Circulating N-terminal atrial natriuretic peptide as a marker for symptomless left-ventricular dysfunction

Early identification of patients with symptomless left-ventricular dysfunction and early pharmacologic intervention may have an impact on the outlook of patients with heart failure. Atrial natriuretic peptide (ANP) is a cardiac hormone that is released as a C-terminal (C-ANP) and an N-terminal peptide (N-ANP). Since N-ANP has reduced clearance rates compared with C-ANP, N-ANP circulates at higher concentrations. Based on the known increased concentration of C-ANP in symptomatic congestive heart failure, our study was designed to evaluate prospectively N-ANP profile and left-ventricular function in subjects with symptomless and symptomatic heart failure, and the role of plasma N-ANP as a marker for early identification of patients with heart failure. 180 patients who were referred for rest and exercise radionuclide angiography for evaluation of left-ventricular function were studied. Blood was taken for measurement of C-ANP and N-ANP before angiography. Patients were grouped according to New York Heart Association (NYHA) heart failure classification and left-ventricular function. Mean (SD) plasma N-ANP concentration in patients with symptomless left-ventricular dysfunction (NYHA class I, n = 70) was 243 (256) pmol/L (range 27-922 pmol/L), and was higher (p < 0.001) than in 25 control subjects (28 pmol/L). A plasma N-ANP concentration above 54 pmol/L (mean +/- 1.96SD of the control group) had a sensitivity of 90% and a specificity of 92% for detection of patients with symptomless left-ventricular dysfunction. We have shown that plasma N-ANP concentrations are significantly increased in patients with symptomless left-ventricular dysfunction and that this peptide can serve as a marker for diagnosis of such patients.     

Hyperproduction of erythropoietin in nonanemic lead-exposed children

The plasma concentration of N-terminal atrial natriuretic peptide (N-ANP) has been shown to be predictive of both clinical status and survival in patients with heart failure. In this analysis the relationship between N-ANP, morbidity and hospitalization time was evaluated in 417 patients with stable, congestive heart failure recruited from an active, outpatient heart failure registry. Hospital admissions along with the duration of stay occurring after the initial N-ANP sampling during the period of data collection were recorded. A total of 755 admissions occurred, accounting for 7917 days' hospitalization. Relative hospitalization times (in-hospital days/observation period) per N-ANP quartiles I-IV were: 1.2 (+/- 2.7)%, 5.5 (+/- 12.2)%, 10.0 (+/- 21.5)% and 20.8 (+/- 34.3)%, respectively. Although N-ANP levels were correlated with age (r = 0.234, p < 0.0001), division by age quartiles did not significantly predict relative hospitalization times. These data indicate that the degree of cardiac endocrine activation and subsequent N-ANP release is related to morbidity in patients with heart failure and that moderate elevation in N-ANP levels is associated with a substantially increased hospitalization time. N-ANP sampling should be of value as a supplement to clinical evaluation in the assessment of the individual patient with this common syndrome.     

Microbiology of Borrelia burgdorferi

The acute (single bout of exercise) and chronic (exercise training) effects of exercise on plasma leptin were investigated in 97 sedentary adult men (n = 51) and women (n = 46) participating in the HERITAGE Family Study. Exercise training consisted of a standardized 20-wk endurance training program performed in the laboratory on a computer-controlled cycle ergometer. Maximal oxygen uptake, body composition assessed by hydrostatic weighing, and fasting insulin level were also measured before and after training. Pre- and posttraining blood samples were obtained before and after completion of a maximal exercise test on the cycle ergometer. Exercise training resulted in significant changes in maximal oxygen uptake (increase in both genders) and body composition (reduction of fat mass in men and increase in fat-free mass in women). There were considerable interindividual differences in the leptin response to acute and chronic effects of exercise, some individuals showing either increase or reduction in leptin, others showing almost no change. On average, leptin levels were not acutely affected by exercise. After endurance training was completed, leptin levels decreased significantly in men (from 4.6 to 3.9 ng/ml; P = 0.004) but not in women. However, after the training-induced changes in body fat mass were accounted for, the effects of exercise training were no longer significant. Most of the variation observed in leptin levels after acute exercise or endurance training appears to be within the confidence intervals of the leptin assay. We conclude that there are no meaningful acute or chronic effects of exercise, independent of the amount of body fat, on leptin levels in humans.     

Impact of habitual cocaine smoking on the physiologic response to maximum exercise

BACKGROUND: Habitual smoking of alkaloidal cocaine (crack) has been reported to be associated with a number of cardiopulmonary complications that may not be clinically obvious but could potentially interfere with normal physiologic responses to exercise and thus impair maximum exercise performance. STUDY OBJECTIVE: To evaluate the impact of regular use of cocaine on maximum exercise. DESIGN: Observational study in crack users and age- and gender-matched control subjects. SUBJECTS: Thirty-five habitual cocaine smokers (21 male and 14 female) and 29 age-matched sedentary control nonsmokers of cocaine (15 male and 14 female), all of whom were in good general health. METHODS: In these subjects, we compared physiologic responses to symptom-limited, incremental maximal exercise performed on a cycle ergometer using a ramp protocol. Comparisons were made for men and women separately. RESULTS: For both men and women, long-term cocaine smokers had a reduced aerobic capacity (maximum oxygen consumption) compared with control nonsmokers but did not show evidence of ventilatory limitation, reduced gas exchange threshold, increased physiologic dead space, or gas exchange abnormality at maximum exercise compared with the healthy control subjects. Although cocaine smokers had reduced maximum heart rates compared with control subjects, the relationship between submaximal heart rate and oxygen uptake was normal, indicating a normal cardiovascular response pattern. However, effort perception was similar between the two groups despite the difference in heart rate at maximum exercise, suggesting the possibility of perceptual dysfunction for effort. Differences in aerobic capacity between the crack users and nonusers could not be explained by differences in physical fitness or altered perception of dyspnea. CONCLUSION: In the subjects we studied, long-term cocaine smoking was associated with reduced maximum exercise performance, probably due to poor motivation or altered effort perception. No other identifiable physiologic abnormality appeared to limit exercise in the habitual crack users.     

Hemodynamic interaction of propranolol and digitalis in patients with arterial hypertension (author's transl)

Central hemodynamics at rest and during supine ergometer exercise have been studied in 12 hypertensive subjects and three healthy persons before and 20 min after 5 mg of intravenous propranolol. Cardiac output (CO) decreased by 19% at rest (p less than 0.001) and by 15% during exercise (p less than 0.001). Pulmonary capillary wedge pressure (PCP) during exercise rose after beta-blockade by 56% to 28 mm Hg (p less than 0.001); a similar increase could be observed in pulmonary artery pressure (PAP) and right atrial mean pressure (RAM). Brachial artery mean pressure at rest did not change significantly; during exercise this value was 6% below the pretreatment level (p less than 0.001). In order to evaluate the influence of digitalis on beta-blocker induced hemodynamic changes, measurements were repeated 30 min after administration of 0.6 mg beta-Methyldigoxin intravenously. After addition of digitalis, average PCP during exercise was significantly lower than after beta-blockade alone (22.8 mm Hg, p less than 0.001). Likewise, PAP and RAM after digitalis were lower than after propranolol alone. CO did not change following digitalis administration. These findings indicate that digitalis partially counteracts the elevation of filling pressures induced by beta-blocking agents but leaves CO unchanged.     

Cardiac output and pulmonary gas exchange at maximal exercise after atrial redirection for complete transposition

AIMS: To assess the determinants of exercise capacity and exercise oxygenation after atrial redirection for complete transposition. METHODS AND RESULTS: At graded bicycle ergometry, including respiratory and arterial blood gas analyses, intra-arterial blood pressure recording, and cardiac output determination (dye-dilution technique), we tested 17 post-Mustard/Senning patients, 8.9-22.0 years old (mean 14.5, SD 4.0). Reference data were obtained by similar methods. At maximal exercise, oxygen uptake (29.6 ml x kg(-1) x min(-1)) and heart rate (167 beats x min(-1)) were low (P<0.001). Right-to-left shunts were detected in five patients. Arterial oxygen partial pressure and saturation fell in all subjects (P<0.0001). In 15/16 (94%) the alveolar-arterial oxygen partial pressure difference was > +2 SD. In 13/15 (87%) stroke volumes fell during exercise. Cardiac output per oxygen uptake was low (P<0.0001), which implies a high arteriovenous oxygen difference and a low mixed venous oxygen content at peak exercise. CONCLUSION: The low exercise capacity was caused by a combination of low maximally attained heart rate and falling stroke volumes. The impaired arterial oxygenation may be caused by a combination of pulmonary ventilation/perfusion mismatch, a low mixed venous content and atrial shunting in some patients.     

Short-term effects of bracing on exercise performance in mild idiopathic thoracic scoliosis

In adolescent idiopathic thoracic scoliosis (ITS) working capacity may be reduced during exercise. Despite concern about its usefulness, bracing is still being used in ITS. Thus the effects of bracing on exercise performance need to be examined. We studied six females, ages 12-15 years who had mild ITS (Cobb angle range 20-35 degrees). Pulmonary volumes, maximal voluntary ventilation (MVV), breathing pattern, the lowest (most negative in sign) pleural pressure during sniff maneuver (Pplsn), and pleural pressure swings (Pplsw) were measured first. Then, Pplsw, O2 uptake (VO2), CO2 output (VCO2), heart rate (HR) at rest and during progressive incremental exercise on a cycling ergometer (10 watts/min) were recorded. The exercise test was performed under control conditions without bracing (C) and after 7 days of bracing with the braced on (B). Dyspnea was measured by a modified Borg scale. At rest, bracing mildly affected total lung capacity and forced vital capacity (p < 0.03 for both) but not breathing pattern, Pplsn, or Pplsw (%Pplsn), a measure of respiratory effort. Furthermore, bracing did not consistently affect maximum work rate (WRmax). In both B and C VO2 was below (< 70%) the predicted value, VE was below (< 45%) MVV, and HR reserve was < 15 beats/min, indicating some cardiovascular deconditioning. On the other hand, respiratory frequency (Rf) increased more in B than in C (p < 0.03). In addition, Pplsw, Pplsw (%Pplsn), and Pplsw (%Pplsn)/VT, an index of neuroventilatory dissociation (NVD) of the respiratory pump, were greater in B (p < 0.03 for all). At a similar work rate, the Borg rating score was greater with bracing on than off, and the difference (delta Borg) tended to relate to concurrent changes in Pplsw (%Pplsn)/VT (r2 = 0.71; p < 0.07). We conclude that bracing affects respiratory effort, NVD, and dyspnea score during progressive exercise. These effects are consistent with increased lung elastance. Diminished exercise tolerance in patients with mild ITS probably reflects impaired physical fitness but is not affected by bracing. Training programs proposed for this subset of patients to increase peripheral muscle performance might also consider NVD of the respiratory pump.     

Mechanism of adsorption of human albumin to titanium in vitro

1. This study explored the hypothesis that atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-natriuretic peptide (CNP) have differing antiproliferative and antihypertrophic effects on pulmonary artery (PA) and thoracic aorta (TA) smooth-muscle cells (SMCs). 2. Cultured cells were exposed to 5% fetal calf serum (FCS) and angiotensin II (A-II) to induce DNA and protein synthesis, respectively. 3. ANP (10(-7) M) significantly reduced thymidine uptake in TA by 31% +/- 2% (P < or = 0.01) but not in PA (P > or = 0.05). 4. In parallel experiments, BNP (10(-7) M) significantly reduced thymidine uptake in TA (-22% +/- 5%, P < or = 0.01), but not in PA cells (P > or = 0.05). 5. CNP (10(-7) M) did not significantly alter thymidine uptake in TA cells exposed to FCS, but it did significantly reduce uptake in PA (-28.5% +/- 4%) 2(P < or = 0.05). 6. Blunting by ANP (10(-7) M) of the A-II (10(-8) M)-induced increase in protein synthesis was significantly greater in PA than in TA cells. 7. However, BNP and CNP (10(-7) M) exerted similar antihypertrophic effects on TA and PA cells exposed to A-II. 8. The antiproliferative effects of BNP and ANP exceed those of CNP in TA SMCs, but CNP appears to be the most effective antiproliferative agent in PA SMCs. In addition, PA-derived SMCs are more sensitive to the antihypertrophic effects of ANP than TA-derived cells, suggesting phenotypic differences. The findings indicate that the natriuretic peptides may play complementary roles in modulating SMC proliferation and protein synthesis.     

Exercise tolerance in patients with Ebstein's anomaly

OBJECTIVES: The purpose of this study was to identify the determinants of exercise tolerance in patients with Ebstein's anomaly. BACKGROUND: Patients with Ebstein's anomaly of the tricuspid valve may have exercise limitation that improves after surgical repair. METHODS: One hundred seventeen patients performed cycle ergometry for a total of 124 tests (preoperative test in 76 patients, postoperative test in 23, test but no operation in 18, preoperative and postoperative test in 7). Multiple linear regression analysis was used to identify predictors of maximal oxygen uptake, oxygen saturation and heart rate at peak exercise. RESULTS: Age at the time of exercise ranged from 6 to 60 years (median 15). An atrial septal defect was present in 67 patients (88%) preoperatively. Compared with the preoperative group, the postoperative group had significantly higher maximal oxygen uptake (mean [+/- SD] 20.5 +/- 7.4 vs. 25.3 +/- 7.0 ml/kg body weight per min, p = 0.006). Postoperative rest and exercise blood oxygen saturation was higher than that measured preoperatively (p = 0.0001). Six of seven patients tested before and after the operation showed improved exercise tolerance. Preoperatively, major predictors of maximal oxygen uptake were oxygen saturation at rest (p = 0.01) and age (p = 0.0001). Preoperatively, the major predictor of oxygen saturation at peak exercise was rest oxygen saturation (p = 0.0001), and major predictors of peak exercise heart rate were rest heart rate (p = 0.01) and rest oxygen saturation (p = 0.01). In the postoperative group, predictors of maximal oxygen uptake included age at exercise testing, male gender and heart size. CONCLUSIONS: Definitive operation for Ebstein's anomaly results in improved exercise tolerance. Before the operation, rest oxygen saturation is the major predictor of exercise tolerance, oxygen saturation at peak exercise and peak heart rate. Postoperatively, age, gender and heart size influenced maximal oxygen uptake.     

Different secretion patterns of adrenomedullin, brain natriuretic peptide, and atrial natriuretic peptide during exercise in hypertensive and normotensive subjects

The purpose of this study was to investigate the effect of exercise on plasma concentrations of adrenomedullin, brain natriuretic peptide (BNP), and atrial natriuretic peptide (ANP) in patients with essential hypertension (n = 15) and in normotensive controls (n = 10). Exercise consisted of two fixed workloads, 40 and 80 watts of work load using a supine bicycle ergometer. Plasma levels of all three peptides at rest were significantly higher in hypertensives than in controls. Plasma concentrations of ANP increased with exercise in both groups and had greater increments in hypertensive patients than in normotensives. Plasma concentrations of BNP increased only in patients with hypertension and the levels of increase correlated with basal plasma BNP levels (r = 0.94, p < 0.001) and with left ventricular mass (r = 0.62, p < 0.01) determined by echocardiography. In contrast, plasma adrenomedullin did not change with exercise in either group. These results suggest that secretion patterns of these peptides are regulated by different mechanisms and that the amount and kind of peptides mobilized by exercise may depend on the underlying diseases or pathophysiologic condition.     

Prognostic value of plasma catecholamines, plasma renin activity, and plasma atrial natriuretic peptide at rest and during exercise in congestive heart failure: comparison with clinical evaluation, ejection fraction, and exercise capacity

Survival in congestive heart failure is related to plasma catecholamines and atrial natriuretic peptide at rest, but the prognostic importance of changes during exercise is unknown. The aim of this study was to evaluate the prognostic value of catecholamines and atrial natriuretic peptide at rest and during maximal exercise in congestive heart failure, and to compare it to clinical and exercise test variables and left ventricular ejection fraction. One hundred ninety consecutive patients (136 men and 54 women; median age, 66 years; range, 42-75 years) with clinically stable congestive heart failure were included. Sixteen patients were in New York Heart Association class I, 87 in class II, 83 in class III, and 4 in class IV. Left ventricular ejection fraction was 0.30 (range, 0.06-0.74). Total survival after 1 year was 79%, after 2 years, it was 68%. Prognostic variables at univariate analysis were: plasma noradrenaline at rest (P < .0001), plasma adrenaline at rest (P = .049), and atrial natriuretic peptide at rest (P = .016). During exercise, plasma catecholamines and plasma atrial natriuretic peptide increased significantly; the change, however, was not related to survival. Six variables carried significant, independent prognostic information in a multivariate analysis: left ventricular ejection fraction (P = .03), plasma noradrenaline at rest (P = .009), New York Heart Association class III + IV (P = .005), increase in heart rate during exercise < or = 35 min-1 (P < .0001), serum creatinine > 121 mumol/L (P = .004), and serum urea > 7.6 mmol/L (P = .007). Patients with congestive heart failure have a poor survival despite intensive medical treatment. Plasma catecholamines and plasma atrial natriuretic peptide are elevated at rest and rises further during exercise; the increase, however, is not related to mortality. Plasma noradrenaline at rest contributes with further prognostic information despite knowledge of clinical and exercise variables and was the only neurohormonal variable with independent, significant prognostic information on survival.     

Short and medium-term influence of physical activity on immune parameters

Physical stress induces different changes in immune parameters depending on effort schedule and/or customary physical training. The mechanisms whereby they take place and the occurrence of possible tolerance after repeated effort have not been conclusively elucidated. We studied short and medium-term exercise-induced changes in immune parameters after a standard physical effort (24' of cycle ergometer up to the 80% of maximal heart rate, daily for 5 days) in a group of healthy untrained controls. White Blood Cells, lymphocyte subsets, plasmatic catecholamine and cortisol levels, IgG and IL2receptor (IL2R) levels were determined. Most of the observed changes were strictly acute effort-related and disappeared within 3 hours (except for shifts in CD4+ CD45RA+ and CD4+ CD45RA- lymphocytes): they were concomitant to a transient sympathetic activation proved by heart rate (HR) and Norepinephrine (NE) increase. The medium-term effects of repeated daily effort included only a questionable rise in CD19+ and CD3+ CD4- CD8- cells. As far as possible tolerance mechanisms are concerned, we did not detect any change in either the direction or the entity of effort-induced changes in our controls after repeated effort. Study of strictly standardized exercise protocols is mandatory before clinical applications of physical activity in the approach to the treatment of disimmune diseases.     

Complement resistance of capsulated strains of Aeromonas salmonicida

1. We investigated the effect of exercise on plasma adrenomedullin, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations and studied the relationship between these peptides and haemodynamic parameters in nine patients with old myocardial infarction (MI) and in eight normal subjects. 2. The exercise protocol consisted of two fixed work loads (40 and 80 W) for 4 min each and venous blood samples were taken at rest, during each exercise stage and after exercise while monitoring the mean arterial pressure (MAP) and heart rate (HR). In MI, pulmonary arterial pressure (PAP), pulmonary capillary wedge pressure (PCWP), left ventricular end-diastolic pressure (LVEDP) and cardiac output (CO) were measured throughout exercise. 3. Adrenomedullin levels did not significantly increase with exercise. Adrenomedullin levels correlated with PAP and PCWP at rest (P < 0.05). Atrial natriuretic peptide levels correlated with PAP, PCWP and LVEDP throughout exercise (P < 0.05) but, on multiple regression analysis, PCWP correlated only with ANP (P < 0.01). Brain natriuretic peptide levels correlated with LVEDP throughout exercise (P < 0.01) and its increment correlated closely with basal BNP levels at rest (P < 0.01). 4. These results suggest that adrenomedullin does not respond to the acute haemodynamic changes of exercise, whereas ANP responds to it and PCWP is the major stimulus factor. Brain natriuretic peptide responds to exercise in proportion to the basal synthesis of BNP in patients with left ventricular dysfunction and LVEDP may play a role in increasing BNP during exercise.     

Effect of acute bicarbonate administration on exercise responses of COPD patients

Patients with severe chronic obstructive pulmonary disease (COPD) are limited in their exercise tolerance by the level of ventilation (VE) they can sustain. We determined whether acutely increasing blood bicarbonate levels decreased acid stimulation to the respiratory chemoreceptors during exercise, thereby improving exercise tolerance. Responses were compared with those obtained during 100% O2 breathing (known to reduce VE in these patients) and to the responses of healthy young subjects. Participants were six patients with severe COPD (forced expired volume in 1 s = 31 +/- 11% predicted) but without chronic CO2 retention and 5 healthy young subjects. Each subject performed three incremental cycle ergometer exercise tests: 1) control, 2) after ingestion of 0.3 g.kg-1 of sodium bicarbonate and 3) while breathing 100% O2. During these tests VE was measured continuously and arterialized venous blood (patients) or arterial blood (healthy subjects) was sampled serially to assess acid base variables. Bicarbonate loading increased standard bicarbonate by 4-6 mmol.L-1 and this elevation persisted during exercise. In both groups, bicarbonate loading resulted in a substantially higher arterial pH; arterial PCO2 was either unchanged (healthy subjects) or mildly (averaging 5 torr) higher (COPD patients). However, in neither group did bicarbonate loading result in an altered VE response to exercise or an increase in exercise tolerance. In contrast, superimposing hyperoxia on bicarbonate ingestion yielded, on average, 24% reduction in VE and 50% increase in peak work rate in the patients (but not in the healthy young subjects). We conclude that acute bicarbonate loading is not an ergogenic aid in patients with severe COPD.     

Atrial septal defect in adults: cardiopulmonary exercise capacity before and 4 months and 10 years after defect closure

OBJECTIVES: The purpose of the study was to evaluate the cardiopulmonary exercise capacity and ventilatory function in adults with atrial septal defect (ASD) preoperatively and 4 months and 10 years postoperatively. BACKGROUND: Only few data are available on cardiopulmonary exercise tolerance after ASD closure, but detailed knowledge might be helpful for indication for defect closure in certain patients. METHODS: The study was performed in adult patients (mean [+/-SD] age at operation 39.9 +/- 11.5 years; left-right shunt 9.6 +/- 5.6 liters/min; pulmonary/systemic flow ratio 2.8 +/- 1.2; mean pulmonary artery pressure 18.2 +/- 6.2 mm Hg). Cardiopulmonary exercise testing was performed with a bicycle ergometer. We determined peak oxygen uptake, anaerobic threshold, performance at anaerobic threshold and maximal performance in relation to these variables in a normal group. Ventilatory function at rest was expressed by vital capacity, maximal voluntary ventilation and forced expiratory volume in 1 s. RESULTS: Preoperatively, ventilatory function at rest was only moderately reduced to approximately 75% to 85%. Four months postoperatively we found no significant improvement, but 10 years postoperatively ventilatory function at rest was normalized. Preoperative cardiopulmonary exercise capacity was markedly reduced to 50% to 60%; early postoperatively it was only slightly higher, but late postoperatively exercise capacity significantly improved and was completely normalized. CONCLUSIONS: Although preoperative cardiopulmonary capacity in adult patients with nonrestrictive ASD was significantly decreased, some improvement was seen at 4 months postoperatively, with complete restitution to normal at 10 years after shunt closure.     

Mechanical Properties of Large Arteries in Mother and Fetus during Normal and Diabetic Pregnancy

Cardiodilatin (CDD)/atrial natriuretic peptide (ANP) is a 28-amino acid peptide hormone known to be synthesized in the heart of a large number of different vertebrates. It plays an important role in the regulation of blood pressure and natriuresis/diuresis. Since the cardiovascular system of the horse has to meet the highest requirements concerning its physiological performance, we intended to characterize the cardiodilatin/atrial natriuretic peptide system of this species. By means of immunohistochemistry and immunoelectron microscopy, we precisely identified auricular cardiocytes as the loci of CDD/ANP synthesis. Using aortic smooth muscle relaxation assay and CDD/ANP-ELISA, we succeeded in isolating the biologically active prohormone. We subsequently cloned the equine cDNA of the CDD/ANP precursor protein and deduced its primary sequence. The entire precursor protein is in good agreement with the CDD/ANP prohormones of other mammals. The deduced theoretical average Mr of equine CDD/ANP-1-126 is 13,764, corresponding to the molecular weight of purified peptide determined by ESI-MS. Our findings suggest that equine CDD/ANP is produced in auricular cardiocytes and the predominant storage form of CDD/ANP in the auricle is the prohormone CDD/ANP-1-126.     

Nutritional state and exercise tolerance in patients with COPD

We hypothesized that in patients with COPD, poor nutritional status adversely influences exercise tolerance by limiting aerobic capacity of exercising muscles. In 28 patients with stable COPD, we correlated nutritional status with gas exchange indexes obtained during maximal incremental cycle ergometer exercise and with respiratory function parameters. On the basis of percent of ideal body weight (%IBW), patients were divided into three groups (GP): GP1 (n = 8, %IBW < 90); GP2 (n = 13, %IBW > or = 90 < 110); and GP3 (n = 7, %IBW > or = 110). When compared with normally nourished individuals (GPs 2 and 3), malnourished GP1 patients showed greater reduction in maximal workload and in peak O2 uptake (VO2 peak), with earlier onset of metabolic acidosis (anaerobic threshold [AT]); in addition, indexes reflecting O2 cost of ventilation were higher in GP1. Nutritional status could be correlated with exercise tolerance (VO2 peak, r = 0.82, p < 0.0001), with onset of metabolic acidosis (AT, r = 0.69, p < 0.0001) and with dead space/tidal volume ratio (VD/VT, r = -0.59, p < 0.001). Body weight was inversely correlated with indexes that are likely to reflect the increase in O2 cost of ventilation. We conclude that in patients with stable COPD, (1) malnutrition significantly affects muscle aerobic capacity and exercise tolerance, and (2) high wasted ventilation and O2 cost of ventilation may be responsible for the weight loss.     

Exercise capacity in patients with beta-thalassemia major: relation to left ventricular and atrial size and function

OBJECTIVES: The objective of this study was to examine the association between exercise capacity and echocardiographic indexes of atrial and ventricular function and size in patients with beta-thalassemia major. BACKGROUND: In patients with beta-thalassemia major, the assessment of cardiac function with echocardiography alone does not always correspond to their functional status. Peak oxygen uptake and anaerobic threshold, on the other hand, constitute 2 objective and reproducible determinants of exercise capacity in patients with heart failure. METHODS AND RESULTS: Forty consecutive patients (22 women and 18 men, 18 to 30 years old) who were in stable condition while receiving regular transfusions and 30 age- and sex-matched control subjects were studied. At 2 to 3 days after the last transfusion, each subject underwent complete echocardiographic study followed by cardiopulmonary exercise testing. Left atrial volumes (maximal [Vmax], at onset of atrial systolic [Vp], and minimal [Vmin]) and left ventricular volumes were measured with the biplane area-length method, and left atrial active emptying fraction (ACTEF) and left ventricular ejection (LVEF) fraction were calculated. Peak oxygen uptake (Vo 2 max) and anaerobic threshold (AT) were also estimated. After transfusion, patients with beta-thalassemia major had reduced Vo 2 max and AT and greater left atrial volume in comparison with control subjects. Also, ACTEF and LVEF were significantly lower in the patient group. Moreover, Vo2 max and AT were inversely related to Vmax (r = -0.74 and r = -0.80, respectively) and directly related to ACTEF (r = 0.85 and r = 0.82, respectively) in beta-thalassemia major, whereas they were poorly related to LVEF (r = 0.50 and r = 0. 53, respectively). In the control group, Vo 2 max and AT parameters were related to Vmax and ACTEF in a similar way to that in the beta-thalassemia group. CONCLUSIONS: In patients with beta-thalassemia major, exercise capacity does not correlate with left ventricular dimensions and function. On the contrary, left atrial size and systolic dysfunction are probably predictors of decreased exercise capacity.     

Atrial natriuretic peptides in the heart and hemolymph of the oyster, Crassostrea virginica: a comparison with vertebrates

1. The content of atrial natriuretic peptides (ANPs) in the auricles of oysters, Crassostrea virginica, was significantly (P < 0.01) greater than in their ventricles. 2. High-performance gel permeation chromatography (HP-GPC) followed by ANF radioimmunoassay revealed two peaks in both oyster and vertebrate (rat) hearts--a major peak where the 12.6-14 kDa ANF prohormone elutes and a smaller peak where the pure human form of ANF elutes. 3. HP-GPC evaluation followed by proANF 31-67 radioimmunoassay revealed only an ANF-like prohormone while HP-GPC followed by proANF 1-30 radioimmunoassay revealed the ANF prohormone and a proANF 1-30-like peptide in oyster and rat hearts. 4. ANPs concentrations in hemolymph were 940 +/- 129, 225 +/- 25, and 100 +/- 10 pg/ml by the proANF 1-30, proANF 31-67, and ANF radioimmunoassays, respectively. 5. Atrial natriuretic-like peptides are present in the oyster heart in molecular species similar to vertebrate species and these peptides are also present in hemolymph.