Validity of the cardiofrequency meter for the assessment of cardiac autonomic control in individuals with spinal cord injury

Abstract

Introduction: In spinal cord injuries, changes in the sympathetic nervous system can occur, which modify the cardiac autonomic control and, consequently, there is an increased risk of mortality due to cardiovascular issues. Cardiac autonomic control can be assessed by heart rate variability (HRV), with the electrocardiogram being the gold standard method. Its use, however, is limited to laboratory environments, requiring the search for tools that can be equally useful for this purpose and that allow a practical application in daily life. Objective: To investigate the validity of the cardiofrequency meter in the assessment of cardiac autonomic control in individuals with spinal cord injury. Methods: Cross-sectional study with 28 individuals, divided into three groups: 10 with paraplegia, 09 with quadriplegia, and 09 without spinal cord injury. The electrocardiogram and cardiofrequency meter signals were measured at rest, in a sitting position, for 10 minutes. The window of the last 5 minutes was used for counting RR intervals and
subsequent calculation of HRV indices (linear methods in the domains of time and frequency). Comparisons were made between the study subgroups (Anova of a factor with Tukey's post hoc) and the verification of the validity of the measurements generated from the cardiofrequency meter were verified by the intraclass correlation coefficient (ICC2,1) and by the graphical approach of Altman and Bland. The level of statistical significance was 5%. Results: In the time domain, both in the group with quadriplegia and in the group with paraplegia, excellent reliability was observed (ICC2.1> 0.75; p <0.01) in all HRV indices considered. In the frequency domain, in the group with paraplegia, all indexes also presented reliability classified as excellent. In the quadriplegia group, the reliability of the VLF (p = 0,69; Loa = -1099,8; 712,8) and LF/HF (p = 0,68; Loa = -4,4; 4,3) indices were classified as unacceptable (ICC2.1
<0.40) and the others acceptable or excellent. Conclusion: The cardiofrequency meter proved to be a valid instrument for the assessment of HRV in individuals with spinal cord injury and sequelae of paraplegia and quadriplegia.