LOSS OF CIRCADIAN BLOOD PRESSURE RHYTHM INTEGRITY IN NON-DIPPER NORMOTENSIVE AND HYPERTENSIVE SUBJECTS.

PEREZ-LLORET S; RISK M; CARDINALI D; SANCHEZ, R; RAMIREZ A

Milan, Italia

Congreso; Congreso de la Sociedad Europea de Hipertension; 2005

OBJECTIVE: To evaluate the integrity of circadian and ultradian blood pressure (BP) rhythms in dipper and non-dipper normotensive and hypertensive subjects. METHODS: Observation transversal study including 452 subjects. After 24 h ABPM (Spacelab 90207), the mean BP 24 h rhythm was fitted with 12, 8, 6, 4, 3, 2 and 1.5 h harmonics (Fast Fourier Transform). Subjects with mean daytime systolic and diastolic BP greater than 135/85mmHg or under antihypertensive treatment were classified as hypertensives (247 subjects). Subjects were classified as non-dipper (110 normotensives and 114 hypertensives) if nocturnal dip was lower than 10% of daytime systolic. Day-time and night-time periods were arbitrarily defined based on fixed clock-time intervals (nighttime: 23:00 h to 07:00 h). Data is expressed as Mean±SEM and analyzed by a two-way ANOVA, with hypertension diagnosis and dip status as main factors. Adjustments for age, gender, BMI and pharmacological treatment were always performed. RESULTS: On average, hypertensive subjects were older (53.0±0.9years) and fatter (27.5±0.3kg/m2) than normotensives (Age: 45.0±1.0years, p<0.001; BMI: 26.3±0.3kg/m2, p<0.01). The 24h (10.0±0.2mmHg) and 12h (6.0±0.2mmHg) rhythms amplitudes were increased in hypertensives compared to normotensives (24h: 9.0±0.2 and 12h: 5.2±0.2mmHg, p<0.01) and reduced in non-dipper patients (24h: 7.5±0.2mmHg; 12h: 5.0±0.2mmHg) compared to the dipper subjects (24h: 11.6±0.2mmHg; 12h: 6.2±0.2 mmHg; p<0.01). The percentage of ABPM variability that could be explained by fitting the 24 h rhythm and the seven harmonics was significantly reduced in non-dippers (68±0.7%) compared to dippers (79±0.7%; p<0.001). This reduction was found in the 24 and 12h rhythms but not in the 8 to 1.5h rhythms. Moreover, The contribution of the 8 to the 1.5h harmonics to the total fit was increased in non-dippers (34±0.9%) compared to the dipper ones (20±0.9%; p<0.001). Although Time to peak (TTP) was similar among the four groups the patients, the variability was greater in the non-dipper group (4.9h) as compared to the dippers (4.3h; Chi-Sq= 22.0 p=0.005). CONCLUSION: Preservation of ultradian rhythm amplitude and integrity in non-dippers could be indicating that the observed desynchronization was the result of ultradian rhythm decoupling. Further studies are in progress to support this hypothesis.