Linear and nonlinear analysis of heart rate variability in healthy subjects and after acute myocardial infarction in patients

The objectives of this study were to evaluate and compare the use of linear and nonlinear methods for analysis of heart rate variability (HRV) in healthy subjects and in patients after acute myocardial infarction (AMI). Heart rate (HR) was recorded for 15 min in the supine position in 10 patients with AMI taking β-blockers (aged 57 ± 9 years) and in 11 healthy subjects (aged 53 ± 4 years). HRV was analyzed in the time domain (RMSSD and RMSM), the frequency domain using low- and high-frequency bands in normalized units (nu; LFnu and HFnu) and the LF/HF ratio and approximate entropy (ApEn) were determined. There was a correlation (P < 0.05) of RMSSD, RMSM, LFnu, HFnu, and the LF/HF ratio index with the ApEn of the AMI group on the 2nd (r = 0.87, 0.65, 0.72, 0.72, and 0.64) and 7th day (r = 0.88, 0.70, 0.69, 0.69, and 0.87) and of the healthy group (r = 0.63, 0.71, 0.63, 0.63, and 0.74), respectively. The median HRV indexes of the AMI group on the 2nd and 7th day differed from the healthy group (P < 0.05): RMSSD = 10.37, 19.95, 24.81; RMSM = 23.47, 31.96, 43.79; LFnu = 0.79, 0.79, 0.62; HFnu = 0.20, 0.20, 0.37; LF/HF ratio = 3.87, 3.94, 1.65; ApEn = 1.01, 1.24, 1.31, respectively. There was agreement between the methods, suggesting that these have the same power to evaluate autonomic modulation of HR in both AMI patients and healthy subjects. AMI contributed to a reduction in cardiac signal irregularity, higher sympathetic modulation and lower vagal modulation.

Linear and nonlinear analysis of heart rate variability in healthy subjects and after acute myocardial infarction in patients.

The objectives of this study were to evaluate and compare the use of linear and nonlinear methods for analysis of heart rate variability (HRV) in healthy subjects and in patients after acute myocardial infarction (AMI). Heart rate (HR) was recorded for 15 min in the supine position in 10 patients with AMI taking ß-blockers (aged 57 ± 9 years) and in 11 healthy subjects (aged 53 ± 4 years). HRV was analyzed in the time domain (RMSSD and RMSM), the frequency domain using low- and high-frequency bands in normalized units (nu; LFnu and HFnu) and the LF/HF ratio and approximate entropy (ApEn) were determined. There was a correlation (P < 0.05) of RMSSD, RMSM, LFnu, HFnu, and the LF/HF ratio index with the ApEn of the AMI group on the 2nd (r = 0.87, 0.65, 0.72, 0.72, and 0.64) and 7th day (r = 0.88, 0.70, 0.69, 0.69, and 0.87) and of the healthy group (r = 0.63, 0.71, 0.63, 0.63, and 0.74), respectively. The median HRV indexes of the AMI group on the 2nd and 7th day differed from the healthy group (P < 0.05): RMSSD = 10.37, 19.95, 24.81; RMSM = 23.47, 31.96, 43.79; LFnu = 0.79, 0.79, 0.62; HFnu = 0.20, 0.20, 0.37; LF/HF ratio = 3.87, 3.94, 1.65; ApEn = 1.01, 1.24, 1.31, respectively. There was agreement between the methods, suggesting that these have the same power to evaluate autonomic modulation of HR in both AMI patients and healthy subjects. AMI contributed to a reduction in cardiac signal irregularity, higher sympathetic modulation and lower vagal modulation.

Cryopreservation of swine ovarian tissue: effect of different cryoprotectants on the structural preservation of preantral follicle oocytes.

The present study aimed to test different cryoprotectants on cryopreservation of pig ovarian tissue. Pig ovaries (n=3) were collected at a local slaughterhouse. From each ovary, ten cortex samples were taken. One was immediately fixed (control) and another placed in short-term tissue incubation (STTI control). The other 8 samples were cryopreserved, in pairs, using 4 different cryoprotectants: dimethyl sulphoxide (Me2SO - 1.5M), ethylene glycol (EG - 1.5M), propanediol (PROH - 1.5M) and glycerol (GLY - 10%), all with 0.4% sucrose. Samples were slow cooled and stored in liquid nitrogen for 7 days. After thawing and cryoprotectant removal, one sample from each treatment was immediately fixed and the other was placed in short-term tissue incubation (STTI) for 2h and then fixed. Samples were processed for histology and transmission electron microscopy. The percentages of morphologically normal follicles (MNF) in cryopreserved tissue using Me2SO (67.0+/-4.9), EG (81.8+/-1.4) and PROH (55.9+/-9.9) were significantly lower (P<0.05) than observed in fresh control tissue (97.7+/-1.2). When ovarian tissue was cryopreserved with GLY, no morphologically normal follicles could be found (0%). After STTI, PROH showed a significantly lower percentage of MNF when compared with all other treatments and the control. After ultrastructural analysis, follicles cryopreserved with Me2SO and EG showed some small alterations, but no signs of advanced degeneration. Overall, these were similar to follicles from the control group. In conclusion, it is possible to cryopreserve preantral follicles from pig ovarian tissue using Me2SO or EG.