Speciation in aqueous solutions of nitric acid.

In this study, speciation in aqueous solutions of nitric acid at 25 °C was assessed in two independent ways. First, Raman experiments were carried out and interpreted in terms of free nitrate ions, ion pairs and neutral HNO(3) molecules. In parallel, a model was developed to account for the formation of these two kinds of pairs. It was based on an extension of the binding mean spherical approximation (BiMSA), or associative MSA (AMSA), in which the size and the charge of the ions in the chemical pair may differ from those of the free ions. A simultaneous fit of the osmotic coefficient and of the proportion of free ions (obtained from Raman spectroscopy experiments) led to an estimation of the speciation in nitric acid solutions. The result obtained using this procedure was compared with the estimation obtained from the Raman experiments.

[Cardiac resynchronization in congestive heart failure: role of Doppler echocardiography in patient selection]. / Resynchronisation cardiaque dans l'insuffisance cardiaque: intérêt de l'échodoppler pour la sélection des patients et l'évaluation de la stimulation.

Cardiac echodoppler is an efficient tool to analyse cardiac mechanic loop. Diastolic and systolic desynchronisation criteria are analysed. It should allow a more efficient selection of patients who could take benefit of resynchronization therapy, but also to choose resynchronization system, to program optimal atrioventricular delay, interventricular delay and to evaluate resynchronization efficiency. However, this tool should be evaluated in large studies in order to compare it to electrocardiogram.

[Resynchronization of the failing heart by pacing]. / Resynchronisation du coeur défaillant par la stimulation.

Cardiac pacing has been proposed for patients with advanced heart failure refractory to optimal drug treatment and having conduction disorders to resynchronize mechanical activity of the heart. Activation asynchronism as caused by bundle branch block results in alteration of systolic function and arrhythmias. A too short or too long atrio-ventricular delay can also affect diastolic ventricular filling. Early clinical studies showed a benefit of very long atrioventricular delays shortening, not confirmed by further studies. Direct stimulation of the left ventricle was beneficial in acute hemodynamic studies. Three controlled clinical studies now completed, PATH-CHF, MYSTIC and MIRACLE have showed a functional benefit. Other studies (COMPANION, CARE-HF) are currently in process to evaluate the effect on survival and the interest to associate an automatic defibrillator. Technical aspects are also under investigation: optimal lead placement in the coronary venous system, types of leads, special pacing devices. This paper reports the experience of the first 50 patients treated with multisite pacing in Aix-en-Provence general hospital, 33 men and 17 women, 71 years of mean age, on NYHA class III or IV, and showing QRS width above 120 ms. During the follow-up (mean duration 16 months) 15 deaths (30%) happened. The benefit on NYHA class was 1.34; rehospitalization rate was low. Coronary sinus access was successful in 100% of cases. Sixteen per cent had a reintervention for lead displacement or threshold elevation. Left atrioventricular crosstalk, observed in six patients, supports the use of devices with three independent channels. Echocardiography is of interest for responders identification, optimal device programming and follow-up.

[Intrinsic sinus node dysfunction in adolescence during anorexia nervosa]. / Dysfonction sinusale intrinsèque de l'adolescence au cours d'une anorexie mentale.

A seventeen year old girl with anorexia nervosa (32 kg; 165 cm) was admitted as an emergency after syncope with severe bradycardia resistant to atropine monitored over a one week period. Autonomic blockade confirmed the intrinsic character of the sinus node dysfunction with chronotropic incompetence on exercise. Secondarily, a Mobitz I second degree AVB was observed. A DDDR pacemaker was implanted with an excellent functional result. With a one year follow-up, the bradycardia persists but body weight has increased. The authors discuss the physiopathology of this case: in the literature, the classical bradycardia of anorexia nervosa is sensitive to vagolytic drugs and only exceptionally as intense as in this patient. Sinus node dysfunction is very rare in the young in the absence of congenital heart disease. It is possible that the bradycardia had become chronic in this case.

Comparison of standard one-minute treadmill exercise and strandness test (absolute walking distance) in relation to site of lesion, walking distance, and diastolic blood flow velocity (Doppler curves).

In 215 outpatients suffering from occlusive arterial disease of the lower limbs the authors compared the decrease in the ratio of ankle systolic pressure to brachial systolic pressure according to whether the treadmill exercise was limited to one minute or extended until pain forced the patient to stop. After a one-minute walk the pressure index always decreased significantly, especially when walking was restricted. The decrease in the pressure index was generally greater when the exercise was continued until the absolute walking distance, and the recovery time was usually twice as long. The fall in the pressure index was significantly greater for patients with single and multiple iliac stenoses than for those with stenoses at lower levels. In patients having a diastolic blood flow velocity on Doppler curves at rest, not modified by walking, a maximum drop in peripheral pressure was recorded after walking for one minute. In this instance there was no intensification of the decrease in peripheral pressure, unlike in patients without a diastolic blood flow velocity at rest. This one-minute test is not a maximal hemodynamic response, but it is sufficient for the appreciation of ischemia during exercise, according to the different parameters measured.

[Possible role of a cardiac factor in limiting the walking perimeter in the treadmill test in the arteritis patient]. / Part possible d'un facteur cardiaque dans la limitation du périmètre de marche lors de l'épreuve sur tapis roulant chez l'artéritique.

Electrocardiographic modifications appearing during a treadmill test undergone by 145 patients with arterio-sclerosis obliterans at stage II without coronary antecedents and with normal resting electrocardiograms were studied. Twenty per cent of the patients had to discontinue the test (slope 12%, 3,8 km/h). A repolarization anomaly of ischemia type appeared in 13% of the cases (19 patients) and a rhythm disorder in 1%. Hence systematic monitoring of the electrocardiogram during walking test can enable subjects with high coronary risk to be singled out.