Effect of systemic arterial hypertension on intrinsic cardiac variability and the modulating role of aerobic physical training.

• Grant number: 22/08973-7
• Support Opportunities: Scholarships in Brazil - Master
• Start date: November 01, 2022
• End date: February 28, 2025
• Field of knowledge: Health Sciences - Physiotherapy and Occupational Therapy
• Principal Investigator: Hugo Celso Dutra de Souza
• Grantee: Kelly Yoshida de Melo
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

Introduction: Heart rate variability (HRV) is determined by physiological mechanisms with different frequencies of occurrence. Among them, the autonomic nervous system stands out through its sympathetic and parasympathetic components. However, the intrinsic heart rate also has variability (iHRV) that may reflect cardiac adaptations induced by different physiological and pathological conditions, such as aerobic physical exercise and systemic arterial hypertension (SAH), respectively, and influencing the modulation of the HRV. In this case, we suspect that cardiovascular diseases, such as SAH, but also aerobic physical training, can modify the iHRV. Objectives: To investigate whether there are differences in the iHRV between normotensive and spontaneously hypertensive rats (SHR; spontaneously hypertensive rats), and the relationship with the autonomic modulation of HRV. Additionally, we will investigate whether aerobic physical training influences the iHRV and whether there is a relationship with pacemaker heart rate. Methods: Thirty-six 18-week-old rats will be studied, divided into two groups; a group of normotensive rats (n=18) and a group of hypertensive rats (n=18). Each group will be subdivided into 2 smaller groups; a group of untrained rats; and a group of rats trained for 12 weeks by means of swimming in daily sessions of 45 min. The analysis of HRV will be performed by recording the intervals of heartbeats with the animals awake, before and after the double autonomic heart block with atropine and propranolol. In turn, the iHRV analysis will be performed using pulse interval recordings obtained with the Langendorff technique in an isolated heart. The variability analysis methodology will involve linear and non-linear methods.