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Biomedical subjects

A Politi

Publications and source records attributed to A Politi.

At least 19 recordsLinked to original sources

Phase transition in a radiation-matter interaction with recoil and collisions.

The standard model introduced to describe the collective atomic recoil of an ensemble of atoms interacting with a strong electromagnetic field has been here extended by the inclusion of collisions with a buffer gas. As a result, we find that in the thermodynamic limit the coherent emission of radiation exhibits a continuous phase transition upon increasing the pump intensity. The output laser field is strictly larger than 0 only above a critical value. We find that the transition is not associated with the onset of spatial ordering but rather with the onset of a synchronization between the polarization phase and spatial position. A coherence parameter is introduced to characterize the phase transition.

Journal Article↗

Fractures in heterogeneous two-dimensional systems.

A two-dimensional triangular lattice with bond disorder is used as a testing ground for fracture behavior in heterogeneous materials in strain-controlled conditions. Simulations are performed with two interaction potentials (harmonic and Lennard-Jones types) and different breaking thresholds. We study the strain range where the fracture progressively develops from the first to the last breakdown. Scaling properties with the lattice size are investigated: no qualitative difference is found between the two interaction potentials. Clustering properties of the broken bonds are also studied by grouping them into disjoint sets of connected bonds. Finally, the role of kinetic energy is analyzed by comparing overdamped with dissipationless dynamics.

Journal Article↗

Dynamic localization of Lyapunov vectors in Hamiltonian lattices.

The convergence of the Lyapunov vector toward its asymptotic shape is investigated in two different one-dimensional Hamiltonian lattices: the so-called Fermi-Pasta-Ulam and Phi(4) chains. In both cases, we find an anomalous behavior, i.e., a clear difference from the previously conjectured analogy with the Kardar-Parisi-Zhang equation. The origin of the discrepancy is eventually traced back to the existence of nontrivial long-range correlations both in space and time. As a consequence of this anomaly, we find that, in a Hamiltonian lattice, the largest Lyapunov exponent is affected by stronger finite-size corrections than standard space-time chaos.

Journal Article↗

Acute and mid-term results of phosphorylcholine-coated stents in primary coronary stenting for acute myocardial infarction.

The aim of this pilot study was to evaluate the safety and efficacy of the BiodivYsio phosphorylcholine-coated stent in the primary treatment of acute myocardial infarction. The BiodivYsio stent (Biocompatible) is a balloon-expandable stent, laser etched from a 316 L stainless steel tube. This device is coated with phosphorylcholine, a synthetic, hemocompatible phospholipid polymer that has been shown in experimental studies to reduce platelet and protein adhesion to the surface of the metal. One hundred consecutive patients within 24 hr of symptoms of onset of acute MI, treated with primary PTCA, were enrolled. After PTCA, stenting was attempted in all eligible lesions (reference diameter > or = 2.5 mm; no bend lesion > 45 degrees ). Poststenting regimens contained ticlopidine (500 mg/day) and aspirin (325 mg/day) and 6-12 hr of heparin infusion. Procedural success (TIMI > or = II and residual stenosis < 30%) was obtained in 70/74 cases (95%). TIMI grade III was restored in 90% of cases. In the patient group with procedural success (70 cases), 70 BiodivYsio stents were placed. After stenting, diameter stenosis decreased from 96% +/- 11% to 22% +/- 12% (P < 0.01) and minimal luminal diameter increased from 0.13 +/- 0.29 to 2.47 +/- 0.43 (P < 0.01). Nominal stent diameter was between 3.0 and 4.0 mm (mean, 3.5 +/- 0.4 mm). Stent length was between 11 and 28 mm (mean, 17 +/- 4.5 mm). Clinical follow-up was obtained in all patients; angiographic follow-up was performed in 65/70 (93%). No acute or subacute thrombosis was reported. Two in-hospital major adverse cardiac events (MACE) were reported due to a nontreated left main disease that required coronary artery bypass graft (CABG) surgery. At follow-up, MACE were found in 9 of 68 patients (13%), target lesion revascularization (TLR) in 6%, and CABG in the remaining 6%. Primary stenting with phosphorylcholine-coated stent leads to excellent short- and mid-term clinical outcomes and is associated with a restenosis rate of 12%.

Aged↗

Intercellular Ca2+ wave propagation through gap-junctional Ca2+ diffusion: a theoretical study.

Intercellular regenerative calcium waves in systems such as the liver and the blowfly salivary gland have been hypothesized to spread through calcium-induced calcium release (CICR) and gap-junctional calcium diffusion. A simple mathematical model of this mechanism is developed. It includes CICR and calcium removal from the cytoplasm, cytoplasmic and gap-junctional calcium diffusion, and calcium buffering. For a piecewise linear approximation of the calcium kinetics, expressions in terms of the cellular parameters are derived for 1) the condition for the propagation of intercellular waves, and 2) the characteristic time of the delay of a wave encountered at the gap junctions. Intercellular propagation relies on the local excitation of CICR in the perijunctional space by gap-junctional calcium influx. This mechanism is compatible with low effective calcium diffusivity, and necessitates that CICR can be excited in every cell along the path of a wave. The gap-junctional calcium permeability required for intercellular waves in the model falls in the range of reported gap-junctional permeability values. The concentration of diffusive cytoplasmic calcium buffers and the maximal rate of CICR, in the case of inositol 1,4,5-trisphosphate (IP3) receptor calcium release channels set by the IP(3) concentration, are shown to be further determinants of wave behavior.

Animals↗

Synthesis and preliminary biological characterization of a new potential (125)I-radioligand for dopamine and serotonin receptors.

The synthesis and a preliminary biological characterization of a new class of N-benzyl-aminoalcohols which have serotonin (5-HT(2)) and dopamine (D(2)) receptor affinity is described. In vitro competition binding studies were conducted with the new molecules and (3)H-spiperone on crude membrane preparation from rat striatum and frontal cortex. One of these compounds, 3-benzylamino-1-(4-fluoro-2-iodophenyl)-propan-1-ol (6f), whose IC(50) values are in the micromolar range for both the D(2) and 5-HT(2) receptors, was prepared in iodine-125 labelled form (6i) by nucleophilic substitution of the bromine atom of 3-benzylamino-1-(2-bromo-4-fluorophenyl)-propan-1-ol (6d). In the in vivo studies, conducted on rats, the radiolabelled molecule 6i shows a good capacity to cross the blood-brain barrier (BBB) with a mean value of first pass cerebral extraction (E) of ca. 50% when the regional cerebral blood flow, measured with microsphere technique, is in the experimental animal's physiologic range (0.8-1 mL/min/g). A preliminary in vitro autoradiographic distribution on coronal rat brain slices of the radioiodinated molecule showed that it was preferentially localized in the striatum and in the cerebral regions rich in dopamine- and serotonin receptors, even if a high non-specific binding was observed.

Animals↗

Hypothesis and development of a minimally invasive approach for percutaneous transmyocardial revascularization with holmium laser.

BACKGROUND: Percutaneous transluminal myocardial revascularization (PTMR) is a new procedure to improve perfusion of the ventricular wall for patients with intractable angina and untreatable by surgery or conventional catheter-based intervention. Actually PTMR requires femoral approach to utilize 8F-9F system device. We now report the feasibility study of PTMR using a laser delivered through a novel Eclipse system and new 6F and 7F guiding catheters that allow to perform PTMR even in patients with peripheral vascular disease and particularly suitable for alternative small vascular access. METHODS: Percutaneous vascular access for PTMR treatment was obtained via the femoral or radial artery. A 6F or 7F mono-directional catheter carrying flexible fiber optics was used with a Holmium laser (Eclipse system) and was placed across the aortic valve into the left ventricular cavity to create channels of 5 mm in depth from the endocardial surface into the myocardial tissue. From June 1999 to September 2000, 39 patients (28 males, 11 females, mean age 72 +/- 8 years, range 58-86 years) underwent PTMR with the Eclipse system. Preoperative mean Canadian Cardiovascular Society (CCS) angina class was 3.5 +/- 0.5 and previous myocardial procedures had been performed in 39 patients (18 coronary artery bypass graft and 31 coronary angioplasty). RESULTS: The procedure was well tolerated and a procedural success was obtained in all patients (100%). We performed a mean of 19 +/- 7 channels in a mean fluoroscopy time of 21 +/- 9 min. We report only one procedural complication: one embolic stroke (2.4%). No hospital major adverse cardiac events were observed. The average length of hospital stay was 3.1 days. The mean CCS angina class at entry was 3.5 and it declined from 3.5 +/- 0.5 to 1.25 +/- 0.8 at discharge. At the follow-up of 8.2 +/- 3.9 months the mean CCS was 1.5 +/- 0.7. CONCLUSIONS: This experience confirmed the safety and technical feasibility of PTMR with this mini-invasive approach with a reduction in operative and fluoroscopy time. The PTMR with the 6F or 7F guiding catheter is feasible in high risk patients even when the femoral approach is contraindicated. Immediate and short-term results confirm that a clinical improvement is obtained in most patients.

Aged↗

[Acute myocardial infarction during labor: report of a case and review of the literature].

Acute myocardial infarction in pregnancy is a rare condition with substantial risk of maternal and fetal death. There is very little information about the use in this setting of percutaneous coronary interventional therapy. Together with literature review on this topic, we present the case of a 33-year-old 39-week pregnant woman who sustained during labor an acute transmural anterior myocardial infarction. Immediately after successful cesarean section, she was treated by primary percutaneous coronary angioplasty and direct stenting of the left anterior descending coronary artery with maternal and fetal excellent outcome.

Adult↗

Convective lyapunov exponents and propagation of correlations

We conjecture that in one-dimensional spatially extended systems the propagation velocity of correlations coincides with a zero of the convective Lyapunov spectrum. This conjecture is successfully tested in three different contexts: (i) a Hamiltonian system (a Fermi-Pasta-Ulam chain of oscillators); (ii) a general model for spatiotemporal chaos (the complex Ginzburg-Landau equation); (iii) experimental data taken from a CO2 laser with delayed feedback. In the last case, the convective Lyapunov exponent is determined directly from the experimental data.

Journal Article↗

Finite thermal conductivity in 1D lattices

We discuss the thermal conductivity of a chain of coupled rotators, showing that it is the first example of a 1D nonlinear lattice exhibiting normal transport properties in the absence of an on-site potential. Numerical estimates obtained by simulating a chain in contact with two thermal baths at different temperatures are found to be consistent with those based on linear response theory. The dynamics of the Fourier modes provides direct evidence of energy diffusion. The finiteness of the conductivity is traced back to the occurrence of phase jumps. Our conclusions are confirmed by the analysis of two variants of this model.

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First-order phase transition in a (1+1)-dimensional nonequilibrium wetting process

A model for nonequilibrium wetting in 1+1 dimensions is introduced. It comprises adsorption and desorption processes with a dynamics that generically does not obey detailed balance. Depending on the rates of the dynamical processes the wetting transition is either of first or second order. It is found that the wet (unbound) and the nonwet (pinned) states coexist and are both thermodynamically stable in a domain of the dynamical parameters that define the model. This is in contrast with equilibrium transitions where coexistence of thermodynamically stable states takes place only on the transition line.

Journal Article↗

Intermittent 6-month low-dose dobutamine infusion in severe heart failure: DICE multicenter trial.

BACKGROUND: Patients with end-stage heart failure are often refractory to maximal oral therapy, and they have high mortality rates, poor quality of life, and frequent hospitalizations with elevated health care costs. Intermittent dobutamine therapy has been suggested as an additional option in this clinical setting. METHODS AND RESULTS: Thirty-eight patients clinically stable for at least 48 hours with standard treatment, New York Heart Association (NYHA) functional class III or IV, cardiac index </=2.2 L/min/m(2), and left ventricular ejection fraction </=30% were randomly assigned to ambulatory intermittent dobutamine or optimal standard treatment. Dobutamine was infused at 2.5 microgram/kg/min with a portable pump 48 hours/week for 6 months. The primary study end point was the reduction of hospitalizations for worsening of congestive heart failure (CHF); changes in NYHA functional class, 6-minute walking test, and mortality rates were secondary end points. During the 6-month follow-up, all patients in dobutamine and control groups underwent weekly clinical visits with serum sodium and potassium measurement. Baseline characteristics were age 65 +/- 2 years, NYHA class III/IV 17/21, ejection fraction 22% +/- 1%, and cardiac index 1.89 +/- 0.1 L/min/m(2), without differences between treatment groups. Hospitalizations for all causes over a 6-month period were 17 and 11 in control and dobutamine groups; 11 of 17 and 7 of 11 were for worsening CHF. Four control patients but none in the dobutamine group had 2 or more hospitalizations for worsening of CHF. There were no significant differences in NYHA functional class and in 6-minute walking test. Three patients in the control group died and 5 in the dobutamine group died. Two patients in the dobutamine group underwent heart transplantation. Protocol was discontinued in the dobutamine group for severe ventricular arrhythmias (1 patient), infusion system failure (1 patient), and consent withdrawal (1 patient). In 3 patients in the dobutamine group, drug dose was increased to 5 microgram/kg/min because of CHF. CONCLUSIONS: Six-month intermittent low-dose dobutamine administration was well tolerated by patients with severe CHF; it did not improve the functional status and did not significantly increase the mortality rate as found with higher dobutamine doses in other studies. Hospitalizations for all causes and for worsening of CHF tended to be fewer in the dobutamine group.

Adult↗

External cardioversion of atrial fibrillation: role of paddle position on technical efficacy and energy requirements.

AIM: To define the effect of defibrillator paddle position on technical success and dc shock energy requirements of external cardioversion of atrial fibrillation. METHODS: 301 patients (mean (SD) age 62 (11) years) with stable atrial fibrillation were randomly assigned to elective external cardioversion using anterolateral paddle position (ventricular apex-right infraclavicular area; group AL (151 patients)) or anteroposterior paddle position (sternal body-angle of the left scapula; group AP (150 patients)). A step up protocol was used, delivering a 3 J/kg body weight dc shock, then a 4 J/kg shock (maximum 360 J), and finally a second 4 J/kg shock using the alternative paddle location. RESULTS: The two groups were comparable for the all clinical variables evaluated. The cumulative percentage of patients successfully converted to sinus rhythm was 58% in group AL and 67% in group AP with low energy dc shock (NS); this rose to 76% in group AL and to 87% in group AP with high energy dc shock (p = 0.013). Thirty seven patients in group AL and 19 in group AP experienced dc shock with the alternative paddle position; atrial fibrillation persisted in 10/37 in group AL and in 10/19 in group AP. Mean dc shock energy requirements were lower for group AP patients than for group AL patients, at 383 (235) v 451 (287) J, p = 0.025. Arrhythmia duration was the only factor that affected the technical success of external cardioversion (successful: 281 patients, 80 (109) days; unsuccessful: 20 patients, 193 (229) days; p < 0.0001). The success rate was lower if atrial fibrillation persisted for > 6 months: 29 of 37 (78%) v 252 of 264 (95%); p = 0.0001. CONCLUSIONS: An anteroposterior defibrillator paddle position is superior to an anterolateral location with regard to technical success in external cardioversion of stable atrial fibrillation, and permits lower dc shock energy requirements. Arrhythmia duration is the only clinical variable that can limit the restoration of sinus rhythm.

Adult↗

[Tracheal stenosis due to metastatic adenopathic compression from breast carcinoma].

Paratracheal lymph-nodal metastases secondary of breast cancer aren't frequent in this kind of cancer. Here is described the case of a 76-years-old woman come to our note for ingravescent dyspnoea caused by metastatic adenopathy compression of the tracheal lumen. After excluding other treatments, a tracheal stent is put on. The obstruction gets better right away, the initial severe respiratory symptoms are improved and the ventilation is almost normal.

Aged↗

[Primary angioplasty in acute myocardial infarct with or without a stent implant: the experience and results at 6 months in the first 200 patients].

BACKGROUND: Although it is superior to thrombolysis, primary PTCA does have some limitations, both in hospital (recurrent ischemia and reinfarction due to reocclusion of the infarct-related artery) and at the six-month follow-up (high rate of late restenosis). Coronary stenting is a promising way of solving some of these problems, even if its use in patients with acute myocardial infarction could prove to be controversial because of intracoronary thrombus. In this study, we propose two procedural strategies in the treatment of the infarct-related artery (IRA): the search for optimal angiographic results after PTCA ("stent-like result"--SLR--with residual stenosis < or = 20%--no dissection--TIMI III flow) or intracoronary stenting when SLR was not obtained after a second inflation. METHODS AND RESULTS: From December 1995 to May 1998, 200 patients with AMI underwent direct PTCA or rescue PTCA because of failed thrombolysis. There were 143 men and 57 women, mean age 65 (range 36-84). Nineteen patients were in cardiogenic shock and 25 were in Killip class > II. Recanalization of the IRA was achieved in 196 patients (98%). In four patients, it was not possible to cross total occlusion with the guide-wire. SLR post-PTCA was achieved in 40 patients (20%). Stents were placed in 147 patients (75%), with "elective" implantation in 73 lesions because of suboptimal results after PTCA in 41, and early loss or coronary dissection with threatening occlusion in 33. In nine patients without SLR, stenting was not performed because of diffuse disease of the IRA. In-hospital complications included ten deaths (8 of 19 patients with cardiogenic shock at admission and 2 with multivessel disease and severe left ventricular dysfunction). None of the patients required emergency coronary bypass for procedural complications. One patient had a subacute thrombosis on the third day after bail-out stent implantation (re-PTCA). Five patients required elective bypass surgery to complete revascularization for multivessel disease with ten days after the surgical procedure. At the six-month follow-up, one patient had died of cardiogenic shock. Eleven (5%) patients with bail-out procedures underwent coronary bypass surgery or PTCA. Thirty-one patients (31/168) had recurrence of ischemia: 15 patients in the stent group, 11 in SLR group and 5 in the non-SLR group. Re-PTCA was performed in 20 patients, CABG in five and medical therapy in six. Other patients were angina-free at follow-up. CONCLUSIONS: Based on our experience, seeking optimal angiographic results with or without (SLR) stent implantation is a safe and effective operative approach to achieve the best procedural and clinical outcome and reduce complications in patients undergoing PTCA for AMI.

Aged↗

Percutaneous transmyocardial revascularization with holmium laser in patients with refractory angina: a pilot feasibility study.

BACKGROUND: Percutaneous transluminal myocardial revascularization (PTMR) is a new procedure to improve perfusion of the ventricular wall for patients with intractable angina that is untreatable by surgery or conventional catheter-based intervention. PTMR allows the creation of myocardial channels through the controlled delivery of holmium laser energy from the ventricular chamber. Preliminary studies in animals and human subject have yielded promising results. We now report the feasibility study of PTMR using a laser delivered through a novel Eclipse system, and we present the results of this sole therapy in patients with severe coronary disease and angina refractory to maximal medical treatment angina (III-IV CCS). METHODS: Percutaneous vascular access for PTMR treatment was obtained via the femoral artery. A 9F directional catheter carrying flexible fiber optics was used with a holmium laser (Eclipse system) and was placed across the aortic valve into the left ventricle cavity to create channels with a depth of 5 mm from the endocardial surface into the myocardial tissue. From April to November 1998, 15 patients underwent PTMR with Eclipse system. Two patients were female; the mean age was 66 +/- 8 (range 59-74). Five patients had a severe LV dysfunction (FE < 30%). Preoperative angina class was III in 10 patients and IV in 5 and previous myocardial procedures had been performed in all patients. RESULTS: The procedure was well tolerated and procedural success was obtained in 14 of 15 patients. There was one myocardial perforation because of guiding-catheter manipulation (pericardial drainage in fourth day). We performed a mean of 13 +/- 4 channels in a mean fluoro time of 23 +/- 11 min. Upon release and during follow-up (5.3 months +/- 4.2, range 2-10), angina class had significantly improved in 14 of 14 patients with complete PTMR treatment, with 4 asymptomatic patients, 6 patients in CCS I, 3 in CCS II, 2 in CCS III and only one patient hospitalized due to angina. CONCLUSION: This pilot study confirmed the safety and technical feasibility of PTMR. Immediate and short-term results confirm that a clinical improvement is obtained in most patients. Although these are early clinical benefits, the true efficacy of this approach will necessarily be defined by a randomized trials with prospectively-defined endpoints and with PTMR compared with medical therapy.

Aged↗

[Non-cardiac transcatheter intervention: operative possibilities in a hemodynamics laboratory].

INTRODUCTION: New possibilities for transcatheter treatment of the cardiovascular system are guaranteed with the improvement of materials and the availability of new devices. Nevertheless, a rationalization of the potential activity in this sector seems to be necessary, and it could arise through the presence of Catheterization Laboratories "open" to diagnostic procedures and therapy that are not confined to the coronary system. This clinical study reports the experiences and results of our work in this field. MATERIALS AND METHODS: During the period from May 1995 to May 1997, our laboratory performed 205 diagnostic procedures that did not involve the coronary system. Based on this diagnostic work, there emerged 91 cases with an indication for transcatheter intervention, which was subsequently performed at our laboratory. There were 68 peripheral angioplasty procedures on the iliofemoral axis, 2 angioplasties of the subclavian artery, 8 of the renal artery, 2 procedures involving the treatment of A-V fistulas, one case of femoral pseudoaneurysm treatment and 10 cases of transcutaneous pericardiotomy performed with a balloon catheter. All the procedures were performed by our laboratory staff using materials that are normally at our disposal. RESULTS: Successful results were obtained in 65 out of the 68 peripheral angioplasty procedures and in all of the 8 renal and 2 subclavian angioplasties. The positioning of the endoprosthesis for the closure of the A/V fistula was effective in one of the two cases. The transcatheter treatment of the femoral pseudoaneurysm was successful. In all cases where a pericardiotomy was performed with a balloon catheter, there was no reoccurrence of cardiac tamponade during the follow-up period. No complications were noted as a result of any of the procedures. CONCLUSIONS: Our experience documents how it is possible to increase the diagnostic and therapeutic options in a Catheterization Laboratory. However, willingness on the part of the staff to update their skills continually and collaborate with other specialists is necessary in order to maintain optimal operative standards.

Adult↗

[Massive pulmonary embolism after blunt chest trauma: considerations on pathogenesis and therapy].

A blunt chest trauma may provoke many different kinds of cardiac injury, particularly myocardial contusion, sometimes causing subsequent acute myocardial infarction or cardiac arrest by ventricular tachyarrhythmia in the absence of structural lesions. We describe a case of acute massive pulmonary embolism after a blunt chest impact caused when the patient was kicked by a horse. The patient showed progressive dyspnea three days after the trauma. The diagnosis was reached by non-invasive means and finally confirmed by pulmonary angiography. Because of the contraindication to thrombolytic therapy, we performed percutaneous catheter and guide-wire clot fragmentation with at least partial immediate success and subsequent favorable course. We discuss possible pathophysiological mechanisms to explain this case, which has no precedents in the literature.

Angiography↗