Audrey Borghi-Silva

Is heart rate variability a feasible method to determine anaerobic threshold in progressive resistance exercise in coronary artery disease

BACKGROUND Recent studies have shown that the magnitude of the metabolic and autonomic responses during progressive resistance exercise (PRE) is associated with the determination of the anaerobic threshold (AT). AT is an important parameter to determine intensity in dynamic exercise. OBJECTIVES To investigate the metabolic and cardiac autonomic responses during dynamic resistance exercise in patients with Coronary Artery Disease (CAD). METHOD Twenty men (age = 63±7 years) with CAD [Left Ventricular Ejection Fraction (LVEF) = 60±10%] underwent a PRE protocol on a leg press until maximal exertion. The protocol began at 10% of One Repetition Maximum Test (1-RM), with subsequent increases of 10% until maximal exhaustion. Heart Rate Variability (HRV) indices from Poincaré plots (SD1, SD2, SD1/SD2) and time domain (rMSSD and RMSM), and blood lactate were determined at rest and during PRE. RESULTS Significant alterations in HRV and blood lactate were observed starting at 30% of 1-RM (p<0.05). Bland-Altman plots revealed a consistent agreement between blood lactate threshold (LT) and rMSSD threshold (rMSSDT) and between LT and SD1 threshold (SD1T). Relative values of 1-RM in all LT, rMSSDT and SD1T did not differ (29%±5 vs 28%±5 vs 29%±5 Kg, respectively). CONCLUSION HRV during PRE could be a feasible noninvasive method of determining AT in CAD patients to plan intensities during cardiac rehabilitation.ABSTRACT Background Recent studies have shown that the magnitude of the metabolic and autonomic responses during progressive resistance exercise (PRE) is associated with the determination of the anaerobic threshold (AT). AT is an important parameter to determine intensity in dynamic exercise. Objectives To investigate the metabolic and cardiac autonomic responses during dynamic resistance exercise in patients with Coronary Artery Disease (CAD). Method Twenty men (age = 63±7 years) with CAD [Left Ventricular Ejection Fraction (LVEF) = 60±10%] underwent a PRE protocol on a leg press until maximal exertion. The protocol began at 10% of One Repetition Maximum Test (1-RM), with subsequent increases of 10% until maximal exhaustion. Heart Rate Variability (HRV) indices from Poincaré plots (SD1, SD2, SD1/SD2) and time domain (rMSSD and RMSM), and blood lactate were determined at rest and during PRE. Results Significant alterations in HRV and blood lactate were observed starting at 30% of 1-RM (p<0.05). Bland-Altman plots revealed a consistent agreement between blood lactate threshold (LT) and rMSSD threshold (rMSSDT) and between LT and SD1 threshold (SD1T). Relative values of 1-RM in all LT, rMSSDT and SD1T did not differ (29%±5 vs 28%±5 vs 29%±5 Kg, respectively). Conclusion HRV during PRE could be a feasible noninvasive method of determining AT in CAD patients to plan intensities during cardiac rehabilitation.

Relationship between entropy and symbolic analysis indices of heart rate variability in patients with coronary artery disease with and without diabetes mellitus

The aim of this study was to evaluate the relationship between Shannon entropy (SE) and symbolic analysis (SA) of heart rate variability at rest in 3 groups: patients with coronary artery disease (CAD), CAD with diabetes mellitus (CAD-DM), and healthy individuals (H). We evaluated 44 men into the groups (CAD, n=16, CAD-DM, n=13 and H, n=15). The R-R intervals (R-Ri) were recorded at rest in the supine position for 15 minutes. SA analysis classified patterns of R-Ri according to the number of variations into stable and unstable patterns. Significant and negative correlation was found between SE and the percentage of stable patterns for CAD and CAD-DM. Positive correlation was found between SE and the percentage of unstable patterns in all the groups. We conclude that complexity of cardiovascular control had a positive relationship with the cardiac parasympathetic modulation in all groups and negative relationship with the sympathetic modulation in CAD and CAD-DM groups.

Short-term complexity of cardiovascular oscillations during orthostatic change in aging

Complexity of R-R intervals (RR) and systolic arterial pressure (SAP) variability were computed to detect the aging process influence over cardiovascular control in resting supine (REST) and standing position (STAND). One hundred healthy subjects were divided into five groups (n=20 for each), according to age: 21-30; 31-40; 41-50; 51-60; 61-70. The RR and SAP series were recorded for 15 minutes at REST and STAND. Short sequences of RR and SAP were analyzed by conditional entropy. At REST, RR complexity showed reduction with age in 61-70, and SAP complexity decreased, starting from 31-40. Changes in cardiovascular control complexity, induced by STAND, reveal the difficulty of elderly individuals in dealing with sympathetic stressors.

Baroreflex response to orthostatic challenge: Effect of aging

Aging causes changes in cardiovascular control. The aim of the study was to analyze the effects of age on baroreflex sensitivity of healthy individuals of different ages, through cross-spectral analysis. One hundred and ten individuals divided into 5 age groups were evaluated. Heart period (HP) and systolic blood pressure (SBP) were derived from ECG and blood pressure signals recorded simultaneously for 15 minutes in the supine and orthostatic position. The gain of the transfer function from SBP to HP was taken as an index of baroreflex sensitivity (BRSgain) and computed in low (LF) and high frequency (HF). In both positions and in both bands, BRSgain fell with age, thus suggesting a decrease magnitude of the HP response to SAP changes with age.