Background: Aortic valve insufficiency (AI) at the time of left ventricular assist device (LVAD) insertion needs to be corrected, however there is little known about how to manage bioprosthetic valvular AI. Case presentation: A 55-year-old female with dilated cardiomyopathy who previously had a bioprosthetic aortic valve replacement needed a LVAD as a bridge to transplant. Her left ventricular ejection fraction was 10% and had mild to moderate transvalvular AI. She underwent a HeartWare HVAD insertion along with aortic valvular coaptation stitch repair (Park's stitch) to the bioprosthetic valve. Conclusion: Her AI improved to trivial with minimal ejection through the bioprosthetic valve. She was transplanted 6 months following the surgery. A Park's stitch to the bioprosthetic aortic valve with more than mild AI might be a good option for bridge to transplant patient.

No description available.

Calcific aortic valvular disease (CAVD) is the most common valvular pathology in the developed world. CAVD results in calcifications forming on the aortic valve leaflets, inhibiting proper closure and causing complications of stenosis and regurgitation. Although, the mechanisms behind the disease initiation are unknown, it is believed to be a cell-mediated phenomenon, and not the result of passive degradation of the valve as once believed due to the increased prevalence with age. Currently, there are no pharmaceutical options for the prevention or reversal of calcifications, the only treatment option is complete valve replacement, an imperfect solution. Hindering the development of potential therapeutics is that currently there are no adequate animal models which replicate the calcification and cell death seen in disease explanted valves. An in vitro model has been develop where valvular interstitial cells (VICs), the main cell type of the valve, are seeded at high density into tissue culture polystyrene dishes and cultured with TGF-β1. This results in VICs activating to the myofibroblast phenotype and forming cell aggregates. Due to currently unknown mechanisms, apoptosis occurs within the center of the aggregates and calcification ensues. Although simplistic, this model has been used to show that rate and frequency of aggregation is affected by cellular tension; conditions of high tension increase aggregation response, while conditions of low tension prevent aggregation and calcification from occurring. It is important to note; however, that despite its wide usage, the current model is limited as the aggregation and subsequent calcification are random occurrences and are not consistent across literature where same conditions for control samples are used. The motivation of the presented work is two-fold. First, high intracellular tension has been suggested as one of the mechanisms leading to disease in the valve. Despite the clear and important role of cell tension, VIC tension has never before been measured in a dynamic environment. The ways in which dynamic stimulation affects individual VIC tension is not known. In aim one, a method is developed to allow for long-term cyclic stretch of VICs with measurement of cell traction force. It was found that cyclic stretch decreased cell tension in cells with high prestress and increased cell tension for conditions of low prestress. Combined, these findings indicate a homeostatic cellular tension which is dependent upon the mechanical environment. In the second aim, a novel method for creating VIC aggregates is validated. Micro-contact printing, essentially “stampingâ€� of a protein in a defined pattern, is used to create circular aggregates on polyacrylamide gels. This method allows for the separation of the aggregation from the subsequent calcification, an improvement over the current in vitro model. The method is then used to explore the role of the distribution of tension in the initiation of disease

O expressivo número de brasileiros que necessitam correção anatômica da estenose valvar aórtica acentuada e que não realizam cirurgia de substituição valvar devido ao risco proibitivo justifica a necessidade de investigação, tanto da efetividade no cenário clínico real quanto dos custos impostos ao Sistema Único de Saúde e aos planos de saúde suplementar brasileiros pela incorporação do implante transcateter de valva aórtica, que tem se demonstrado efetivo mas oneroso, internacionalmente. No primeiro artigo da tese, avaliaram-se os desfechos intra-hospitalares, a sobrevida e o reembolso pela internação hospitalar de 41 pacientes com idade média de 78,7 ± 6,3 anos, estenose valvar aórtica acentuada, com recusa cirúrgica e decisão multidisciplinar por tratamento transcateter entre outubro de 2010 e outubro de 2015. Os sujeitos foram seguidos prospectivamente por um período mediano de 15,2 (4,5 – 25,6) meses e a sobrevida estimada em 1 e 2 anos foi de 73,2% e 64,1%, respectivamente. Identificou-se que hipertensão pulmonar e revascularização miocárdica cirúrgica prévia estavam independentemente associadas à menor sobrevida. O valor mediano reembolsado pelos pacientes atendidos pelo Sistema Único de Saúde foi R$ 108.634,34 (101.051,05 – 127.255,27) e R$ 115.126,77 (94.603,21 – 132.603,01) para aqueles internados por planos de saúde suplementar ou particulares, sendo o respectivo valor mediano reembolsado pela prótese valvar de R$ 82.000,00 (82.000,00 – 95.450,00) e 84.050,00 (75.000,00 – 92.400,00) Em um grupo de 585 procedimentos de troca valvar aórtica cirúrgica em indivíduos com idade ≥ 60 anos, realizados entre janeiro de 2010 e dezembro de 2015 na mesma instituição, a mortalidade intra-hospitalar estava associada à idade e foi de 5,9% naqueles com idade entre 60 e 70 anos, 10,8% entre 70 e 80 anos e de 22,2% ≥ 80 anos. O reembolso mediano foi de R$ 14.035,96 (11.956,11 – 16.644,90) para os internados pelo Sistema único de Saúde e R$ 20.273,97 (15.358.03 – 32.815,49) pelos planos de saúde suplementar ou particulares. No segundo artigo da tese, identificou-se que do total de 819 pacientes consecutivamente incluídos no Registro Brasileiro de Implante de Bioprótese Aórtica por Cateter entre janeiro de 2008 e outubro de 2015, 15 (1,8%) sofreram perfuração do ventrículo esquerdo. Os pacientes que apresentaram perfuração eram mais idosos (85,4 ± 6,3 vs. 81,5 ± 7,3 anos, p=0,038), predominantemente mulheres (80,0% vs. 50,5%, p=0,024), apresentavam maior fração de ejeção (67,3 ± 7,8% vs. 58,6 ± 15,0%, p=0,001), menor massa ventricular esquerda (203,9 ± 47,1g vs. 247,6 ± 78,7g, p=0,039) e menor altura do tronco da coronária esquerda (11,2 ± 5,4mm vs. 14,0 ± 3,3mm, p=0,034). Os preditores independentes de perfuração do ventrículo esquerdo foram idade e fração de ejeção. No terceiro artigo, descreve-se um caso de ablação septal para tratamento de miocardiopatia hipertrófica obstrutiva assimétrica para posterior implante transcateter de valva aórtica, sugerindo que esta seja uma estratégia factível quando da concomitância dessas duas condições Em conclusão, os desfechos do tratamento transcateter da estenose valvar aórtica acentuada em pacientes inoperáveis são compatíveis com aqueles do cenário idealizado dos ensaios clínicos randomizados, apesar de estarem associados a custos maiores que os anteriormente estimados por painéis de especialistas. O tratamento cirúrgico, por sua vez, apresentou mortalidade maior que aquela idealizada ou relatada como usual. A hipercinesia do ventrículo esquerdo pode favorecer o trauma determinado pelo guia metálico, posicionado em seu interior para realização do procedimento, estando a fração de ejeção independentemente associada à chance de perfuração. Ainda, a ablação septal por álcool eletiva, anterior ao implante transcateter da valva aórtica, é uma abordagem factível para pacientes com hipertrofia ventricular esquerda assimétrica obstrutiva associada à estenose valvar aórtica. / The expressive number of Brazilians who require an anatomic correction for severe aortic valve stenosis and who do not undergo valvar replacement surgery due to prohibitive risk justifies the need to investigate both the effectiveness in the real clinical scenario and the costs imposed to the Public Health System and the Supplementary Health System for the incorporation of the transcatheter aortic valve implantation, which has been shown to be effective but onerous, internationally. In the first article of the thesis, the in-hospital outcomes, long-term survival and reimbursement for 41 patients, with a mean age of 78.7 ± 6.3 years, sever aortic valve stenosis, with surgical refusal and multidisciplinary decision for transcatheter treatment, between October 2010 and October 2015 are described. Subjects were prospectively followed for a median period of 15.2 (4.5 - 25.6) months and the estimated survival at 1 and 2 years was 73.2% and 64.1%, respectively. It was identified that pulmonary hypertension and previous coronary artery bypass grafting were independently associated with lower survival. Median reimbursed values by the Public Health System was R$ 108,634.34 (101,051.05 - 127,255.27) and by supplementary health plans was R$ 115,126.77 (94,603.21 - 132,603.01). The respective median values reimbursed for the valve prosthesis was R$ 82,000.00 (82,000.00 - 95,450.00) and 84,050.00 (75,000.00 - 92,400.00) In a group of 585 surgical aortic valve replacement procedures in subjects aged ≥ 60 years, performed between January 2010 and December 2015 in the same institution, in-hospital mortality was associated with age and was 5.9% in those with age between 60 and 70 years, 10.8% between 70 and 80 years and 22.2% in ≥ 80 years. The median reimbursement was R$ 14,035.96 (11,956.11 - 16,644.90) for those hospitalized by the Public Health System and R$ 20,273.97 (15,358.03 - 32,815.49) by supplementary or private health plans. In the second article of the thesis, it was identified that of the total of 819 patients consecutively included in the Brazilian Registry of Aortic Bioprosthesis Implantation by Catheter (RIBAC) between January 2008 and October 2015, 15 (1.8%) suffered perforation of the left ventricle. Patients with perforation were older (85.4 ± 6.3 vs. 81.5 ± 7.3 years, p=0.038), predominantly women (80.0% vs. 50.5%, p=0.024), had a higher ejection fraction (67.3 ± 7.8% vs. 58.6 ± 15.0%, p=0.001), lower left ventricular mass (203.9 ± 47.1g vs. 247.6 ± 78, 7g, p=0.039) and shorter distance between the aortic annulus and the left main coronary artery ostium (11.2 ± 5.4mm vs. 14.0 ± 3.3mm, p=0.034). The independent predictors of left ventricular perforation were age and ejection fraction. In the third article, a case of septal ablation was described for the treatment of asymmetric obstructive hypertrophic cardiomyopathy for posterior transcatheter aortic valve implantation, suggesting that this is a feasible strategy when these two conditions are concomitant In conclusion, the outcomes of transcatheter treatment of severe aortic stenosis in inoperable patients are compatible with those in the ideal scenario of randomized clinical trials, although they are associated with higher costs than previously estimated by expert panels. Surgical treatment, on the other hand, presented higher mortality than that idealized or reported as usual. The left ventricle hyperkinesia may favor the trauma determined by the metallic guide, positioned inside it to perform the procedure, the ejection fraction being independently associated with the chance of perforation. Furthermore, elective alcohol septal ablation, prior to transcatheter aortic valve implantation, is a feasible approach for patients with obstructive asymmetric left ventricular hypertrophy associated with aortic valve stenosis.

Vascular calcification is a prominent cardiovascular condition found worldwide. This condition is predominantly found in the elderly population, and patients who suffer from chronic kidney disease, due to an imbalance of serum phosphate and calcium levels. For many years, vascular calcification was believed to be a passive pathological process which develops with ageing and/or lifestyle. Little has been documented about the disease until the 20th century, when interest in cardiovascular research grew amongst scientists. Indeed, vascular calcification underpins severe clinical outcomes and cardiovascular diseases have been labelled the global leading cause of death. Calcific aortic valve diseases (CAVD) is a progressive degenerative condition characterised by the development of lipo-calcification around the aortic valve leaflets leading to severe aortic stenosis and aortic regurgitation, which may ultimately lead to heart failure. At present there are no pharmaceutical therapies that can stop its progression and its molecular mechanisms are not fully understood. Recent findings have suggested that vascular smooth muscle cell (VSMC) calcification shares many common features with physiological skeletogenesis via the release of matrix vesicles (MVs), which are specialised structures that initiate mineralisation during bone formation. The ability for MVs to nucleate calcium and phosphate highly depend on their protein composition, as this may vary depending on active cell signalling and the microenvironment. This mechanism involving MV-regulated calcification has yet to be examined in CAVD. In this study, examined whether calcium and/or phosphate regulate VIC-derived MVs to induce calcification in the aortic valve. I used a primary rat valve interstitial cell (VIC) model, coupled with stenotic human valve tissues to characterise and study the mechanisms underpinning CAVD. X-ray fluorescence and diffraction analysis showed the mineral found in calcified human aortic valves to be hydroxyapatite (HA), the main component in bone. Additional imaging studies employing transmission electron microscopy (TEM) revealed particles that were similar in size and morphology to skeletal MVs. To further characterise VIC-derived MVs in vitro, I harvested MVs from rat VICs, and subsequently studied their protein composition using Isobaric tag for relative and absolute quantitation (iTRAQ) mass spectrometry. The data obtained from the proteomics analysis was compared to previous published studies on MV proteins derived from osteoblasts and VSMCs. The results showed the upregulation of numerous calcification regulators in MVs isolated from all 3 cell types, in particular, the Annexin family, which are known calcium binding proteins. Further studies conducted with Annexin 6, an established calcium regulator in arterial calcification, revealed its colocalisation with MV-enriched areas in calcified human aortic valve tissue suggesting it may play an important role in calcium regulation during CAVD.

A normal aortic valve has three leaflets; however, 1- 2% of children are born with an aortic valve with two leaflets, referred to as congenital bicuspid aortic valves (BAV). Recent in vivo studies have shown that flow development past the bicuspid valves into the ascending aorta is markedly different from that past the normal tri-leaflet aortic valve. This difference may lead to the bicuspid valve having a higher rate of ascending aortic root dissection, a pathology that can potentially result in fatality. Using computational fluid dynamics we aim to evaluate the alterations in flow development in the ascending aorta with BAV compared to healthy tri-leaflet valves (TAV) and relate the alterations in flow-induced stresses with higher incidences of aortic dissection in patients with BAV. Simplified models based on the geometry and dimensions from published literature were developed. The preliminary results show that there is a difference in flow development between the BAV and the tri-leaflet valve. This is visible by the differences in wall shear stress and dynamic pressure distribution in the ascending aorta. The conclusion drawn from this is that there are marked differences in the ascending aortic flow development with BAV compared to that with TAV which may lead to dissection of the aortic arch.

Experiments described in this thesis address the pathogenesis of aortic valve sclerosis/stenosis using a bench to bedside approach. In particular, the thesis begins with development of a technique using ultrasonic backscatter analyses to quantitate the early stages of aortic stenosis. Subsequent chapters utilized this methodology to quantitate aortic valve structural changes in a model and intervention study of aortic stenosis in rabbits. The last chapters are human studies designed to identify factors associated with presence of aortic sclerosis/stenosis; with particular interest in potential association of endothelial dysfunction/inflammation/platelet aggregation with abnormal aortic valve structure quantitated by ultrasonic backscatter. In Chapter 1 (Introduction) the relevant literature is reviewed. Development of ultrasonic backscatter to quantitate aortic sclerosis (Chapter 2) Aortic valve sclerosis (ASc) is detected when there is visual assessment of focal increases in echogenicity of the aortic valve most commonly assessed by echocardiography. However, there is no previously described method to quantitate degree of aortic valve structural abnormality as ASc is not associated with marked hemodynamic obstruction quantifiable by Doppler echocardiography. The current study used ultrasonic backscatter to quantitate aortic valve structural abnormality in patients assessed as having ASc based on valve appearances, compared to young healthy volunteers with normal aortic valves. The results of the study indicate: 1) that the mean levels of aortic valve backscatter in ASc patients are approximately 60% greater than in young healthy volunteers (ie aortic valve backscatter scores ≥ 16dB are not consistent with normal aortic valve structure), 2) ultrasonic backscatter scores in ASc patients are directly correlated with subjective scoring of sclerosis and with a positive trend with transvalvular pressure gradients in patients with mild-moderate aortic stenosis, and most importantly, 3) ultrasonic backscatter is a reproducible technique, with mean differences between estimates based on repeat echocardiograms of 2.3 ± 1.7 (9.1%). These results indicate that ultrasonic backscatter could be used as a quantitative measure of aortic valve structural abnormality in epidemiology and for examination of interventions. In vivo studies Development of an animal model of aortic stenosis with vitamin D2 (Chapter 3) The aim of the study was to develop an appropriate animal model for AS. The study used vitamin D2 alone at 25,000IU/4 days weekly (vit-D2) for 8 weeks to induce AS in rabbits. Results showed that: 1) rabbits in the vit-D2 group had significantly increased in transvalvular velocity and pressure gradients compared to rabbits in the control group (normal chow + drinking water); this was consistent for aortic valve ultrasonic backscatter scores; 2) aortic valve immunohistochemistry/histology showed marked calcification, neutral lipids, macrophage, and leukocyte infiltrations for rabbits in the vit- D2 group (ie consistent with histology of human AS); 3) significant elevation of asymmetric dimethylarginine (ADMA) concentrations in the vit-D2 group occurred compared to controls over the 8 weeks treatment period; the change in ADMA concentrations correlated significantly with the change in transvalvular pressure gradients for rabbits in the vit-D2 group; 4) rabbits in the vit-D2 group had significantly impaired endothelium-dependent acetylcholine-induced aortic relaxation, and this effect was completely abolished by the nitric oxide synthase inhibitor (L-NAME); 5) the addition of 0.5% cholesterol-supplemented diet to the vitamin D2 regimen did not accentuate the development of AS. Thus, treatment with vitamin D2 at 25,000IU/4 days weekly for 8 weeks significantly induced AS with similar aortic valve pathology to that of human AS; therefore, the model is suitable for use in examining potential therapeutic interventions in AS. Effects of ramipril on development of AS in rabbits (Chapter 4) Using this animal model, this study aimed to examine the effects of the angiotensinconverting enzyme inhibitor (ACEi) ramipril on development of AS. Rabbits (n=28) treated for 8 weeks were divided into 2 groups: (a) vitamin D2 alone (n=10) (normal chow + 25,000IU vitamin D2 in drinking water); (b) vitamin D2/Ramipril (n=12) (normal chow+25,000IU vitamin D2/Ramipril (0.5mg/kg) in drinking water). Six further rabbits constituted a normal reference group (no treatment was given). The results for comparisons between vitamin D2/ramipril vs vitamin D2 alone were as follows: 1) ramipril-treated rabbits had significantly less severe hemodynamic obstructions (p<0.05, for both) as assessed by transvalvular velocity, and aortic valve area; with borderline reduction in aortic valve backscatter (p=0.08); 2) ramipril significantly reduced plasma ADMA concentrations; 3) there was improvement in acetylcholine-induced aortic relaxation (p=0.056), with significant improvement in sodium nitroprusside-induced relaxation (p<0.05); 4) there was a strong inverse correlation between acetylcholineinduced aortic relaxation and aortic valve backscatter score (0<0.001), thus providing further evidence of the potential role of nitric oxide in retarding the development of AS in this model. These data provide a strong rationale for the inception of a randomized trial of ACE inhibition as a strategy for limitation of AS progression in humans. Human studies Aortic stenosis is associated with elevated plasma levels of asymmetric dimethylarginine (ADMA) concentrations in humans (Chapter 5). Given the findings that aortic stenosis induced by vitamin D2 in rabbits also caused elevation of plasma ADMA concentrations, a physiological inhibitor of nitric oxide synthase, a mediator and marker of endothelial dysfunction and an indicator of incremental cardiovascular risk. The study sought to determine whether plasma ADMA concentrations are elevated independently of pre-existing coronary risk factors in subjects with at least moderate aortic stenosis (n=42) compared to age-matched patients with normal aortic valves (n=42): as determined both by visual assessment and with aortic valve backscatter scores < 16dB. Results for this study were as follows: 1) plasma ADMA concentrations were not statistically different between the AS and non-AS group (median 0.59 vs 0.54 µmol/L, p=0.13, Mann-Whitney test) on univariate analysis; 2) backward stepwise multiple linear regression showed the presence of AS was a significant predictor of elevated ADMA concentrations (p=0.04, 95% CI =0.001, 0.072). 3) in addition, elevated plasma ADMA concentrations were also associated with history of atrial fibrillation (p=0.009, 95% CI=0.015, 0.100), and negatively associated with creatinine clearance (p=0.01, 95% CI=-0.002, 0.000), and the use of statin therapy (p=0.01, 95% CI=-0.081, -0.011). Therefore, in conclusion, this study found that AS is independently associated with elevation of ADMA concentrations, beyond that implied by “conventional” risk factors for endothelial dysfunction. The clinical status of AS as an incremental marker of cardiovascular risk may reflect ADMA-mediated endothelial dysfunction. Assessment of factors associated with ASc in a random ageing population study (Chapter 6). There have been few clinical studies of factors associated with ASc. Previous population studies have established that ASc is an independent correlate of incremental risk of coronary events. Having established that patients with AS have increased plasma ADMA concentrations (Chapter 5), it was now aimed to determine whether subjects with increased aortic valve backscatter scores (ASc) also have other markers of endothelial dysfunction/NO effects, independent of preexisting coronary risk factors. The study was designed to identify such anomalies, if they existed, on an incremental basis to other putative correlates of ASc, including coronary risk factors, renal dysfunction and vitamin D levels. Random selected subjects (n=253) aged between 51 to 77 years were evaluated. All patients underwent transthoracic echocardiography examination; aortic valve ultrasonic backscatter score (AVBS), was used to quantitate echogenicity of the aortic valve. Conventional coronary risk factors were identified on history. Integrity of NO generation/response was assessed via (i) plasma ADMA concentrations; (ii) inhibition of platelet aggregation by the NO donor sodium nitroprusside (SNP); (iii) aortic augmentation index (AIx), a measure of arterial stiffness/wave reflection. All putative correlations with AVBS were examined by univariate and stepwise multiple linear regression analyses. On the basis of echocardiographic appearances, ASc was present in 63 subjects (25.4%); mean AVBS scores was 14.9±4.6dB (SD) vs 11.2±3.9dB (SD) in the presence vs absence of ASc (p<0.001). Univariate analyses revealed that platelet responsiveness to NO was inversely correlated with AVBS (β=-0.16, p=0.02); but [ADMA] and AIx were not. On multiple linear regression, significant correlates of increased AVBS were: (i) advanced age (β=0.21, p=0.003), (ii) low body mass index (β=-0.23, p=0.001); and (iii) impaired platelet responsiveness to NO (β=-0.16, p=0.02). In Chapter 7, the implications of the overall findings in this thesis are discussed in relation to future perspective. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1309350 / Thesis(Ph.D.) -- School of Medicine, 2008

Bisher existiert keine nicht-invasive/ nicht-operative Therapie der Aortenklappenstenose. Als wichtiger Zeitpunkt für eine präventive Maßnahme, zur Verhinderung der Ausbildung einer hömodynamisch relevanten Aortenklappenstenose, kann das Stadium der Aortenklappensklerose angesehen werden. Dieses frühe Erkrankungsstadium verfügt über zahlreiche pathophysiologische Parallelen zur Atherosklerose, für die eine positive Rolle der Prävention durch körperliche Aktivität erwiesen ist. Ziel dieser Arbeit war die Durchführung der Sekundärprävention der kalzifizierenden Aortenklappenerkrankung durch körperliches Training. Um mögliche Effekte dieser Intervention zu eruieren, wurden LDLR-/--Mäuse mit bereits bestehenden pathologischen Aortenklappenveränderungen über einen Zeitraum von 16 Wochen körperlichem Training unterzogen. Durch morphologische, serumanalytische, immunhistochemische und Genexpressionsanalysen konnte abschließend eine Quantifizierung der Effekte körperlichen Trainings - in der Zielsetzung der Sekundärprävention - realisiert werden.

Aortic stenosis is a life-threatening valvular heart disease. At the onset of symptoms, a patient’s prognosis becomes poor and the risk of death rapidly increases. Aortic valve replacement surgery remains the gold standard in treatment for aortic stenosis. However, in the total population of patients with severe aortic stenosis, about one third are deemed inoperable due to their high surgical risk. In recent years, the development of transcatheter aortic valve implantation (TAVI), a non-invasive heart valve replacement procedure brought hope for the elderly, high-risk and inoperable aortic stenosis patient population pool. A literature review was performed to examine the safety, efficacy and effectiveness evidence for transcatheter aortic valve treatment option. The results showed that TAVI is a safe treatment option, however the effectiveness for the whole patient population is unknown. The adoption of this alternative treatment option is certainly coupled with multiple dimension of impact from a public health perspective. It remains inconclusive whether TAVI is an effective treatment option to be adopted. / published_or_final_version / Public Health / Master / Master of Public Health

Endothelial cells (ECs) form the inner lining of all blood vessels in the body, and coat the outer surfaces of heart valves. Because ECs are anchored to extracellular matrix proteins and are positioned between flowing blood and underlying interstitium, ECs are constantly exposed to hemodynamic shear, and act as a semi-permeable barrier to blood-borne factors. In vitro cell culture flow (ICF) systems have been employed as laboratory tools for testing endothelial properties such as adhesion strength, shear response, and permeability. Recently, advances in microscale technology have introduced microfluidic systems as alternatives to conventional ICF devices, with a multitude of practical advantages not available at the macroscale. However, acceptance of microfluidics as a viable platform has thus far been reserved because utility of microfluidics has yet to be fully demonstrated. For biologists to embrace microfluidics, engineers must validate microscale systems and prove their practicality as tools for cell biology. Microfluidic devices were designed, fabricated, and implemented to study properties of two EC types: aortic ECs and valve ECs. The objective was to streamline experimentation to reveal phenotypic traits of the two types and in the process demonstrate the usefulness of microfluidics. The first task was to develop a protocol to isolate pure populations of valve ECs because reported methods were inadequate. Dispase and collagenase in combination for leaflet digestion followed by clonal expansion of cell isolates was optimal for obtaining pure valve EC populations. Using a parallel microfluidic network, we discovered that valve ECs adhered strongly and spread well only on fibronectin and not on type I collagen. In contrast, aortic ECs adhered strongly on both proteins. Both aortic and valve ECs were then exposed to shear and analyzed for cell orientation. Morphological analyses showed aortic and valve ECs both aligned parallel to flow when sheared in a macroscale flow chamber, but aortic ECs aligned perpendicular to flow when sheared in a microchannel. Finally, a microfluidic membrane device was designed and characterized as a potential tool for measuring albumin permeability through sheared endothelial monolayers. Overall, these studies revealed novel EC characteristics and phenomena, and demonstrated accessibility of microfluidics for EC studies.