Heart rate variability and heart rate turbulence in mild to moderate aortic stenosis

Background: Mild to moderate aortic stenosis (AS) is believed to have a good prognosis but in a recent study, mortality has been found to be significantly higher than normal controls. Heart rate (HR) variability and HR turbulence both of which reflect the autonomic tonus have prognostic value in several disease states. In this study, our aim was to study these parameters in mild to moderate AS and find whether any relationship is present between these parameters and echocardiographic findings. Methods: Asymptomatic 43 patients with mild to moderate aortic stenosis were included in our study. Echocardiographic parameters and 24-hour Holter ECG recordings for the detection of HR variability and HR turbulence indices were obtained and these indices were compared to 50 controls selected from the patients who had similar clinical characteristics with the AS patients. Correlation between the echocardiographic findings of AS patients and HR variability and HR turbulence indices was also studied. Results: All the time domain HR variability parameters except mean RR interval, RMSSD and pNN50 were significantly lower in the AS group. LFnu and LF/HF ratio were higher and Hfnu was lower indicating an increased sympathetic tonus in AS group. Among HR turbulence parameters, turbulence onset was disturbed with statistical significance. Echocardiographic findings indicating diastolic functions especially myocardial performance index and Em/Am ratio had significant correlations with the HR variability and HR turbulence parameters in AS patients. Conclusions: Sympathetic activation indicated by HR variability and HR turbulence parameters is demonstrated in patients with mild to moderate AS. This activation may lead to arrhythmic complications and it is found to be related to the echocardiographic parameters showing diastolic functions.