June 29, 2011 — In patients with chronic kidney disease (CKD),
ambulatory blood pressure (BP) monitoring, especially at night, appears
to be more accurate than office BP measurement in predicting risk for
renal and cardiovascular events, according to new research.
Roberto Minutolo, MD, PhD, from the Division of Nephrology, Second University of Naples, Italy, and colleagues reported their findings in the June 27 issue of the Archives of Internal Medicine.
According to the researchers, ambulatory BP measurement "allows a
better risk stratification in essential hypertension compared with
office blood pressure measurement, but its prognostic role in
nondialysis [CKD] has been poorly investigated."
They also point out
that office BP readings may be influenced by white coat hypertension in
this setting.
To investigate the accuracy of ambulatory BP in predicting risk in
patients with CKD, Dr. Minutolo and colleagues compared daytime and
nighttime systolic and diastolic BP with office BP measurements in 436
consecutive patients with CKD.
The average age of the patients was approximately 65 years, and their mean glomerular filtration rate was 42.9 mL/minute/1.73 m2. About one third of the patients had diabetes and/or cardiovascular disease, and 41.7% were women.
Researchers measured the patient's BP 3 times during a morning office
visit and outfitted the patient with an ambulatory BP monitor that took
readings every 15 minutes during the day and every half hour at night.
They also obtained 3 more in-office BP readings the next day, when
patients returned. Participants also recorded their activities in a
diary.
Mean systolic over diastolic blood pressure measured in-office was
146/82 mm Hg; daytime ambulatory measurement was 131/75 mm Hg, and
nighttime measurement was 122/66 mm Hg.
During a median 4.2 years of follow-up, 155 patients had a renal
endpoint (end-stage renal disease or renal death), and 103 patients had a
cardiovascular endpoint (fatal or nonfatal cardiovascular events).
Compared with patients with a lower ambulatory daytime systolic BP of
between 126 and 135 mm Hg, those with higher values were 2 to 3 times
more likely to have a cardiovascular endpoint, and nearly twice as
likely to have a renal endpoint.
In patients with higher nighttime ambulatory systolic BP, the risk
for a cardiovascular endpoint was increased 2.5- to 4-fold, and the risk
for a renal endpoint was increased by about 2-fold compared with the
patients with the reference systolic BP value of 106 to 114 mm Hg.
In contrast, office measurement of BP did not predict risk for a renal or cardiovascular endpoint, the researchers found.
Patients who were "nondippers" and those who were "reverse dippers"
had an increased risk for renal death and cardiovascular events. There
was a 2-fold greater risk for cardiovascular events in nondipper and
reverse-dipper subgroups, and their risk for renal death increased by
62% and 72%, respectively, in comparison with dippers.
"This study demonstrates that ambulatory BP monitoring is a better
predictor of renal and cardiovascular end points compared with office BP
measurement in patients with CKD," the researchers conclude.
"Given the importance of detecting BP elevation and of dealing with
it efficiently and promptly, it is both exciting and challenging to see a
report like the one by Minutolo and colleagues," state David Goldsmith,
FRCP, from Guy's Hospital in London, United Kingdom, and Adrian Covic,
MD, PhD, from the C. I. Parhon University Hospital in Iasi, Romania, in a
related invited commentary.
According to the commentators, "there will be those who will question
the time, effort, and expense of running an ambulatory BP service."
However, selected cohorts of patients may benefit from ambulatory BP
monitoring, the authors add.
"This new study by Minutolo and colleagues makes that case stronger
for our patients with CKD," they write. "It is now harder to defend
reliance on clinic BP measurement alone if we nephrologists are serious
about targeted BP intervention."
This study was not commercially supported. The authors and editorialists have disclosed no relevant financial relationships.
Arch Intern Med. 2011;171:1090-1098, 1098-1099. Article Abstract Commentary Extract
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