Analysis of Conduction Intervals in Normal Electrophysiological Studies: Establishment of Reference Values the Brazilian Population

Abstract Background In the investigation of cardiac rhythm disorders, a normal electrophysiological (EPS) study is associated with a favorable prognosis. One of the normality criteria is established by conduction intervals within expected range. Objective To establish reference values in EPS for the intracavitary conduction intervals (PA, AH and HV) in a Brazilian population. Methods A retrospective cohort study of the first 1,500 patients submitted to EPS ablation was performed at Instituto de Cardiologia do Rio Grande do Sul, Brazil. The EPS was considered normal if the test was performed for diagnostic purpose; absence of induced arrhythmias; and conduction intervals within the expected range. The REDCap software was used for data collection and management, and the SPSS Statistics 22.0 used for data analysis. Continuous variables were compared with Student's t-test for independent samples and categorical variables with the chi-square test (X 2 ). Values of p ≤ 0.05 were considered significant. Results A total of 124 (8.3%) with EPS considered normal were included; mean age was 52 ± 21 years, and 63 were male. The mean values in milliseconds of PA, AH and HV were 23 ± 9, 88 ± 25 and 44 ± 7, respectively. The PA, AH, and HV percentile ranges were 13 - 25, 81-107 and 40 - 52, respectively. When the patients were divided into three age groups (1 to 18 years, 19 to 64 years and 65 or more), we observed that the group of older patients had significantly higher values of PA, AH and HV compared with younger patients. Conclusion This study showed that intracavitary conduction intervals in a sample of the Brazilian population were similar to previously published studies. Elderly patients tend to have higher values of intracavitary conduction intervals in EPS. Future studies including broader age ranges could enable the acquisition of more reliable and reproducible reference values. (Int J Cardiovasc Sci. 2020; [online].ahead print, PP.0-0)

Sex-related differences in the effects of high-fat diets on DHEA-treated rats.

Several studies have investigated the beneficial effects of dehydroepiandrosterone (DHEA) on lipid and glucose metabolism. However, many of these studies are inconclusive about the effects of DHEA administration on metabolic disorders, and there appear to be sex-related differences in the effects of DHEA treatment. Few animal studies have addressed the effects of DHEA on diet-induced metabolic disorders. The present study sought to ascertain whether sex differences exist in the effects of a high-fat diet (HFD) on weight gain, adiposity, and biochemical and hormonal parameters in DHEA-treated rats. Rats were fed a HFD for 4 weeks and simultaneously received treatment with DHEA (10 mg/kg by subcutaneous injection) once weekly. Body weight, retroperitoneal fat depot weight, serum glucose, insulin, and leptin levels, and hepatic lipids were measured. HFD exposure increased the adiposity index in both sexes, the hepatic triglyceride content in both sexes, and the hepatic total cholesterol level in males. Moreover, the HFD induced an increase in blood glucose levels in both sexes, and hyperinsulinemia in males. In this experimental model, DHEA treatment reduced hepatic triglyceride levels only in females, regardless of HFD exposure. Exposure to a HFD, even if it does not cause obesity, may enhance risk factors for metabolic disorders, and males are more sensitive to this effect. DHEA treatment can help prevent metabolic derangements, but its effect varies with sex.

Asymmetric effects of low doses of progesterone on GABA(A) receptor α4 subunit protein expression in the olfactory bulb of female rats.

The aim of this study was to evaluate the effect of progesterone on the protein expression of α4 subunit of GABA(A) receptor, serotonin transporter (SERT), Akt, Erk, and caspase-3 in the olfactory bulb (OB) of female rats exposed to the forced swimming test (FST). Female rats were injected daily with progesterone (0.4 mg/kg body mass) or vehicle during 2 complete oestrous cycles and exposed to the FST, and the protein expression of GABA(A) receptor α4 subunit, SERT, Akt, Erk, and caspase-3 in the OB were evaluated. Progesterone increased the expression of the α4 subunit in the right OB and decreased its expression in the left OB, although it did not change the expression of other proteins. In summary, our findings indicate that progesterone has an asymmetric modulatory effect on the expression of GABA(A) receptor α4 subunit in the OB. This effect could be related to the antidepressant-like effect of progesterone in female rats.

Effect of low doses of progesterone in the expression of the GABA(A) receptor α4 subunit and procaspase-3 in the hypothalamus of female rats.

Progesterone is a steroid which regulates neural function, thereby modulating neurotransmission, cell survival, and behavior. Previous studies by our group have shown that chronic administration of low doses of progesterone in diestrus II female rats has an antidepressant-like effect in the forced swimming test (FST). Depression is associated with the several neurotransmitters systems, including GABA and serotonin, and with neurodegeneration and cell death in some brain circuits. The aim of this study was to verify the effect of progesterone on the protein expression of the GABA(A) receptor α4 subunit, serotonin transporter (SERT), Akt, extracellular signal-regulated kinase (Erk), and caspase-3 in the hypothalamus of diestrus II female rats exposed to the FST. Female rats were treated with a daily injection of progesterone (0.4 mg/kg) or vehicle, during two complete oestrous cycles. On the day of the experiment, the animals were euthanized 30 min after the FST, the hypothalamus was dissected and protein expression of GABA(A) receptor α4 subunit, SERT, Akt, Erk, and caspase-3 was evaluated. Progesterone increased the expression of GABA(A) receptor α4 subunit but did not change the expression of SERT. Progesterone decreased the expression of procaspase-3 in the hypothalamus without changing the activation of Akt and Erk in this structure. In summary, our results suggest that progesterone acts to increase the expression of the GABA(A) receptor α4 subunit and decrease the expression of procaspase-3 in the hypothalamus of female rats. Such effects may be involved in the antidepressant-like effect of progesterone in female rats exposed to the FST.