The rapid spread of SARS-COV-2 Omicron variant in Italy reflected early through wastewater surveillance.

The SARS-CoV-2 Omicron variant emerged in South Africa in November 2021, and has later been identified worldwide, raising serious concerns. A real-time RT-PCR assay was designed for the rapid screening of the Omicron variant, targeting characteristic mutations of the spike gene. The assay was used to test 737 sewage samples collected throughout Italy (19/21 Regions) between 11 November and 25 December 2021, with the aim of assessing the spread of the Omicron variant in the country. Positive samples were also tested with a real-time RT-PCR developed by the European Commission, Joint Research Centre (JRC), and through nested RT-PCR followed by Sanger sequencing. Overall, 115 samples tested positive for Omicron SARS-CoV-2 variant. The first occurrence was detected on 7 December, in Veneto, North Italy. Later on, the variant spread extremely fast in three weeks, with prevalence of positive wastewater samples rising from 1.0% (1/104 samples) in the week 5-11 December, to 17.5% (25/143 samples) in the week 12-18, to 65.9% (89/135 samples) in the week 19-25, in line with the increase in cases of infection with the Omicron variant observed during December in Italy. Similarly, the number of Regions/Autonomous Provinces in which the variant was detected increased from one in the first week, to 11 in the second, and to 17 in the last one. The presence of the Omicron variant was confirmed by the JRC real-time RT-PCR in 79.1% (91/115) of the positive samples, and by Sanger sequencing in 66% (64/97) of PCR amplicons. In conclusion, we designed an RT-qPCR assay capable to detect the Omicron variant, which can be successfully used for the purpose of wastewater-based epidemiology. We also described the history of the introduction and diffusion of the Omicron variant in the Italian population and territory, confirming the effectiveness of sewage monitoring as a powerful surveillance tool.

Electrospun bioresorbable heart valve scaffold for tissue engineering.

Currently marketed mechanical or biological prosthetic heart valves are regarded as valid substitutes for native heart valves suffering from degenerative pathologies. These devices require strict follow-up due to dysfunctions or post-surgical complications. Potential drawbacks of these medical devices are calcification, tearing of the cusps, thromboembolism and hemolysis. In this context, a tissue engineering approach offers a promising alternative scenario. In this paper, a trileaflet poly(epsilon-caprolactone) (PCL) heart valve scaffold prototype has been manufactured by electrospinning technique using a custom-made rotating target. Process parameters were selected in order to achieve suitable microstructure and mechanical performance. The electrospun heart valve prototype was functionally characterized by means of a pulse duplicator in order to evaluate the mechanical/hydraulic response to the imposed testing conditions. Leaflets synchronously opened in the ejection phase and the proper apposition of the leaflets prevented high leakage volumes in the diastolic phase. This preliminary study suggests a successful perspective for the proposed approach in designing a novel tissue engineered bioresorbable heart valve.

Time-resolved PIV technique for high temporal resolution measurement of mechanical prosthetic aortic valve fluid dynamics.

Prosthetic heart valves (PHVs) have been used to replace diseased native valves for more than five decades. Among these, mechanical PHVs are the most frequently implanted. Unfortunately, these devices still do not achieve ideal behavior and lead to many complications, many of which are related to fluid mechanics. The fluid dynamics of mechanical PHVs are particularly complex and the fine-scale characteristics of such flows call for very accurate experimental techniques. Adequate temporal resolution can be reached by applying time-resolved PIV, a high-resolution dynamic technique which is able to capture detailed chronological changes in the velocity field. The aim of this experimental study is to investigate the evolution of the flow field in a detailed time domain of a commercial bileaflet PHV in a mock-loop mimicking unsteady conditions, by means of time-resolved 2D Particle Image Velocimetry (PIV). The investigated flow field corresponded to the region immediately downstream of the valve plane. Spatial resolution as in "standard" PIV analysis of prosthetic valve fluid dynamics was used. The combination of a Nd:YLF high-repetition-rate double-cavity laser with a high frame rate CMOS camera allowed a detailed, highly temporally resolved acquisition (up to 10000 fps depending on the resolution) of the flow downstream of the PHV. Features that were observed include the non-homogeneity and unsteadiness of the phenomenon and the presence of large-scale vortices within the field, especially in the wake of the valve leaflets. Furthermore, we observed that highly temporally cycle-resolved analysis allowed the different behaviors exhibited by the bileaflet valve at closure to be captured in different acquired cardiac cycles. By accurately capturing hemodynamically relevant time scales of motion, time-resolved PIV characterization can realistically be expected to help designers in improving PHV performance and in furnishing comprehensive validation with experimental data on fluid dynamics numeric modelling.

Beat to beat analysis of mechanical heart valves by means of return map.

Three mechanical heart valves (two bileaflet prostheses and a tilting one) were investigated in a basic hardware setup in order to evaluate with a hydrophone their opening and closing action in time and in amplitude of each beat. The recorded signal was then segmented into the series of cycles xi(t) having a temporal duration equal to the working period imposed on the valve. Two return maps were defined, in order to evaluate the degree of dispersion of the resulting scatter plot: (i) the amplitude map xi(t) versus xi+1(t); (ii) the delay map for the closure of the valve within each beat versus the successive ones. To evaluate the results obtained, two indices were proposed based on both the degree of dispersion and the deviation of the regression line of the resulting scatter plot with respect to the bisector of the map plane. The tilting disc valve showed a lower degree of dispersion, both in the amplitude signal and in the closure time delays, with respect to the other two bileaflet heart valves. The methodology proposed here could be regarded as an alternative non-invasive tool to investigate the dynamic behaviour of prosthetic heart valves, especially in the case of their suspected failure.

Time dependent non-Newtonian numerical study of the flow field in a realistic model of aortic arch.

A three-dimensional time dependent numerical simulation was performed in a geometric model of aortic arch complete with a realistic aortic root and major branches originating from the arch, for a peak Reynolds number set at 2200 and Womersley number set at 20.4. The computational fluid dynamic analysis was aimed to provide spatial and temporal distribution of the shear stress all along the entire model together with the velocity patterns, related both to the non planar geometry of the aortic system here considered and to the pulsatility imposed on the numerical model to simulate physiologic conditions. A non-Newtonian evolving fluid was considered to account for the actual rheological nature of blood; a comparison on the incidence of wall shear stress, implementing a Newtonian fluid, was also made as reference. The spatial shear stress pattern, within the cardiac cycle, was shown to have higher values in correspondence to the inner wall of the aortic arch and the sites where the major vessels originated from the arch itself. The velocity patterns, on transversal sections of the aorta, resulted in highly skewed morphology. The resulting complex fluid dynamics, established in the aortic arch and in its branches, can be related to the possible endothelium response to mechanical stimuli, induced by wall shear stress, in the promotion of inflammatory events.

Endothelin and mechanical properties of the carotid artery in Wistar-Kyoto and spontaneously hypertensive rats.

The aim of this study is to evaluate the role of endothelin in the control of the static mechanical properties of in vitro carotid arteries from 14-week-old Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). An in vitro preparation in which the artery was allowed to longitudinally elongate similarly to the in situ carotid artery was employed. The diameter of in vitro carotid arteries subjected to static pressures (from 25 to 200 mmHg in 25 mmHg steps) was determined by videomicroscopy and computer-assisted image analysis, the cross-sectional compliance- and distensibility-pressure curves being then derived. The role of endothelin was assessed by incubating carotid arteries with the selective ETA and ETB endothelin receptor antagonists BQ123 and BQ788, respectively. These effects were compared with those observed under control conditions, as well as with those following complete abolition of vascular smooth muscle tone by potassium cyanide (KCN). Carotid diameter was significantly larger, and compliance and distensibility significantly smaller, in SHR compared to WKY rats. Local incubation with BQ123 was associated with significant dilations as well as significant increases in cross-sectional compliance and distensibility in both strains. This was even more pronounced with KCN, while BQ788 had no effect. The results of the present study suggest that: (i) endothelin exerts a tonic stiffening effect on the in vitro common carotid artery; (ii) this effect is mediated via the ETA endothelin receptor, and (iii) the stiffening effect of endothelin is exerted to a similar extent in the carotid arteries of normotensive WKY and SHR rats.

ET(A)/ET(B) receptor antagonist bosentan inhibits neointimal development in collared carotid arteries of rabbits.

The contribution of endothelin to the genesis of neointimal development in collared rabbit carotid arteries, a widely accepted model of atherosclerosis, was investigated. Three sets of rabbits were studied. In the first group, a non-occlusive, biologically inert silastic collar was positioned around the right carotid artery of the rabbit. In another group, the application of the collar was accompanied by endothelial denudation via a Fogarty arterial balloon catheter, while the third group of animals underwent only endothelial denudation. After two weeks, intimal hyperplasia of a similar degree was observed in all groups. The administration of the nonselective ET(A)/ET(B) receptor antagonist Bosentan, significantly reduced both the neointimal area and the intima/media area ratio in all groups. However, the beneficial effects of Bosentan were less pronounced in balloon injured vessels than in collared ones. The results of the present study indicate that i) endothelin has a key role in the development of intimal hyperplasia following arterial collaring, ii) the contribution of endothelin to intimal hyperplasia is greater in collared arteries that in balloon injured ones, and iii) the nonselective ET(A)/ET(B) receptor antagonists are potential tools for the prevention of intimal hyperplasia.

The influence of the leaflets' curvature on the flow field in two bileaflet prosthetic heart valves.

A successful mechanical prosthetic heart valve design is the bileaflet valve, which has been implanted for the first time more than 20 years ago. A key feature of bileaflet valves is the geometry of the two leaflets, which can be very important in determining the flow field. Laser Doppler anemometry (LDA) was used to perform an accurate study of the velocity and turbulence shear stress peak values (TSS(max)) fields at four distances from the valve plane. TSS(max) is a relevant parameter to assess the risk of hemolysis and platelet activation associated to the implantation of a prosthetic device, continuously interacting with blood. Two bileaflet valves were tested: the St. Jude HP and the Sorin Bicarbon, of the same nominal size (19mm). The former has flat leaflets, whereas the latter's leaflets have a cylindrical surface. A high regime (CO: 6l/min) was imposed, in order to test the two valves at maximum Reynolds number and consequent turbulence generation. The flat-leaflet design of the St. Jude generates a TSS field constant with distance; on the contrary, the Bicarbon's shear stress field undergoes an evident development, with an unexpected central peak at a distance comparable to the valve's dimensions (21mm). The two bileaflet valves tested, although very similar in design, behave very differently as for their turbulence properties. In particular, the concept of curved wake leads to conclude that the curvature of the leaflets' surface must be identified as an important parameter, which deserves careful attention in PHV design and development.

On the monodimensional approach to the estimation of the highest reynolds shear stress in a turbulent flow.

The measurement of the Reynolds stress tensor, or at least of some of its components, is a necessary step to assess if the turbulence associated with the flow near prosthetic devices can damage blood constituents. Because of the intrinsic three dimensionality of turbulence, in general, a three-component anemometer should be used to measure directly the components of the Reynolds stress tensor. However, this can be practically unfeasible, especially in vivo; therefore, it is interesting to investigate the possibility of characterizing the turbulent flows that may occur in the circulatory system with the monodimensional data that a less complete equipment (e.g., a pulsed ultrasound Doppler) can yield. From the general expression of the Reynolds stress tensor, the highest shear stress can be deduced, as well as the Reynolds normal stress in the main flow direction. The relation between these two quantities, which is an issue already addressed in previous works, can thus be rigorously formulated in terms of some characteristic parameters of the Reynolds stress tensor, the principal normal stresses and the angles that the directions that define them form with the main flow direction. An experimental verification of the ratio of the two above-mentioned quantitites for the flow across bileaflet valves, investigated by means of two-dimensional laser Doppler anemometry, will illustrate the limitations of the monodimensional approach estimating the maximum load on blood constituents.

A discussion on the threshold limit for hemolysis related to Reynolds shear stress.

Turbulence-related damage to blood is a major problem with the use of prosthetic devices, such as mechanical heart valves. An often-cited paper by Sallam and Hwang (1984). Biorheology 21, 783-797) quantified the threshold for hemolysis to be about 400 N m(-2), a value that has hitherto contributed to the evaluation of the potential dangerousness of a medical implantable device. We propose a discussion of the mentioned experiment, based on the application of stress analysis concepts to the original measurements: this is necessary to assess the peak turbulence shear stress value that could have been found in Sallam and Hwangs experiment, with a suitable orientation of the measurement axes. The result of our theoretical discussion is that the threshold value of 400 N m(-2) could probably be considerably underestimated: following this point of view, a 3-D stress analysis shows that the peak turbulence shear stress at the inception of hemolysis should be at least 600 N m(-2). This result, obtained on the basis of the study of RBCs' response to a turbulent environment, indicates that blood particles are probably more resistant to short-time shear stresses than it was thought.

Flow on the symmetry plane of a total cavo-pulmonary connection.

The flow inside a total cavo-pulmonary connection, a bypass operation of the right heart adopted in the presence of congenital malformation, is here studied for a specific geometry which has been recently introduced in clinics. The analysis has been performed by preliminary experimental observation and a novel Navier-Stokes formulation on the symmetry plane. This method, once some basic hypotheses are verified, allows to reproduce the flow on the symmetry plane of a three-dimensional field by using an extension of the two-dimensional approach. The analysis has confirmed the existence of a central vortex showing that it is not a real vortex (i.e. a place with accumulation of vorticity) but, rather, a weakly dissipative recirculating zone. It is surrounded by a shear layer that becomes spontaneously unsteady at moderately high Reynolds number. The topological changes and energy dissipation have been analysed in both cases of unbalanced and of balanced pulmonary artery and caval flows.

Hydraulic functional characterisation of aortic mechanical heart valve prostheses through lumped-parameter modelling.

Lumped-parameter modelling techniques are proposed as a method for studying the hydraulic characteristics of mechanical prosthetic heart valves (PHVs). The global hydraulic behaviour of PHVs in the open position was modelled by taking into account the (nonlinear) resistive and (linear) inertial factors governing the time-dependent relationship between transvalvular pressure drop and fluid flow rate, and neglecting the leaflets' opening and closure transient phenomena. Statistically defined indices associated to the parameters' values attest how properly the model describes PHV hydraulic behaviour. Local fluid dynamics is not modelled with this approach. The proposed method was implemented in a software program and applied to the characterisation of the aortic StJude Medical, StJude Medical Hemodynamic Plus and CarboMedics PHVs, basing on steady- and pulsatile-flow hydraulic-bench experimental data. The results showed that reliable parameters expressing hydraulic resistance can be derived from steady-flow data (R(2)>0.995). Inertance parameters derived from pulsatile-flow experiments are liable to a degree of uncertainty (confidence intervals up to 17%), however, comparing the reconstructed vs. measured pressure drop during systolic time demonstrates that this deficiency is mostly due to the missing description of initial, transient oscillations presumably related to the leaflets' opening (not modelled).

Computational model of the fluid dynamics of a cannula inserted in a vessel: incidence of the presence of side holes in blood flow.

Vascular access methods, performed by the insertion of cannulae into vessels, may disturb the physiological flow of blood, giving rise to non-physiological pressure variations and shear stresses. To date, the hydrodynamic behaviour of the cannulae has been evaluated comparing their pressure loss-flow rate relationships, as obtained from in vitro experiments using a monodimensional approach; this methodology neither furnish information about the local fluid dynamics nor the established flow field in specific clinical work conditions. Since the shear stress is a critical factor in the design of artificial circulatory devices, more knowledge should be necessary about the local values assumed by the haemodynamic parameters during cannulation. An alternative way to investigate the fluid dynamic as accurately as possible is given by numeric studies. A 3D model of cannula concentrically placed in a rigid wall vessel is presented, with the finite element methodology used to numerically simulate the steady-state flow field in two different venous cannulation case studies, with two cannulae having a central hole and two or four side holes, respectively, with the same boundary conditions. Lower velocity and shear stress peak values have been computed for the model with four side holes upstream of the central hole, in the region of the cannula where the inlet flows meet and towards cannula's outlet, due to the increased flow symmetry and inlet area with respect to the model with two side holes. Starting from the investigation of different cannula designs, numerically assessing the local fluid dynamics, indications can be drawn to support both the design phase and the device optimal clinical use, in order to limit risks of biomechanical origin. Thus the presence of four side holes implied, as a consequence of the greater inlet area and of the increased symmetry, a less disturbed blood flow, together with reduced shear stress values. Furthermore, results show that the numerical simulations furnished useful informations on the interaction between vessel and cannula, e.g. on the fluid dynamics establishing in the free luminal space left, in the vessel, by the inserted cannula.

A statistical approach to the quantitative comparison of pulsatile flow in vitro data of prosthetic heart valve testing.

BACKGROUND AND AIMS OF THE STUDY: In vitro evaluation and animal testing are fundamental steps in the assessment of prosthetic heart valves before their use in clinical practice. Valve testing under pulsatile conditions is the best in vitro simulation of cardiac valve function, and the ensuing results should support the surgeon's decision concerning the time of valve replacement. However, limits in hydraulic reproduction of cardiac function and differences in protocol implementation of in vitro testing lead to difficulties in obtaining reliable and comparable results. Debate among researchers and standardizing bodies about discrepancies in results becomes critical in light of the European CE certification of implantable medical devices. An interlaboratory environment has been created at the Biomedical Engineering unit of the Istituto Superiore di Sanita in Rome, which uses differing test apparatus to evaluate prosthetic heart valves in vitro, in order to define significant measurement parameters and procedures that produce comparative data. METHODS: Two prosthetic valves-a tilting disc and a bileaflet valve-each sized 29 mm, were tested in the aortic position on two different pulse duplicators (PDs), namely the Dynatek MP1 and a system developed at the University of Sheffield. The common protocol adopted was the FDA Interlaboratory Comparison Testing Protocol. Original software was used to manage all test phases, thus minimizing operator-dependent variability in both systems and imposing strict control of experimental conditions. Statistical analysis performed on the data followed two approaches: (i) separate fitting of the two regression equations of pressure drop-flow rate relationship obtained for each valve on both PDs, and (ii) application of a multiple regression model, to fit a single regression equation of pressure drop-flow rate relationship, using data obtained from both PDs for each valve. In addition, an additional independent (dummy) variable was introduced. RESULTS AND CONCLUSIONS: Using this approach, the valve parameter range was obtained and, by imposing strict control of the experimental set-up, the coincidence of the two valve power laws, estimated by each of the two PDs, was studied.

The cytologic diagnosis of gastric carcinoma related to the histologic type.

In gastric smears obtained by direct vision fiberoptic brush technique from 78 patients with carcinoma of the stomach, an attempt was made to recognize cytologically the histologic type of the tumor with reference to Lauren's classification. The cytologic diagnosis of intestinal type carcinoma was made in 36/45 positive cases on the basis of an abundant cellularity and the presence of rather large pleomorphic cohesive cells often arranged in sheets with a moderately increased N/C ratio. One case of intramucous and two of "early" invasive carcinoma revealed malignant cells which did not differ from those of the advanced cases. In these cases as well as in some of the advanced ones, atypical epithelial cells were found in addition to the malignant ones; these cells could have derived from the histologic areas of atypical hyperplasia of the gastric mucosa surrounding the carcinoma. 14/15 cases of advanced diffuse carcinoma of the stomach could be cytologically identified on the basis of a scanty cellularity and the presence of rather small, monomorphic poorly differentiated cells with a high N/C ratio. The cytologic diagnosis of the mixed-type carcinoma was made in 2/5 positive cases on the basis of the presence of an admixture of both cell types described above. In two cases of the mixed-type carcinoma, only intestinal type cells were found. In the smears of nine cases of intestinal type carcinoma, one of which was intramucous, and of one case of mixed-type carcinoma, the tumor cells could not be specified. 13/78 cases (16.7%) showed negative cytology. The overall accuracy rate was 83.3 per cent. The statistical analysis of a number of cytologic parameters indicated that morphologic differences between Type I and Type D carcinomas of the stomach do exist and that they can be evaluated for differential diagnostic purposes.

Prosthetic heart valve evaluation in vitro: critical aspects of data comparability.

The technology of heart valve substitution has considerably improved in the last few years, but its reliability after implantation is still not good enough, hence the need to study new valve design and improve quality testing. Different pulse duplicators are used for heart valve testing, but the results depend very much on the system adopted and the measurement protocol. Tests on two pulse duplicators currently used at the Biomedical Engineering Laboratory at the Istituto Superiore di Sanità, Rome, are reported here. The most significant parameters for valve evaluation were measured following each system's own protocol. Attention was focused on vascular load tuning when setting up the system and on the relationship between drive unit flow waveform and valve regurgitation and energy loss measurements. Standardization criteria must be defined in order to ensure the reliable comparability of in vitro testing results.

19 mm sized bileaflet valve prostheses' flow field investigated by bidimensional laser Doppler anemometry (part I: velocity profiles).

The investigation of the flow field downstream of a cardiac valve prosthesis is a well established task. In particular turbulence generation is of interest if damage to blood constituents is to be assessed. Several prosthetic valve flow studies are available in literature but they generally concern large-sized prostheses. The FDA draft guidance requires the study of the maximum Reynolds number conditions for a cardiac valve model to assess the worst case in turbulence by choosing both the minimum valve diameter and a high cardiac output value as protocol set up. Within the framework of a national research project regarding the characterization of cardiovascular endoprostheses, the Laboratory of Biomedical Engineering is currently conducting an in-depth study of turbulence generated downstream of bileaflet cardiac valves. Four models of 19 mm sized bileaflet valve prostheses, namely St Jude Medical HP Edwards Tekna, Sorin Bicarbon, and CarboMedics, were studied in aortic position. The prostheses were selected for the nominal annulus diameter reported by the manufacturers without any assessment of the valve sizing method. The hemodynamic function was investigated using a bidimensional LDA system. Results concern velocity profiles during the peak flow systolic phase, at high cardiac output regime, highlighting the different flow field features downstream of the four small-sized cardiac valves.

19 mm sized bileaflet valve prostheses' flow field investigated by bidimensional laser Doppler anemometry (part II: maximum turbulent shear stresses)

The investigation of the flow field generated by cardiac valve prostheses is a necessary task to gain knowledge on the possible relationship between turbulence-derived stresses and the hemolytic and thrombogenic complications in patients after valve replacement. The study of turbulence flows downstream of cardiac prostheses, in literature, especially concerns large-sized prostheses with a variable flow regime from very low up to 6 L/min. The Food and Drug Administration draft guidance requires the study of the minimum prosthetic size at a high cardiac output to reach the maximum Reynolds number conditions. Within the framework of a national research project regarding the characterization of cardiovascular endoprostheses, an in-depth study of turbulence generated downstream of bileaflet cardiac valves is currently under way at the Laboratory of Biomedical Engineering of the Istituto Superiore di Sanita. Four models of 19 mm bileaflet valve prostheses were used: St Jude Medical HP, Edwards Tekna, Sorin Bicarbon, and CarboMedics. The prostheses were selected for the nominal Tissue Annulus Diameter as reported by manufacturers without any assessment of valve sizing method, and were mounted in aortic position. The aortic geometry was scaled for 19 mm prostheses using angiographic data. The turbulence-derived shear stresses were investigated very close to the valve (0.35 D0), using a bidimensional Laser Doppler anemometry system and applying the Principal Stress Analysis. Results concern typical turbulence quantities during a 50 ms window at peak flow in the systolic phase. Conclusions are drawn regarding the turbulence associated to valve design features, as well as the possible damage to blood constituents.

The role of usable length in the compliance measurement of vascular prostheses.

In this study we investigated the dependence of the mechanical properties and in particular of the radial compliance of a vascular prosthesis as a function of its usable length. Radial compliance was measured at 60 bpm and in the pressure range 80-120 mmHg. Starting from compliance measurements a simple model was used to calculate the pulse wave velocity and the reflection coefficients between 6 mm and 8 mm grafts (knitted and woven) with iliac and subclavean artery of similar diameter. The results provide an indication of the influence of usable length on the compliance and diameter mismatch at the anasthomosis between graft and host artery.

Proposal for a quantitative description of blood spiral flow in medical devices.

The association between specific blood flow patterns and blood behaviour through medical devices suggests that a Lagrangian study may be a useful instrument for the evaluation of the thrombogenic and/or hemolytic potential of certain devices' geometries and biomaterials. In this study a description of blood particle trajectories in terms of their spiral contents is proposed; such a mathematical description for blood spiral flow, computed along several pathlines, is tested for a quantitative determination of the spiralled motion of blood flow into two three-dimensional numerical models, having different design characteristics, of venous cannula inserted in a vessel. As the influence of vortical flow conditions have been observed to have both beneficial and detrimental influence on blood behaviour in terms of blood-device interaction, of the degradation of its components, and of the efficiency of mass-exchange (in red cells oxygenation and plasma filtration, for example), the herein proposed method for the description of spiral laminar motion may be a helpful instrument to build up a tool to investigate, for example, the existence of correlations between level of spiral flow and geometry (as in the present investigated test case), rather than the effects of blood-surface contact. The results obtained in this test case investigation, confirm the effectiveness of the proposed function for a quantitative analysis of spiral flow in medical devices.