Oberdan Parodi

Bio: Oberdan Parodi is an academic researcher from National Research Council. The author has contributed to research in topics: Coronary artery disease & Intravascular ultrasound. The author has an hindex of 14, co-authored 55 publications receiving 714 citations. Previous affiliations of Oberdan Parodi include University of Siena & University of Florence.

Computer simulation of three-dimensional plaque formation and progression in the carotid artery.

Abstract: Atherosclerosis is becoming the number one cause of death worldwide. In this study, three-dimensional computer model of plaque formation and development for human carotid artery is developed. The three-dimensional blood flow is described by the Navier-Stokes equation, together with the continuity equation. Mass transfer within the blood lumen and through the arterial wall is coupled with the blood flow and is modeled by a convection-diffusion equation. The low-density lipoproteins transports in lumen of the vessel and through the vessel tissue are coupled by Kedem-Katchalsky equations. The inflammatory process is modeled using three additional reaction-diffusion partial differential equations. Fluid-structure interaction is used to estimate effective wall stress analysis. Plaque growth functions for volume progression are correlated with shear stress and effective wall stress distribution. We choose two specific patients from MRI study with significant plaque progression. Plaque volume progression using three time points for baseline, 3- and 12-month follow up is fitted. Our results for plaque localization correspond to low shear stress zone and we fitted parameters from our model using nonlinear least-square method. Determination of plaque location and composition, and computer simulation of progression in time for a specific patient shows a potential benefit for the prediction of disease progression. The proof of validity of three-dimensional computer modeling in the evaluation of atherosclerotic plaque burden may shift the clinical information of MRI from morphological assessment toward a functional tool. Understanding and prediction of the evolution of atherosclerotic plaques either into vulnerable or stable plaques are major tasks for the medical community.

Womersley Number-Based Estimates of Blood Flow Rate in Doppler Analysis: In Vivo Validation by Means of Phase-Contrast MRI

Abstract: A common clinical practice during single-point Doppler analysis is to measure the centerline maximum velocity and to recover the time-averaged flow rate by exploiting an assumption on the shape of velocity profile (a priori formula), either a parabolic or a flat one. In a previous study, we proposed a new formula valid for the peak instant linking the maximum velocity and the flow rate by including a well-established dimensionless fluid-dynamics parameter (the Womersley number), in order to account for the hemodynamics conditions (Womersley number-based formula). Several in silico tests confirmed the reliability of the new formula. Nevertheless, an in vivo confirmation is missing limiting the clinical applicability of the formula. An experimental in vivo protocol using cine phase-contrast MRI (2-D PCMRI) technique has been designed and applied to ten healthy young volunteers in three different arterial districts: the abdominal aorta, the common carotid artery, and the brachial artery. Each PCMRI dataset has been used twice: 1) to compute the value of the blood flow rate used as a gold standard and 2) to estimate the flow rate by measuring directly the maximum velocity and the diameter (i.e., emulating the intravascular Doppler data acquisition) and by applying to these data the a priori and the Womersley number-based formulae. All the in vivo results have confirmed that the Womersley number-based formula provides better estimates of the flow rate at the peak instant with respect to the a priori formula. More precisely, mean performances of the Womersley number-based formula are about three times better than the a priori results in the abdominal aorta, five times better in the common carotid artery, and two times better in the brachial artery.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Persistent activation of coagulation mechanism in unstable angina and myocardial infarction.

Abstract: BACKGROUND The blood coagulation system is activated in the acute phase of unstable angina and acute myocardial infarction. However, it remains unclear whether augmented function of the hemostatic mechanism serves only as a marker of the acute thrombotic episode or whether a hypercoagulable state persists for a prolonged period after clinical stabilization. METHODS AND RESULTS We prospectively measured the plasma concentrations of prothrombin fragment 1 + 2 (F1 + 2) and fibrinopeptide A (FPA) in consecutive patients presenting with unstable angina (n = 81) or acute myocardial infarction (n = 32), respectively. At 6 months, plasma determinations were repeated in patients experiencing an uneventful clinical course (unstable angina, n = 57; myocardial infarction, n = 23). We quantitated the plasma levels of F1 + 2 and FPA in control patients with stable angina (n = 37) or healthy individuals (n = 32) who were matched for age and sex. The median plasma concentrations of F1 + 2 and FPA are significantly higher in patients presenting with unstable angina (F1 + 2, 1.08 nmol/L; FPA, 2.4 nmol/L) or acute myocardial infarction (F1 + 2, 1.27 nmol/L; FPA, 3.55 nmol/L) compared with patients with stable angina (F1 + 2, 0.74 nmol/L; FPA, 1.3 nmol/L; P < .0001) or healthy individuals (F1 + 2, 0.71 nmol/L; FPA, 0.80 nmol/L; P < .0001). At 6 months, the median plasma levels of F1 + 2 in patients exhibiting an uneventful clinical course did not differ from values obtained at admission (unstable angina, 1.26 versus 1.07 nmol/L, P = NS; myocardial infarction, 1.22 versus 1.29 nmol/L, P = NS), whereas the median plasma levels of FPA in the same two subpopulations were significantly reduced (unstable angina, 1.1 versus 2.9 nmol/L, P = .0003; myocardial infarction, 1.1 versus 3.0 nmol/L; P = .0028). CONCLUSIONS During the acute phase of unstable angina and myocardial infarction, patients exhibit increased coagulation system activity. Over the next 6 months, patients with unstable angina or myocardial infarction experiencing an uneventful clinical course manifest a persistent hypercoagulable state with minimal generation of fibrin.

Clinical review: Scoring systems in the critically ill

Abstract: General illness severity scores are widely used in the ICU to predict outcome, characterize disease severity and degree of organ dysfunction, and assess resource use. In this article we review the most commonly used scoring systems in each of these three groups. We examine the history of the development of the initial major systems in each group, discuss the construction of subsequent versions, and, when available, provide recent comparative data regarding their performance. Importantly, the different types of scores should be seen as complementary, rather than competitive and mutually exclusive. It is possible that their combined use could provide a more accurate indication of disease severity and prognosis. All these scoring systems will need to be updated with time as ICU populations change and new diagnostic, therapeutic and prognostic techniques become available.