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Biomedical subjects

B Mettauer

Publications and source records attributed to B Mettauer.

At least 37 records · Page 2Linked to original sources
PubMed1999

Lung membrane diffusing capacity, heart failure, and heart transplantation.

The pulmonary diffusing capacity for carbon monoxide (DLCO) is reduced in chronic heart failure and remains decreased after heart transplantation. This decrease in DLCO may depend on a permanent alteration after transplantation of one or the other of its components: diffusion of the alveolar capillary membrane or the pulmonary capillary blood volume (Vc). Therefore, we measured DLCO, the membrane conductance, and Vc before and after heart transplantation. At the time of hemodynamic measurements, the Roughton and Forster method of measuring DLCO at varying alveolar oxygen concentrations was used to determine the membrane conductance, Vc, DLCO/alveolar volume (VA), the membrane conductance/VA and thetaVc/VA (theta = carbon monoxide conductance of blood, VA = alveolar volume) in 21 patients with class III to IV heart failure before and after transplantation, and in 21 healthy controls. Transplantation normalized pulmonary capillary pressure and increased cardiac index. DLCO was decreased before transplantation (7.11 vs 10.0 mmol/min/kPa in controls), but DLCO/VA was normal (1.67+/-0.44 vs 1.71+/-0.26 mmol/min/kPa/L in controls). DLCO/VA remained unchanged after transplantation, because the decrease in Vc (82+/-30 vs 65+/-18 ml before and after transplantation) and thetaVc/VA was not compensated by the changes in membrane conductance (11+/-4 vs 12+/-5 mmol/min/kPa before and after transplantation, respectively) and membrane conductance/VA. We conclude that the decrease in DLCO in patients with chronic heart failure is due to a restrictive ventilatory pattern because their DLCO/VA remains normal; the decrease in the membrane conductance is compensated by the increase in Vc. After transplantation, the decrease in Vc due to normalization of pulmonary hemodynamics is not completely compensated for by an increase in membrane conductance. Because the membrane conductances, measured before and after transplantation, are negatively correlated with duration of heart failure, its abnormal pulmonary hemodynamics may have irreversibly altered the alveolar capillary membrane.

Adult↗
PubMed1998

Skeletal muscle response to short endurance training in heart transplant recipients.

OBJECTIVES: We sought to examine the effects of endurance training on the ultrastructural characteristics of skeletal muscle in heart transplant recipients (HTRs) and age-matched control subjects (C). BACKGROUND: Deconditioning is one of the factors involved in the peripheral limitation of exercise capacity of HTRs, and training has proven to be beneficial. METHODS: Biopsies of the vastus lateralis muscle, analyzed by ultrastructural morphometry, and quadriceps muscle cross-sectional area, assessed by computed tomography (CT), were performed in 12 HTRs and 7 age-matched C before and 6 weeks after an endurance training program. Maximal oxygen uptake (peak VO2) was determined by an incremental exercise test. Additionally muscle biopsies were performed before and after a 6-week control period in four HTRs to check for spontaneous improvement. RESULTS: Training resulted in similar increases in peak VO2 (11% in HTRs, 8.5% in C), ventilatory threshold (23% in HTRs, 32% in C) and total endurance work (54% in HTRs, 31% in C). Volume density of total mitochondria increased significantly (26% in HTRs, 33% in C) with a predominant increase of subsarcolemmal mitochondrial volume density (74% in HTRs, 70% in C). The capillary/fiber ratio increased by 19% in C only. In the nontrained group, none of the structural markers was spontaneously modified. CONCLUSIONS: Six weeks of endurance training in HTRs and C led to similar improvements of aerobic work capacity. However, the decreased muscular capillary network in HTRs remained unchanged with training. Immunosuppressive therapy might be responsible for the discrepancy between the normal mitochondrial content and the reduced capillary supply of these patients.

Adult↗
PubMed1997

Moderate endurance training has no effect on the parathyroid function of heart transplant patients.

The benefit of retraining for heart transplant recipients (HTR) is now well established. The rehabilitation of these patients can be compromised by osteopenia and bone fractures. The resting levels of parathyroid hormone (PTH) and exercise-induced increases are higher in HTR than in healthy controls. To evaluate the effect of a moderate endurance training programme on parathyroid activity, six HTR, an average of 18 months after transplant, and seven healthy sedentary controls have been studied. None of the subjects had a history of bone disease. Two exercise tests (square wave endurance exercise tests, SWEET) with identical work rates were performed before and after training. Intact PTH, ionized calcium (Ca2+), phosphorus (Pi) and pH were measured at rest, during exercise and in the recovery periods. Training consisted of a 45-min SWEET three times a week for 6 weeks. Levels of Ca2+, Pi and PTH showed a significant increase during the exercise session in both groups. Ca2+ and Pi levels decreased rapidly after the cessation of exercise whereas PTH reached a peak at the 10th min of the recovery in both groups. This increase in PTH was significantly higher in HTR than in controls. However, despite a significant improvement of total endurance work (+ 28% in HTR, +29% in controls) this endurance training had no effect on resting levels of PTH, plasma Ca2+ or Pi, nor on their exercise-induced variations. The exercise-induced decrease in pH was less pronounced after training which is evidence of training. We conclude that a short endurance training programme does not alter the moderate hyperparathyroidism of HTR. The effect of such a training programme on bone mass and bone mineral density needs now to be evaluated.

Acid-Base Equilibrium↗
PubMed1996

Effect of short-term endurance training on exercise capacity, haemodynamics and atrial natriuretic peptide secretion in heart transplant recipients.

Exercise tolerance of heart transplant patients is often limited. Central and peripheral factors have been proposed to explain such exercise limitation but, to date, the leading factors remain to be determined. We examined how a short-term endurance exercise training programme may improve exercise capacity after heart transplantation, and whether atrial natriuretic peptide (ANP) release may contribute to the beneficial effects of exercise training by minimizing ischaemia and/or cardiac and circulatory congestion through its vasodilatation and haemoconcentration properties. Seven heart transplant recipients performed a square-wave endurance exercise test before and after 6 weeks of supervised training, while monitoring haemodynamic parameters, ANP and catecholamine concentrations. After training, the maximal tolerated power and the total mechanical work load increased from 130.4 (SEM 6.5) to 150.0 (SEM 6.0) W (P < 0.05) and from 2.05 (SEM 0.1) to 3.58 (SEM 0.14) kJ.kg-1 (P < 0.001). Resting heart rate decreased from 100.0 (SEM 3.4) to 92.4 (SEM 3.5) beats.min-1 (P < 0.05) but resting and exercise induced increases in cardiac output, stroke volume, right atrial, pulmonary capillary wedge, systemic and pulmonary artery pressures were not significantly changed by training. Exercise-induced decrease of systemic vascular resistance was similar before and after training. After training arterio-venous differences in oxygen content were similar but maximal lactate concentrations decreased from 6.20 (SEM 0.55) to 4.88 (SEM 0.6) mmol.l-1 (P < 0.05) during exercise. Similarly, maximal exercise noradrenaline concentration tended to decrease from 2060 (SEM 327) to 1168 (SEM 227) pg.ml-1. A significant correlation was observed between lactate and catecholamines concentrations. The ANP concentration at rest and the exercise-induced ANP concentration did not change throughout the experiment [104.8 (SEM 13.1) pg.ml-1 vs 116.0 (SEM 13.5) pg.ml-1 and 200.0 (SEM 23.0) pg.ml-1 vs 206.5 (SEM 25.9) pg.ml-1, respectively]. The results of this study suggested that the significant improvement in exercise capacity observed after this short-term endurance training period may have arisen mainly through peripheral mechanisms, associated with the possible decrease in plasma catecholamine concentrations and reversal of muscle deconditioning and/or prednisone-induced myopathy.

Adult↗
PubMed1996

Structure of skeletal muscle in heart transplant recipients.

OBJECTIVES: This study sought to define the ultrastructural characteristics of skeletal muscle in heart transplant recipients (HTRs) in relation to exercise capacity compared with that in age-matched control subjects. BACKGROUND: Muscle structural features seem to play an important role in the limitation of exercise capacity of HTRs long after transplantation. METHODS: The structure of the vastus lateralis muscle was analyzed by ultrastructural morphometry in 16 HTRs and 20 healthy control subjects. Maximal oxygen consumption (peak Vo2) was determined by an incremental exercise test. RESULTS: Peak Vo2 was significantly lower (by 35%) in HTRs. Fiber size, volume density of mitochondria and intramyocellular lipid deposits were not significantly different between HTRs and control subjects. In contrast, the capillary density and the capillary/fiber ratio were both significantly reduced in HTRs (by 24% and 27%, respectively). CONCLUSIONS: A normal volume density of mitochondria and a reduced capillary network are the main characteristics of muscle ultrastructure in HTRs by 10 months after transplantation. The muscle structural abnormalities and reduced exercise capacity might be related to immunosuppressive therapy with cyclosporine and corticosteroids as well as deconditioning.

Adult↗
PubMed1996

Persistent exercise intolerance following cardiac transplantation despite normal oxygen transport.

UNLABELLED: To define the respective roles of the periphery and central oxygen transport in the exercise limitation of heart transplanted patients (HTR), we compared 11 HTR (15.1 +/- 10.8 months after transplantation) to six age and weight matched normal controls (C), during an incremental exercise test (30 W/3 min steps; supine position), up to peak exercise level. The C stopped between 120 and 240 W (mean = 180 +/- 39 W), whereas the HTR all reached 90 W, with a significantly lower oxygen uptake (VO2), cardiac index (CI) and arterio-venous oxygen difference (AVO2D) values (respectively VO2: 16.6 +/- 2.6 vs 30.0 +/- 9.3 ml.min-1.kig-1 STPD; CI: 6.84 +/- 1.10 vs 10.55 +/- 2.86l.min-1.m-2; AVO2D: 94 +/- 13 vs 109 +/- 9 ml.l-1; all p < 0.05) but with similar lactate (LA) values (respectively 7.25 +/- 1.98 vs 7.71 +/- 1.55 mmol.l-1; p = NS). At the 90 W step which corresponds to the peak level that all the HTR reached, the C were close to their anaerobic threshold and showed similar parameters of oxygen transport (VO2: 17.4 +/- 2.0; CI: 7.50 +/- 0.41; AVO2D:90 +/- 10) but a lower lactate level (LA: 2.93 +/- 4.76; p < 0.002). At the same intermediate exercise levels VO2, CI and AVO2D were similar in both groups, while the closely matched LA and ventilation increased faster in HTR, reaching significantly higher levels as soon at the 30 W step. This evidence for an increased anaerobic exercise energy generation in HTR suggests that the periphery participates significantly in their exercise limitation, a phenomenon that might be improvable by retraining. VALUES: means+/-standard deviation.

Cardiac Output↗
PubMed1996

Short endurance training improves lactate removal ability in patients with heart transplants.

Eight male patients with heart transplants at least a year after the operation were submitted to a 6-wk endurance training program and explored for their blood lactate kinetics before and after exercise. The tests consisted of a bicycle exercise upgraded by 20 W every 2 min until volitional fatigue. Training induced a significant (P < 0.025) decrease in lactate concentrations from the 40-W to the 120-W exercise step and a significant increase (P < 0.025) in the time into exercise (9.87 +/- 0.87 min vs 7.17 +/- 0.90 min) at which a lactate concentration of 2 mmol.l-1 was reached. Lactate recovery curves were significantly lower (P < 0.036) after training than before training, except at minutes 1, 2, 8, and 60. The fits of a biexponential mathematical model to the lactate recovery curves reveal a significant (P < 0.036) training-induced increase (+71%) in the slow-velocity constant gamma 2v of the model. In view of the functional meaning given to this parameter, namely the ability to remove lactate, it is concluded that training lowers blood lactate concentrations during exercise and recovery in patients with heart transplants at least in part by raising the efficiency with which lactate is removed, and that the ability to remove lactate can be a valuable criterion to evaluate physical fitness.

Adult↗
PubMed1995

Training effects on the hydromineral endocrine responses of cardiac transplant patients.

Cardiac transplant patients manifest several haemodynamic changes as well as altered peripheral responses to exercise which may disrupt body fluid regulation. This study examined the effect on an endurance training programme on the exercise-induced hydromineral endocrine responses of heart transplant patients. Seven patients underwent a square-wave exercise test before and after a 6-week training programme. The tests were performed at the same absolute intensity but, during training, the workload was increased to maintain the same relative exercise intensity. Pretraining results were compared to those obtained from age-matched controls. Training improved physical capacity, producing a significant increase in maximal tolerated power and workload between the first and last training session (P < 0.05, P < 0.001, respectively). Haematocrit and osmolality were increased in both groups at the end of exercise (P < 0.01) but changes observed post-training did not differ from pretraining values. Apart from atrial natriuretic peptide (ANP), which showed significantly higher concentrations at rest and during exercise (P < 0.01), the changes in hydromineral hormones of the patients resembled those of the controls. Basal plasma renin activity (PRA) was slightly raised prior to training (P < 0.07) compared to the controls and post-training. For both PRA and aldosterone, a significant training effect was revealed when both the exercise-stimulated increase and postexercise decline were considered (P < 0.05), possibly reflecting lower noradrenaline concentrations. Training had no effect on either basal or exercise stimulated ANP levels, which is compatible with the theory that ANP regulation is largely under mechanical rather than sympathetic nervous system control.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Parathyroid function in cardiac transplant patients: evaluation during physical exercise.

The survival rate of heart transplant patients has increased considerably since the development of new immunosuppressive drugs. In the long term, however, cardiac transplantation results in a high incidence of osteoporosis which represents a major functional handicap. To examine whether patients in the early stages have impaired phosphocalcic metabolism, intact parathyroid hormone (PTH 1-84), native osteocalcin, ionized Ca++ and pH were measured at rest and during muscular exercises a dynamic test used to override circadian and ultradian PTH variations. A group of 12 patients receiving the usual immunosuppressive therapy, which is mainly an association of cyclosporin and prednisolone, and 8 sedentary control subjects performed a square-wave endurance test at the same relative intensity for 30 min. No patient had previous bone disease and the period since transplantation was 12.2 +/- 2.7 months. For the transplant patients, initial PTH concentrations and responses to exercise were higher (P < 0.01) compared to the control subjects with a dramatic increase after 10 min of recovery. From higher (P < 0.001) resting concentrations, osteocalcin further increased during exercise (P < 0.01) in the heart transplant group but not in the control subjects. In both groups pH showed the same time-course with a rapid fall during exercise (P < 0.05) and Ca++ concentrations increased during the exercise period. (P < 0.01 for patients; P < 0.05 for controls) with a significant fall in both groups after 10 min of recovery (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Late complication of a Greenfield filter associating caudal migration and perforation of the abdominal aorta by a ruptured strut.

We report the case of a 67-year-old woman who was admitted for surgical removal of a Greenfield filter that had been inserted 7 years before because of recurrent deep vein thrombosis associated with pulmonary embolism. This complication appeared on a plain abdominal radiogram that showed a 7 cm distal migration of the filter, a 30-degree angulation, and rupture of a strut at the level of the hub. Computed tomography, aortography, and ascending cavography demonstrated that the inferior vena cava was perforated by the struts and that the ruptured strut had penetrated the infrarenal aorta. As demonstrated by scanning electron microscopy, the fracture was due to a structural defect of the strut at its insertion point within the hub, with no sign of corrosion. Energy-dispersive radiography analysis failed to demonstrate impurity in the metal composition.

Aged↗
PubMed1994

Prevention by NMDA receptor antagonists of the centrally-evoked increases of cardiac inotropic responses in rabbits.

1. The purpose of this study was to investigate further the role of the excitatory amino acid (EAA) system of neurotransmission, particularly of the NMDA receptor, in the central regulation of cardiac function. 2. Electrical stimulation of the paraventricular nucleus of the hypothalamus (PVN) in pentobarbitone anaesthetized rabbits induced a cardiovascular response mainly characterized by a positive inotropic effect, hypertension and a marked increase in the myocardial oxygen demand index. 3. The intracerebroventricular (i.c.v.) or intravenous (i.v.) injection of different EAA antagonists acting on different sites of the NMDA receptor/channel complex dose-dependently blunted the excitatory cardiovascular effects of PVN stimulation. 4. 5,7 Dichlorokynurenic acid was used as a specific glycine site antagonist and 2-amino-5-phosphonovaleric acid was used to block the agonist recognition site; ketamine was used as a channel blocker site antagonist and ifenprodil as a blocker of the polyamine binding site. 5. 5,7 Dichlorokynurenic acid (125 and 250 micrograms kg-1, i.c.v.) virtually abolished the cardiovascular responses, inducing only haemodynamic depression at the highest dose used. 2-Amino-5-phosphonovaleric acid (0.1 to 1.0 mg kg-1, i.c.v.) elicited a reduction of the peak values observed during PVN stimulation which was accompanied by a decrease of the basal cardiovascular parameters. Ketamine (2.5 and 10 mg kg-1) and ifenprodil (1 mg kg-1), injected intravenously, blocked the haemodynamic response induced by PVN stimulation without marked reduction of the basal haemodynamics. 6. It is concluded that glutamate neurotransmission is not only involved in vasomotor tone control but also in the central control of cardiac function and can therefore modulate the myocardial oxygen demand.

2-Amino-5-phosphonovalerate↗
PubMed1993

Safety and efficacy of a new transpulmonary echo contrast agent in echocardiographic studies in patients.

OBJECTIVES: This study was designed to investigate in patients the effect of a new transpulmonary echo contrast agent, made from 5% human serum albumin (Albunex), on systemic and pulmonary hemodynamics and the influence of the contrast doses on left ventricular opacification. BACKGROUND: New intravenous transpulmonary echo contrast agents are promising, allowing contrast stress echocardiography and myocardial contrast echocardiography. Nevertheless, some shortcomings still remain. Thus, the pulmonary hypertension observed in pigs after Albunex injection should be investigated in humans, and the optimal dose of contrast agent remains to be determined because previous experiments indicated that the left ventricular opacification and attenuation are dose dependent. METHODS: Albunex in doses of 0.08 and 0.22 ml/kg was successively injected intravenously in 20 catheterized patients; in 11 of them, anti-inflammatory drugs were withdrawn to avoid the blocking of an eventual thromboxane-mediated pulmonary artery hypertension. Systemic blood pressure and pulmonary artery, capillary wedge and right atrial pressures were continuously monitored. Cardiac output, left ventricular fractional shortening and blood gases were determined 5 min before and 5 and 10 min after each injection. The left ventricular opacification was qualitatively assessed by three independent observers using a grading scale from 0 to 3, with 0 indicating an absence of contrast effect and 3 indicating full opacification. RESULTS: No clinical, hemodynamic or respiratory adverse reactions were observed in any patient. Irrespective of doses, a left ventricular opacification grade > or = 2 was observed in 74% of the 35 injections that could be evaluated. This percentage increased to 94% when the higher dose group was considered alone. CONCLUSIONS: This first report of the effect of Albunex injected intravenously on pulmonary artery pressures in humans demonstrates that this contrast agent appears to be safe. The significant left ventricular opacification obtained in a majority of patients without an important increase in attenuation supports the use of the higher dose of the contrast agent.

Albumins↗