Starptautiski citējamas publikācijas
Abstract
This prospective multicenter registry used intravascular ultrasound (IVUS) in patients with definite stent thrombosis (ST) to compare rates of incomplete stent apposition (ISA), stent fracture and stent expansion in patients treated with drug-eluting (DES) versus bare metal (BMS) stents. ST is a rare, but potential life threatening event after coronary stent implantation. The etiology seems to be multifactorial.
124 patients with definite ST were assessed by IVUS during the acute ST event. The study was conducted in 15 high-volume percutaneous coronary intervention -centers in the Nordic-Baltic countries.
In early or late ST there were no differences in ISA between DES and BMS. In very late ST, ISA was a more frequent finding in DES than in BMS (52% vs.16%; p=0.005) and the maximum ISA area was larger in DES compared to BMS (1.1±2.3mm(2) vs. 0.1±0.5mm(2); p=0.004). Further, ISA was more prevalent in sirolimus-eluting than in paclitaxel-eluting stents (58% vs. 37%; p=0.02). Stent fractures were found both in DES (16%) and BMS (24%); p=0.28, and not related to time of stent thrombosis occurrence. For stents with nominal diameters ≥2.75mm, 38% of the DES and 22% of the BMS had a minimum stent area of less than 5mm(2); p=0.14.
Very late stent thrombosis was more prevalent and associated with more extensive ISA in DES than in BMS treated patients. Stent fracture was a common finding in ST after DES and BMS implantation.
Chieffo A., Meliga E., Latib A., Park S.J., Onuma Y., Capranzano P., Valgimigli M., Jegere S., Makkar R.R., Palacios I.F., Kim Y.H., Buszman P.E., Chakravarty T., Sheiban I., Mehran R., Naber C., Margey R., Agnihotri A., Marra S., Capodanno D., Leon M.B., Moses J.W., Fajadet J., Lefevre T., Morice M.C., Erglis A., Tamburino C., Alfieri O., Serruys P.W., Colombo A. Drug-Eluting Stent for Left Main Coronary Artery Disease: The DELTA Registry: A Multicenter Registry Evaluating Percutaneous Coronary Intervention Versus Coronary Artery Bypass Grafting for Left Main Treatment. JACC Cardiovasc Interv. 2012 Jul;5(7):718-27. PubMed PMID: 22814776.
http://www.ncbi.nlm.nih.gov/pubmed/22814776
https://interventions.onlinejacc.org/article.aspx?articleid=1217884
Abstract
The aim of this study was to compare, in a large all-comers registry, major adverse cardiac and cerebrovascular events (MACCE) after percutaneous coronary intervention (PCI) with first-generation drug-eluting stents (DES) versus coronary artery bypass grafting (CABG) in unprotected left main coronary artery (ULMCA) stenosis.
Percutaneous coronary intervention with DES implantation in ULMCA has been shown to be a feasible and safe approach at midterm clinical follow-up.
All consecutive patients with ULMCA stenosis treated by PCI with DES versus CABG were analyzed in this multinational registry. A propensity score analysis was performed to adjust for baseline differences in the overall cohort.
In total 2,775 patients were included: 1,874 were treated with PCI versus 901 with CABG. At 1,295 (interquartile range: 928 to 1,713) days, there were no differences, at the adjusted analysis, in the primary composite endpoint of death, cerebrovascular accidents, and myocardial infarction (MI) (adjusted hazard ratio [HR]: 1.11; 95% confidence interval [CI]: 0.85 to 1.42; p = 0.47), mortality (adjusted HR: 1.16; 95% CI: 0.87 to 1.55; p = 0.32), or composite endpoint of death and MI (adjusted HR: 1.25; 95% CI: 0.95 to 1.64; p = 0.11). An advantage of CABG over PCI was observed in the composite secondary endpoint of MACCE (adjusted HR: 1.64; 95% CI: 1.33 to 2.03; p < 0.0001), driven exclusively by the higher incidence of target vessel revascularization with PCI.
In our multinational all-comers registry, no difference was observed in the occurrence of death, cerebrovascular accidents, and MI between PCI and CABG. An advantage of CABG over PCI was observed in the incidence of MACCE, driven by the higher incidence of target vessel revascularization with PCI.
Prati F., Guagliumi G., Mintz G.S., Costa M., Regar E., Akasaka T., Barlis P., Tearney G.J., Jang I.K., Arbustini E., Bezerra H.G., Ozaki Y., Bruining N., Dudek D., Radu M., Erglis A., Motreff P., Alfonso F., Toutouzas K., Gonzalo N., Tamburino C., Adriaenssens T., Pinto F., Serruys P.W., Di Mario C.; for the Expert's OCT Review Document. Expert review document part 2: methodology, terminology and clinical applications of optical coherence tomography for the assessment of interventional procedures. Eur Heart J. 2012 May 31. [Epub ahead of print] PubMed PMID: 22653335.
http://www.ncbi.nlm.nih.gov/pubmed/22653335
http://eurheartj.oxfordjournals.org/content/33/20/2513.long
Abstract
In the OCT Expert Review Document on Atherosclerosis, a comprehensive description of the physical principles for OCT imaging and time domain (TD) catheters (St Jude Medical, Westford, MA, USA) was provided.
The main advantage of FD-OCT is that the technology enables rapid imaging of the coronary artery, using a non-occlusive acquisition modality. The FD-OCT catheter (DragonflyTM; St Jude Medical) employs a single-mode optical fibre, enclosed in a hollow metal torque wire that rotates at a speed of 100 r.p.s. It is compatible with a conventional 0.014″ angioplasty guide wire, inserted into a short monorail lumen at the tip. The frequency domain optical coherence tomography lateral resolution is improved in comparison with TD-OCT, while the axial resolution did not change. These features, together with reduced motion artefacts and an increased maximum field of view up to 11 mm, have significantly improved both the quality and ease of use of OCT in the catheterization laboratory. However, the imaging depth of the FD-OCT is still limited to 0.5-2.0 mm.
Kumsars I., Narbute I., Thuesen L., Niemelä M., Steigen T.K., Kervinen K., Sondore D., Holm N.R., Lassen J.F., Christiansen E.H., Maeng M., Jegere S., Juhnevica D., Erglis A. Side branch fractional flow reserve measurements after main vessel stenting: a Nordic-Baltic Bifurcation Study III substudy. EuroIntervention. 2012 Feb 20;7(10):1155-61. doi: 10.4244/EIJV7I10A186. PubMed PMID: 22334314.
http://www.ncbi.nlm.nih.gov/pubmed/22334314
Abstract
The substudy was performed to evaluate the acute and eight-month follow-up effect of final kissing balloon dilatation (FKBD) on fractional flow reserve (FFR) in the side branch (SB) after main vessel (MV) stenting.
We included 75 patients in the Nordic-Baltic Bifurcation Study III FFR substudy: 42 in the FKBD group and 33 in the no-FKBD group. Complete angiographic and FFR eight-month follow-up was obtained in 25 (60%) patients in the FKBD group and 21 (63%) patients in the no-FKBD group. In the FKBD group the post-PCI mean SB FFR was significantly higher compared to the no-FKBD group (0.92 vs. 0.85, respectively; p=0.011). No significant difference in FFR value between treatments was detected at eight-month follow-up (0.91 vs. 0.87; p=0.19). There were no significant changes in mean SB FFR during the follow-up period (0.92 vs. 0.91; p=0.80) in the FKBD group and (0.87 vs. 0.87; p=0.91) in the no-FKBD group.
FKBD in simple stenting of bifurcation lesions improved acute functional outcome in SB compared to leaving the SB jailed. No significant difference was detected at follow-up. In both groups there was no significant functional late loss during follow-up. Thus, both strategies were equally effective in ensuring that side branch jailing would not cause ischaemia in the long term.
Erglis A., Dzērve V., Pahomova-Strautiņa J., Narbute I., Jēgere S., Mintāle I., Ligere R., Apinis P., Lejnieks A., Misiņa D., Rozenbergs A. A population-based cross-sectional study of cardiovascular risk factor in Latvia. Medicina (Kaunas). 2012;48(6):310-6. PubMed PMID: 22885365.
http://www.ncbi.nlm.nih.gov/pubmed/22885365
http://medicina.kmu.lt/1206/1206-06e.pdf
Abstract
To date, the epidemiological studies of noncommunicable diseases in Latvia were more episodic and covered only selected areas. The first national cross-sectional population-based survey of cardiovascular risk factors after regaining independence was carried out to provide reliable information on the cardiovascular risk factor profile in adults.
Computerized random sampling from the Registry of Latvian population was carried out. A total of 6000 enrolled subjects aged 25-74 years were divided into 10 age subgroups. The data of 3807 respondents (63.5% of all) were included into the final analysis.
The mean number of cardiovascular risk factors was 2.99±0.026 per subject: 3.45±0.043 and 2.72±0.030 for men and women, respectively. Of all the respondents, 75.2% had an increased total cholesterol level. Hypercholesterolemia was found in almost 56% of men and 41% of women in the age group of 25-34 years. Hyperglycemia was documented in 34.1% of the respondents (41.6% of men and 29.8% of women). More than two-thirds (67.8%) of the persons were overweight, while obesity was found in 25.6% of men and 32.6% of women. Arterial hypertension was identified in 44.8% of the respondents; its prevalence was higher in men than women (52.9% vs. 40.2%). There were more current smokers among men than women (30.5% vs. 11.4%).
The levels of cardiovascular risk factors in Latvia were found to be relatively high. The data can be utilized as baseline characteristics that can be compared down the road including the monitoring of health prevention activities.
Leja M., Cine E., Rudzite D., Vilkoite I., Huttunen T., Daugule I., Rumba-Rozenfelde I., Pimanov S., Liepniece-Karele I., Pahomova J., Purmalis K., Eglitis J., Pirags V., Dzerve V., Erglis A. Prevalence of Helicobacter pylori infection and atrophic gastritis in Latvia. Eur J Gastroenterol Hepatol. 2012 Dec;24(12):1410-7. Doi:10.1097/MEG.0b013e3283583ca5. PubMed PMID: 23114744.
http://www.ncbi.nlm.nih.gov/pubmed/23114744
Abstract
Helicobacter pylori infection and atrophic gastritis are related to an increased risk for gastric cancer. There is a decrease in global H. pylori prevalence. We analyzed the prevalence of H. pylori infection in Latvia by the plasma IgG test and the presence of atrophy by means of pepsinogen testing.
This subanalysis was carried out on a randomly selected cross-sectional sample of a general population of adults to access cardiovascular risk factors. Plasma samples were screened for H. pylori IgG (cutoff value 24 U/ml), and pepsinogens (Pg) I and II. Pg cutoff values of PgI/PgII ≤ 3 and PgI ≤ 70 ng/ml were used to assess the prevalence of atrophy of any grade and PgI/PgII ≤ 2 and PgI ≤ 30 ng/ml for advanced atrophy.
Altogether, 3564 serum samples were available for the study (2346 women, 1218 men; median age 54 years). Of the tested individuals, 79.21% were H. pylori positive, with no difference between sexes. The prevalence increased with age (P<0.001). Atrophy of any grade was identified in 1444 individuals (40.52%) and advanced atrophy in 475 individuals (13.33%). Linear association with age was present in both response types (P<0.001). The prevalence of atrophy of any grade was higher in women (41.73%) than in men (38.18%; P=0.04); this difference was lost for advanced atrophy (women 13.98%, men 12.07%; P=0.1).
The prevalence of H. pylori infection or atrophy remains high in Latvia. Determining the right cutoff value is critically important for pepsinogen-based atrophy detection in Europe in order to objectively stratify gastric cancer risk.
Agnelli G., George D.J., Kakkar A.K., Fisher W., Lassen M.R., Mismetti P., Mouret P., Chaudhari U., Lawson F., Turpie A.G.; SAVE-ONCO Investigators (Krievins D.). Semuloparin for thromboprophylaxis in patients receiving chemotherapy for cancer. N Engl J Med. 2012 Feb 16;366(7):601-9. PubMed PMID: 22335737.
http://www.ncbi.nlm.nih.gov/pubmed/22335737
http://www.nejm.org/doi/full/10.1056/NEJMoa1108898
Abstract
Patients receiving chemotherapy for cancer are at increased risk for venous thromboembolism. Limited data support the clinical benefit of antithrombotic prophylaxis.
In this double-blind, multicenter trial, we evaluated the efficacy and safety of the ultra-low-molecular-weight heparin semuloparin for prevention of venous thromboembolism in patients receiving chemotherapy for cancer. Patients with metastatic or locally advanced solid tumors who were beginning to receive a course of chemotherapy were randomly assigned to receive subcutaneous semuloparin, 20 mg once daily, or placebo until there was a change of chemotherapy regimen. The primary efficacy outcome was the composite of any symptomatic deep-vein thrombosis, any nonfatal pulmonary embolism, and death related to venous thromboembolism. Clinically relevant bleeding (major and nonmajor) was the main safety outcome.
The median treatment duration was 3.5 months. Venous thromboembolism occurred in 20 of 1608 patients (1.2%) receiving semuloparin, as compared with 55 of 1604 (3.4%) receiving placebo (hazard ratio, 0.36; 95% confidence interval [CI], 0.21 to 0.60; P<0.001), with consistent efficacy among subgroups defined according to the origin and stage of cancer and the baseline risk of venous thromboembolism. The incidence of clinically relevant bleeding was 2.8% and 2.0% in the semuloparin and placebo groups, respectively (hazard ratio, 1.40; 95% CI, 0.89 to 2.21). Major bleeding occurred in 19 of 1589 patients (1.2%) receiving semuloparin and 18 of 1583 (1.1%) receiving placebo (hazard ratio, 1.05; 95% CI, 0.55 to 1.99). Incidences of all other adverse events were similar in the two study groups.
Semuloparin reduces the incidence of thromboembolic events in patients receiving chemotherapy for cancer, with no apparent increase in major bleeding.
Ķīsis K., Krieviņš D., Naškoviča K., Gediņš M., Šavlovskis J., Ezīte N., Lietuvietis E., Zariņš K. Quality of life after endovascular abdominal aortic aneurysm repair: nellix sac-anchoring endoprosthesis versus open surgery. Medicina (Kaunas). 2012;48(6):286-91. PubMed PMID: 22885361.
http://www.ncbi.nlm.nih.gov/pubmed/22885361
http://medicina.kmu.lt/1206/1206-02e.pdf
Abstract
An increasing number of patients with abdominal aortic aneurysms are treated using endovascular rather than open surgical techniques. The Vascular Surgery Center, P. Stradins Clinical University Hospital, has the largest worldwide experience using a new type of endoprosthesis, which fills and anchors the device in the aneurysm sac. Within the framework of a clinical trial, the quality-of-life evaluation of patients treated using this type of device was carried out.
A cohort study was conducted from 2008 to 2011 comparing the quality of life (QOL) of patients after abdominal aortic aneurysm repair with either the new endovascular treatment method (EVAR) or open surgery (OS). Each group comprised 20 patients, and the quality-of life-evaluation was performed using the SF-36 questionnaire before operation, 1 month after operation, and 1 year after operation.
One month after operation, an improved QOL was documented in the EVAR group (47 [SD, 3] in the EVAR group vs. 38 [SD, 3] in the OS group, P<0.001). One year after operation, a significant improvement in QOL persisted although the difference between the groups diminished (48 [SD, 4] in the EVAR group vs. 42 [SD, 3] in the OS group, P<0.001).
The patients with abdominal aortic aneurysms who underwent EVAR using the new sac-anchoring endoprosthesis have improved health-related quality of life compared to the patients undergoing open surgical repair. The improvement in quality of life remained slightly better in the EVAR group 1 year after operation.
Kalejs M., Lacis R., Kasyanov V., Ozolanta I., Abdel Sayed P., Stradins P., Von Segesser L.K. Comparison of radial deformability of stent posts of different aortic bioprostheses. Interact Cardiovasc Thorac Surg. 2012 Nov 1. [Epub ahead of print] PubMed PMID: 23117234.
http://www.ncbi.nlm.nih.gov/pubmed/23117234
http://icvts.oxfordjournals.org/content/early/2012/11/01/icvts.ivs457.l…
Abstract
Little is known about the stent deformability required for optimal stented heart valve bioprosthesis design. Therefore, two bioprosthetic valves with known good long-term clinical results were tested. The strain in the radial direction of the stent posts of these valves was compared with contemporary bioprosthetic valves and a native porcine aortic root.METHODSMedtronic Intact and Carpentier-Edwards Standard (CES), and four contemporary bioprostheses, including one self-expanding prosthesis, were tested with three sonomicrometry probes per valve fixed at commissure attachment points. The mean values from 2400 data points from three measurements of the interprobe distances were used to calculate the radius of the circle circumscribed around the three probes. Changes in the radius of the aortic root at pressures 70-90 and 120-140 mmHg (pressure during diastole and systole) and that of the stent posts at 70-90 and 0-10 mmHg (transvalvular pressure gradient during diastole and systole) were compared.
An increase in radius by 7.3 ± 2.6, 8.7 ± 0.0 and 3.9 ± 0.0% for the porcine aortic root, CES and Intact valves, respectively, was observed during transition from diastolic to systolic pressure and less for contemporary bioprostheses-mean 2.5 ± 0.9%, lowest 1.2 ± 0.0.
The results indicate that the radial deformability of bioprosthetic valve stent posts can be as low as 1.2% for xenoaortic and 3.0% for xenopericardial prostheses with no compromise of valve durability. Although these results suggest that valve stent post-deformability might not be of critical importance, a concrete answer to the question of the significance of stent deformability for valve durability can be obtained only by acquiring long-term follow-up results for valve prostheses with rigid stents.
Starptautiski citējamos izdevumos PIEŅEMTAS publikācijas
Toorop G.J., Krievins D.K., de Borst G.J., Moll F.L. Mechanical stimulation of the carotid sinus baroreflex by an implantable device: first experience in man. J Vasc Surg, 2012, accepted.
Bergmane I., Lacis A., Lubaua I., Jakobsons E., Erglis A. Follow-up of the Patients after Stem Cell Transplantation for Pediatric Dilated Cardiomyopathy. Pediatric Transplantation, 2012, accepted (Manuscript ID: PEDTRANS-12-O-0081.R2)
Starptautiski citējamos izdevumos IESNIEGTAS publikācijas
Kasyanov V., Moreno-Rodriguez R., Kalejs M., Ozolanta I., Stradins P., Wen X., Yao H., Mironov V. Comparative analysis of structural, biochemical and material properties of fetal and adult porcine mitral heart valve leaflets. Journal of Materials Science: Materials in Medicine, 2012, under review.
Citos izdevumos pieņemtas publikācijas
Stradins, P., Kalejs, M., Lacis, R., Ozolanta, I., Murovska, M., Kasyanov, V. Polymer nanofiber materials matching the mechanical properties of native aortic valve. Pieņemts publicēšanai RSU Zinātniskie raksti, 2012
Stradins, P., Kalejs, M., Priedite, V., Lacis, R., Ozolanta, I., Murovska, M., Kasyanov, V. Fibroblast growth on nanofiber material matrices and changes to their mechanical properties. Pieņemts publicēšanai RSU Zinātniskie raksti, 2012
Publikācijas konferenču materiālos
Sondore D., Strenge K., Trusinskis K., Juhnevica D., Narbute I., Erglis A. Significant Correlation Between Coronary And Carotid Atherosclerotic Plaque Components By Intravascular Ultrasound Virtual Histology In Patients With Generalized Atherosclerosis. Abstract. Tramscatheter Cardiovascular Therapeutics (TCT) Symposium, October 22-26, 2012, Miami, USA. J Am Coll Cardiol. 2012;60 (17_S):B80-B81. WOS: 000310210101084 (Datu bāze: WoS)
http://content.onlinejacc.org/article.aspx?articleid=1383554
Abstract
Also there are differences in the carotid and coronary vasculature, both vascular distributions are believed to share common pathway in disease progression. However, little is known about atherosclerotic plaque composition and morphological differences between carotid and coronary artery disease. The aim of the study was to determine correlation between intravascular ultrasound virtual histology (IVUS-VH) defined atherosclerotic plaque components in coronary and carotid artery atherosclerotic lesions.
In a single-center prospective study 100 consecutive patients (60 men and 40 women) with mean age 69.61±8.44 years were enrolled. All patients were scheduled for carotid and/or coronary artery stenting and underwent IVUS-VH examination of coronary and carotid plaque before intervention. Statistical comparison between coronary and carotid artery plaque composition according to IVUS-VH was done with Pearson correlation.
High percentage of necrotic core was found both in coronary (22.55±7.30) and carotid (19.84±9.35) artery plaques, r=0.459, p<0.001. Percentage of dense calcium (13.58±8.15 vs. 7.67±5.64, r=0.557, p<0.001), fibrolipids (12.54±9.08 vs. 19.55±9.96, r=0.379, p<0.001) and fibrotic tissue (51.72±10.33 vs. 53.42±7.95, r=0.422, p<0.001) showed moderate, statistically significant correlation between coronary and carotid arteries, respectively
We found significant correlations of IVUS-VH determined atherosclerotic plaque components between coronary and carotid arteries in patients with atherosclerosis involving both arterial beds.
Trusinskis K., Juhnevica D., Strenge K., Sondore D., Narbute I., Jegere S., Zarakauska L., Erglis A. Higher inter-cellular-adhesion molecule 1 levels in ST-segment elevation myocardial infarction patients associates with plaque vulnerability in non-culprot lesions at 10 months follow-up. Abstract. 61st Annual Scientific Session of the American College of Cardiology (ACC) 2012, March 24-27, 2012, Chicago, USA. J Am Coll Cardiol. 2012;59(13s1):E559. WOS:000302326700560 (Datu bāze: WoS)
http://content.onlinejacc.org/article.aspx?articleid=1204633
Abstract
Several studies have reported risks of adverse late and early cardiac outcomes associated with elevated levels of inter-cellular-adhesion molecule 1 (ICAM-1) in acute coronary patients. ICAM-1 cause the migration of the monocytes into the intima of the coronary artery thus playing an important role in inflammatory cascade. Plaque composition is another indicator for extent of ongoing inflammation in coronary lesion. We hypothesized that higher ICAM-1 levels could be related to plaque vulnerability in non-culprit lesions.
A total of 65 patients presenting with ST-segment elevation myocardial infarction (STEMI) at Latvian Centre of Cardiology were prospectively enrolled in this study. After thrombus aspiration, IVUS with i-Map tissue characterisation (Qivus 2.0, Medis medical imaging systems by, Leiden, the Netherlands) of the infarct-related artery followed by stent implantation was done. Fibrotic and necrotic tissue were analyzed as categorical values. As cut off points of procentual plaque composition for necrotic and fibrotic tissue were defined as 30% and 60%, respectively.
Higher levels of ICAM-1 at index event were associated with necrotic tissue above 30% at distal segment (433.71±250.58 vs 269.88±106.97(ng/ml), p=0.004) and proximal segment (359.22±195.22 vs 240.94±80.43(ng/ml), p=0.004). Similarly, higher levels of ICAM-1 at follow-up were associated with necrotic tissue above 30% at distal segment (480.35±282.20(ng/ml) vs 263.25±114.59(ng/ml), p=0.001) and proximal segment (360.63±208.98(ng/ml) vs 234.81±95.91(ng/ml), p=0.007). Lower levels of ICAM-1 at index event were associated with fibrotic tissue above 60% at distal segment (270.79±107.82 vs 403.69±242.16(ng/ml), p=0.013) and proximal segment (243.90±83.90 vs 333.82±185.11(ng/ml), p=0.024). Lower levels of ICAM-1 at follow-up were associated with fibrotic tissue above 60% at distal segment (264.62±115.39 vs 433.21±277.57(ng/ml), p=0.007) and proximal segment (236.86±101.56 vs 334.13±196.16(ng/ml), p=0.033).
Higher levels of ICAM-1 were associated with plaque vulnerability in non-culprit lesions in STEMI patients at 10 month follow-up.
Kauliņa, A., Voita, D. Integratīvās mācību metodikas efektivitāte specifisku lasīšanas traucējumu mazināšanā sākumskolā. RPIVA 6. starptautiskās zinātniskās konferences Teorija praksei mūsdienu sabiedrības izglītībā rakstu krājums. Zinātniskie raksti, 2012, 152-157. lpp. Rīga: RPIVA. ISBN 978-9934-8215-9-2
http://www.rpiva.lv/pdf/6_starptzinkonf.pdf
Kalejs, M., Stradins, P., Priedite, V., Lacis, R., Ozolanta, I., Kasyanov, V. Polymer Nanofiber Materials Matching The Mechanic Properties Of Native Aortic Valve. 5th Biennial Meeting on Heart Valve Biology and Tissue Engineering. Mykonos, Grieķija, 18.-20. maijs, 2012.
http://www.qscience.com/doi/full/10.5339/qproc.2012.heartvalve.4.48
Read More: http://www.qscience.com/doi/full/10.5339/qproc.2012.heartvalve.4.48
Abstract
Porous electrospun nanofiber materials are very promising as matrices for heart valve tissue engineering. Not only biocompatibility is important for this material but also the mechanical features - it has to be strong enough to withhold the pressure after implantation as well as deformable enough for better distribution of shear stress along its surface. Deformability is also crucial for stimulation of fibre production by fibroblasts on these matrices. Altogether 8 differing density variants of electrospun nanofiber materials from gelatine, polyurethane (PUR), polylactic acid (PLA) and polycaprolactone (PCL) were analysed using uniaxial tensile tests. Data were compared to mechanical properties of porcine aortic valve (AV) leaflets in radial and circumferential directions. Data are presented as means ± standard deviation. In circumferential direction modulus of elasticity (E) of native porcine AV is 9.7±1.3MPa and - 1.0±0.2MPa in radial. Ultimate stress and strain is 44.8±5.9% and 2.3±0.6 MPa in circumferential and 95.6±31.4% and 0.5±0.2MPa in radial direction for native leaflets. Closest of the materials to match the mechanical properties of porcine AV in circumferential direction was PUR with density 6.2 g/sqm showing E of 3.9±0.5 MPa, ultimate stress and strain - 5.3±1.68MPa and 141.8±43.9MPa respectively. Closest to match radial direction was gelatine with density 5.7 g/sqm showing E of 0.64±0.14 MPa, ultimate stress and strain - 0.38±0.05MPa and 82.53±10.20MPa respectively. Native AV leaflets have a non-linear and anisotropic response to stress in uniaxial tensile tests. Hence to model as precisely as possible their mechanical properties we suggest to use a combined material made in a sandwich fashion with layers of gelatine on the outside and PUR in the middle with their fibbers predominantly orientated in perpendicular directions. The other tested materials PLA and PCL either lacked strength to mimic leaflets in circumferential direction or deformability required for the radial direction.
Kalejs, M., Stradins, P., Lacis, R., Ozolanta, I., Kasyanov, V. Mechanical Properties Of Bioprostheses Leaflets Compared To Human Aortic Valves. 5th Biennial Meeting on Heart Valve Biology and Tissue Engineering, Mykonos, Grieķija, 18.-20. maijs, 2012.
http://www.qscience.com/doi/full/10.5339/qproc.2012.heartvalve.4.47
Abstract
Heart valve bioprostheses suffer from gradual tissue deterioration, which has a causal link with valve tissue mechanical properties. Limited data on mechanical properties of commercially available bioprostheses comparing them to native human aortic valves (AV) is available. Our objective was to determine the mechanical properties of several contemporary bioprostheses and compare them with native human and porcine aortic valves. Leaflets from 5 unchanged human AV, collected from cadaveric hearts and 5 porcine AV, and from 3 of each kind of bioprostheses - Medtronic Hancock II, Sorin Soprano and Medtronic Freestyle were analysed using uniaxial tensile tests in radial and circumferential directions. Data are presented as means ± standard deviation. In both tested directions there's a shift to the stress axis of stress-strain curve for HancockII prostheses and even more for Soprano prostheses when compared to native human valves. In circumferential direction modulus of elasticity (E) of native human AV is 15.34±3.84MPa, porcine AV - 9.7±1.3MPa, Freestyle - 9.0±3.0MPa, HancockII - 22.5±2.2MPa and Soprano - 29.5±6.0MPa. In radial direction E of native human AV is 1.98±0.15MPa, porcine AV - 1.0±0.2MPa, Freestyle - 0.8±0.3MPa, HancockII - 2.5±0.2MPa and Soprano - 15.8±5.4MPa. Xeno-aortic bioprostheses have a non-linear and anisotropic response to stress in uniaxial tensile tests similar to native AV leaflets. HancockII has gained mechanical strength but lost tissue elasticity compared to native valve tissue. Leaflets of Soprano prostheses are even more rigid and lack pronounced material anisotropy. These differences in mechanical properties may accelerate deterioration of bioprostheses, causing altered stress distribution within valve leaflets. These data provide important information about what mechanical properties future valve substitutes should conform to.
