Topography of brain electrical activity: a bioengineering approach

The aim of this work is to describe a system for the mono- and bi-dimensional analysis of brain electrical activity. The analysis was carried on either by visual inspection of mono- and bi-dimensional data, or by automatic feature extraction from the bidimensional data. Because of the importance of visual inspection for the analysis of experimental data, particular care was devoted to optimize the displayed data perceptually. For automatic screening of large amounts of data (and to allow long term studies of clinical records), statistical facilities were also provided. One purpose of the system was to develop image processing algorithms oriented toward biomedical images, that could be easily implemented on special purpose, low cost hardware, like VLSI or microcomputer arrays. This was possible because of the modularity of the larger part of bidimensional processing, such as interpolation and statistical analysis. Results of an experiment on Visual Evoked Response are presented, showing that through abidimensional analysis of the recorded data the resolution achievable in the localization of brain electrical activity can be increased to less than 1 cm.     

Cardiac energetics analysis after aortic valve replacement with 16-mm ATS mechanical valve

The 16-mm ATS mechanical valve is one of the smallest prosthetic valves used for aortic valve replacement (AVR) in patients with a very small aortic annulus, and its clinical outcomes are reportedly satisfactory. Here, we analyzed the left ventricular (LV) performance after AVR with the 16-mm ATS mechanical valve, based on the concept of cardiac energetics analysis. Eleven patients who underwent AVR with the 16-mm ATS mechanical valve were enrolled in this study. All underwent echocardiographic examination at three time points: before AVR, approximately 1 month after AVR, and approximately 1 year after AVR. LV contractility (end-systolic elastance [Ees]), afterload (effective arterial elastance [Ea]), and efficiency (ventriculoarterial coupling [Ea/Ees] and the stroke work to pressure–volume area ratio [SW/PVA]) were noninvasively measured by echocardiographic data and blood pressure measurement. Ees transiently decreased after AVR and then recovered to the pre-AVR level at the one-year follow-up. Ea significantly decreased in a stepwise manner. Consequently, Ea/Ees and SW/PVA were also significantly improved at the one-year follow-up compared with those before AVR. The midterm LV performance after AVR with the 16-mm ATS mechanical valve was satisfactory. AVR with the 16-mm ATS mechanical valve is validated as an effective treatment for patients with a very small aortic annulus. The cardiac energetics variables, coupling with the conventional hemodynamic variables, can contribute to a better understanding of the patients’ clinical conditions, and those may serve as promising indices of the cardiac function.     

Prospects for microtechnology and nanotechnology in bioengineering of replacement microvessels

CONTEXT: Due to its anticipated curative potential, therapeutic angiogenesis recently became a major preoccupation for the biomedical research community. Most of the related work reported to date employs either biochemical or genetic tools. OBJECTIVE: To identify opportunities for application of the current developments in microtechnology and nanotechnology to the field of therapeutic angiogenesis. DATA SOURCES: Survey of recent English-language literature on microvascular tissue engineering in the context of therapeutic angiogenesis. We include our results regarding the role played by microtopographical cues in the progression of angiogenesis, such as those produced during processing of the extracellular matrix by chronic inflammatory cells. CONCLUSION: While notable accomplishments have been identified in the field of tissue engineering of larger vessels, reports on purposeful assembly of microvascular structures with the ability to be transferred in vivo by implantation are still scarce. Under these circumstances, we suggest the development of a new class of implantable biomedical microdevices, that is, "angiogenesis assist devices" (or "angiochips"), and we indicate some of their conceivable applications.     

Cardiac myxoma of the tricuspid valve in a dog

A case of cardiac myxoma arising from the tricuspid valve is described in an 8-year-old dog that had suffered intermittent episodes of syncope. At surgical operation, a large, irregular, gelatinous mass was found attached to the septal leaflet of the tricuspid valve. The excised tumour, measuring 5x4x3.5 cm, had a grey-to-yellow, friable, mucoid, multilobulated and polypoid appearance, with focal haemorrhage. Histologically, the tumour consisted of a hypocellular mass of a myxoid matrix, rich in acid mucopolysaccharides, with a supporting structure of spindle-like, elongated or stellate cells scattered in an abundant stroma. The surface of the mass was covered by a single layer of endothelial-like cells. Immunohistochemistry revealed that the surface cells of the mass were positive for the endothelial marker CD34 and the constituent cells within the mass reacted positively and uniformly with antibodies to vimentin and alpha-smooth muscle actin. The dog died 36 h after the operation and, at necropsy, wide dissemination of myxomatous embolization to the intrapulmonary arteries was found.     

Re-do mitral valve replacement for a bioprosthetic valve with central transvalvular leakage in a patient with ischemic cardiomyopathy: a case report

Journal of Artificial Organs - Transvalvular leakage (TVL) of a prosthetic heart valve is not negligible regurgitant flow in patients with critically low contractile function. Although the opening...     

Defining valve performance: importance and difficulties in testing heart valve replacement devices.

Defining and assessing the performance of heart valve replacement devices is difficult. This article is a brief discussion of the problems and present state of the art.     

Cardiac transgenic matrix metalloproteinase-2 expression induces myxomatous valve degeneration: a potential model of mitral valve prolapse disease

IntroductionMyxomatous mitral valve “degeneration” with prolapse (MVP) is the most frequent form of nonischemic mitral valve disease. In myxomatous valves, interstitial cells express extracellular matrix-degrading enzymes and it has been postulated that matrix metalloproteinases (MMPs) contribute to these changes.MethodsWe generated mice with cardiac-specific expression of constitutively active MMP-2 under the control of the α-myosin heavy chain promoter.ResultsThese mice are normal at 4–6 months of age; at 12–14 months the mitral valves and chordae tendineae exhibit severe myxomatous change with echocardiographic MVP. Myxomatous change was also evident to a lesser extent in the aortic valves. Myxomatous changes were heterogeneous and limited to the left side of the heart with major disorganization of collagen bundles within the lamina fibrosa. Alcian blue/PAS-stained valves revealed massive accumulation of acidic glycosoaminoglycans within the lamina spongiosa, consistent with valvular interstitial cell differentiation to a chondrocytic phenotype. Cells with the histologic features of hypertrophied chondrocytes were found within the chordae tendineae and the tips of the mitral papillary muscles.ConclusionThis report demonstrates that increased activity of a single enzyme, MMP-2, within a transgenic context reproduces many of the features of the human MVP syndrome. The cardiac-specific MMP-2 transgenic mouse potentially provides a unique experimental platform for the evaluation of nonsurgical therapies based on the underlying pathophysiology of this disease.     

Mechanical valve replacement of the systemic atrioventricular valve in children

In children with systemic atrioventricular valve disease (SAVVD), reconstructive surgery is the primary goal. However, in cases with severely dysplastic valves or failed repair, valve replacement is the only option. The purpose of this study was to assess the early and late outcome following mechanical valve replacement in SAVVD. Between 1989 and 2003, 31 children underwent mechanical valve replacement (19 St. Jude Medical, 12 Carbomedics) in SAVVD (27 mitral, 3 tricuspid in corrected transposition of the great arteries, 1 common in an univentricular heart) at our institution. The ages ranged from 3 months to 15 years (mean 4 years) and body weight varied between 4.2 and 57 kg (mean 13.3 kg). The size of prostheses ranged between 16 and 31 mm (mean 23.9 mm). The main indication for valve replacement was severe insufficiency of left atrioventricular valve (84%); 84% of the patients had had a previous cardiac operation. The overall hospital mortality was 6.5% The mean follow up was 7.7 years (range 2-13 years). Ninety percent of children represent sinus rhythm, 87% are in NYHA class I. All patients were placed on a regimen of Phenprocoumon aiming to maintain the international normalized ratio (INR) between 3.0 and 4.0. Since 1994, INR self-management of oral anticoagulation was performed either by the patient or his or her parents. There was no anticoagulation-related complication in this patient group. Mechanical valve replacement in left atrioventricular valve disease carries a low operative risk across the spectrum of pediatric age despite previous operations in most cases. Long-term survival and quality of life are good in nearly all cases. The rate of anticoagulation-related complications is very low, especially when INR self management is performed.     

儿童心脏瓣膜置换手术技巧及效果

目的总结14例儿童心脏瓣膜置换术的经验,探讨儿童瓣膜置换的手术指征、瓣膜选择、手术技术和术后抗凝治疗等问题。方法全组14例中10例为先天性心脏瓣膜病变,3例风湿性病变,1例先天性室间隔缺损致心内膜炎、主动脉瓣膜菌栓。在中低温体外循环下手术,二尖瓣置换7例,主动脉瓣置换6例,二尖瓣置换 主动脉瓣置换1例。均采用机械瓣。若合并其它先天性心脏畸形或三尖瓣关闭不全,同期矫治。术后常规应用华法林抗凝。结果本组手术死亡1例,12例心功能恢复至I级,1例心功能II级。发生1例感染性心内膜炎,治愈。均坚持采用华法林抗凝,无血栓栓塞及抗凝相关并发症发生,瓣膜功能良好。结论儿童心脏瓣膜置换术采用机械瓣效果较好;应用低强度的华法林进行抗凝治疗安全可靠。     

儿童心脏瓣膜置换手术技巧及效果

目的 总结1999年9月至2006年9月14例儿童心脏瓣膜置换术的经验。探讨儿童瓣膜置换的手术指征、辩膜选择、手术技术和术后抗凝治疗等问题。方法 全组14例中10例为先天性心脏瓣膜病变，3例风湿性病变，1例先天性室间隔缺损致心内膜炎、主动脉瓣膜菌栓。在中低温体外循环下手术，二尖瓣置换7例，主动脉瓣置换6例，二尖瓣置换＋主动脉瓣置换1例。均采用机械瓣。若合并其它先天性心脏畸形或三尖瓣关闭不全，同期矫治。术后常规应用华法林抗凝。结果 本组手术死亡1倒，12例心功能恢复至Ⅰ级，1例心功能Ⅱ级。发生1例感染性心内膜炎，治愈。均坚持采用华法林抗凝，无血栓栓塞及抗凝相关并发症发生，辩膜功能良好。结论 儿童心脏瓣膜置换术采用机械瓣效果较好；应用低强度的华法林进行抗凝治疗安全可靠。     

Bioengineering aspects of heart valve replacement

Biomedical engineering inputs have been important in the design, development and testing of substitute heart valves as well as in the pre- and post-operative management of patients with cardiac valve disease. This paper is a review of heart valve replacement whose goal is the enhancement of future bioengineering contributions. We review the approach to the patient with valvular heart disease, and the sources of early and late postoperative pathology with emphasis on complications of the prostheses used. Major significant problem areas relate to the noninvasive evaluation of cardiovascular function (both before and after surgery), device design, hemodynamics, and the need for thromboresistant and durable materials.     

Hormone replacement therapy and bone mineral density: a co-twin approach

OBJECTIVE: Our objective was to estimate the difference in bone mass at clinically relevant sites within female twin pairs who were discordant for use of hormone replacement therapy (HRT). METHODS: We studied 46 female twin pairs who were discordant for HRT use. Bone mineral content and density were measured at the lumbar spine, total hip, femoral neck, 13 total forearm, and the total body. HRT use, calcium intake, physical activity, alcohol intake, and lifetime smoking were determined by questionnaire. RESULTS: Within a pair, lumbar spine bone mineral density was significantly greater in past and current HRT users compared with nonusers (6.2% +/- 2.0%; P = 0.006). In those pairs who were currently using HRT, the within-pair difference in lumbar spine bone density was 7.8% +/- 2.1% (P = 0.002), and a significant within-pair difference in forearm bone density (5.1 +/- 2.1%; P = 0.02) was apparent. A significant difference (4.6%; P = 0.03) was observed in total body bone mineral content when an adjustment was made for age, lean mass, fat mass, and height. CONCLUSIONS: In keeping with randomized clinical trial findings, these results indicate that HRT in routine clinical use protects significantly against menopausal bone loss at the lumbar spine and the forearm. Our results also quantify the magnitude of the benefit of HRT on bone density that might be anticipated in clinical practice.     

Therapeutic neovascularization: contributions from bioengineering

A number of pathological entities and surgical interventions could benefit from therapeutic stimulation of new blood vessel formation. Although strategies designed for promoting neovascularization have shown promise in preclinical models, translation to human application has met with limited success when angiogenesis is used as the single therapeutic mechanism. While clinical protocols continue to be optimized, a number of exciting new approaches are being developed. Bioengineering has played an important role in the progress of many of these innovative new strategies. In this review, we present a general outline of therapeutic neovascularization, with an emphasis on investigations using engineering principles to address this vexing clinical problem. In addition, we identify some limitations and suggest areas for future research.