle D-shape during systole to a flat (and less eccentric) D-shape during diastole. Prosthetic MV devices, including heart valves and annuloplasty rings, are designed based on these two configurations, with the circular design of some prosthetic heart valves (PHVs) being an approximation of the less eccentric, flat D-shape. Characterizing the effects of these geometrical variations on the filling efficiency of the left ventricle (LV) is required to understand why the flat D-shaped annulus is observed in the native MV during diastole in addition to optimizing the design of prosthetic devices. We hypothesize that the D-shaped annulus reduces energy loss during ventricular filling. An experimental left heart simulator (LHS) consisting of a flexible-walled LV physical model was used to characterize the filling efficiency of the two mitral annular geometries. The strength of the dominant vortical structure formed and the energy dissipation rate (EDR) of the measured fields, during the diastolic period of the cardiac cycle, were used as metrics to quantify the filling efficiency. Our results indicated that the O-shaped annulus generates a stronger (25% relative to the D-shaped annulus) vortical structure than that of the D-shaped annulus. It was also found that the O-shaped annulus resulted in higher EDR values throughout the diastolic period of the cardiac cycle. The results support the hypothesis that a D-shaped mitral annulus reduces dissipative energy losses in ventricular filling during diastole and in turn suggests that a symmetric stent design does not provide lower filling efficiency than an equivalent asymmetric design.


Asunto(s)
Prótesis Valvulares Cardíacas , Ventrículos Cardíacos/anatomía & histología , Válvula Mitral/anatomía & histología , Válvula Mitral/fisiología , Modelos Cardiovasculares , Función Ventricular Izquierda/fisiología , Biomimética/métodos , Velocidad del Flujo Sanguíneo , Simulación por Computador , Diseño Asistido por Computadora , Análisis de Falla de Equipo , Humanos , Modelos Anatómicos , Diseño de Prótesis , Volumen Sistólico/fisiología
14.
J Biomech Eng ; 137(4): 045001, 2015 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-25587891

RESUMEN

Due to expensive nature of clinical trials, implantable cardiac devices should first be extensively characterized in vitro. Prosthetic heart valves (PHVs), an important class of these devices, have been shown to be associated with thromboembolic complications. Although various in vitro systems have been designed to quantify blood-cell damage and platelet activation caused by nonphysiological hemodynamic shear stresses in these PHVs, very few systems attempt to characterize both blood damage and fluid dynamics aspects of PHVs in the same test system. Various numerical modeling methodologies are also evolving to simulate the structural mechanics, fluid mechanics, and blood damage aspects of these devices. This article presents a completely hemocompatible small-volume test-platform that can be used for thrombogenicity studies and experimental fluid mechanics characterization. Using a programmable piston pump to drive freshly drawn human blood inside a cylindrical column, the presented system can simulate various physiological and pathophysiological conditions in testing PHVs. The system includes a modular device-mounting chamber, and in this presented case, a 23 mm St. Jude Medical (SJM) Regents® mechanical heart valve (MHV) in aortic position was used as the test device. The system was validated for its capability to quantify blood damage by measuring blood damage induced by the tester itself (using freshly drawn whole human blood). Blood damage levels were ascertained through clinically relevant assays on human blood while fluid dynamics were characterized using time-resolved particle image velocimetry (PIV) using a blood-mimicking fluid. Blood damage induced by the tester itself, assessed through Thrombin-anti-Thrombin (TAT), Prothrombin factor 1.2 (PF1.2), and hemolysis (Drabkins assay), was within clinically accepted levels. The hydrodynamic performance of the tester showed consistent, repeatable physiological pressure and flow conditions. In addition, the system contains proximity sensors to accurately capture leaflet motion during the entire cardiac cycle. The PIV results showed skewing of the leakage jet, caused by the asymmetric closing of the two leaflets. All these results are critical to characterizing the blood damage and fluid dynamics characteristics of the SJM Regents® MHV, proving the utility of this tester as a precise system for assessing the hemodynamics and thrombogenicity for various PHVs.


Asunto(s)
Prótesis Valvulares Cardíacas/efectos adversos , Ensayo de Materiales/instrumentación , Flujo Pulsátil , Tromboembolia/etiología , Humanos , Hidrodinámica , Activación Plaquetaria , Presión , Diseño de Prótesis , Reología , Tromboembolia/fisiopatología , Adulto Joven
16.
J Heart Valve Dis ; 23(4): 387-94, 2014 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-25803964

RESUMEN

BACKGROUND AND AIM OF THE STUDY: Aortic valve (AV) calcification is a major cause of morbidity and mortality, yet the molecular mechanisms involved are poorly understood. Hence, an ex vivo model of calcification in intact AVs was developed in order to test the role of orthophosphate and pyrophosphate (PPi), both of which factors are known to influence vascular calcification. METHODS: Porcine AV leaflets were cultured in serum-free medium under static conditions for eight days, over which time leaflet architecture and viability were preserved. Calcification was measured as the incorporation of 45Ca, with confirmation by Alizarin Red staining. RESULTS: Calcification required both a high phosphate concentration (3.8 mM) and removal of PPi with alkaline phosphatase or inorganic pyrophosphatase. Calcification occurred predominantly on the fibrosa and was arrested by the bisphosphonate etidronate, a non-hydrolyzable analog of PPi. Leaflets released PPi into the medium, and this was enhanced by MLS38949, a specific inhibitor of tissue non-specific alkaline phosphatase (TNAP). Furthermore, leaflets synthesized PPi from extracellular ATP, which was reduced by ß,γ-methylene-ATP, an inhibitor of ectonucleotide pyrophosphorylase phosphodiesterase (NPP1). CONCLUSION: The ex vivo AV calcification model developed in the present study showed that extracellular PPi, produced by valvular tissue, is a potent inhibitor of valvular calcification. In addition to synthesis, hydrolysis by TNAP also controls PPi levels and calcification. The results suggest that a decreased synthesis or increased hydrolysis of pyrophosphate may contribute to valvular calcification, and that bisphosphonates or inhibitors of TNAP are potential preventive strategies of the process. TNAP are potential preventive strategies.


Asunto(s)
Estenosis de la Válvula Aórtica/metabolismo , Estenosis de la Válvula Aórtica/patología , Válvula Aórtica/patología , Calcinosis/metabolismo , Calcinosis/patología , Difosfatos/metabolismo , Fosfatos/metabolismo , Fosfatasa Alcalina/administración & dosificación , Animales , Válvula Aórtica/metabolismo , Ácido Etidrónico/administración & dosificación , Femenino , Pirofosfatasas/administración & dosificación , Porcinos , Técnicas de Cultivo de Tejidos
17.
J Heart Valve Dis ; 23(2): 171-6, 2014 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-25076547

RESUMEN

BACKGROUND AND AIM OF THE STUDY: Anterior leaflet flail resulting from elongated or ruptured marginal chordae is frequently diagnosed among adults, and is amenable to surgical repair. The study aim was to investigate the efficacy of three surgical techniques, namely neochordoplasty, limited triangular resection and edge-to-edge repair, to correct anterior leaflet flail in an in-vitro experimental model. METHODS: Seven porcine mitral valves were evaluated in a pulsatile heart simulator before surgical manipulation, after anterior marginal chordae transection, and with each surgical repair. Marginal chordal transection induced leaflet flail with moderate mitral regurgitation (MR). Following the confirmation of MR via direct flow measurements, it was corrected by three repairs: neochordoplasty with ePTFE sutures, limited triangular resection, and edge-to-edge repair. The post-repair valve hemodynamics were quantified under pulsatile conditions of 120 mmHg peak transmitral pressure and 5 l/min cardiac output at 70 beats/min. Hemodynamic, geometric and echocardiographic indices were also measured. RESULTS: Transecting the marginal chordae induced A2 prolapse and produced the regurgitant fraction to 18.7 +/- 10.2%. Surgical repair effectively reduced the regurgitant fraction to 6.9 +/- 6.3% (p = 0.019 to prolapse, p = 0.0117 to baseline) with neochordae, to 5.8 +/- 7.0% (p = 0.03 to prolapse, p = 0.0378 to baseline) with triangular resection, and to 13.3 +/- 10.2% (p = 0.2091 to prolapse, p = 0.0045 to baseline) with edge-to-edge repair. Remnant regurgitation was largest with edge-to-edge repair compared to limited leaflet resection and neochordoplasty, though central leaflet coaptation was restored equally by the three repairs, with mild systolic leaflet restriction after repair. CONCLUSION: Anterior leaflet repair and a reduction in MR is achievable with the three techniques, although neochordoplasty and triangular resection proved superior to edge-to-edge repair in eliminating MR.


Asunto(s)
Cuerdas Tendinosas/cirugía , Implantación de Prótesis de Válvulas Cardíacas , Hemodinámica , Anuloplastia de la Válvula Mitral , Insuficiencia de la Válvula Mitral/cirugía , Válvula Mitral/cirugía , Técnicas de Sutura , Animales , Cuerdas Tendinosas/diagnóstico por imagen , Cuerdas Tendinosas/fisiopatología , Modelos Animales de Enfermedad , Implantación de Prótesis de Válvulas Cardíacas/efectos adversos , Válvula Mitral/diagnóstico por imagen , Válvula Mitral/fisiopatología , Anuloplastia de la Válvula Mitral/efectos adversos , Insuficiencia de la Válvula Mitral/diagnóstico , Insuficiencia de la Válvula Mitral/fisiopatología , Prolapso de la Válvula Mitral/etiología , Prolapso de la Válvula Mitral/fisiopatología , Flujo Pulsátil , Técnicas de Sutura/efectos adversos , Ultrasonografía
18.
J Heart Valve Dis ; 23(1): 79-87, 2014 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-24779332

RESUMEN

BACKGROUND AND AIM OF THE STUDY: Mitral valve geometry is significantly altered secondary to left ventricular remodeling in non-ischemic and ischemic dilated cardiomyopathies. Since the extent of remodeling and asymmetry of dilatation of the ventricle differ significantly between individual patients, the valve geometry and tethering also differ. The study aim was to determine if mitral valve geometry has an impact on the efficacy of surgical repairs to eliminate regurgitation and restore valve closure in a validated experimental model. METHODS: Porcine mitral valves (n = 8) were studied in a pulsatile heart simulator, in which the mitral valve geometry can be precisely altered and controlled throughout the experiment. Baseline hemodynamics for each valve were measured (Control), and the valves were tethered in two distinct ways: annular dilatation with 7 mm apical papillary muscle (PM) displacement (Tether 1, symmetric), and annular dilatation with 7 mm apical, 7 mm posterior and 7 mm lateral PM displacement (Tether 2, asymmetric). Mitral annuloplasty was performed on each valve (Annular Repair), succeeded by anterior leaflet secondary chordal cutting (Sub-annular Repair). The efficacy of each repair in the setting of a given valve geometry was quantified by measuring the changes in mitral regurgitation (MR), leaflet coaptation length, tethering height and area. RESULTS: At baseline, none of the valves was regurgitant. Significant leaflet tethering was measured in Tether 2 over Tether 1, but both groups were significantly higher compared to baseline (60.9 +/- 31 mm2 for Control versus 129.7 +/- 28.4 mm2 for Tether 1 versus 186.4 +/- 36.3 mm2 for Tether 2). Consequently, the MR fraction was higher in Tether 2 group (23.0 +/- 5.7%) than in Tether 1 (10.5 +/- 5.5%). Mitral annuloplasty reduced MR in both groups, but remnant regurgitation after the repair was higher in Tether 2. After chordal cutting a similar trend was observed with trace regurgitation in Tether 1 group at 3.6 +/- 2.8%, in comparison to 18.6 +/- 4.2% in the Tether 2 group. CONCLUSION: In this experimental model, the tethering geometry of the mitral valve impacts the valve hemodynamics after annuloplasty and chordal cutting. The quantitative assessment of valve geometry may help in tailoring a repair to the specific tethering pattern.


Asunto(s)
Cuerdas Tendinosas/cirugía , Anuloplastia de la Válvula Mitral , Insuficiencia de la Válvula Mitral/cirugía , Válvula Mitral/patología , Animales , Dilatación Patológica , Ecocardiografía , Hemodinámica , Imagenología Tridimensional , Válvula Mitral/cirugía , Modelos Animales , Modelos Cardiovasculares , Músculos Papilares/patología , Porcinos
19.
J Heart Valve Dis ; 23(5): 642-50, 2014 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-25799715

RESUMEN

BACKGROUND AND AIM OF THE STUDY: The effects of the implantation angle of bileaflet mechanical heart valves (BMHVs) on the sinus region and downstream flow profiles were investigated. Three-dimensional numerical simulations of BMHVs were performed under physiologic pulsatile flow conditions. The study aim was to examine how the flow fields of different aortic sinus shapes and the downstream aortic arch geometry would be affected by implantation angle. METHODS: Two geometric models of sinus were investigated: a simplified axisymmetric sinus; and a three-sinus aortic root model, with two different downstream geometries, namely a straight pipe and a simplified curved aortic arch. A 29 mm St. Jude Medical BMHV geometric model was used and positioned at four different angles (0 degrees, 30 degrees, 60 degrees and 90 degrees). RESULTS: The simulation results showed variation in downstream flow profiles at different implantation angles. Generally, at position Z = 1D along the centerline (where Z refers to the axis normal to the x-y plane and D is the inlet diameter), the triple-jet structures were observed with a slight shift of the center jet for three-sinus aortic cases. Apparent differences were observed at position Z = 2D and 4D, such as higher velocity profiles at the inner arch wall. The flow field downstream of the valve implanted at 0 degrees (anatomic position) showed the smallest overall asymmetry at peak systole, while the flow field downstream of the valve implanted at 90 degrees (anti-anatomic position) exhibited high regions of recirculation. CONCLUSION: Valve orientation was found not to affect the shear stress distribution significantly in the downstream aorta, and this was in agreement with the findings of earlier studies.


Asunto(s)
Válvula Aórtica/fisiología , Válvula Aórtica/cirugía , Implantación de Prótesis de Válvulas Cardíacas/métodos , Prótesis Valvulares Cardíacas , Hemodinámica , Modelos Cardiovasculares , Aorta Torácica/anatomía & histología , Aorta Torácica/fisiología , Velocidad del Flujo Sanguíneo , Humanos , Diseño de Prótesis , Seno Aórtico/anatomía & histología , Seno Aórtico/fisiología , Estrés Mecánico
20.
J Biomech Eng ; 136(10): 101009, 2014 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-25070372

RESUMEN

Bileaflet mechanical heart valves (BMHVs) are among the most popular prostheses to replace defective native valves. However, complex flow phenomena caused by the prosthesis are thought to induce serious thromboembolic complications. This study aims at employing a novel multiscale numerical method that models realistic sized suspended platelets for assessing blood damage potential in flow through BMHVs. A previously validated lattice-Boltzmann method (LBM) is used to simulate pulsatile flow through a 23 mm St. Jude Medical (SJM) Regent™ valve in the aortic position at very high spatiotemporal resolution with the presence of thousands of suspended platelets. Platelet damage is modeled for both the systolic and diastolic phases of the cardiac cycle. No platelets exceed activation thresholds for any of the simulations. Platelet damage is determined to be particularly high for suspended elements trapped in recirculation zones, which suggests a shift of focus in blood damage studies away from instantaneous flow fields and toward high flow mixing regions. In the diastolic phase, leakage flow through the b-datum gap is shown to cause highest damage to platelets. This multiscale numerical method may be used as a generic solver for evaluating blood damage in other cardiovascular flows and devices.


Asunto(s)
Sangre , Prótesis Valvulares Cardíacas/efectos adversos , Modelos Cardiovasculares , Flujo Pulsátil , Velocidad del Flujo Sanguíneo , Plaquetas/fisiología , Humanos
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