Objective:The objective was to compare National Institutes of Health (NIH) funding rates and application success rates among surgeon and nonsurgeon-scientists over the past 2 decades. Summary Background Data: Surgeons may be capable of accelerating the translation of basic research into new clinical therapies. Nevertheless, most surgeon-scientists believe they are at a disadvantage in competing for peer-reviewed funding, despite a recent emphasis on "translational science" by organizations such as the NIH. Methods: We accessed databases from the NIH and the American Association of Medical Colleges. Results: Although total competing NIH awards rose 79.2% from 5608 to 10,052, the much smaller number of surgical awards increased only by 41.4% from 157 to 222. There was a small but statistically significant difference between total NIH and surgical application success rates (29% vs. 25%, P Ͻ 0.01). However, the persistently low percent of NIH funding going to surgical investigators was due primarily to the very small number of surgical applications, and to a much smaller increase in the absolute number of applications over time (464 vs. 23,847). As a result, the number of grants per 100 faculty members was more than 4 times higher among nonsurgical than surgical faculties at US medical schools. Conclusion: NIH funding to academic surgeons is declining relative to their nonsurgical colleagues. This trend will likely be reversed only by an increase in the number of grant applications submitted by surgeon-scientists. Structural changes in surgical training programs, and in the economics of academic surgery, may support a greater contribution of surgeon-scientists to the success of translational research. (Ann Surg 2008;247: 217-221)
Objectives-Both the Young Laplace law and finite element (FE) based methods have been used to calculate left ventricular (LV) wall stress. We tested the hypothesis that the Young Laplace law is able to reproduce results obtained with FE method.Methods-Magnetic resonance (MRI) images with non-invasive tags were used to calculate 3D myocardial strain in five sheep 16 weeks after anteroapical myocardial infarction and in one of those sheep 6 weeks after a Dor procedure. Animal specific FE models were created from the remaining five animals using MRI images obtained at early diastolic filling. FE based stress in the fiber, cross fiber and circumferential directions was calculated and compared to stress calculated with (Young Laplace law) and without (Modified Laplace) the assumption that wall thickness is very much less than the radius of curvature.Results-First,circumferential stress calculated with the Modified Laplace law is closer to results obtained with the FE method than stress calculated with the Young Laplace law. However, there are pronounced regional differences with the largest difference between Modified Laplace and FE occurring especially in the inner and outer layers of the infarct borderzone. Also, stress calculated with Modified Laplace is very different than stress in the fiber and cross fiber direction calculated with FE. As a consequence, the Modified Laplace law is inaccurate when used to calculate the effect of the Dor procedure on regional ventricular stress. Conclusion-The FE method is necessary to determine stress in the LV with post infarct and surgical ventricular remodeling. An alternative approach to quantifying ventricular wall stress and stiffness is mathematical modeling based on the conservation laws of continuum mechanics, the most versatile of which is the finite element (FE) method. Keywords[11] The FE method used in this study for continuum analysis of the heart includes several features that are uncommon in conventional FE methods. First, the constitutive relationship is non-linear and anisotropic [12,13] with direction based directly on measured 3-D myofiber angle distributions. [14,15] Next, the models undergo large or finite deformation with difference in dimensions between the enddiastole (ED) and end-systole (ES) that is greater than 10%. More recent models now also include the transmural heterogeneity of cellular excitation-contraction coupling mechanisms.[16]We calculated stress with (Young Laplace law) and without (Modified Laplace) the assumption that wall thickness is very much less than the radius of curvature with large deformation finite element methods using data collected from sheep after antero-apical myocardial infarction (MI) and after Dor procedure. We tested the hypothesis that stress in the circumferential direction calculated with Laplace law is equal to values obtained with the FE method. Since stress in the cross fiber direction is likely to cause volume overload hypertrophy and stress in the fiber direction is likely to cause pressure overload hy...
Even though studies on isolated papillary muscles and cardiomyocytes can be applied to the mechanics of a beating heart, it is not always easy for physicians to relate these findings to clinical medicine. Thus, it is important to extend the studies to intact heart either in simulations or in animal models and even better to validate the results with human subjects. Advances in engineering and computer technology have allowed us to bridge the gap between physiology and mechanics. Cardiomyocyte stress/strain relates to muscle energy expenditure, which dictates oxygen and substrate utilization. Appreciation of this sequential relationship by clinicians will facilitate the logical development and assessment of therapies. Theory of finite element analysis (FEA) can predict cardiac mechanics under normal and pathologic conditions. Imaging studies provide an avenue to relate these predictions indirectly to experimental studies. In this fashion, we can understand the mechanical basis for the micro- and macroanatomical twisting motion of the beating heart. The purposes of this manuscript are: (1) to examine the terms that are traditionally used to describe mechanical stresses and strain within the ventricle, (2) to explore the three-dimensional organization of cardiomyocytes that influences global ventricular function, (3) to apply mechanical measures to both single cardiomyofibrils and the intact ventricle (4) to evaluate mathematical and computer models used to characterize cardiac mechanics, and (5) to outline the clinical methods available to measure ventricular function and relate findings from FEA to pathologic conditions.
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