IJCS | Volume 33, Nº4, July and August 2020

of vagus influence on the heart; LF (Low Frequency): associated with baroreceptor reflex with values between 0.04 and 0.15Hz, resulting from the joint action of the parasympathetic and sympathetic components on the heart, with predominance of sympathetic; LF/HF ratio is calculated and provide sympathetic / parasympathetic balance. The limitation of implementation this technique includes the presence of all no sinus rhythm, heart transplant, pacemaker activity and the presence of atrioventricular block. The measurement of HRV is extremely important for clinical understanding of physiological variables, since the increase in HRV indicates good physiological adaptation, while the reduction has been pointed out as a predictor of diseases or the occurrence of adverse events in patients with previous diseases. Numerous conditions have been described as responsible for measurable autonomic changes through HRV, such as: several heart diseases, nervous anorexia, epilepsy, asthma, anxiety disorders, obesity, hypertension and diabetes mellitus. Diabetes mellitus (DM) is a global health epidemic thought tobe affecting415millionpeopleworldwide,with a further 318 million suffering with glucose intolerance and at increased risk of developing the disease. Type II DM is a multifactorial polygenic inheritance form of diabetes, comprising about 90% all DM cases. About 75% may manifest sustained elevated blood glucose levels as early as in the fifth decade of life. Cardiac autonomic neuropathy (CAN) is a common underdiagnosed complication of DM. 7 Interestingly, subtle autonomic neurologic deficits have also been documented earlier in the course of diabetes and during the prediabetic period in subjects with impaired glucose tolerance in comparisonwith healthy individuals. The impact of CAN on patients with DM can be devastating, and it has been shown that impaired autonomic system can be associated with increased mortality, cardiovascular disease (CVD), chronic kidney disease (CKD), and morbidity in DM. CAN has several risk factors that are common to other diabetes-related vascular complications, such as: glycemic control, diabetes duration and CVD risk factors. Besides that, several genes have been linked to the development and progression of diabetic polyneuropathy and CAN, among which are TCF9L2, APOE, and ACE. 8 CAN, usually, only becomes symptomatic in the later stages of the disease and the vagus nerve is usually the first nerve to be affected, resulting in symptoms of sympathetic predominance. Subclinical CAN is initially limited to baroreceptor abnormalities and reduction in HRV, but as the disease progresses, cardiac involvement becomes more evident and symptomatic with resting tachycardia, reduced exercise tolerance, orthostatic hypotension, QT prolongation, silent ischemia, cardiomyopathy and CKD. 6 Early determination of CAN is vital to the success of therapeutic input, as it has been suggested that cardiovascular denervation may be reversible if diagnosed soon after onset, through a combination of nonpharmacological and pharmacological approaches, including lifestyle modification, intensive glycemic control, and treating underlying risk factors, such as hyperlipidemia and hypertension. 9 Dias-Filho et al. 10 , conducted a Brazilian multicenter study to evaluate cardiac autonomic modulation of adolescents with a family history of diabetic parents. They selected 69 teenagers from state public schools, aged 11 to 18 years, 23 with family history of diabetes. The authors managed to investigate nonmetabolic traits of early putative phenotypic expression of diabetes, specifically on the autonomic modulation of the heart. They have found that teenagers with parental history of diabetes, as compared to those with no such familial history, showed slight but significant overall reduction in heart rate variability, with a particular effect on the vagal limb of heart rate modulation. The study protocol consisted of the analysis of heart rate variability, blood pressure, anthropometric measurements, and body composition. They also used questionnaires to evaluate level of physical activity, sexual maturation, and sleep quality and all variables were paired with no significant difference between the 2 groups. When the group of individuals with a family history of diabetes was comparedwith the control group, statistically significant differences were observed in SDNN (43.9 ± 2.2 vs. 53.5 ± 2.6 ms), RMSSD (41.9 ± 3.3 vs. 52.4 ± 3.2 ms), SD1 (29.7 ± 2.3 vs. 37.1 ± 2.3 ms), SD2 (54.1 ± 2.6 vs. 66.66 ± 3.5 ms), and LF (496.0 ± 49.5 vs. 728 ± 71.6 ms²) and HF (1050.0 ± 120.4 vs. 737.4 ± 98.5 ms²). They concluded that global autonomic modulation is decreased in adolescents with a family history of diabetes. These important findings suggest an early decrease in vagal tone in adolescents with diabetic parents, suggesting that the sympathetic / vagal imbalance in this population could be an earlier mark of disease and might be considered to optimize non-pharmacological measures that would prevent the development of diabetes in the future. 369 Nunes & Benchimol-Barbosa Autonomic modulation in hereditary diseases Int J Cardiovasc Sci. 2020; 33(4):368-370 Editorial