CHICAGO—Ambulatory blood pressure (BP) monitoring with collection of BP readings over 24 hours may better predict, in cases of nondialysis chronic kidney disease (CKD), whether patients will experience end-stage renal disease, mortality or cardiovascular events that require hospitalization, according to a report in the June 27 issue of Archives of Internal Medicine.
An ambulatory blood pressure monitor (ABPM) is worn under a patient’s clothing and automatically takes BP readings at repeated intervals of the day and night; this information is collected and brought to the physician’s office for analysis. ABPM may help mitigate the possible effects of “white coat hypertension,” in which a patient’s BP artificially increases simply because of visiting a physician’s office. According to background information in the article, this phenomenon is especially prevalent in CKD. Additional research suggests that nighttime BP, removed from physical, emotional and other stresses, may be a better measure of a patient’s actual BP status and his or her risk for cardiovascular problems.
Roberto Minutolo, MD, PhD, from the Second University of Naples in Italy, and colleagues conducted a study of patients with CKD whose blood pressure was routinely monitored at four Italian nephrology clinics. They recruited 436 participants between 2003 and 2005. Researchers measured each patient’s BP three times during a morning office visit, outfitted him or her with an ABPM that took readings every 15 minutes during the day and every half hour at night, and obtained three more in-office BP readings the next day when patients returned. Participants also kept diaries of their activities, to help researchers interpret the results.
During a median followup time of 4.2 years, 86 patients experienced end-stage renal disease and 69 died; researchers also recorded 63 cardiovascular events that were not fatal and 52 deaths related to cardiovascular problems. Risk of both renal and cardiovascular outcomes was highest in participants whose daytime systolic blood pressure (SBP) was 135 mm Hg (milligrams of mercury) or above. The same risk was found for participants in the highest quintile of diastolic blood pressure (DBP), or who had nighttime SBP readings of 124 mm HG or higher. Additionally, nighttime DBP of 70 mm Hg or higher was a predictor of cardiovascular events and end-stage renal disease. “In contrast,” the authors note, “office BP measurement (either SBP or DBP) did not predict cardiovascular or renal events.”
The study suggests that ABPM may be a more useful tool than office BP measurements in assessing the risk that a patient with CKD will experience serious renal or cardiovascular events, and that its predictive value appears independent of other risk factors for these conditions. “Of interest, the lack of predictive value of office BP measurement, as well as office BP target level, raises concerns regarding the adequacy of recommendations of hypertension guidelines that are derived mainly from expert opinion and post hoc analyses rather than randomized trials.” They concluded that “interventional studies based on ABPM rather than office BP measurement are urgently required in this high-risk population.”