The cardiac torsion as a sensitive index of heart pathology: A model study.

The torsional behaviour of the heart (i.e. the mutual rotation of the cardiac base and apex) was proved to be sensitive to alterations of some cardiovascular parameters, i.e. preload, afterload and contractility. Moreover, pathologies which affect the fibers architecture and cardiac geometry were proved to alter the cardiac torsion pattern. For these reasons, cardiac torsion represents a sensitive index of ventricular performance. The aim of this work is to provide further insight into physiological and pathological alterations of the cardiac torsion by means of computational analyses, combining a structural model of the two ventricles with simple lumped parameter models of both the systemic and the pulmonary circulations. Starting from diagnostic images, a 3D anatomy based geometry of the two ventricles was reconstructed. The myocytes orientation in the ventricles was assigned according to literature data and the myocardium was modelled as an anisotropic hyperelastic material. Both the active and the passive phases of the cardiac cycle were modelled, and different clinical conditions were simulated. The results in terms of alterations of the cardiac torsion in the presence of pathologies are in agreement with experimental literature data. The use of a computational approach allowed the investigation of the stresses and strains in the ventricular wall as well as of the global hemodynamic parameters in the presence of the considered pathologies. Furthermore, the model outcomes highlight how for specific pathological conditions, an altered torsional pattern of the ventricles can be present, encouraging the use of the ventricular torsion in the clinical practice.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.jmbbm.2015.10.00

Resistenza termica di contatto nei componenti elettronici di potenza

Quaderno di Dipartimento FT/HT-6 di Aprile 199

Drug release in coronary bifurcation stenting.

The treatment of coronary bifurcation lesions represents a challenge for the interventional cardiologists due to the lower rate of procedural success and the higher rate of restenosis. The advent of drug eluting stents (DES) has dramatically reduced restenosis and consequently the request for re-intervention [1]. The aim of the present work is to provide further insight about the effectiveness of DES by means of computational analysis that combine virtual stent implantation, fluid dynamics and drug release for different stenting protocols used in the treatment of a coronary artery bifurcation. An explicit dynamic finite element model is developed in order to provide realistic configurations of the implanted device used to perform fluid dynamics analysis by means of a previously developed [2,3] finite element method coupling the blood flow and intramural plasma filtration in rigid arteries. To efficiently model the drug release, a multiscale strategy is adopted, ranging from lumped parameter model accounting for drug release, to fully 3-D models for drug transport to the artery [4]. Differences in drug delivery to the artery are evaluated with respect to local drug dosage. The model allowed to compare alternative stenting configurations thus suggesting guidelines in the treatment of coronary bifurcations lesions and addressing clinical issues such as the effectiveness of drug delivery to lesions in the side branch, as well as the influence of incomplete strut apposition and overlapping stents

An immersed boundary method for drug release applied to drug eluting stents dedicated to arterial bifurcations

We address an immersed boundary method applied to the study of cardiovascular drug eluting stents deployed in coronary bifurcations. The problem involves the interaction of arterial deformations, hemodynamics and controlled drug release. Resorting to an immersed boundary method facilitates the handling of complex stent pattern and simplifies the definition of the mathematical model for drug release

A mechanical simulator of cardiac wall kinematics

Aim of this study is to develop a mechanical simulator (MS) reproducing cardiac wall kinematics [i.e., radial (R), longitudinal (L) and rotational (RT) motions] to test piezoelectric gyroscopic sensors (GS) that are able to measure cardiac torsion that has proved to be a sensitive index of cardiac performance. The MS consists of three brushless motors controlled by a dedicated software either separately or simultaneously reproducing the three main cardiac wall movements (R, L, RT) obtained by implementing different physiologic or pathologic velocity profiles derived from in vivo data. GS accuracy (max % error) was experimentally tested by connecting it to the MS driven in velocity in different working conditions [i.e., cardiac period (515-1030 ms), RT angle (4-16 degrees), GS axis inclination (0-90 degrees) with respect to the cardiac rotation axis]. The MS reproduced the tested velocity profiles well. The GS showed high accuracy in measuring both physiologic and pathologic RT velocity profiles, whereas they proved insensitive to R and L motions. GS axis inclination influenced measurements; however, it was possible to correct this taking the inclination angle cosine into account. The MS proved to be a useful tool to study cardiac wall kinematics and test GS reliability with a view to in vivo application

Cardiac biomechanics in patient-specific multi-scale models of single ventricle circulation

Patient-specific models of single ventricle circulation represent a powerful tool to investigate ventricular functionality. In this study, we adopt a multi-scale approach that couples a 0D circulatory model of the patient circulation to a 3D structural model of the ventricle. To investigate this particular condition a group of patients affected by hypoplastic heart syndrome have been considered

Ulcerative colitis associated with leukocytoclastic vasculitis of the skin

Ulcerative colitis may be associated with a number of skin lesions such as erythema nodosum and pyoderma gangrenosum. We here describe an unusual case of a 33-year-old-caucasian male with ulcerative colitis and skin lesions diagnosed as leukocytoclastic vasculitis. An initial treatment with oral deflazacort led to little benefit, while treatment with oral mesalazine caused remission of the skin and intestinal manifestations in 2 weeks. © 2008 Editrice Gastroenterologica Italiana S.r.l

Computational fluid dynamic simulations of patient-specific stented coronary bifurcations

One of the relevant phenomenon associated with in-stent restenosis in coronary arteries is an altered haemodynamics in the stented region. Computational fluid dynamics (CFD) offers the possibility to investigate the haemodynamics at a level of detail not always accessible within experimental techniques. CFD can quantify and correlate the local haemodynamics structures which might lead to in-stent restenosis. The aim of this work is to study the fluid dynamics of realistic stented coronary artery models which replicate the complete clinical procedure of stent implantation. Two cases of pathologic left anterior descending coronary arteries with their bifurcations are reconstructed from computed tomography angiography and conventional coronary angiography images. Results of wall shear stress and relative residence time show that the wall regions more prone to the risk of restenosis are located next to stent struts, to the bifurcations and to the stent overlapping zone for both investigated cases. Considering a bulk flow analysis, helical flow structures are generated by the curvature of the zone upstream from the stent and by the bifurcation regions. Helical recirculating microstructures are also visible downstream from the stent struts. This study demonstrates the feasibility to virtually investigate the haemodynamics of patient-specific coronary bifurcation geometries

Family history, body mass index, selected dietary factors, menstrual history, and risk of moderate to severe acne in adolescents and young adults.

BACKGROUND: Genetic and environmental components may contribute to acne causation. OBJECTIVE: We sought to assess the impact of family history, personal habits, dietary factors, and menstrual history on a new diagnosis of moderate to severe acne. METHODS: We conducted a case-control study in dermatologic outpatient clinics in Italy. Cases (205) were consecutive those receiving a new diagnosis of moderate to severe acne. Control subjects (358) were people with no or mild acne, coming for a dermatologic consultation other than for acne. RESULTS: Moderate to severe acne was strongly associated with a family history of acne in first-degree relatives (odds ratio 3.41, 95% confidence interval 2.31-5.05). The risk was reduced in people with lower body mass index with a more pronounced effect in male compared with female individuals. No association with smoking emerged. The risk increased with increased milk consumption (odds ratio 1.78, 95% confidence interval 1.22-2.59) in those consuming more than 3 portions per week. The association was more marked for skim than for whole milk. Consumption of fish was associated with a protective effect (odds ratio 0.68, 95% confidence interval 0.47-0.99). No association emerged between menstrual variables and acne risk. LIMITATIONS: Some degree of overmatching may arise from choosing dermatologic control subjects and from inclusion of mild acne in the control group. CONCLUSIONS: Family history, body mass index, and diet may influence the risk of moderate to severe acne. The influence of environmental and dietetic factors in acne should be further explore