Patterns of heart rate variability and cardiac autonomic modulations in controlled and uncontrolled asthmatic patients.

Background: Previous heart rate variability (HRV) studies in asthmatic subjects (AS) demonstrate predominance of parasympathetic drive concomitant with low HRV, which is against the general belief that enhanced parasympathetic modulation improves HRV. The aim of this study was to compare patterns of HRV and cardiac autonomic modulations of AS to healthy control subjects (HS).

Methods: Eighty AS and forty HS were enrolled in the study. Asthma control test and spirometry were used to discriminate uncontrolled (UA) from controlled (CA) asthmatic patients. Natural logarithmic (Ln) scale of total power (TP), very low frequency (VLF), low frequency (LF) and high frequency (HF) were used to evaluate HRV. Normalized low frequency (LF Norm) and high frequency (HF Norm) were used to determine sympathetic and parasympathetic autonomic modulations respectively.

Results: CA patients achieved significantly higher LnTP, LnLF, LnHF and HF Norm but lower LF Norm and LnLF/HF compared with UA patients (p < 0.05). Although CA patients showed increased HRV and augmented vagal modulation compared with HS, these findings were no longer significant following adjustment for mean heart rates and anti-asthma treatment. All measured HRV parameters were not significantly different in UA patients compared with the HS (p > 0.05).

Conclusions: CA is associated with enhanced parasympathetic modulations and higher HRV compared with UA. However, neither CA nor UA patients had different autonomic modulations and/or HRV compared with HS.