impaired heart rate variability in patients with mitral annular calcification an observational study objective the aim of the present study was to study time indices of heart rate variability hrv in patients with mitral annular calcification macmethods a crosssectional observational study was performed fifty patients with echocardiographic evidence of mac and 50 age and gendermatched control subjects without echocardiographic evidence of mac were included all the study participants underwent 2dimensional echocardiographic examinations and 24hour holter monitoring for hrv analysis studentt mannwhitney u and chisquare tests were used for statistical analysisresults hypertension and coronary artery disease were more common in the mac group than in the control group all hrv parameters including mean rr interval sdnn sdann sdnn index pnn50 and rmssd were reduced in the mac group when compared with the control group p005 for all in hypertensive subgroup all hrv parameters except mean rr interval were diminished in patients with mac when compared with those without mac p005 for all in nonhypertensive subgroup all hrv parameters were also diminished in patients with mac when compared with those without mac in the subgroup of patients with coronary artery disease patients had lower hrv parameters except mean rr interval pnn50 and rmssd in comparison to those without mac p005 for all in the subgroup of patients without coronary artery disease all hrv parameters were depressed in patients with mac in comparison to those without mac p005 for allconclusion our findings indicate that mac was associated with reduced heart rate variability which possibly reflects decreased parasympathetic tone with a predominant activity of the sympathetic tone