Heart rate variability study in adult Nigerian subjects with sickle cell disease during vaso-occlusive crisis.

Context: Autonomic nervous system (ANS) dysfunction assessed by abnormalities in heart rate variability (HRV) is thought to play a role in the pathophysiology of sickle cell disease (SCD). There is suggestion that changes in ANS may occur in SCD subjects during episodes of vaso-occlusive crises (VOC).

Aims: The aim of this study was to evaluate the ANS by determining the HRV in patients with SCD during VOC.

Settings and Design: This was a cross-sectional observational study.

Materials and Methods: HRV studies were carried out in 76 participants with SCD during episodes of VOC. Eighty-two SCD participants in steady state served as controls.

Statistical Analysis Used: Comparison of two independent groups with Student's t-test and Mann-Whitney's test, and multiple linear regressions were also carried out.

Results: Participants with SCD and VOC had significant reductions in the time-domain HRV parameters of standard deviation of RR intervals (45.8 [59.36] ms vs. 66.3 [129.2] ms, P = 0.0073) and root mean square of successive differences of RR intervals (48.3 [87.66] ms vs. 74.2 [174.5] ms, P = 0.0015). The frequency-domain HRV indices of low frequency (145.8 [81.62] ms2 vs. 157.5 [68.9] ms2 , P = 0.1442) and high frequency (145.0 [118.40] ms2 vs. 146.3 [90.3] ms2 , P = 0.3683) were similar between the two groups. Age and the heart rate were the major independent relations of the HRV parameters.

Conclusions: Time-domain HRV parameters were impaired during crises in participants with SCD. This finding suggests further impairment of ANS activity in SCD patients during crises. Further studies are needed to clarify the prognostic implication of these findings.