Modeling mitral valve stenosis: A parametric study on the stenosis severity level

New computational techniques providing more accurate representation of human heart pathologies could help uncovering relevant physical phenomena and improve the outcome of medical therapies. In this framework, the present work describes an efficient computational model for the evaluation of the ventricular flow alteration in presence of mitral valve stenosis. The model is based on the direct numerical simulation of the Navier–Stokes equations two-way coupled with a structural solver for the left ventricle and mitral valve dynamics. The presence of mitral valve stenosis is mimicked by a single-parameter constraint acting on the kinematics of the mitral leaflets.Four different degrees of mitral valve stenosis are considered focusing on the hemodynamic alterations occurring in pathologic conditions. The mitral jet, generated during diastole, is seen to shrink and strengthen when the stenosis gets more severe. As a consequence, the kinetic energy of the flow, the tissues shear stresses, the transvalvular pressure drop and mitral regurgitation increase. It results that, as the stenosis severity level increases, the geometric and effective orifice areas decrease up to 50% with respect the normal case due to the reduced leaflets mobility and stronger blood acceleration during the diastolic phase. The modified intraventricular hemodynamics is also related to a stronger pressure gradient that, for severe stenosis, can be more than ten times larger than the healthy valve case. These computational results are fully consistent with the available clinical literature and open the way to the virtual assessment of surgical procedures and to the evaluation of prosthetic devices.     

Structure and orientation of collagen fibres in human mitral valve

The structure and distribution of collagen fibres in chordae tendineae, anterior leaflet and annulus fibrous of human mitral valve has been investigated using high and small angle X-ray diffraction. The molecular packing of collagen in native mitral valve components is very similar to that in native rat tail tendon. The distribution and orientation of collagen fibres in unstretched and stretched specimens has been deduced by the arcing of the high and small angle meridional reflections. Collagen fibres, which are aligned along the chordae tendineae, are preferentially distributed along the branchings of the chordae into the anterior leaflet and then course towards the annulus fibrous. However, in the anterior leaflet a considerable amount of collagen fibres are organized in a tridimensional isotropic network even after high deformation of the tissue.     

Absence of Cardiac Valve Dysfunction in Obese Patients Treated with Sibutramine

BACH, DAVID S., AILA M. RISSANEN, CARL M. MENDEL, GILLIAN SHEPHERD, STEVEN R. WEINSTEIN, FINIAN KELLY, TIMOTHY B. SEATON, BABABHAI PATEL, TUULA A. PEKKARINEN, AND WILLIAM F. ARMSTRONG. Absence of cardiac valve dysfunction in obese patients treated with sibutramine. Obes Res. Objective: Serotonin-releasing agents prescribed as weight-loss medications have been implicated as a cause of acquired aortic and mitral valve abnormalities. Sibutramine hydrochloride (MERIDIA®) is a serotonin and norepi-nephrine reuptake inhibitor with proven efficacy of weight reduction. The purpose of this study was to determine the incidence of cardiac valve disease in sibutramine-treated patients. Research Methods and Procedures: Obese patients with type 2 diabetes mellitus enrolled in an ongoing double-blind, placebo-controlled, parallel-arm, 12-month study of sibutramine (followed by a 12-month open label extension) underwent transthoracic echocardiographic imaging and color Doppler interrogation for assessment of cardiac valve anatomy and function. Results: A total of 210 patients were evaluated. Of these, 133 were receiving sibutramine (72 in the double-blind period), and 77 were receiving placebo. The mean ± Standard Deviation age was 54±9 years, and the mean duration of treatment was 229±117 days (approximately 7. 6 months). The prevalence of left-sided cardiac valve dysfunction was low and similar for the two treatment groups (sibutramine 31133, or 2. 3%; placebo 2/77, or 2. 6%). All five cases were cases of aortic insufficiency; four were mild, one was severe (in a placebo patient). All three sibutramine cases were patients over age 50; two had a history of systemic hypertension. Conclusion: The prevalence of left-sided cardiac valve dysfunction was not higher than background in obese patients treated with sibutramine for an average of 7. 6 months.     

A surgeon’s quest

This last part of surgery, namely, operations, is a reflection on the healing art; it is a tacit acknowledgement of the insufficiency of surgery. It is like an armed savage who attempts to get that by force which a civilised man would get by stratagem. John Hunter [Palmer John (ed.) 1835 The works of John Hunter, Vol. 1 (London: Longman)]