Hydration and Ionic Conductivity of Model Cation and Anion-Conducting Ionomers in Buffer Solutions (Phosphate, Acetate, Citrate).

We studied the gravimetric and volumetric water uptake and ionic conductivity of two model ionomers, cation-conducting sulfonated poly(ether ether ketone) (SPEEK) and anion-conducting polysulfone-trimethylammonium chloride (PSU-TMA), after immersion in phosphate, acetate, and citrate buffer solutions. The equilibrium swelling of SPEEK and PSU-TMA ionomer networks was determined as a function of the pH and buffer composition. The hydration data can be interpreted using the osmotic swelling pressure dependence on the ion-exchange capacity of the ionomers and the concentration of the electrolyte solutions. In the case of SPEEK, anisotropic swelling is observed in diluted buffer solutions, where the swelling pressure is higher. The large water uptake observed for citrate ions is due to the large hydration of this bulky anion. The ionic conductivity is related to the conducting ions and, in the case of SPEEK, to sorbed excess electrolyte. The highest ionic conductivity is observed after immersion in phosphate buffers. Ionic cross-linking is, for the first time, observed in the case of an anion-conducting ionomer in the presence of divalent citrate ions, which limits the volumetric swelling and decreases the ionic conductivity of PSU-TMA.

Analysis of temperature-promoted and solvent-assisted cross-linking in sulfonated poly(ether ether ketone) (SPEEK) proton-conducting membranes.

Sulfonated poly(ether ether ketone) (SPEEK) membranes were thermally treated at temperatures between 120 and 160 degrees C. Water uptake measured at different relative humidity values or by full immersion in water between 25 and 145 degrees C was found to depend very strongly on previous thermal treatment and casting solvent. Water-uptake coefficient values as low as 10-15 even upon immersion in water at 100 degrees C were obtained with membranes treated at 160 degrees C. This effect is related to cross-linking by SO2 bridges between macromolecular chains. An important role is also played by the casting solvent: among the investigated solvents, dimethylsulfoxide (DMSO) gave the best results. A chemical kinetics model is outlined that permits the estimation of the relevant kinetic parameters, especially the activation energy of the cross-linking reaction, which was found to be about 60 kJ/mol. These results are of significant importance for the improvement of proton-exchange membrane fuel cells.

Effects of different types of exercise training followed by detraining on endothelium-dependent dilation in patients with recent myocardial infarction.

BACKGROUND: In coronary artery disease, exercise training (ET) is associated with an improvement in endothelial function, but little is known about the relative effect of different types of training. The purpose of this study was to prospectively evaluate the effect of different types of ET on endothelial function in 209 patients after a first recent acute myocardial infarction. METHODS AND RESULTS: Endothelial function was evaluated before and after 4 weeks of different types of ET and after 1 month of detraining by measuring flow-mediated dilation and von Willebrand factor levels at baseline and after ET. Patients were randomized into 4 groups: group 1, aerobic ET (n=52); group 2, resistance training (n=54); group 3, resistance plus aerobic training (n=53); and group 4, no training (n=50). At baseline, flow-mediated dilation was 4.5+/-2.6% in group 1, 4.01+/-1.6% in group 2, 4.4+/-4% in group 3, and 4.3+/-2.3% in group 4 (P=NS). After ET, flow-mediated dilation increased to 9.9+/-2.5% in group 1, 10.1+/-2.6% in group 2, and 10.8+/-3% in group 3 (P<0.01 versus baseline for all groups); it also increased in group 4 but to a much lesser extent (to 5.1+/-2.5%; P<0.01 versus trained groups). The von Willebrand factor level after ET decreased by 16% (P<0.01) similarly in groups 1, 2, and 3 but remained unchanged in group 4. Detraining returned flow-mediated dilation to baseline levels (P<0.01 versus posttraining). CONCLUSIONS: In patients with recent acute myocardial infarction, ET was associated with improved endothelial function independently of the type of training, but this effect disappeared after 1 month of detraining.

[Value and limitations of sport in cardiac patients]. / Intérêt et limites du sport chez le cardiaque.

Regular physical exercise increases effort capacity, the quality of life, and improves symptoms in all cardiac patients. In addition, and much more importantly, all studies show a close correlation between exercise and the reduction of mortality and morbidity with a beneficial effect on the progression of atherosclerosis. This relationship is particularly well documented in patients with coronary artery disease. Exercise has a beneficial effect due to its action on all the principal coronary risk factors, an endothelial dysfunction, coagulability and prevention of thrombosis and an autonomic nervous system tone. All forms of physical activity and some sports may therefore be considered by these patients. In some cases, competitive sport may be permitted, in accordance with popular social custom. In order to obtain these cardiocirculatory protection, physical exercise and sporting activities should be the object of a personalised therapeutic prescription which takes into account the intensity, the type of effort, its duration and frequency. Indeed, if the intensity of the exercise is too low, these patients may not obtain the desired benefits. On the other hand, excessively intensive exercise could trigger serious adverse effects such as severe arrhythmias, sudden death or an acute coronary syndrome. It is, therefore, essential before "prescribing" exercise to perform a preliminary evaluation to stratify the patient's risk and in order to recommend appropriate and well adapted exercise programs.

Thermal stability and thermodynamic properties of hybrid proton-conducting polyaryl etherketones.

The thermal and structural stability of sulfonated cross-linked PEEK (polyether ether ketone) and its silicon-containing class II hybrid derivatives were characterized by combination of mass spectrometry, infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. Thermodynamic properties of the hybrids were determined, including glass-transition temperature, degree of crystallinity, and thermal stability. The decomposition processes of the hybrid polymers could be consistently interpreted and their energetics quantitatively determined. The introduction of inorganic silanol moieties improves the thermal stability compared to sulfonated products.

Nanocomposite polymeric electrolytes to record electrophysiological brain signals in prolonged, unconventional or extreme conditions.

Chemically stable nanocomposite iono-conducting polymeric membranes (based on lithium salts and nanocrystalline oxide powders dispersed in a polymethyl methacrylate matrix) performed successfully in the recording of human brain responses to visual stimulation. Impedance was higher than that of conventional electrodes. However, the electrophysiological signals recorded by acid Al(2)O(3) and neutral Al(2)O(3) 5 wt.% and 10 wt.% nanocomposite gel electrolytes were comparable to those obtained with standard electrodes, even without preliminary skin cleaning and in the absence of gel electrolytes allowing better contact with and skin-electrode ionic conductance. The electrochemical and mechanical characteristics of these membranes make them fit for human and animal research, for clinical application (specifically in emergencies, prolonged electrophysiological recordings), or in unconventional or extreme conditions when fluid electrolytes are unsuitable (e.g., biomedical space research).

A simple and versatile Sol-Gel method for the synthesis of functional nanocrystalline oxides.

MxOy nanometric powders (Nb2O5, In2O3, and ZrO2) have been efficiently synthesized at low temperatures with the use of simple precursors and with no acid or base catalysis or stabilizing agents. The powders have been characterized by Thermogravimetry/Differential Thermal Analysis, X-ray diffraction, and scanning electron microscopy. The oxides obtained have well-defined crystalline structures, exhibit homogeneity, and crystallite sizes ranging from 9 to 16 nm in diameter.

Impact of physical training and detraining on endothelium-dependent vasodilation in patients with recent acute myocardial infarction.

BACKGROUND: There is evidence that aerobic exercise improves endothelial function in healthy subjects as well as in patients with chronic heart failure. However, it is unknown whether this effect occurs in patients with recent myocardial infarction (AMI). METHODS: Fifty-two patients with a recent first uncomplicated AMI underwent endothelial function evaluation before and after 3 months of moderate aerobic exercise training. We measured brachial artery vasomotor reactivity using flow-mediated dilation (FMD), a cold pressor (CP) test, and sublingual nitroglycerin. Patients were randomized into 2 groups: 28 patients (G1) underwent training, while 24 patients (G2) served as controls. Brachial artery vasomotor reactivity was reassessed after 1 month of detraining (DT). RESULTS: At baseline the FMD was 1.66% +/- 4.11% in G1 and 2.04% +/- 3.4% in G2 (P = NS) and vasoconstriction was evident after a CP test. The diameter reduction was -4.1% +/- 3.89% in G1 and -4.39% +/- 5.67% in G2 (P = NS). At follow-up the FMD had increased to 9.39% +/- 4.87% in G1 (P <.01) and to 4.4% +/- 3.9% in G2 (P <.01 vs G1). Vasoconstriction during a CP test was observed only in G2. Endothelium-independent vasodilation was unchanged in both groups. Effort tolerance increased by 32% in G1 patients (P <.01 versus G2) and was correlated with FMD change (R = 0.51, P <.01). After detraining the FMD was significantly reduced in G1 (P <.01) and a further vasoconstriction was evident after CP testing. CONCLUSIONS: Exercise training improves endothelium-dependent vasodilation in post-AMI patients. This improvement is associated with a significant increase in exercise tolerance. These benefits disappeared after detraining.

[Bi-ventricular synchronous pacing and heart failure]. / Resincronizzazione ventricolare e insufficenza cardiaca.

After initial trials of conventional DDD pacing in dilated cardiomyopathies, the concept of multisite stimulation was introduced in 1994. This new indication of heart failure treatment is based on the correction of myocardial contraction and relaxation asynchronies. European pilot studies including few patients were followed by two multicenters randomized trials (MUSTIC and MIRACLE) that confirmed a significant improvement of functional capacity, quality of life and hemodynamic status. Intraventricular delay and QRS duration shortening seems to be the best predictor of clinical success. Patients with more depressed functional and hemodynamic status seems to benefit most from this therapeutic approach. Two studies (CARE HF and COMPANION) are still conducted which will provide further insight into the effectiveness in terms of prognosis of cardiac resynchronisation therapy in this patient population.

The role of work simulation tests in a comprehensive cardiac rehabilitation program.

BACKGROUND: One of the goals of a comprehensive cardiac rehabilitation (CR) program is the patient's return to his or her usual activities. The aims of this paper were to implement an occupational evaluation protocol in a CR and to assess patients' hemodynamic responses and ventricular arrhythmias during work simulation tests. METHODS: After an 8-week outpatient CR, 132 patients performed work simulation, lifting (MH-L) and carrying (MH-C) tests. ECG, heart rate and blood pressure were constantly monitored. RESULTS: The comparison of physiological responses during work simulation and a standard exercise testing provided the following results: 1) maximal heart rate, blood pressure and double product values during WS and MH tests were significantly lower (p < 0.001) than those measured during exercise testing; 2) higher (p < 0.001) double product values were achieved during MH-C as compared to MH-L and work simulation; 3) arrhythmias were more frequent during MH-L as compared to exercise test (p < 0.001). The increment of double product was reached much faster during work simulation and MH tests as compared to exercise testing: according to the multivariate analysis this was a predictor of a greater incidence of arrhythmias. The incidence of arrhythmias during work simulation tests and MH was significantly higher in patients with reduced tolerance to effort, valvular replacement, arrhythmias during holter monitoring, low ejection fraction and effort silent ischaemia. CONCLUSIONS: Work simulation test provide a more personal functional assessment, complementary to the exercise testing. It appears particularly useful in patients with higher functional impairment who are at a higher risk of arrhythmias.

Chronic infusion of dobutamine and nitroprusside in patients with end-stage heart failure awaiting heart transplantation: safety and clinical outcome.

BACKGROUND: in patients with severe heart failure additional therapeutic support with intravenous inotropic or vasodilator drugs is frequently employed in an attempt to obtain hemodynamic and clinical control. No data comparing the use and efficacy of chronic intravenous inotropic and vasodilator therapy in patients with advanced heart failure are available. AIMS: we evaluated, in a group of patients with advanced heart failure undergoing chronic infusion with dobutamine or nitroprusside, in addition to optimized oral therapy, (1) the safety of chronic infusion, (2) the efficacy of both drugs in managing unloading therapy and (3) clinical outcome of the two therapeutic strategies. METHODS: one hundred and thirteen patients receiving optimized oral therapy, in functional class III/IV with symptoms and signs of refractory heart failure and requiring additional pharmacological support with either intravenous dobutamine or nitroprusside were evaluated. Clinical and therapeutic management and clinical outcome of the two groups were considered. RESULTS: dobutamine was administered for 12 h/day for 20+/-23 days at a dosage of 7+/-3 microg/kg/min to 43 patients. The mean dose of nitroprusside was 0.76+/-0.99 microg/kg/min. The mean duration of use of this drug, administered as a 12-h/day infusion was 22+/-38 days. Nitroprusside infusion allowed greater doses of short-term ACE-inhibitors to be used compared to pre-infusion (ACE-inhibitor dose: 55+/-30 mg/day vs. 127+/-30 mg/day P<0.0001) and during dobutamine infusion (ACE-inhibitor dose: 85+/-47 mg/day vs. 127+/-30 mg/day P<0.002). Nitroprusside unlike dobutamine significantly improved the NYHA functional class. Of the 113 patients, 109 (97%) had a cardiac event during a mean follow-up of 337+/-264 days. Forty-four patients required hospitalization for worsening congestive heart failure, 45/113 (39%) patients died during the follow-up and 27/113 (24%) patients had a heart transplant in status one. Hospitalization, because of worsening heart failure was less frequent in the nitroprusside than in the dobutamine subgroup [29/51 (57%) vs. 19/22 (86%) P<0.02]. The overall mortality was 28% (20/70) in the nitroprusside group and 58% (25/43) in the dobutamine group (odds ratio 0.33 CI 0.16 to 0.73 P<0.006). In the group treated with nitroprusside, heart transplantation in status one was performed in 16/33 patients (48%), while in the dobutamine group this was done in 11/14 patients (78%) (odds ratio 0.25 CI 0.06-1.02 P<0.06). There was a significant reduction in the combined end-point of mortality/heart transplantation in status one in patients treated with nitroprusside compared to those treated with dobutamine (36/70 (51%) vs. 36/43 (84%) - (odds ratio 0.34 CI 0.14-0.80 P<0.01). The incidence of adverse events in the patients treated with nitroprusside was similar to that in those treated with dobutamine (20% vs. 17% P=ns). CONCLUSIONS: for patients awaiting heart transplantation chronic intermittent nitroprusside infusions are more effective and safer than dobutamine in relieving symptoms, facilitating unloading therapy management and improving survival. Whether chronic intermittent infusion of nitroprusside could represent a feasible medical strategy in out-patients with severe heart failure remains to be investigated.

[Prognostic evaluation of silent ischemia during exercise in patient with recent infarction. Italian multicenter study. SMISS Group]. / Evaluation du pronostic de l'ischémie silencieuse à l'effort chez des patients avec infarctus récent. Etude italienne multicentrique. Groupe SMISS.

AIM: The aim of the Multicenter Silent Ischemia Study (SMISS), co-ordinated by the Italian Working Group on Cardiac Rehabilitation, was to evaluate prospectively, the prognostic significance of silent myocardial ischemia during exercise testing in patients with proven ischemic cardiac disease. METHODS: Over a period of six months 4389 consecutive patients performing a maximal symptom-limited exercise testing, after drug withdrawal, were enrolled in the 73 ergometric laboratories. All patients were followed up after 12 months, at which time electrocardiogram, examination and clinical history were reassessed. Here we report the results of 1111 patients group with the recent myocardial infarction (inferior 3 months). The follow-up was completed in 1031 (93%) patients. RESULTS: The results of exercise testing were normal in 666 (64.6%) patients; angina alone in 33 (3.2%) patients; silent ischemia in 234 (22.7%) patients; symptomatic ischemia in 98 (9.5%) patients. In 270 patients (26.1%) new events occurred: angina (19.7%); myocardial infarction (3.1%; PTCA (4%); CABG (6%); cardiac death (1.4%). The total events were more common in the patients with exercise induced angina (48.5%) and in those who had exercise induced-symptomatic ischemia (48%), in respect of patients with silent ischemia (29.5%) and of those who had normal testing (20.7%) (p = 0.0001). Myocardial infarction rate was higher in patients with symptomatic ischemia (7.1%) that for those of all other groups (silent ischemia: 1.3%, angina: 3%, normal 3.2%) (p = 0.05). Moreover, the patients with symptomatic ischemia had higher incidence of CABG (p = 0.0001). The mortality rate was low among all patients and did not show differences among the groups. Only among the 31 patients (3%) with blood pressure fall was mortality higher that in patients with a normal blood pressure increase. By multivariate logistic analysis the angina induced by exercise maintained its prognostic significance for all the events, but also other variables were significant: poor exercise tolerance and, between clinical variables angina before myocardial infarction. CONCLUSION: The results showed, in patients who underwent to exercise testing after drug withdrawal, a low incidence of cardiac death and of myocardial infarction on 12 month follow-up; the patients with induced-exercise symptomatic schema had a greater risk for all cardiac events, except for death.

Capillary electrophoresis with laser-induced fluorescence detection: a sensitive method for monitoring extracellular concentrations of amino acids in the periaqueductal grey matter.

The use of capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) for the analysis of microdialysate samples from the periaqueductal grey matter (PAG) of freely moving rats is described. By employing 3-(4-carboxybenzoyl)-2-quinoline-carboxaldehyde (CBQCA) as a derivatization agent, we simultaneously monitored the concentrations of 8 amino acids (arginine, glutamine, valine, gamma-amino-n-butyric acid (GABA), alanine, glycine, glutamate, and aspartate), with nanomolar and subnanomolar detection limits. Two of the amino acids (GABA and glutamate) were analysed in parallel by conventional high-performance liquid chromatography (HPLC) in order to directly compare the two analytical methods. Other CE methods for analysis of microdialysate have been previously described, and this improved method offers greater sensitivity, ease of use, and the possibility to monitor several amino acids simultaneously. By using this technique together with an optimised form of microdialysis technique, the tiny sample consumption and the improved detection limits permit the detection of fast and transient transmitter changes.

[Multicenter study on exercise-induced silent myocardial ischemia: clinical, anamnestic and ergometric parameters in 4389 patients with proven ischemic cardiopathy]. / Studio multicentrico sull'ischemia silente da sforzo-SMISS: parametri clinico-anamnestici ed ergometrici in 4389 pazienti con cardiopatia ischemica nota.

AIM OF THE STUDY: In order to evaluate the incidence and clinical significance of myocardial ischemia during exercise testing (ExT) in patients (pts) with proven ischemic heart disease (Stable Effort Angina = SEA, Myocardial Infarction = MI, PTCA or CABG) 73 ergometric laboratories participated in a multicenter prospective study (SMISS) coordinated by the Italian Working Group on Cardiac Rehabilitation. Here we report the clinical and ergometric parameters. METHODS: Over a period of six months 4,389 consecutive pts were enrolled in the study after performing a maximal limited ExT (25 watts x 3') after drug withdrawal. All pts are followed at 6 and 12 months, at which time electrocardiogram, physical examination and clinical history were reassessed. A preliminary quality control of ECGraphic signal of ischemia was performed. Between the core center and the ergometric laboratories there was an 88% agreement (positive/negative ECG). 617 (14%) pts with angina (Group A), 2621 (59.7%) MI pts (Group B), 313 (7.2%) PTCA pts (Group C1), 838 (19.1%) patients with previous coronary bypass (Group C2) were studied. RESULTS: Interruption criteria were: maximal heart rate (11.7%), fatigue (66.6%), angina (10.9%), dispnea (2.3%), ST depression (13.9%), complex VPBs (2.2%), abnormal blood pressure (3.3%). In all pts the maximal work load was 100.3 +/- 31 W (lower in SEA pts). HR was 141 +/- 20/min at maximal work load (lower in SEA pts). The incidence of complex VPBs was 7.9% (higher in Mi and CABG pts). The results of ExT were: normal in 62% of all pts (21% in SEA pts), angina alone in 3.3% (7.6% in SEA pts and 1.8% in MI pts), symptomatic ischemia in 12.7% (40% in SEA pts, 9.3% in MI pts and 5.7% in CABG pts), silent ischemia in 22% (31.8% in SEA pts, 21.6 in MI pts and 16.6% in CABG pts). All differences were significant (p < 0.01). CONCLUSIONS: In a low risk group of coronary patients the incidence of myocardial ischemia during ExT was 38%. Ischemia was silent in 58% of the patients.

Echocardiographic evidence of increased mitral-aortic separation in discrete subaortic stenosis.

The present study reports the two-dimensional echocardiographic pattern of 6 patients affected by discrete subaortic stenosis. The diagnosis was proven at cardiac catheterization. The echocardiographic picture was characterized by a deformity of the left ventricular outflow tract due to an inward-protruding upper septum and to an elongated and domed mitral-aortic separation. The latter finding has been described in anatomic studies but has never been reported with wide-angle echocardiography.