The role of the autonomic nervous system in the patterns of heart rate fragmentation

Heart rate fragmentation is impaired in type 2 diabetes mellitus patients

AIMS

To evaluate the heart rate fragmentation (HRF) of type 2 diabetes mellitus (T2DM) patients and its relationship with heart rate variability (HRV) indices.

METHODS

One hundred sixty-four men, aged 47-57 years were retrospectively analyzed from a database. Participants were T2DM (n = 82) and apparently healthy (n = 82). R-R interval time series recorded by electrocardiogram were collected at the supine position for 10 to 15 min. From HRF, the percentage of inflection points (PIP), percentage of words with zero, one, two, or three inflections points (W₀, W₁, W₂, W₃), and percentage with only type hard, soft, or mixed inflections points type (W^H, W^S, W^M) were quantified.

RESULTS

T2DM presented higher PIP, W^S, W^M and W₃, while W^H and W₁ was lower compared with healthy (p < 0.05). Moreover, a positive moderate correlation was found between W^H and root mean square of the successive R-R differences (RMSSD) and high frequency (HF) indices. In contrast, a negative moderate correlation was found between W^S and W^M with RMSSD and HF indices.

CONCLUSIONS

T2DM have increased fragmentation patterns, and words grouped by inflection type are more closely related to HRV. The HRF approach might be useful to assess heart rate dynamic abnormalities in males with type 2 diabetes.

Heart rate variability as a biomarker in patients with Chronic Chagas Cardiomyopathy with or without concomitant digestive involvement and its relationship with the Rassi score

Background

Dysautonomia plays an ancillary role in the pathogenesis of Chronic Chagas Cardiomyopathy (CCC), but is the key factor causing digestive organic involvement. We investigated the ability of heart rate variability (HRV) for death risk stratification in CCC and compared alterations of HRV in patients with isolated CCC and in those with the mixed form (CCC + digestive involvement). Thirty-one patients with CCC were classified into three risk groups (low, intermediate and high) according to their Rassi score. A single-lead ECG was recorded for a period of 10–20 min, RR series were generated and 31 HRV indices were calculated. The HRV was compared among the three risk groups and regarding the associated digestive involvement. Four machine learning models were created to predict the risk class of patients.

Results

Phase entropy is decreased and the percentage of inflection points is increased in patients from the high-, compared to the low-risk group. Fourteen patients had the mixed form, showing decreased triangular interpolation of the RR histogram and absolute power at the low-frequency band. The best predictive risk model was obtained by the support vector machine algorithm (overall F1-score of 0.61).

Conclusions

The mixed form of Chagas' disease showed a decrease in the slow HRV components. The worst prognosis in CCC is associated with increased heart rate fragmentation. The combination of HRV indices enhanced the accuracy of risk stratification. In patients with the mixed form of Chagas disease, a higher degree of sympathetic autonomic denervation may be associated with parasympathetic impairment.

Heart rate fragmentation, a novel approach in heart rate variability analysis, is altered in rats 4 and 12 weeks after myocardial infarction

An approach recently proposed to assess ultra-rapid patterns of heart rate variability, namely heart rate fragmentation (HRF), is increased in aging and coronary disease. We aimed to evaluate and to correlate HRF with cardiac functional parameters in a rat model of myocardial infarction (MI). Wistar rats were submitted to MI (n = 18) or sham operation (n = 20), and after 4 or 12 weeks, their arterial pressure was recorded. Subsequently, cardiac function was evaluated by echocardiography. From pulse interval series, HRF patterns with zero, one, two, or three inflection points were estimated, as well as the total percentage of inflection points (PIP). Cardiac function was reduced in MI rats. Ejection fraction was smaller 4 (28 ± 3 vs 68 ± 2%, p < 0.0001) and 12 weeks after MI (38 ± 3 vs 70 ± 3%, p < 0.0001). Fractional shortening was also smaller 4 (13 ± 2 vs 41 ± 2%, p < 0.0001) and 12 weeks after MI (20 ± 2 vs 41 ± 3%, p < 0.0001). PIP was increased in MI rats 4 (74 ± 2 vs 69 ± 1%, p = 0.03) and 12 weeks after surgery (70 ± 2 vs 63 ± 1%, p = 0.02). We found a significant negative correlation between cardiac functional parameters and HRF at both 4 and 12 weeks after MI. These findings reveal that MI increases HRF, reinforcing the importance of this approach to explore pathophysiological conditions. Evaluation of heart rate fragmentation (HRF) in a rat model of myocardial infarction (MI). Wistar rats were submitted to MI (n = 18) or sham operation (n = 20), and after 4 or 12 weeks, their arterial pressure was recorded. Cardiac function was evaluated by echocardiography. From pulse interval series, HRF patterns with zero (W0), one (W1), two (W3), or three (W3) inflection points were estimated, as well as the total percentage of inflection points (PIP). Cardiac function was reduced, while PIP was increased in all MI rats. Fluent patterns (W0 and W1) decreased in MI rats after 12 weeks. Altogether, the findings reveal that MI increases HRF, reinforcing the potential of this approach to explore pathophysiological conditions.