Relation between torsion and cross-sectional area change in the human left ventricle

During the ejection phase, motion of the left ventricular (LV) wall is such that all myocardial fibers shorten to the same extent. In a mathematical model of LV mechanisms it was found that this condition could be satisfied only if torsion around the long axis followed a unique function of the ratio of cavity volume to wall volume. When fiber shortening becomes non-uniform due to cardiac pathology, this pathology may be reflected in aberration of the torsional motion pattern. In the present study we investigated whether the predicted regular motion pattern could be found in nine healthy volunteers, using Magnetic Resonance Tagging. In two parallel short-axis cross-sections, displacement, rotation, and area ejection were derived from the motion of tags, attached non-invasively to the myocardium. Information from both sections was combined to determine area ejection, quantified as the change in the logarithm of the ratio of cavity area to wall area, and torsion, represented by the shear angle on the epicardium. Linear regression was applied to torsion as a function of area ejection. The slope thus found (-0.173 +/- 0.024 rad, mean +/- S.D.) was similar to the slope as predicted by the model of LV mechanics (-0.194 +/- 0.026 rad). In conclusion, the relation between area ejection and torsion could be assessed noninvasively in humans. In healthy volunteers, the relation was close to what was predicted by a mathematical model of LV mechanics, and also close to what was found earlier in experiments on animals. [Journal Article; In English; United States

Cross-validation of a learning climate instrument in a non-western postgraduate clinical environment

Contains fulltext : 191290.pdf (publisher's version ) (Open Access)BACKGROUND: In postgraduate training, there is a need to continuously assess the learning and working conditions to optimize learning. Students or trainees respond to the learning climate as they perceive it. The Dutch Residency Educational Climate Test (D-RECT) is a learning climate measurement tool with well-substantiated validity. However, it was originally designed for Dutch postgraduate trainees and it remains to be shown whether extrapolation to non-Western settings is viable. The dual objective of this study was to revalidate D-RECT outside of a Western setting and to evaluate the factor structure of a recently revised version of the D-RECT containing 35 items. METHODS: We invited Filipino internal medicine residents from 96 hospitals to complete the revised 35-item D-RECT. Subsequently, we performed a confirmatory factor analysis to check the fit of the 9 scale model of the revised 35-item D-RECT. Inter-rater reliability was assessed using generalizability theory. RESULTS: Confirmatory factor analysis unveiled that the factor structure of the revised 35-item D-RECT provided a reasonable fit to the Filipino data, after removal of 7 items. Five to seven evaluations of individual residents were needed per scale to obtain a reliable result. CONCLUSION: Even in a non-Western setting, the D-RECT exhibited psychometric validity. This study validated the factor structure of the revised 35-item D-RECT after some modifications. We recommend that its application be extended to other Asian countries and specialties

Skeletal muscle transverse strain during isometric contraction at different lengths

An important assumption in 2D numerical models of skeletal muscle contraction involves deformation in the third dimension of the included muscle section. The present paper studies the often used plane strain description. Therefore, 3D muscle surface deformation is measured from marker displacements during isometric contractions at various muscle lengths. Longitudinal strains at superficial muscle fibers( - 14 +/- 2.6% at L-0, n = 57) and aponeurosis (0.8 +/- 0.9% at L-0) decrease with increasing muscle length. The same holds for transverse muscle surface strains in superficial muscle fibers and aponeurosis, which are comparable at intermediate muscle length, but differ at long and short muscle length. Because transverse strains during isometric contraction change with initial muscle length, it is concluded that the effect of muscle length on muscle deformation cannot be studied in plane strain models. These results do not counteract the use of these models to study deformation in contractions with approximately - 9% longitudinal muscle fiber strain, as transverse strain in superficial muscle fibers and in aponeurosis tissue is minimal in that case. Aponeurosis surface area change decreases with increasing initial muscle length, but muscle fiber surface area change is - 11%, independent of muscle length. Assuming incompressible muscle material, this means that strain perpendicular to the muscle surface equals 11%. Taking the relationship between transverse and longitudinal muscle fiber strain into account, ii is hypothesized that superficial muscle fibers flatten during isometric contractions. (C) 1999 Elsevier Science Ltd. All rights reserve

Program for laparoscopic urologic skills: a newly developed and validated educational program.

Item does not contain fulltextOBJECTIVE: To develop and evaluate a program for laparoscopic urologic skills (PLUS) to determine the face, content, and construct validation to achieve uniformity and standardization in training residents in urology. METHODS: The PLUS consists of 5 basic laparoscopic tasks. Three tasks were abstracted from the Fundamentals of Laparoscopic Surgery program, and 2 additional tasks were developed under continuous evaluation by expert urologists. Fifty participants were recruited from different hospitals and performed the final PLUS training. They all completed a questionnaire after performance. Three outcome parameters were measured: performance quality, time, and dropped objects. The relationship between laparoscopic experience and the outcome parameters was investigated. RESULTS: Of the 50 participants, 13 were students, 20 were residents, and 17 were urologists. Double-log linear regression analysis for all 5 tasks showed a significant effect (effect size range 0.53-0.82; P < .0005) for laparoscopic experience on performance time. Substantial correlations were found between experience and quality ratings (log-linear regression effect size 0.37; P = .012) and the number of dropped objects (Spearman correlation effect size 0.49; P < .01). The usefulness of the PLUS model as a training tool for basic laparoscopic skills was rated 4.55 on a scale from 1 (not useful) to 5 (useful) (standard deviation 0.58; range 3-5). CONCLUSION: The results of the present study indicated the face, content, and construct validity for the PLUS. The training is considered appropriate for use as a primary training tool for an entry test or as part of a step-wise training program in which basic and procedural laparoscopic skills are integrated.1 april 201