Differentiation between primary and secondary hypertension in children using ambulatory blood pressure monitoring

Objective. To determine whether ambulatory blood pressure monitoring (ABPM) can help differentiate children with secondary hypertension from those with primary hypertension. Methods. Ninety-seven ABPM studies obtained from 85 children followed in a pediatric hypertension clinic were analyzed. Forty studies were performed in patients with primary hypertension, and 57 studies were performed in patients with secondary hypertension. Mean patient age was 13.8 +/- 3.5 [mean +/- standard deviation] years, range 4 to 19.7 years; patients with secondary hypertension were younger and had lower body mass index than patients with primary hypertension. Results. Daytime diastolic and nocturnal systolic blood pressure (BP) loads, defined as the percentage of readings greater than a threshold value, were significantly greater in patients with secondary hypertension compared with patients with primary hypertension. A daytime diastolic BP load of greater than or equal to25% and/or a nocturnal systolic BP load of greater than or equal to50% was highly specific for secondary hypertension. Conclusions. Secondary hypertension in childhood is characterized by daytime diastolic BP elevation and nocturnal systolic BP elevation. This pattern of hypertension on ABPM may be a clue to underlying renal or other organ system pathology in children being evaluated for suspected hypertension and could help to identify children who require more detailed evaluation to determine the cause of their hypertension.