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Biomedical subjects

J P Ribeiro

Publications and source records attributed to J P Ribeiro.

At least 19 recordsLinked to original sources
PubMed2006

Estimation of the lactate threshold from heart rate response to submaximal exercise: the pulse deficit.

In this study, we evaluated the validity of a sharp increase in pulse deficit (PD) as a noninvasive index for estimation of the first lactate threshold (LT (1)) in healthy individuals with various levels of aerobic fitness. Three groups of healthy male subjects participated in the study: 15 sedentary individuals, 14 students of physical education, and 13 competitive athletes. Each subject performed a maximal incremental exercise test on the cycle ergometer for the determination of the LT (1), the second lactate threshold, and peak power output. On different days, subjects performed several 8-min bouts of constant-load exercise on the cycle ergometer, corresponding to each of the power outputs of the maximal test, to evaluate PD, which was calculated as the total number of heart beats of the last 4 min minus the total number of heart beats in the first 4 min of exercise. The three groups presented similar blood lactate, heart rate and pulse deficit responses to exercise. For the first power output up to the LT (1), PD showed no significant changes. For the three groups, a sharp increase in PD was seen at the intensity immediately above LT (1). There was a significant correlation between PD and blood lactate changes from the rest to 4th min of submaximal exercise (r = 0.83, p < 0.05). The power output before a sharp increase in PD detected during constant-load exercise (112 +/- 38 W) and the power output corresponding to the LT (1) detected during the incremental test (111 +/- 37 W, p = 0.323) were similar and strongly correlated (r = 0.99, p = 0.0001). The absolute cut-point value of 25 beats for PD had a sensitivity of 100 %, a specificity of 95 %, and a positive predictive value of 90 % for the detection of LT (1). The determination of PD provides an accurate noninvasive estimate of the LT (1) in healthy young men with different levels of fitness. One 8-min submaximal exercise bout can establish if an individual is exercising above or below the LT (1).

Adult↗
PubMed2005

The role of secondary hyperparathyroidism in left ventricular hypertrophy of patients under chronic hemodialysis.

End-stage renal disease (ESRD) patients frequently develop structural cardiac abnormalities, particularly left ventricular hypertrophy (LVH). The mechanisms involved in these processes are not completely understood. In the present study, we evaluated a possible association between parathyroid hormone (PTH) levels and left ventricular mass (LVM) in patients with ESRD. Stable uremic patients on intermittent hemodialysis treatment were evaluated by standard two-dimensional echocardiography and their sera were analyzed for intact PTH. Forty-one patients (mean age 45 years, range 18 to 61 years), 61% males, who had been on hemodialysis for 3 to 186 months, were evaluated. Patients were stratified into 3 groups according to serum PTH: low levels (< 100 pg/ml; group I = 10 patients), intermediate levels (100 to 280 pg/ml; group II = 10 patients) and high levels (> 280 pg/ml; group III = 21 patients). A positive statistically significant association between LVM index and PTH was identified (r = 0.34; P = 0.03, Pearson's correlation coefficient) in the sample as a whole. In subgroup analyses, we did not observe significant associations in the low and intermediate PTH groups; nevertheless, PTH and LVM index were correlated in patients with high PTH levels (r = 0.62; P = 0.003). LVM index was also inversely associated with hemoglobin (r = -0.34; P = 0.03). In multivariate analysis, after adjustment for age, hemoglobin, body mass index, and blood pressure, the only independent predictor of LVM index was PTH level. Therefore, PTH is an independent predictor of LVH in patients undergoing chronic hemodialysis. Secondary hyperparathyroidism may contribute to the elevated cardiovascular morbidity associated with LVH in ESRD.

Adolescent↗
PubMed2005

Off-pump coronary artery bypass grafting does not reduce lymphocyte activation.

OBJECTIVE: In this study, we test the hypothesis that off-pump coronary bypass surgery might result in less lymphocyte activation than on-pump coronary surgery. We also study the behavior of lymphocyte activation markers during and after surgery. BACKGROUND: Coronary artery bypass surgery is known to be associated with changes of inflammatory mediators, immune function, and early phase lymphocyte activation, which could cause postoperative lymphopenia and lymphocyte unresponsiveness. METHODS: We studied lymphocyte activation response in 28 patients randomized to off-pump (n = 13) or on-pump (n = 15) coronary artery bypass surgery. Expression of CD25, CD26, CD69, and DR on T (CD3+) and B (CD19+) lymphocytes on peripheral blood was assessed through flow cytometry. RESULTS: The response of T lymphocytes and their activation markers, as well as B lymphocytes and their activation markers, was similar after on- and off-pump surgery. Overall, T lymphocytes decreased to the lowest level 9 h after surgery and tended to increase later. For B lymphocytes, there was early reduction with increase on the 1st postoperative day. There was early activation of CD69+ and late activation of CD25+ on T lymphocytes. For B lymphocytes, there was early activation of CD69+ and late activation of DR+. CONCLUSIONS: (1) Compared to on-pump cardiopulmonary bypass, off-pump surgery does not reduce lymphocyte activation. (2) Coronary bypass surgery causes the early activation of lymphocytes, as evidenced by the increased expression of lymphocyte activation markers.

Antigens, CD↗
PubMed2003

ATP diphosphohydrolase in human platelets from patients with coronary arteries heart disease.

ATP diphosphohydrolase is an enzyme described in platelets and may be related to the control of ADP-dependent platelet aggregation. Platelet aggregation in atherosclerotic coronary arteries, and the release of platelet-derived factors, play an important role in coronary artery disease syndromes. In this study, we determined the activity of ATP diphosphohydrolase in platelets from patients with chronic and acute coronary artery disease syndromes and healthy persons. The following groups were studied: healthy persons (group I), patients with chronic heart disease (group II) and acute heart disease (group III). Results did not demonstrate differences between the groups studied. The control group demonstrated a lower range of enzyme activity. The patients from groups II and III had ingested drugs with actions upon the cardiovascular system and the effect, in vitro, of these drugs upon the ATP diphosphohydrolase activity in human platelets was also investigated. The in vitro experiments demonstrated that 2.0 mM acetylsalicylic acid inhibited ATP hydrolysis by human platelets by approximately 55%. Significant correlation was observed between ADP hydrolysis and glucose blood levels in the control group and between ATP hydrolysis and triglycerides in the group II. These results contribute to our understanding of a possible relationship between ATP diphosphohydrolase and thrombogenesis.

Acute Disease↗
PubMed2001

Enhancement of heart rate variability by cholinergic stimulation with pyridostigmine in healthy subjects.

The purpose of this study was to determine the effect of the oral administration of pyridostigmine bromide on indices of heart rate variability (HRV) in healthy young volunteers. Seventeen healthy participants (11 men, 6 women; aged 27 +/- 8 y) submitted to a randomized, crossover, double-blind protocol, in which they received 30 mg pyridostigmine bromide (PYR) or placebo orally at 8-hour intervals for 24 hours, on two separate days. Venous blood samples were collected 2 and 24 hours after the first dose for determination of serum cholinesterase activity. Holter tapes were recorded during the 24-hour period and analyzed using a semiautomatic technique to evaluate time- and frequency-domain indices of HRV and to build three-dimensional return maps for later quantification. Symptoms were mild and occurred similarly during administration of PYR and placebo (p = 0.140). Serum cholinesterase activity was reduced by 15% at 2 hours (p = 0.013) and by 14% at 24 hours (p = 0.010) after the first dose of PYR, but not after administration of placebo. Pyridostigmine administration caused a significant increase in the mean 24-hour R-R interval (placebo: 814 +/- 20 msec; PYR: 844 +/- 18 msec; p = 0.003) and in time-domain indices of HRV, such as the standard deviation of all R-R intervals (SDNN; placebo: 151 +/- 9 msec; PYR: 164 +/- 9 msec; p = 0.017), and the percentage of pairs of adjacent R-R intervals differing by more than 50 msec (pNN50; placebo: 12.8 +/- 1.8%; PYR: 13.9 +/- 1.5%; p = 0.029). Pyridostigmine had no significant effect on frequency-domain indices of HRV, but resulted in significant increase in P2, a parasympathetic index derived from the three-dimensional return map (placebo: 93 +/- 13 msec; PYR: 98 +/- 13 ms; p = 0.029). In conclusion, low-dose pyridostigmine reduced mean heart rate and increased HRV during a 24-hour period in healthy young subjects.

Administration, Oral↗
PubMed2001

Parasympathetic dysautonomia precedes left ventricular systolic dysfunction in Chagas disease.

BACKGROUND: Parasympathetic dysautonomia is an established feature of advanced Chagas cardiomyopathy. However, in the absence of cardiac involvement, the presence of vagal dysfunction remains controversial. In a cross-sectional study, we compared patients with Chagas disease without cardiac involvement and healthy individuals by three different methods to determine whether vagal dysfunction is present in the early phase of Chagas disease. METHODS: Sixty-one patients with Chagas disease without cardiac involvement and 38 controls were submitted to respiratory sinus arrhythmia test and 24-hour Holter monitoring. Vagal heart influences were assessed by the expiratory/inspiratory (E/I) ratio, time-domain indexes of heart rate variability (HRV), and by the quantification of a 3-dimensional return map. RESULTS: The two groups were comparable in terms of left ventricular ejection fraction and left ventricular end-diastolic dimension. Compared with the control group, patients with Chagas disease had significantly lower values of the E/I ratio (mean +/- SD: 1.38 +/- 0.02 and 1.25 +/- 0.02, P <.004) and short-term indexes of HRV (median [interquartile range]-rMSSD: 23 [18-27] and 17 [13-23], P =.00; pNN50: 11 [7-17] and 6 [2-12], P =.00). P(3), a beat-to-beat HRV index derived from the 3-dimensional return map, also was significantly reduced in the Chagas disease group (mean +/- SD: 118 +/- 5 vs 100 +/- 4, P =.00). None of these indexes of vagal heart control were significantly correlated with left ventricular function or to the presence of esophageal radiologic abnormalities. CONCLUSION: Parasympathetic dysautonomia is an independent and early phenomenon in Chagas disease and may precede left ventricular systolic dysfunction.

Adolescent↗
PubMed2001

Contribution of nitric oxide to arterial pressure and heart rate variability in rats submitted to high-sodium intake.

The aim of this study was to determine the contribution of NO to arterial pressure and heart rate variability in normotensive rats subjected to high sodium intake. Arterial pressure, heart rate, and arterial pressure and heart rate variability, baroreflex sensitivity, and pressure responsiveness were measured in male Wistar rats treated for 6 weeks (control and high sodium [1%] intake groups), before and after acute NO synthesis blockade. After treatment, no changes were observed in arterial pressure or heart rate. Arterial pressure variability was increased after sodium intake; however, heart rate variability and baroreflex sensitivity were not modified in high-sodium rats. NO synthase blockade increased arterial pressure in both groups but was higher in the high-sodium group (from 110+/-5 to 162+/-1.5 mm Hg) compared with the control group (from 109+/-6.7 to 144+/-10 mm Hg). The increase in arterial pressure was accompanied by a decrease in heart rate (from 354+/-28 to 303+/-25 bpm in control rats and from 380+/-34 to 298+/-30 bpm in high-sodium rats). NO synthase blockade increased the tachycardic response to sodium nitroprusside in high-sodium rats. Arterial pressure variability, evaluated by a nonlinear method (3D return maps), showed a larger reduction in response to NO synthase inhibition in the high-sodium group (from 162+/-26 to 34.8+/-8.6 for general index of beat-to-beat blood pressure variability) than in the control group (from 58+/-9.6 to 36+/-4.7 for general index of beat-to-beat blood pressure variability). Heart rate variability, evaluated by the SD of the R-R intervals, was not changed in control rats but was increased by NO synthase inhibition in the high-sodium rats (from 9.5+/-0.2 to 21.9+/-1.7 milliseconds). These findings suggest an important role for increased NO production in adaptation to high-sodium intake. The increase in NO system sensitivity in high-sodium intake may contribute to changes in the autonomic nervous system regulating heart rate and, especially, arterial pressure variability.

Animals↗
PubMed2001

Plasma levels of immunoinflammatory markers in De Novo coronary atherosclerosis and coronary restenosis postangioplasty.

OBJECTIVE: To compare circulating plasma levels of immunoinflammatory markers in patients with known de novo coronary artery disease and patients with postangioplasty restenosis. METHODS: Using enzymatic immunoabsorbent assay, we measured plasma levels of soluble interleukin-2 receptosr, tumor necrosis factor alpha, and soluble tumor necrosis alpha receptors I and II in 11 patients with restenosis postcoronary angioplasty (restenosis group), in 10 patients with primary atherosclerosis (de novo group) who were referred for coronary angiography because of stable or unstable angina, and in 9 healthy volunteers (control group). Levels of soluble interleukin-2 receptors were significantly higher in the de novo group compared with that in the restenosis and control groups. Levels were also higher in the restenosis group compared with that in the control group. Plasma levels of tumor necrosis alpha and receptor levels were significantly higher in the de novo group compared to with that in the restenosis and control groups, but levels in the restenosis group were not different from that in the controls. CONCLUSION: Coronary artery disease, either primary or secondary to restenosis, is associated with significant immunoinflammatory activity, which can be assessed by examining the extent of circulating plasma levels of inflammatory markers. Moreover, patients with de novo lesions appear to have increased inflammatory activity compared with patients with restenosis.

Analysis of Variance↗
PubMed2000

Three-dimensional return map: a new tool for quantification of heart rate variability.

BACKGROUND: Several methods are used to study heart rate variability, but they have limitations, which might be overcome by the use of a three-dimensional return map. OBJECTIVES: To evaluate the performance of three-dimensional return map-derived indices to detect (1) sympathetic and parasympathetic modulation to the sinus node and (2) autonomic dysfunction in diabetic patients. METHODS: Six healthy subjects underwent partial and total pharmacological autonomic blockade in a protocol that incorporated vagal and sympathetic predominance. Twenty-two patients with type 2 diabetes mellitus and 12 normal controls participated in the subsequent validation experiment. Three-dimensional return maps were constructed by plotting RRn intervals versus the difference between adjacent RR intervals [(RRn+1)-(RRn)] versus the number of counts, and four derived indices (P1, P2, P3, MN) were created for quantification. RESULTS: Both indices P1 and MN were significantly increased after sympathetic blockade with propranolol, while all indices except P1 were modified after parasympathetic blockade (P < 0.05). During the validation experiments, P1 and MN detected differences between normal controls, and diabetic patients with and without autonomic neuropathy. The overall accuracy of most three-dimensional indices to detect autonomic dysfunction, estimated by the area under the ROC curve, was significantly better than traditional time domain indices. Three-dimensional return map-derived indices also showed adequate reproducibility on two different recording days (intra-class correlation coefficients of 0.69 to 0.82; P < 0.001). CONCLUSIONS: Three-dimensional return map-derived indices are reproducible, quantify parasympathetic as well as sympathetic modulation to the sinus node, and are capable of detecting autonomic dysfunction in diabetic patients.

1-Propanol↗
PubMed2000

Atrial automaticity and atrioventricular conduction in athletes: contribution of autonomic regulation.

Little is known about the sinoatrial automatism and atrioventricular conduction of trained individuals who present a normal resting electrocardiogram. We used transesophageal atrial stimulation, a minimally invasive technique, to evaluate aerobically trained athletes (n = 10) and sedentary individuals (n = 10) with normal resting electrocardiograms, to test the hypothesis that parasympathetic tone, as detected by heart rate variability, could be associated with changes in sinoatrial automatism and atrioventricular conduction. Corrected sinus node recovery time tended to be longer in athletes than in sedentary individuals, but this difference did not reach statistical significance. The Wenckebach point occurred at a lower rate in athletes than in the controls. Over a 24-h period of measurement, the mean RR interval was longer in the athletes than in the sedentary individuals. The mean square root of successive differences (rMSSD) tended to be higher in athletes than in controls, but this difference did not reach statistical significance. There was a moderate correlation (r = 0.48, P < 0.05) between the index of atrioventricular conduction, the rate at the Wenckebach point, and the logarithmically transformed rMSSD. Thus, as a corollary to its effects on the sinus node, where increased parasympathetic tone, decreased sympathetic tone, and non-autonomic components may contribute to sinus bradycardia, it is possible that athletic training may also induce intrinsic adaptations in the conduction system, which could contribute to the higher prevalence of atrioventricular conduction abnormalities observed in athletes.

Adult↗
PubMed1999

Increased plasma levels of soluble vascular cellular adhesion molecule-1 in patients with chest pain and angiographically normal coronary arteries.

AIMS: To assess plasma levels of vascular cellular adhesion molecule-1, a marker of endothelial dysfunction, in patients presenting with coronary syndromes submitted to coronary angiography. METHODS AND RESULTS: Plasma levels of soluble vascular cellular adhesion molecule-1 were measured by enzymatic immunoabsorbent assay in eight patients with angina-like chest pain and angiographically normal coronary arteries; in 14 patients with stable angina and in 18 patients with unstable angina, both with coronary lesions by angiography, and in 10 healthy volunteers. Levels of soluble vascular cellular adhesion molecule-1 were higher in unstable angina patients (1777+/-161 SE pg ml(-1)) compared to patients with stable angina (1178+/-206 SE pg ml(-1), P<0.05). Moreover, patients with angina-like chest pain and normal coronary arteries had significantly higher soluble vascular cellular adhesion molecule-1 levels (2307+/-295 SE pg ml(-1)) compared to stable angina patients (P<0.05), but similar levels compared to unstable angina patients. Patient groups had higher values of soluble vascular cellular adhesion molecule-1 compared to the control group (734+/-97 SE pg ml(-1)). CONCLUSIONS: Increased levels of soluble vascular cellular adhesion molecule-1 are associated with coronary artery disease in patients with anatomically established lesions. In patients free of flow-limiting lesions and angina-like chest pain, high levels of this marker may indicate endothelial dysfunction.

Angina Pectoris↗
PubMed1999

The effects of two aerobic training intensities on ambulatory blood pressure in hypertensive patients: results of a randomized trial.

The effect of different intensities of aerobic exercise on blood pressure remains uncertain. The goal of this trial was to compare the effect of two different levels of aerobic physical training on 24-hour ambulatory blood pressure. In this double-blind parallel-group trial, 28 sedentary hypertensive patients (mean diastolic blood pressure of 90 to 104 mm Hg) were randomly assigned to 10 weeks of physical training at 20% (Group I) or 60% (Group II) of their maximal workload on a cycle ergometer (mean load of 32 and 85 watts, respectively). Maximal oxygen consumption was estimated by the time spent on a mechanical braked Monark bicycle (Monark, Sáo Paulo, Brazil). Indexes of physical fitness were determined by cycle ergometer tests before and after the experimental period. The principal outcome variable was mean 24-hour ambulatory blood pressure. Mean 24 hour systolic blood pressure fell from 137.2+/-14.9 to 135.2+/-12.7 mm Hg in Group I and from 144.4+/-13.3 to 138.6+/-12.9 in Group II (mean between group difference of -2.1 mm Hg, P = 0.479, adjusted for baseline blood pressure). Mean diastolic blood pressure fell from 9.21+/-10.0 to 89.3+/-7.7 mm Hg in Group I and from 93.3+/-5.8 to 90.6+/-6.8 mm Hg in Group II (mean adjusted difference of -0.06, P = 0.765). Nighttime blood pressure did not change in either group. Across all participants, a reduction in systolic blood pressure was significantly associated with improved physical fitness as manifest by increased physical work capacity at heart rate of 130 bpm (PWC130), increased systolic blood pressure at PWC130, and decreased maximum heart rate measured during the cycle ergometer test We conclude that aerobic training programs at 20% and 60% of the maximum work capacity have similar effects on ambulatory blood pressure.

Blood Pressure↗
PubMed1999

Moderate and high intensity exercise training in HIV-1 seropositive individuals: a randomized trial.

HIV-infected individuals are frequently active, but guidelines for exercise in this population lack scientific support, since studies on the effects of exercise training on immunologic variables of HIV-1 positive individuals have shown conflicting results. Exercise capacity, immunologic markers (CD4, CD8 and CD4:CD8 ratio), anthropometric measurements, and depression scores were evaluated to compare the effects of two intensities of aerobic exercise on HIV-1 seropositive individuals. Twenty-one healthy subjects (14 men, 7 women), carriers of the HIV-1 virus (CD4>200 cells x mm(-3)), and inactive for at least 6 months, completed a 12 week exercise training program (36 sessions of 1 h, 3 times per week), in a moderate intensity group (60+/-4% of maximal heart rate) or a high intensity group (84+/-4% of maximal heart rate). Exercise capacity estimated by treadmill time was increased significantly in both moderate intensity (680+/-81 s before; 750+/-151 s after) and high intensity (651+/-122 s before; 841+/-158 s after) groups, but the high intensity group presented a significantly larger increment (p<0.01). There were no significant changes in the immunologic variables, anthropometric measurements or depression scores. Thus, HIV-seropositive individuals that participate in moderate and high intensity exercise programs are able to increase their functional capacity without any detectable changes in immunologic variables, anthropometric measurements or depression scores.

Adult↗
PubMed1999

Management of patients with acute myocardial infarction at five academic medical centers: clinical characteristics, resource utilization, and outcome.

BACKGROUND: Although variability in management of cardiovascular syndromes has been demonstrated among regions, the extent to which variability exists among academic medical centers in different countries in uncertain. METHODS: This retrospective cohort study includes data on consecutive patients (n = 694) with acute myocardial infarction who were admitted to five teaching hospitals from different countries (84, Brigham and Women's Hospital, USA; 97, Iizuka Hospital, Japan; 64, Hospital de Clinicas de Porto Alegre, Brazil; 62, Universitätsklinikum Charité, Germany; and 387, Hôpital Cantonal Universitaire de Genève, Switzerland) during a one-year period. Data were collected via chart review on clinical characteristics, rates of diagnostic and therapeutic interventions, complications and mortality, length of stay, and one-year follow-up outcomes. RESULTS: Patients' clinical characteristics varied among these institutions, with the lowest prevalence of antero-septal myocardial infarction at the US hospital. The US hospital had the lowest rate of use of thrombolytic therapy and did not have the highest rate for any invasive procedure. Average length of stay ranged from 7.7 +/- 4.3 days in the US hospital to 47.2 +/- 27.9 days in the Japanese hospital. There were no differences in one-year mortality among the four institutions (4% to 8%, P = 0.881) for which data were available. CONCLUSIONS: In this nonrandom sample of academic medical centers, the use of aggressive therapies for acute myocardial infarction was at least as common at non-US as US hospitals. Length of stay was much shorter at the US hospital. Despite these variations in management, evidence for differences in outcomes at one year were not detected.

Academic Medical Centers↗
PubMed1998

Sympathetic nervous system representation in time and frequency domain indices of heart rate variability.

This study evaluated the contributions of sympathetic and parasympathetic modulation to heart rate variability during situations in which vagal and sympathetic tone predominated. In a placebo-controlled, randomized, double blind blockade study, six young healthy male individuals received propranolol (0.2 mg x kg(-1)), atropine (0.04 mg x kg(-1)), propranolol plus atropine, or placebo infusions over 4 days. Time-domain indices were calculated during 40 min of rest and 20 min of exercise at 70% of maximal exercise intensity. Spectrum analysis, using fast Fourier transformation, was also performed at rest and during the exercise. The time-domain indices standard deviation of R-R intervals, mean of the standard deviations of all R-R intervals for all 5-min segments, percentage of number of pairs of adjacent R-R intervals differing by more than 50 ms, and square root of the mean of the sum of squares of differences between adjacent R-R intervals were reduced after atropine and propranolol plus atropine. Propranolol alone caused no appreciable change in any of the time-domain indices. At rest, all spectrum components were similar after placebo and propranolol infusions, but following parasympathetic and double autonomic blockade there was a reduction in all components of the spectrum analysis, except for the low:high ratio. During exercise, partial and double blockade did not change significantly any of the spectrum components. Thus, time and frequency-domain indices of heart rate variability were able to detect vagal activity, but could not detect sympathetic activity. During exercise, spectrum analysis is not capable of evaluating autonomic modulation of heart rate.

Adult↗