Biomedical subjects

C Daniele

Publications and source records attributed to C Daniele.

At least 37 records · Page 2Linked to original sources

PubMed2000

Renal infarction: an uncommon mimic presenting with flank pain.

A 39-year-old woman arrived to the emergency department complaining of a constant, progressive, left flank pain, with no beneficial effect from spasmolytic and nonsteroidal antiinflammatory drugs. Two years before, she suffered another episode of right flank pain and stranguria, but instrumental examinations (ultrasonography, urography) remained negative. Besides a mild tenderness in the left flank, physical examination was normal. Blood chemistry panel showed leukocytosis (17.2 x 10(3) mL, neutrophils 82.8%) and a slight increase of serum lactate dehydrogenase (LDH) (543 U/L versus 230 to 460 U/L). Urinanalysis showed a slight hemoglobinuria (0.5 mg/dL), and sediment contained some red cells and leukocytes. Diagnostic examinations (ultrasonography, computed tomography) showed a left renal nonhomogeneous space-occupying lesion, orientative for renal malignancy. She was transferred to the urology department and operated. Both intraoperatory and histological diagnosis was ischemic infarction and, after exclusion of all possible underlying causes, final diagnosis was idiopathic renal infarction. Diagnostic procedures and literature reports are discussed.

Adult↗

PubMed2000

Particle image velocimetry analysis of the flow field in the total cavopulmonary connection.

The total cavopulmonary connection (TCPC) is a common operation, meant to restore a proper pulmonary blood flow in heart defects with only one functional ventricle. It consists of the direct connection of the venae cavae to the pulmonary arteries in a cross-shaped disposition which entails a peculiar hemodynamics: Side effects can occur, such as recirculation zones and pressure drop across the connection. Our study is aimed at the quantitative investigation of the flow field of a successful Fontan-type operation, in view of the clinical importance of assuring a nearly physiological pulmonary blood flow, especially if one considers that many pediatric patients are eligible for this operation. A glass-blown TCPC phantom, realized according to nuclear magnetic resonance data, was employed in a steady-flow loop. Thus, a realistic model of this Fontan-type operation was realized using materials which enable advanced measurement techniques such as particle image velocimetry (PIV). The mean flow rates at each branch of the cavopulmonary shunt could be independently varied with a vertical shift of the corresponding upstream reservoir. The PIV technique was used successfully in identifying the flow field characteristics. The flow field in this TCPC topology was shown to be well organized and regulated by the presence of a vortex at the confluence of the venae cavae. The effect of different loading conditions, which realistically can be found in vivo, is studied with a high spatial resolution, showing the possibility to use pulmonary resistance as a parameter in designing the surgical geometry.

Blood Flow Velocity↗

PubMed2000

Hemodynamic performance of small-size bileaflet valves: pressure drop and laser Doppler anemometry study comparison of three prostheses.

Laser Doppler anemometry (LDA) is a single-point technique which is unparalleled to detect accurately the local properties of the velocity field in a turbulent flow, such as that generated by a prosthetic heart valve (PHV). We propose a correlation between the structure of the flow field in three 19 mm bileaflet PHVs (Sorin Bicarbon, St. Jude Standard, St. Jude HP), investigated at peak systole (6 L/min cardiac output [CO]) with LDA, in kinematic and geometric similarity, and the global parameter of transvalvular pressure drop measured in both steady and pulsatile conditions. The pressure transducers of the same apparatus were used to characterize pressure drops at different flow rates whereas the steady-flow case was studied with a highly accurate tester built in our laboratory. The 2 St. Jude models rank according to their internal orifice diameter (ID) with the standard model (with a smaller ID) providing higher pressure drops for each flow rate. Sorin Bicarbon, due to its leaflet geometry, generates a more complex flow field with respect to the 2 St. Jude flat-leaflet models and shows improved hemodynamical behavior in pulsatile conditions with respect to the stationary case due to differences in pressure recovery. This study can provide insights into a PHV's local flow structure and global hemodynamical parameters.

Blood Flow Velocity↗

PubMed2000

Laser Doppler anemometry study of bidimensional flows downstream of three 19 mm bileaflet valves in the mitral position, under kinematic similarity.

Three small-size (nominal size: 19 mm) bileaflet valves, CarboMedics R (CM), St Jude Standard (SJ) and Sorin Bicarbon (SB), have been tested by means of a two-component laser Doppler anemometry (LDA) system, in the mitral position, in order to assess the potential damage to blood elements entailed by the turbulent flow through them. A high regime (6 l/min cardiac output) was chosen to perform measurements for the worst case in generated turbulence. Two half-diameter profiles, at 13 and 26 mm downstream of the valve plane, have been investigated for each model. Besides velocity profiles, turbulence shear stresses (TSS) are reported, after the application of the stress analysis technique, in order to assess the maximum values of TSS (TSSmax) exerted on blood particles. Results show the typical bileaflet-type velocity profile for SB and SJ, with three jets exiting the valve, whereas CM lacks the central jet, due to instabilities of its flow field. As for TSSmax, CM reaches the highest values, presumably due to leaflets fluttering. SJ's TSSmax profiles maintain similar shapes at the two downstream locations, whereas SB presents an unexpected increase in the peak value of TSSmax, from 13 to 26 mm downstream of the valve plane, probably due to the curved leaflet design. The three prosthetic heart valves (PHVs) tested show many differences as for their turbulence properties, although they are similarly constructed.

Biomechanical Phenomena↗

PubMed2000

Extracorporeal circulation in ewe's foetus: towards a reliable foetal cardiac surgery protocol. A comparison of two cases.

UNLABELLED: Foetal cardiac surgery is the ultimate goal in the treatment of congenital cardiac malformations. The aim of our research is to elucidate some of the features of the necessarily invasive experimental protocol to be used in an animal model of foetal cardiac surgery. In particular, we assessed the foetal placental reactivity to prolonged cardiac bypass in steady-flow conditions. METHODS: Two cases were selected to show the outcome of prolonged (> 30 minutes) extracorporeal circulation (ECC) instituted without oxygenator under steady-flow assistance. Following the instrumentation of the animal (placement of pressure, flow and myocardial fiber length transducers) and the baseline recordings, a 60-minute bypass period was established with an axial turbopump (Hemopump 14 Fr), after systemic heparinisation and artero-venous cannulation. At the end of the circulatory assistance, the cannulae were removed and a 90 minute observation period followed. The cardiac function was assessed by means of indirectly obtained P-V loops. RESULTS: Case A showed a marked reduction in the end-systolic pressure-volume relationship (ESPVR) during ECC, corresponding to a rightward shift of the P-V loop, with a gradual recovery after the assisted circulation. On the contrary, case B was subjected to progressive placental dysfunction, as evidenced by haemogasanalytical data. Consequently, the haemodynamic data also outlined a negative outcome, with high ESPVR values after bypass. CONCLUSIONS: The present study, while confirming the possibility of cardiac intervention in the foetus, underlines the critical role of minimally invasive protocol to limit both foetal stress and placental dysfunction.

Animals↗

PubMed1999

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.

Blood Physiological Phenomena↗

PubMed1999

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.

Blood Vessel Prosthesis↗

PubMed1998

Progression of choroidal atrophy in acute posterior multifocal placoid pigment epitheliopathy.

Acute posterior multifocal placoid pigment epitheliopathy is a non-granulomatous chorioretinitis of uncertain origin that occurs in healthy young adults. The prevailing opinion is that the disease has a good long-term prognosis for visual acuity because it is self-limiting and chorioretinal scars do not enlarge with time. A middle-aged adult male who had acute posterior multifocal placoid pigment epitheliopathy in one eye has been followed for 22 years. After apparent clinical healing of the placoid epithelial lesions, widespread severe choroidal atrophy with visual loss occurred and progressed over years without interruption. To our knowledge this is the second report of progressive deterioration of a supposedly self-limiting chorioretinal disease.

Acute Disease↗

PubMed1998

Principal stress analysis in LDA measurement of the flow field downstream of 19-mm Sorin Bicarbon heart valve.

Heart valve replacement has become, since many years, a common surgical practice. Along with the improvement that the patients' health has derived from it, however, a certain amount of risk could not be avoided, bound to the inevitable hemodynamic disturbances that an artificial device generates. A major shortcoming, often reported, is the formation of thrombus on the edge of the prosthetic valve, with a possible obstruction of the orifices through which blood should normally flow undisturbed. Hemolysis is another possible consequence of the implantation of a mechanical heart valve, generally correlated to turbulence downstream of prosthetic heart valves (PHV). As it is agreed upon by many researchers, the risk of thrombogenicity or hemolysis is higher in those valves that are more subject to promote turbulence and flow separation in the flow through them. In the following paper, we present a study of the turbulence-related shear stress downstream of a bileaflet valve of minimum size (19 mm external diameter) Sorin Bicarbon. This size was chosen, accordingly to the Food & Drug Administration (FDA) draft guidance suggestion to investigate the worst case in turbulence promoted by PHVs, in order to have the highest velocity gradients and shear stresses for the FDA-stated cardiac output (6 1/min), related to maximum Reynolds number conditions. Velocity data were collected with the two-dimensional laser Doppler anemometry (LDA) technique; whereas this approach does not investigate directly all three components of the flow field, in the present case (bileaflet valves) it is not a limitation to the assessment of the maximum turbulence shear stress (TSS), thanks to the two-dimensional flow nature downstream of bileaflet models. Data taken in coincident mode were elaborated in order to determine the maximum shear stress in the measured points in the flow field, using the 2D Principal Stress Analysis (PSA). The consequences of a variable principal normal stress direction all along the measured profile will be illustrated in terms of differences between measured and maximum shear stresses. Results show the need to estimate the maximum values for the TSS and the direction along which it is obtained to correctly define the turbulent flow field downstream of PHVs.

Blood Flow Velocity↗

PubMed1997

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.

Heart Valve Prosthesis↗

PubMed1997

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.

Aortic Valve↗

PubMed1997

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.

Aortic Valve↗

PubMed1996

Pattern dystrophies of the retinal pigment epithelium.

Pattern dystrophies of the retinal pigment epithelium are infrequent fundus abnormalities arranged in various patterns of dots, lines and branches. The basic lesion appears to be yellow deposits of abnormal lipofuscin accumulated within degenerated retinal pigment epithelium cells. Examinations were carried out on two families who had developed different patterned alterations in the retinal pigment epithelium. The proband of family 1 had diffuse changes associated with equatorial folds. One sister had a macular alteration. A daughter was normal; a son had bilateral atrophy of the temporal retinal pigment epithelium. The proband of family 2 had bilateral, symmetrical retinal pigment epithelium lesions that simulated fundus flavimaculatus. His first daughter had a central lesion in her right eye. The second daughter, a peripapillary crescent of hyperpigmentation in her right eye, and circumpapillary chorioretinal atrophy associated with foveolar abnormalities in the left. This report provides further evidence that variable types of pattern dystrophy can occur within a single family pedigree and support the current opinion that all forms of pattern dystrophies are variants of a single pathogenic mechanism.

Adult↗

PubMed1996

[Orthotopic neobladder in women].

In women undergoing radical cystectomy for bladder cancer, orthotopic bladder reconstruction is now a viable alternative to urinary diversion: preservation of the external urethral sphincter by sectioning the urethra 0.5-1 cm distally to the bladder neck allows maintenance of urinary continence without compromising cancer control. 12 cases of bladder reconstruction in women operated on from 1986 to 1995 are presented here. A personal technique for the creation of an ileal neobladder is described: the use of staplers for detubularization of the ileum significantly reduces the operating time ("simplified ileal bladder"). Other important points of technique are as follows: 1. Careful preparation of the bladder neck and proximal urethra, staying above the pubo-urethral ligaments that must be preserved as the distal landmark of dissection; 2. "Nerve-sparing" isolation of the posterolateral wall of the bladder from the vagina; 3. Careful positioning of the pouch in the true pelvis, in order to avoid posterior prolapse of the neobladder. So far, results of bladder reconstruction in this series of patients are encouraging, both from a functional and oncological standpoint.

Cystectomy↗

PubMed1995

Evaluation of tilting disc valves after fatigue life testing: preliminary results within a comparison program.

A fatigue life test, by accelerating the beat rate, simulates several years of virtual life of a prosthetic heart valve in a short period of time. The correlation between the in vivo life of a valve and in vitro testing expectations is as yet not well established, but reproducible test conditions yield precious information about wear and failure. The paper reports a qualitative analysis of mechanical valve wear as part of a comparison program designed to investigate the significance of fatigue testing with the ultimate aim of defining standard guidelines for these type of tests. Two tilting disc valves (29 mm) were subjected to 16 years of fatigue life simulated by means of a Rowan Ash fatigue tester (accelerated rate of 1,200 bpm). Fatigue-induced effects on valve disc and ring surfaces were observed under a monitor microscope to identify wear sites and patterns. A high speed cinematographic system was used to investigate the mechanisms responsible for the wear (wear modes). Valve closure was inspected at a 6,000 frame/s rate. Because of disc rotation during the tilting movement, the points of contact between disc and ring are distributed all around the disc edge but focally on the ring. On both sides of the disc, the surfaces present ring-like concentric grooves. After 16 years of fatigue life the valves showed neither severe wear nor alteration of their fluidodynamic behavior in the pulsatile flow test.

Biomechanical Phenomena↗

PubMed1995

Fundus abnormalities in Cushing's disease: a preliminary report.

Three patients, 2 males and 1 female, with intrasellar, hypersecretive pituitary adenoma were studied. Blood hypertension was present in all and hyperglycemia in 2 (1 male, 1 female). None had neurological signs of compression of the optic disk or chiasma. One patient showed bilateral circumpapillary and multiple retinal pigment epithelium (RPE) detachment with pooling defects and intraretinal leakage from small retinal arterioles. Another had loss of foveolar, macular and retinal reflexes in the right eye; negligible RPE changes became visible with fluorescein angiography. The third, who had developed malignant hypertension, manifested bilateral hypertensive neuroretinopathy and papilledema. The simultaneous improvement of general and ocular symptoms after removal of the pituitary tumor makes a causal relationship possible and even very likely, between the underlying disorder and fundus abnormalities.

Adenoma↗

PubMed1995

Association of peripapillary scars with lesions characteristic of multiple evanescent white-dot syndrome.

Multiple evanescent white-dot syndrome, acute idiopathic blind-spot enlargement syndrome and multifocal choroiditis (pseudo-ocular histoplasmosis syndrome) are fundus diseases of unknown etiology. A single etiological agent or group of similar agents is thought to be responsible for these relatively rare manifestations. A 35-year-old male with associated symptoms of enlargement of the blind spot, evanescent white-dot syndrome and presumed ocular histoplasmosis is described. The association of these highly differentiated fundus abnormalities strengthens the hypothesis of an etiological or pathological linkage within phenotypically variable clinical forms.

Acute Disease↗

PubMed1995

Aggravation of laser-treated diabetic cystoid macular edema after prolonged flight: a case report.

A 62-year-old diabetic woman with pan-retinal laser treatment for non-proliferative, bilateral diabetic retinopathy and cystoid macular edema (CME) demonstrated an acute exacerbation of CME after 42 h of prolonged flight in commercial pressurized aircraft. When travelling by air, vital sensory functions of the human body are affected by a variety of disturbing factors. The most important of these--altitude-related oxygen deficiency--is compensated for by homeostatic mechanisms in healthy subjects. However, even with normal oxygen tension, the diabetic retina is hypoxic because the vascular response to oxygen variation is altered. Increased tissue demand for oxygen, owing to decreased ability of the circulating blood to release oxygen, cannot be met. In our patient, the aggravated CME appeared to result from hemodynamic changes induced by flight. In particular, the prolonged environmental oxygen deficiency may have exacerbated the retinal hypoxia leading to acute, vascular decompensation and dramatic plasma leakage with visual loss.

Aerospace Medicine↗