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Mazzuca Reimberg M.1, Silva Meneses A.1, Pacchi Rodrigues Selmam J.1, Viana A.1, Nascimento M.C.1, Cunha Silva J.1, Dal Corso S.1, de Angelis K.1, de Cordoba Lanza F.1
1Nove de Julho University, Sao Paulo, Brazil
Background: Asthma is a chronic and inflammatory disease prevalent in childhood, and its chronicity may lead to an imbalance of the autonomic system and decreased functional capacity. Heart rate variability (HRV) has been used to identify cardiac prognosis because it measures the cardiac autonomic system. There is a lack of evidence concerning HRV in asthmatic patients, including their functional capacity.
Purpose: The aim of this study was to compare HRV and functional capacity in asthmatic volunteers and matched control pairs.
Methods: A cross-sectional study of 20 asthmatic patients [the asthmatic group (AG)] and 15 age-matched healthy volunteers [the control group (CG)] were evaluated. HRV was recorded during 20 minutes in a sitting position with a heart rate monitor. The low frequency (LF), the high frequency (HF), the relationship between them (LF/HF), and the root mean square of successive differences (RMSSD) were measured. The functional capacity was evaluated by the Incremental Shuttle Walk Test (ISWT) down a 10-m corridor. The walk speed was dictated by an audio signal and the initial speed was 1.74 km/h, which was increased each minute until the maximum possible velocity (10.3 km/h). The ISWT outcome measurement was distance walked (DW).
Results: Preliminary data from the CG and the AG had a mean age of 12 ± 3 years for both groups. The AG had mild to moderate treated asthma (Global Initiative for Asthma [GINA] 3 [2-4]). Lung function, measured by FEV1/FVC, was 88.5 ± 8.7 for the CG and 81.7 ± 10.4 for the AG (P=0.19). The RMSSD was lower in the CG (59.7 ± 44.1 ms) than in the AG (93.6 ± 53.7 ms) (P=0.05). There were no differences between groups for LF (CG, 60.7 ± 16.1 ms vs AG, 58.8 ± 15.3 ms; P=0.72), HF (CG, 36.7 ± 14.0 ms vs AG, 41.1 ± 15.3 ms; P=0.39), and LF/HF (CG, 3.5 ± 3.3 ms vs AG, 2.8 ± 2.4 ms; P=0.48). There was a significant inverse correlation between functional capacity (ISWT) and RMSSD: r=-0.56; P=0.009. There was no statistically significant difference for DW at ISWT between CG (1001.0 ± 345.7 m) and AG (820.7 ± 226.2 m) (P=0.09), but this difference is clinically relevant.
Conclusion(s): This preliminary data shows an increase in parasympathetic modulation in asthma patients compared with the CG, and the higher the RMSSD, the worst the functional capacity.
Implications: It is known that autonomic variability is related to cardiac disorders. Asthma may cause an imbalance in the autonomic system, which may be correlated with worse functional capacity.
Funding acknowledgements: Sao Paulo Research Foundation (FAPESP), grant: 2014/12040-0.
Topic: Paediatrics
Ethics approval: 1.440.862/15
All authors, affiliations and abstracts have been published as submitted.
