Abstract: Objective To investigate the relationship among circadian blood pressure rhythm, autonomic nervous system and
myocardial energy expenditure (MEE) level in patients with primary hypertension. Methods A total of 102 hypertensive and
45 normotensive subjects were recruited. According to blood pressure reduction rate at night, the hypertensive patients were
divided into non-dipper group (NDH group, n=54) with a reduction rate of <10% and dipper group (DH group, n=48) with a
reduction rate of ≥10%. The circadian blood pressure rhythm and heart rate variability were measured with ambulatory blood
pressure monitoring and 24-hour electrocardiograph monitoring, respectively, and MEE was measured by Doppler
echocardiography to analyze their correlations. Results SDNN, SDANN, SDNNindex, RMSSD, PNN50, and HF were
significantly lower in the hypertensive patients than in the control group (P<0.05); these parameters, except for PNN50, were
all significantly lower in NDH group than in DH group (P<0.05). The hypertensive patients had significantly higher MEE than
the control group (P<0.05), and MEE was significantly higher in NDH group than in DH group (P<0.05). Bivariate correlation
analysis showed significant correlations of MEE with SDANN in the hypertensive patients (P<0.01). Conclusion Patients with
primary hypertension, especially those in NDH group, have impaired autonomic nervous system function. The hypertensive
patients in NDH group show a more prominent increase in MEE in relation to sympathetic activation, suggesting the
importance of restoring circadian blood pressure rhythm in the treatment of hypertension.