Smartphone-based particle tracking velocimetry for the in vitro assessment of coronary flows.

The present study adopts a smartphone-based approach for the experimental characterization of coronary flows. Technically, Particle Tracking Velocimetry (PTV) measurements were performed using a smartphone camera and a low-power continuous wave laser in realistic healthy and stenosed phantoms of left anterior descending artery with inflow Reynolds numbers approximately ranging from 20 to 200. A Lagrangian-Eulerian mapping was performed to convert Lagrangian PTV velocity data to a Eulerian grid. Eulerian velocity and vorticity data obtained from smartphone-based PTV measurements were compared with Particle Image Velocimetry (PIV) measurements performed with a smartphone-based setup and with a conventional setup based on a high-power double-pulsed laser and a CMOS camera. Smartphone-based PTV and PIV velocity flow fields substantially agreed with conventional PIV measurements, with the former characterized by lower average percentage differences than the latter. Discrepancies emerged at high flow regimes, especially at the stenosis throat, due to particle image blur generated by smartphone camera shutter speed and image acquisition frequency. In conclusion, the present findings demonstrate the feasibility of PTV measurements using a smartphone camera and a low-power light source for the in vitro characterization of cardiovascular flows for research, industrial and educational purposes, with advantages in terms of costs, safety and usability.

Mismatch between morphological and functional assessment of the length of coronary artery disease.

BACKGROUND: Morphological evaluation of coronary lesion length is a paramount step during invasive assessment of coronary artery disease. Likewise, the extent of epicardial pressure losses can be measured using longitudinal vessel interrogation with fractional flow reserve (FFR) pullbacks. We aimed to quantify the mismatch in lesion length between morphological (based on quantitative coronary angiography, QCA, and optical coherence tomography, OCT) and functional evaluations. METHODS: This is a prospective and multicenter study of patients evaluated by QCA, OCT and motorized fractional flow reserve pullbacks (mFFR). The difference in lesion length between the functional and anatomical evaluations was referred to as FAM. RESULTS: 117 patients (131 vessels) were included. Median lesion length derived from angiography was 16.05 mm [11.40-22.05], from OCT was 28.00 mm [16.63-38.00] and from mFFR 67.12 mm [25.38-91.37]. There was no correlation between QCA and mFFR lesion length (r = 0.124, 95% CI -0.168-0.396, p = 0.390). OCT lesion length did correlate with mFFR (r = 0.469, 95% CI 0.156-0.696, p = 0.004). FAM was strongly associated with the improvement in vessel conductance with percutaneous coronary intervention (PCI), higher mismatch was associated with lower post-PCI FFR. CONCLUSIONS: Lesion length assessment differs between morphological and functional evaluations. The morphological-functional mismatch in lesion length is frequent, and influences the results of PCI in terms of post-PCI FFR. Integration of the extent of pressure losses provides clinically relevant information that may be useful for clinical decision-making concerning revascularization strategy.

Template Matching and Matrix Profile for Signal Quality Assessment of Carotid and Femoral Laser Doppler Vibrometer Signals.

Background: Laser-Doppler Vibrometry (LDV) is a laser-based technique that allows measuring the motion of moving targets with high spatial and temporal resolution. To demonstrate its use for the measurement of carotid-femoral pulse wave velocity, a prototype system was employed in a clinical feasibility study. Data were acquired for analysis without prior quality control. Real-time application, however, will require a real-time assessment of signal quality. In this study, we (1) use template matching and matrix profile for assessing the quality of these previously acquired signals; (2) analyze the nature and achievable quality of acquired signals at the carotid and femoral measuring site; (3) explore models for automated classification of signal quality. Methods: Laser-Doppler Vibrometry data were acquired in 100 subjects (50M/50F) and consisted of 4-5 sequences of 20-s recordings of skin displacement, differentiated two times to yield acceleration. Each recording consisted of data from 12 laser beams, yielding 410 carotid-femoral and 407 carotid-carotid recordings. Data quality was visually assessed on a 1-5 scale, and a subset of best quality data was used to construct an acceleration template for both measuring sites. The time-varying cross-correlation of the acceleration signals with the template was computed. A quality metric constructed on several features of this template matching was derived. Next, the matrix-profile technique was applied to identify recurring features in the measured time series and derived a similar quality metric. The statistical distribution of the metrics, and their correlates with basic clinical data were assessed. Finally, logistic-regression-based classifiers were developed and their ability to automatically classify LDV-signal quality was assessed. Results: Automated quality metrics correlated well with visual scores. Signal quality was negatively correlated with BMI for femoral recordings but not for carotid recordings. Logistic regression models based on both methods yielded an accuracy of minimally 80% for our carotid and femoral recording data, reaching 87% for the femoral data. Conclusion: Both template matching and matrix profile were found suitable methods for automated grading of LDV signal quality and were able to generate a quality metric that was on par with the signal quality assessment of the expert. The classifiers, developed with both quality metrics, showed their potential for future real-time implementation.

Combining shape and intensity dxa-based statistical approaches for osteoporotic HIP fracture risk assessment.

Aiming to improve osteoporotic hip fracture risk detection, factors other than the largely adopted Bone Mineral Density (BMD) have been investigated as potential risk predictors. In particular Hip Structural Analysis (HSA)-derived parameters accounting for femur geometry, extracted from Dual-energy X-ray Absorptiometry (DXA) images, have been largely considered as geometric risk factors. However, HSA-derived parameters represent discrete and cross-correlated quantities, unable to describe proximal femur geometry as a whole and tightly related to BMD. Focusing on a post-menopausal cohort (N = 28), in this study statistical models of bone shape and BMD distribution have been developed to investigate their possible role in fracture risk. Due to unavailable retrospective patient-specific fracture risk information, here a surrogate fracture risk based on 3D computer simulations has been employed for the statistical framework construction. When considered separately, BMD distribution performed better than shape in explaining the surrogate fracture risk variability for the analysed cohort. However, the combination of BMD and femur shape quantities in a unique statistical model yielded better results. In detail, the first shape-intensity combined mode identified using a Partial Least Square (PLS) algorithm was able to explain 70% of the surrogate fracture risk variability, thus suggesting that a more effective patients stratification can be obtained applying a shape-intensity combination approach, compared to T-score. The findings of this study strongly advocate future research on the role of a combined shape-BMD statistical framework in fracture risk determination.

A low-cost scalable 3D-printed sample-holder for agitation-based decellularization of biological tissues.

Decellularized extracellular matrix is one of the most promising biological scaffold supporting in vitro tissue growth and in vivo tissue regeneration in both preclinical research and clinical practice. In case of thick tissues or even organs, conventional static decellularization methods based on chemical or enzymatic treatments are not effective in removing the native cellular material without affecting the extracellular matrix. To overcome this limitation, dynamic decellularization methods, mostly based on perfusion and agitation, have been proposed. In this study, we developed a low-cost scalable 3D-printed sample-holder for agitation-based decellularization purposes, designed for treating multiple specimens simultaneously and for improving efficiency, homogeneity and reproducibility of the decellularization treatment with respect to conventional agitation-based approaches. In detail, the proposed sample-holder is able to house up to four specimens and, immersed in the decellularizing solution within a beaker placed on a magnetic stirrer, to expose them to convective flow, enhancing the solution transport through the specimens while protecting them. Computational fluid dynamics analyses were performed to investigate the fluid phenomena establishing within the beaker and to support the sample-holder design. Exploratory biological tests performed on human skin specimens demonstrated that the sample-holder reduces process duration and increases treatment homogeneity and reproducibility.

Efficacy and Safety of Clopidogrel, Prasugrel and Ticagrelor in ACS Patients Treated with PCI: A Propensity Score Analysis of the RENAMI and BleeMACS Registries.

INTRODUCTION: Real-life data comparing clopidogrel, prasugrel, and ticagrelor for unselected patients undergoing percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS) are lacking, as are data for the temporal distribution of ischemic and bleeding risks. METHODS: A total of 19,825 patients were enrolled from the RENAMI and BleeMACS registries. Both were multicenter, retrospective, observational registries including the data and outcomes of consecutive patients with ACS who underwent primary PCI and were discharged with dual antiplatelet therapy (DAPT). We evaluated the long-term outcome stratified by the different antiplatelet agents. RESULTS: A total of 14,105 patients (71.2%) were treated with clopidogrel, 2364 patients (11.9%) with prasugrel and 3356 patients (16.9%) with ticagrelor. After propensity score matching, at 1 year, prasugrel reduced the incidence of net adverse clinical events (NACE; a composite endpoint of all-cause death, myocardial infarction [MI] and Bleeding Academic Research Consortium [BARC] 3-5 bleeding) (4.2% vs.7.6%, p = 0.002) and of major adverse cardiovascular events (MACE; a composite endpoint of death and MI) compared with clopidogrel (2.6% vs. 5.2%, p = 0.007). Ticagrelor decreased rates of MACE compared with clopidogrel (2.7% vs. 6.2%, p < 0.001), but not of NACE (6.6% vs. 8.7%, p = 0.07). Ticagrelor presented similar performance in terms of MACE compared with prasugrel (2.8% vs. 2.4%, p = 0.56), with a trend towards a reduction in MI (0.2% vs. 0.4%, p = 0.56), but with higher risk of BARC 3-5 bleedings (3.8% vs. 1.7%, p = 0.04). In the daily risk analysis, clopidogrel presented a binomial distribution with a peak of ischemic risk at 3 months, which decreased towards bleedings; prasugrel had a constant equivalence between opposite risks; and ticagrelor constantly reduced recurrent MIs despite higher risk of BARC 3-5 events. CONCLUSION: In real life, ticagrelor is more effective in reducing ischemic events during the first year after ACS, despite an increased risk of major bleedings, while prasugrel assures a better balance between ischemic and bleeding recurrent events.

Uncertainty propagation of phase contrast-MRI derived inlet boundary conditions in computational hemodynamics models of thoracic aorta.

This study investigates the impact that uncertainty in phase contrast-MRI derived inlet boundary conditions has on patient-specific computational hemodynamics models of the healthy human thoracic aorta. By means of Monte Carlo simulations, we provide advice on where, when and how, it is important to account for this source of uncertainty. The study shows that the uncertainty propagates not only to the intravascular flow, but also to the shear stress distribution at the vessel wall. More specifically, the results show an increase in the uncertainty of the predicted output variables, with respect to the input uncertainty, more marked for blood pressure and wall shear stress. The methodological approach proposed here can be easily extended to study uncertainty propagation in both healthy and pathological computational hemodynamic models.

Innovative technologies for the assessment of cardiovascular medical devices: state-of-the-art techniques for artificial heart valve testing.

Prosthetic heart valves (PHVs) are engineered devices used for replacing diseased natural cardiac valves. This article presents several investigational techniques for the evaluation of the performance of these clinical devices, whose implantation is not completely free of drawbacks. The state-of-the-art in the technological approach for PHV testing is addressed. As the fluid dynamics of PHVs are particularly complex, the main focus will be on experimental velocimetric techniques and computational analysis. A methodology for the analysis of the valve's signature, in terms of its characteristic sound in the opening and closing phases, is also presented. The aforementioned techniques are necessary to guarantee an operational life of the implanted device as free as possible from clinical complications. It can be realistically expected that this characterization will help designers in improving PHV performance.