PP.07.26] REPRODUCIBILITY OF CIRCADIAN BLOOD PRESSURE VARIATIONS IN CHRONIC KIDNEY DISEASE PATIENTS

Abstract

Objective: Previous studies have demonstrated a significant link between the circadian rhythm of blood pressure (BP) and cardiovascular events, namely that the absence of a nocturnal fall in BP and an exaggerated morning BP surge, are associated with more severe target organ damage and increased cardiovascular risk in chronic kidney disease (CKD) patients. Aim of our study was to investigate the reproducibility of circadian BP variations in CKD patients. Design and method: A total of 35 CKD patients underwent 24-h ambulatory BP monitoring at baseline and 1 month. Morning BP surge was defined as the sleep-trough surge, calculated by subtracting the morning BP (mean of 4 readings over 2 hours just after wake-up) from the lowest nocturnal BP (mean of 3 readings centered around the lowest nighttime BP) and as the prewaking surge (morning BP minus the 4 readings over 2 hours before waking). The degree of nocturnal BP dipping (%) was calculated as 100[1 – nighttime BP/daytime BP] for both systolic and diastolic BP. Dippers were defined as subjects with nocturnal BP fall >10% and non-dippers as patients with nocturnal BP fall <10%. Nocturnal hypertension was defined as nighttime SBP >= 120 mmHg and/or DBP >= 70 mmHg. Statistical analysis was performed by means of reliability analysis (intraclass correlation coefficient (ICC)) for continuous variables and kappa agreement coefficient for categorical variables. Results: The ICC for sleep-trough surge was 0.360 (p = 0.097) and for prewaking surge was 0.541 (p = 0.012). As far as systolic and diastolic dipping are concerned, the ICC values were 0.674 (p = 0.001) and 0.371 (p = 0.087), respectively. The kappa agreement coefficient for systolic non-dippers was 0.517 (p = 0.002), for diastolic non-dippers was 0.157 (p = 0.332), and for nocturnal hypertensives was 0.208 (p = 0.215). Conclusions: Prewaking morning BP surge is more reproducible than sleep-trough surge in CKD patients. Systolic BP dipping demonstrates greater reproducibility than diastolic BP dipping and nocturnal hypertension in CKD patients.