Whereas the diurnal fall of BP (dipping) is an important prognostic marker in patients with chronic renal failure (CRF), the integrity of physiologic ultradian (i.e., shorter than 24 h) cardiovascular rhythms in patients with CRF is unknown. Also, the relationship between conventional dipping analysis and Fourier spectral rhythm analysis has not been examined in renal hypertension. The prevalence and dimensions of the circadian and three ultradian (12, 8, and 6 h) cardiovascular rhythms were studied by ambulatory BP monitoring in 214 children (aged 3 to 18 yr) with CRF (stage 2 to 4 chronic kidney disease) and no antihypertensive treatment compared with 938 healthy control subjects, and the relationship of rhythm characteristics to conventional dipping parameters, renal function, proteinuria, and serum electrolytes was assessed. The CRF cohort exhibited significantly reduced amplitudes of the circadian and all ultradian cardiovascular rhythms studied (all P < 0.01). Moreover, all BP and most heart rate rhythms showed significantly delayed acrophases (time of peak; P < 0.01). Whereas conventional BP dipping parameters (day/night difference, day/night ratio) and the 24-h BP amplitude were independent of renal function, the 8-h BP amplitude was positively correlated with GFR (r = 0.3, P = 0.01) and inversely correlated with the urinary protein/creatinine ratio (r = -0.27, P < 0.05), and the 6-h BP amplitude was inversely correlated with proteinuria (r = -0.3, P < 0.02). Children who displayed 24- or 12-h cardiovascular rhythms had significantly lower serum calcium levels than children without these rhythms. In summary, children with CRF display not only blunted circadian but also blunted ultradian cardiovascular rhythms. Ultradian but not circadian rhythms or conventional dipping parameters are quantitatively associated with renal function and proteinuria.

Adults with T2DM have been shown to have abnormalities of ABP that correlate with incipient diabetic nephropathy, as reflected by the presence of MA.Little is known about whether similar manifestations of end organ damage are present in the growing cohort of children with this disease.We enrolled 22 (12 female) minority (7 African-American, 13 Hispanic Carribean, 2 other) postpubertal adolescents (14.7Ϯ1.9 years of age, range 11.8 to 18.1) diagnosed with T2DM within the past three years.Their mean body mass index was 34.8Ϯ7.2(range 22.0 -51.7) kg/m 2 and their mean hemoglobin A1C was 7.6%Ϯ2.0(range 5.5-13.6).ABP monitoring was performed and a 24 hour urine was collected.Blood was obtained for a fasting lipid profile, blood urea nitrogen, creatinine, hemoglobin A1C, homocysteine, and C reactive protein.We found that 36.4% of subjects had MA (defined as Ն30mg of microalbumin/24 hour).68.2% were classified as systolic nondippers (nocturnal decline in mean systolic BPϽ10%).There were significant associations between the presence of MA and the presence of a mean daytime systolic BP (SBP)Ͼ95th percentile (pϭ0.007, by Fisher's Exact test) and a mean nocturnal SBP Ͼ95th percentile (pϭ0.022).There was also a significant association between the presence of MA and the daytime SBP load (pϭ0.022) and nighttime diastolic BP load (pϭ0.031)being greater than 40%.The mean daytime SBP was significantly greater in subjects with MA compared to those without MA (127Ϯ9 mmHg vs 118Ϯ7 mmHg, pϭ0.014, by Mann-Whitney test).Those with MA had a mean daytime SBP load that was significantly higher than those without MA (49.1%Ϯ20 vs 17.9%Ϯ16.8,pϭ0.005).There were no significant differences between those with and without MA regarding their sex, race, age, family history of hypertension, duration of T2DM, diabetes medications, waist-hip-ratio, hemoglobinA1c, homocysteine, or C reactive protein.This study is the first to examine the prevalence of ABP abnormalities and MA in adolescents with T2DM.As in adults, adolescents with T2DM exhibit abnormalities of ABP that are associated with evidence of incipient nephropathy.Long term follow-up studies are needed to further delineate the renal and cardiovascular sequelae of T2DM in this population.

: Wednesday, June 16, 2004: POSTER SESSIONS: Poster Session 44: BP Measurements and Hemodynamics

To assess the prevalence and characteristics of physiological circadian (24-hour) and ultradian (12-, 8-, and 6-hour) rhythms of mean arterial blood pressure (BP) and heart rate (HR), we analyzed 24-hour ambulatory BP profiles from 938 healthy school children aged 5 to 18 years. Cosine harmonics were fitted by Fourier analysis, and an amplitude and acrophase (time of peak) were calculated for each rhythm. Ninety percent of children displayed circadian rhythmicity of BP, independent of age, whereas circadian HR rhythmicity decreased with puberty from 96% to 87% (P<0.0001). Puberty had marked effects on the prevalence of ultradian rhythmicity: 12- and 6-hour rhythms increased for BP (27% to 47%, P<0.0001; 18% to 25%, P=0.01) and HR (36% to 47%, 17% to 31%, both P=0.001), whereas 8-hour BP rhythms decreased (34% to 23%, P=0.002). Median amplitudes were 10.1, 5.9, 5.6, and 5.2 mm Hg for the 24-, 12-, 8-, and 6-hour BP rhythms, respectively, and 13.4, 7.7, 6.8, and 6.4 bpm for HR. The acrophase occurred at approximately 14:00 hours, 8:00 hours, 5:30 hours, and 2:00 hours (military time) for the four BP rhythms, and at 13:30 hours, 08:30 hours, 01:50 hours, and 02:00 hours for HR. For the combined curve, the peak-trough difference was 25.9 mm Hg and 35 bpm for BP and HR, respectively, with the peaks occurring at 13:50 hours and 13:10 hours. There was marked association between BP and HR rhythms, both for prevalence (P<0.0001 for coupling of BP and HR rhythms of the same period length) and timing, with a median time lag of BP after HR acrophase of only 21, 16, 13, and 5 minutes for the four rhythms, respectively.