Nonlinear dynamics of cardiovascular autonomic regulation during the sustained weight test in patients with type 2 diabetes mellitus
Description
Introduction: The analysis of non-linear dynamics of cardiovascular autonomic regulation based on heart rate variability has not been previously studied in patients with type 2 diabetes mellitus using the sustained weight test as an inducer of cardiovascular hyperreactivity. Objective: To determine the variations in the non-linear dynamics of cardiovascular autonomic regulation during the sustained weight test in patients with type 2 diabetes mellitus. Method: A quasi-experimental, before-after study with a control group, from June-August 2018, at the No. 1 School of Medicine in Santiago de Cuba. We worked with 15 patients suffering from type 2 diabetes mellitus without other associated disease and 15 healthy subjects, to whom the sustained weight test was applied. Results: In patients with diabetes mellitus, when performing the sustained weight test, there was a significant increase in the hemodynamic parameters TAS, TAD, TAM and FC. In the sample entropy, a parameter that evaluates the adaptability of the systems, there is a significant decrease (2.28 ± 0.33 vs. 1.83 ± 0.47 ms; p = 0.003143). The value of the C statistic of the sample entropy at baseline was established at 0.973, being the variable with the highest predictive capacity. Conclusions: In patients with type 2 diabetes mellitus during the sustained weight test, there was a decrease in the complexity of cardiovascular autonomic regulation, the basal sample entropy was the indicator of greater efficacy in the identification of cardiovascular autonomic alterations.
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The study involved a study group comprising 15 patients diagnosed with type 2 diabetes (6 men and 9 women) and a control group consisting of 15 healthy subjects . An interview, physical examination, and control electrocardiogram were conducted to rule out any cardiac rhythm abnormalities. At the beginning of the electrocardiogram recording session in the morning (8:30-12:00 a.m.), subjects were seated in a comfortable chair in a room with a controlled temperature between 24 and 27 °C, and dim lighting. Under these conditions, they were allowed to rest for 10-15 minutes to better adapt to the local conditions. Hemodynamic records, including blood pressure, and autonomic electrophysiological records through electrocardiogram were then taken; electrodes were placed after cleaning the skin with alcohol, and measurements were performed for 5 minutes. Next, in a seated position, isometric exercise was performed, consisting of holding a 500-gram weight with the left upper limb extended at a right angle to the body for 2 minutes. At 1 minute and 50 seconds into the exercise, blood pressure was measured in the right upper limb. The left upper limb was lowered at 2 minutes, and electrocardiographic measurement continued until completing 5 minutes. Heart rate variability was analyzed during both rest and isometric exercise. Electrocardiographic signal processing involved the discrimination of R-waves and the calculation of RR intervals. Subsequent processing of digitized records included visual inspection for quality assessment, artifact detection, and editing to remove identified artifacts. Discrimination of R-wave peaks in the digitized signal and calculation of RR intervals were performed using the Sabarimalai-Manikandan and Soman17 method. The set of RR intervals obtained was stored and constituted the data series for all subsequent heart rate variability analysis. Preprocessing of RR intervals and analysis of heart rate variability were conducted using the HRVAS® program (https://sourceforge.net/projects/hrvas/) by Ramshur18, allowing preprocessing of RR interval series and calculation of nonlinear indicators. A 20% threshold filter of the previous interval was used to detect ectopic beats in the RR interval series. Ectopic intervals were replaced using cubic polynomial interpolation. Data were processed using the SPSS 21.0 statistical package, and results are expressed as mean values and standard deviations for variables subjected to non-parametric analysis with the Mann-Whitney U test for independent samples, comparing healthy individuals with diabetics (between-group comparison). Additionally, a non-parametric analysis was performed using the Wilcoxon signed-rank test for related samples (within-group comparison), with a significance level of p < 0.05. The discriminatory capacity of variables was assessed using the C statistic (area under the ROC curve [receiver operating characteristic]).