HEART RATE VARIABILITY IN DIPPERS AND IN NON-DIPPERS
Background: In normal cases nocturnal blood pressure falls between 10-20% compared daytime blood pressure (dipper pattern).The non-dipping pattern of ambulatory blood pressure (BP) is associated with secondary hypertension and target organ damage. Our aim was to investigate the difference of heart rate variability (HRV) between non-dippers and dippers.
Methods: Blood pressure (BP) variability we can estimate as a standard deviation of ambulatory BP monitoring obtained by every 15 to 20 minutes measurement. The ambulatory BP and HR were monitored every 20 minutes with a fully automatic device (validated device, ABPM-04 Meditech, Hungary). We used the cuff-oscillometric method for analysis. Participants were told to carry on with their normal daily activities during measurement. Ambulatory BP monitoring were performed 1837 patients in our clinic. We measured the blood pressure and heart rate parameters. The criteria of non dipping pattern was: diurnal index <10%. We performed Student-t test between the two groups (SPSS 16, Chicago IL).
Results: Non-dipping pattern was found in 1098 cases, dipping pattern in 738 cases. The 24-hour systolic blood pressure in non-dipping group (NDG) was 133.51±16.37 mmHg, in the dipping group (DG) was 127.44±13.69 mmHg (p<0.001) and the diastolic was 75.13±12.34 mmHg (NDG) and 75.35±11.69 mm Hg (DG), N.S. The heart rate was lower in the NDG than in the DG, 69.55±9.73 beat/min vs 70.49±9.23 beat/min (p<0.05). The heart rate variability was higher in the DG than in the NDG, 8.59±4.16 vs 9.98±3.33 (p<0.0001).
Conclusion: In non-dipping group we found lower heart rate variability. Presumably reflecting altered function of the sympathetic nervous system, the baroreceptor oscillations are shifted to lower frequencies. In non dipping patients the lower HRV may exert poor prognosis in hypertension. Further investigation need to established the long term consequence of this.