Key result
In healthy subjects, heart rate variability increases proportionally with the RR-interval, but this relationship is lost in chronic Chagas disease, particularly in the deceleration phase, indicating cardiac vagal incompetence.
Why the study?
Does phase rectification of RR-interval histogram analysis detect differences in cardiac autonomic modulation between patients with chronic Chagas disease and healthy controls?
Cross-Sectional (n=40)
No
Does phase rectification of RR-interval histogram analysis detect differences in cardiac autonomic modulation between patients with chronic Chagas disease and healthy controls?
Absolute Event Rate: -0.0003% vs 0.0008%
p-value: p=<0.05
Phase-rectified RR-interval histogram analysis demonstrates that patients with chronic Chagas disease lose the normal proportional increase in heart rate variability during the parasympathetic deceleration phase, indicating cardiac vagal incompetence.
Phase-rectified analysis may identify vagal incompetence in Chagas; leaves open its role in risk stratification.
BACKGROUND: In chronic Chagas disease (ChD), impairment of cardiac autonomic function bears prognostic implications. Phase‑rectification of RR-interval series isolates the sympathetic, acceleration phase (AC) and parasympathetic, deceleration phase (DC) influences on cardiac autonomic modulation. OBJECTIVE: This study investigated heart rate variability (HRV) as a function of RR-interval to assess autonomic function in healthy and ChD subjects. METHODS: Control (n = 20) and ChD (n = 20) groups were studied. All underwent 60-min head-up tilt table test under ECG recording. Histogram of RR-interval series was calculated, with 100 ms class, ranging from 600-1100 ms. In each class, mean RR-intervals (MNN) and root-mean-squared difference (RMSNN) of consecutive normal RR-intervals that suited a particular class were calculated. Average of all RMSNN values in each class was analyzed as function of MNN, in the whole series (RMSNNT), and in AC (RMSNNAC) and DC (RMSNNDC) phases. Slopes of linear regression lines were compared between groups using Student t-test. Correlation coefficients were tested before comparisons. RMSNN was log-transformed. (α < 0.05). RESULTS: Correlation coefficient was significant in all regressions (p < 0.05). In the control group, RMSNNT, RMSNNAC, and RMSNNDC significantly increased linearly with MNN (p < 0.05). In ChD, only RMSNNAC showed significant increase as a function of MNN, whereas RMSNNT and RMSNNDC did not. CONCLUSION: HRV increases in proportion with the RR-interval in healthy subjects. This behavior is lost in ChD, particularly in the DC phase, indicating cardiac vagal incompetence.
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Nasario‐Junior et al. (2015) conducted a cross-sectional in Chronic Chagas disease (n=40). Chronic Chagas disease vs. Healthy sedentary controls was evaluated on Linear correlation of root-mean-squared difference of consecutive normal RR-intervals in the deceleration phase (Ln RMSNNDC) with mean RR-intervals (MNN) (p=<0.05). In healthy subjects, heart rate variability increases proportionally with the RR-interval, but this relationship is lost in chronic Chagas disease, particularly in the deceleration phase, indicating cardiac vagal incompetence.
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