Júlio César Crescêncio

Measurement of anaerobic threshold during dynamic exercise in healthy subjects: comparison among visual analysis and mathematical models

The anaerobic threshold (AT) during dynamic physical exercise is a good parameter to quantify oxygen uptake and transport which reflects the functional cardiorespiratory reserve in men. The increasing use of computerized ergospirometric systems has allowed recording, processing and plotting ventilatory variables, cycle by cycle, on a real time basis. So, response changes in carbon dioxide production (VCO/sub 2/) may be used as a non-invasive measurement of AT. In the present study a custom software was developed to apply bi-segmental models (linear-linear and linear-quadratic) using the least square method for fitting VCO/sub 2/ data. The lowest value of the residual sum of squares found in VCO/sub 2/ graphic plots corresponded to AT, expressed as oxygen uptake. Data analysis showed that, despite the good correlation documented between the linear-linear model and the classical visual method, the mathematical method underestimates the AT values when compared to the visual one.

Improved endothelial function and reversal of myocardial perfusion defects after aerobic physical training in a patient with microvascular myocardial ischemia.

The objective of this report is to document the effects of an aerobic training program on myocardial perfusion, and endothelial function abnormalities, and on the relief of angina in a patient with microvascular myocardial ischemia. A 53-year-old female patient exhibited precordial pain on effort and angiographically normal coronaries. Her symptoms had been present for 4 yrs despite pharmacologic treatment for the control of risk factors, with myocardial perfusion scintigraphy revealing an extensive reversible perfusion defect. She was submitted to aerobic training for 4 mos, obtaining significant improvement of the anginal symptoms. Additionally, after the aerobic training program, scintigraphy revealed the disappearance of the myocardial perfusion defect, with a marked improvement of endothelium-dependent vasodilatory response and an improved quality-of-life score. These results suggest that aerobic training can improve endothelial function, leading to a reduction of ischemia and an improved quality-of-life in patients with microvascular myocardial ischemia.

Influence of Aging, Tidal Volume, and Respiratory Rate on Doppler Echocardiographic Indices of Diastolic Function in Normal Male Subjects: A Quantitative Evaluation

Background: Although the influence of respiration on ventricular filling, as evaluated by Doppler technique, and the evaluation of diastolic velocities of mitral valve annulus (MVA), as measured by Doppler tissue imaging (DTI), can provide valuable information for the study of left ventricular (LV) diastolic function, the concomitant effects of aging, tidal volume (TV), and respiratory rate (RR) on these velocities have not been quantitatively investigated. Methods: We evaluated 12 normal male volunteers (Group I) aged 20–26 years (mean: 22.8) and 8 normal subjects aged 41 to 54 years old (mean: 45.9) (Group II). Using DTI we measured peak early (Ea) and late (Aa) velocities of longitudinal axis expansion at lateral and medial MVA. Doppler mitral and tricuspid flow velocities were measured: peak early (E) and late (A) inflow velocity, early (Ei) and late (Ai) flow integral, and deceleration time of peak early mitral flow velocity (DT). Respiratory cycles were simultaneously recorded at RR of 9, 12, 15, and 18 cycles/min and TV of 600 and 900 mL during respiration (RESP). Results and conclusions: (1) E, A, and Ai in MV had negligible change during respiration, but Ei was significantly reduced during inspiration; (2) DT reduced slightly with inspiration, but the change was significant only with TV of 900 mL; (3) an important increase of E in right ventricular flow was observed during inspiration; (4) variations of RR and TV did not significantly influence right and left ventricular inflow in normal subjects, in the conditions of this investigation; (5) a significant increase of Ea at medial MVA was documented during inspiration only in young subjects; (6) a significant decrease of Aa at medial MVA was observed during inspiration in both groups of volunteers; (7) RR and TV did not influence MVA velocities in young and adult subjects; (8) a consistent reduction in Ea and a significant increase in Aa were observed with increasing age; (9) these changes were more conspicuous and consistent than those documented in ventricular filling when young and middle‐age men are compared, suggesting that the DTI is more sensitive to detect changes in diastolic function; and (10) in addition, these data suggest that, for evaluation of diastolic function, in clinical context, it is not necessary to control rigorously RR or TV.

Aerobic Training after Myocardial Infarction: Remodeling Evaluated by Cardiac Magnetic Resonance

Background Numerous studies show the benefits of exercise training after myocardial infarction (MI). Nevertheless, the effects on function and remodeling are still controversial. Objectives To evaluate, in patients after (MI), the effects of aerobic exercise of moderate intensity on ventricular remodeling by cardiac magnetic resonance imaging (CMR). Methods 26 male patients, 52.9 ± 7.9 years, after a first MI, were assigned to groups: trained group (TG), 18; and control group (CG), 8. The TG performed supervised aerobic exercise on treadmill twice a week, and unsupervised sessions on 2 additional days per week, for at least 3 months. Laboratory tests, anthropometric measurements, resting heart rate (HR), exercise test, and CMR were conducted at baseline and follow-up. Results The TG showed a 10.8% reduction in fasting blood glucose (p = 0.01), and a 7.3-bpm reduction in resting HR in both sitting and supine positions (p < 0.0001). There was an increase in oxygen uptake only in the TG (35.4 ± 8.1 to 49.1 ± 9.6 mL/kg/min, p < 0.0001). There was a statistically significant decrease in the TG left ventricular mass (LVmass) (128.7 ± 38.9 to 117.2 ± 27.2 g, p = 0.0032). There were no statistically significant changes in the values of left ventricular end-diastolic volume (LVEDV) and ejection fraction in the groups. The LVmass/EDV ratio demonstrated a statistically significant positive remodeling in the TG (p = 0.015). Conclusions Aerobic exercise of moderate intensity improved physical capacity and other cardiovascular variables. A positive remodeling was identified in the TG, where a left ventricular diastolic dimension increase was associated with LVmass reduction.

Use of the Wasserman equation in optimization of the duration of the power ramp in a cardiopulmonary exercise test: a study of Brazilian men

This study aimed to analyze the agreement between measurements of unloaded oxygen uptake and peak oxygen uptake based on equations proposed by Wasserman and on real measurements directly obtained with the ergospirometry system. We performed an incremental cardiopulmonary exercise test (CPET), which was applied to two groups of sedentary male subjects: one apparently healthy group (HG, n=12) and the other had stable coronary artery disease (n=16). The mean age in the HG was 47±4 years and that in the coronary artery disease group (CG) was 57±8 years. Both groups performed CPET on a cycle ergometer with a ramp-type protocol at an intensity that was calculated according to the Wasserman equation. In the HG, there was no significant difference between measurements predicted by the formula and real measurements obtained in CPET in the unloaded condition. However, at peak effort, a significant difference was observed between oxygen uptake (V˙O2)peak(predicted)and V˙O2peak(real)(nonparametric Wilcoxon test). In the CG, there was a significant difference of 116.26 mL/min between the predicted values by the formula and the real values obtained in the unloaded condition. A significant difference in peak effort was found, where V˙O2peak(real)was 40% lower than V˙O2peak(predicted)(nonparametric Wilcoxon test). There was no agreement between the real and predicted measurements as analyzed by Lin’s coefficient or the Bland and Altman model. The Wasserman formula does not appear to be appropriate for prediction of functional capacity of volunteers. Therefore, this formula cannot precisely predict the increase in power in incremental CPET on a cycle ergometer.

Physical training as non-pharmacological treatment of neurocardiogenic syncope.

Background Characterized as a sudden and temporary loss of consciousness and postural tone, with quick and spontaneous recovery, syncope is caused by an acute reduction of systemic arterial pressure and, therefore, of cerebral blood flow. Unsatisfactory results with the use of drugs allowed the nonpharmacological treatment of neurocardiogenic syncope was contemplated as the first therapeutic option. Objectives To compare, in patients with neurocardiogenic syncope, the impact of a moderate intensity aerobic physical training (AFT) and a control intervention on the positivity of head-up tilting test (HUT) and orthostatic tolerance time. Methods Were studied 21 patients with a history of recurrent neurocardiogenic syncope and HUT. The patients were randomized into: trained group (TG), n = 11, and control group (CG), n = 10. The TG was submitted to 12 weeks of AFT supervised, in cycle ergometer, and the CG to a control procedure that consisted in 15 minutes of stretching and 15 minutes of light walk. Results The TG had a positive effect to physical training, with a significant increase in peak oxygen consumption. The CG did not show any statistically significant change before and after the intervention. After the intervention period, 72.7% of the TG sample had negative results to the HUT, not having syncope in the revaluation. Conclusion The program of supervised aerobic physical training for 12 weeks was able to reduce the number of positive HUT, as it was able to increase tolerance time in orthostatic position during the HUT after the intervention period.

The effect of acute magnesium loading on the maximal exercise performance of stable chronic obstructive pulmonary disease patients.

OBJECTIVE: The potential influence of magnesium on exercise performance is a subject of increasing interest. Magnesium has been shown to have bronchodilatatory properties in asthma and chronic obstructive pulmonary disease patients. The aim of this study was to investigate the effects of acute magnesium IV loading on the aerobic exercise performance of stable chronic obstructive pulmonary disease patients. METHODS: Twenty male chronic obstructive pulmonary disease patients (66.2±8.3 years old, FEV1: 49.3±19.8%) received an IV infusion of 2 g of either magnesium sulfate or saline on two randomly assigned occasions approximately two days apart. Spirometry was performed both before and 45 minutes after the infusions. A symptom-limited incremental maximal cardiopulmonary test was performed on a cycle ergometer at approximately 100 minutes after the end of the infusion. ClinicalTrials.gov: NCT00500864 RESULTS: Magnesium infusion was associated with significant reductions in the functional residual capacity (-0.41 l) and residual volume (-0.47 l), the mean arterial blood pressure (-5.6 mmHg) and the cardiac double product (-734.8 mmHg.bpm) at rest. Magnesium treatment led to significant increases in the maximal load reached (+8 w) and the respiratory exchange ratio (0.06) at peak exercise. The subgroup of patients who showed increases in the work load equal to or greater than 5 w also exhibited significantly greater improvements in inspiratory capacity (0.29 l). CONCLUSIONS: The acute IV loading of magnesium promotes a reduction in static lung hyperinflation and improves the exercise performance in stable chronic obstructive pulmonary disease patients. Improvements in respiratory mechanics appear to be responsible for the latter finding.

Addition of Protein in Carbohydrate Supplementation Does not Improve Performance of Amateur Runners in Exercise above the Anaerobic Threshold

There is no consensus in the literature that supports the inclusion of protein in the carbohydrate supplement in endurance exercise. The purpose of this study was to compare the physical performance of amateur runners under three different supplementation protocols: placebo (PLA), carbohydrate (CHO) and carbohydrate plus protein (CHO + PTN). Twelve amateur runners performed three exercise protocols on separate occasions consisting of 60 initial minutes with intensity referring to the Anaerobic Threshold (AT) and then 10% above the AT until exhaustion. Supplements (150 mL) were ingested 15 minutes before starting the activity and every 20 minutes until the first hour of exercise. Biochemical analyzes (blood glucose and lactate) and rating of perceived exertion (RPE) were measured before, during and after exercise protocols. Total caloric intake (Kcal) and macronutrients (g) were evaluated in the 24 hours preceding each exercise protocol. The time of exhaustion was higher for the CHO group when compared to the PLA group (24.6±13.6 vs. 15.2±8.9 minutes, p = 0.001) and the CHO + PTN group (24.6±13.6 vs. 18.6±8.4 minutes, p = 0.01). In general, glycemia was higher for the CHO and CHO + PTN groups when compared to the PLA group at all times whereas lactate, RPE and dietary assement did not show great differences. Our results suggest that, unlike supplementation with CHO alone, the addition of PTN in CHO supplements does not result in improved performance for the studied population and exercise intensity.

Influence of Aerobic Training on The Mechanics of Ventricular Contraction After Acute Myocardial Infarction: A Pilot Study

The study of myocardial contractility, based on the new anatomical concepts that govern cardiac mechanics, represents a promising strategy of analysis of myocardial adaptations related to physical training in the context of post-infarction. We investigated the influence of aerobic training on physical capacity and on the evaluation parameters of left ventricular contraction mechanics in patients with myocardial infarction. Thirty-one patients (55.1 ± 8.9 years) who had myocardial infarction in the anterior wall were prospectively investigated in three groups: interval training group (ITG) (n = 10), moderate training group (MTG) n = 10) and control group (CG) (n = 10). Before and after 12 weeks of clinical follow-up, patients underwent cardiopulmonary exercise testing and cardiac magnetic resonance imaging. The trained groups performed supervised aerobic training on treadmill, in two different intensities. A statistically significant increase in peak oxygen uptake (VO2) was observed in the ITG (19.2 ± 5.1 at 21.9 ± 5.6 ml/kg/min, p < 0.01) and in the MTG 18.8 ± 3.7 to 21.6 ± 4.5 ml/kg/min, p < 0.01). The GC did not present a statistically significant change in peak VO2. A statistically significant increase in radial strain (STRAD) was observed in the CG: basal STRAD (57.4 ± 16.6 to 84.1 ± 30.9%, p < 0.05), medial STRAD (57.8 ± 27, 9 to 74.3 ± 36.1%, p < 0.05) and apical STRAD (38.2 ± 26.0 to 52.4 ± 29.8%, p < 0.01). The trained groups did not present a statistically significant change of the radial strain. The present study points to a potential clinical application of the parameters of ventricular contraction mechanics analysis, especially radial strain, to discriminate post-infarction myocardial adaptations between patients submitted or not to aerobic training programs.

Influence of aerobic exercise training on left ventricular remodeling and neurohumoral response in patients with myocardial infarction

Purpose: The effects of aerobic training on ventricular remodeling (VR) and neurohumoral activation after myocardial infarction (MI) have not been completely elucidated. It was investigated the influence of aerobic training on physical fitness, on VR and neurohumoral response after MI. Methods: Sixteen patients with anterior wall myocardial infarction were randomized into two groups: training (TG=8) and control (CG=8). TG patients performed moderate-intensity aerobic training. Before and after a 12-week follow-up all patients underwent cardiac magnetic resonance, cardiopulmonary exercise testing and blood sampling for measurement of NT-proBNP. Results: In the follow-up, there was a significant increase in the ΔO2 pulse in the TG (6.4 ± 1.2 to 8.1 ± 1.7; p=0.01), with no significant change in the CG (7.0 ± 2.3 to 6.9 ± 3.0; p>0.99). It was observed an increase of LV mass/EDV ratio from 0.72 ± 0.19 to 0.96 ± 0.30 g.ml-1 (p=0.007) in the CG, but no change in the TG from 0.89 ± 0.33 to 0.96 ± 0.26 g.ml-1 (p=0.54). There was a significant decrease of NT-proBNP at rest and at effort peak in both groups. Conclusion: Aerobic training seems to have a protective effect over the spontaneous process of LV concentric remodeling after myocardial infarction, and it promotes an improvement of the LV systolic performance during dynamic physical effort, without triggering adverse neurohumoral activation. Correspondence to: Giovani Luiz De Santi, Division of Cardiology, Medical School of Ribeirao Preto, University of Sao Paulo, Av. Bandeirantes, n 3.900, Ribeirao Preto-SP, Brazil, Zip: 14048-900; Tel: +551636022599, +551636022782, +553498020315; Fax: +551636021504; E-mail: giovanidesanti@usp.br