Ambulatory blood pressure monitoring for high-risk women, and masked htn

​Hypertension after pre-eclampsia is common, though masked hypertension is the most prevalent variety (see htn ambulat bp 1 yr after preeclamp HNT2018 in dropbox, or DOI: 10.1161/HYPERTENSIONAHA.117.10338​).

Details:

--200 women from the Follow-Up Pre-Eclampsia Outpatient Clinic in The Netherlands

--all with severe pre-eclampsia, defined as organ damage (SBP >160 or DBP>110; marked proteinuria, eg >5gm/24h; oliguria, cerebral/visual disturbances; pulmonary edema; impaired liver function; thrombocytopenia) or fetal growth restriction.

--mean age 31.6; white 83%/African descent 11%/Asian 7%; pre-existing htn 15%; nulliparity 70%; HELLP syndrome 14%; first trimester BMI 24; first trimester BP 120/74;

--clinic-based blood pressure and 24-hour ambulatory blood pressure monitoring (ABPM) measured 1 year after delivery. Clinic BP was assessed after 5 minutes of rest, not speaking, and other standard procedures

--hypertension defined as:

    --clinic BP >140/90

    --daytime average ABPM >135/85

    --nighttime average ABPM >120/70

--24-hr ABPM: they also assessed dipping (normal, where ratio of night vs day ABPM =0.8-0.9: reflecting the normal decrease at night), nondippers (0.9-1.0), reverse dippers (>1.0)

Results:

--41.5% of women had hypertension by ABPM, whereas 24.0% were diagnosed by clinic-based measurement

--of those with hypertension:

    --masked hypertension (normal clinic blood pressure, high ABPM): 17.5%

    --sustained hypertension (both clinic and ABPM high): 14.5%

    --white-coat hypertension (high clinic BP, normal ABPM): 9.5%

    --and, 46% had abnormal dipping patterns (where the systolic BP does not decrease as is normal on nighttime ABPM; this can happen even when the overall 24-hr ABPM is normal)

Commentary:

--Pre-eclampsia is common, about 3-5% of pregnancies, and it increases the lifetime risk of cardiovascular disease; especially if the pre-eclampsia is severe, where there is a 7-fold increase

--women with pre-eclampsia are also at risk for subsequent hypertension, though prior studies only assessed clinic-based blood pressures. 

--this study showed that almost twice as many women had abnormal ABPM vs clinic-based blood pressure.  But is this clinically significant?? [the simple answer: "yes"]

    --there have been several studies showing that ABPM correlates much better than office-based blood pressure with clinical cardiovascular events.  One of the most dramatic ones i've seen was done in 2003, where 1963 patients were followed for 5 years (see htn ABPM cardiovas events NEJM2003 in dropbox, or Clement DL. New Engl J Med 2003; 348:2407). The graph below from the study shows a higher incidence of cardiovascular events in those with higher ABPM, and this was true for each of the office-based systolic pressures: ie, systolic <140, 140-159, and >160.  Those with systolic >160 but normal ABPM (white coat hypertension​) had 1/2 the cardiovasc events as those with high ABPM. And those with normal office BP <140 but normal ABPM had even less than 1/2 the clinical event rate of those with high ABPM (masked hypertension). Another study of patients with refractory hypertension by office-based measurement found that 40% of 556 patients were in fact normotensive on ABPM (see htn refractory  salles arch int med 2008 in dropbox, or Salles GF. Arch Intern Med 2008; 168: 2340); they followed the patients for 4.8 years and found that, as opposed to ABPM, office-based blood pressure had no prognostic value for hard cardiovascular endpoints (fatal or nonfatal cardiovasc events, as well as all-cause and cardiovasc mortality). see http://gmodestmedblogs.blogspot.com/2017/11/new-aha-hypertension-guidelines.html which supports using ABPM in the new hypertension guidelines, and a slew of prior blogs at http://gmodestmedblogs.blogspot.com/search/label/hypertension  )

    --also, see http://gmodestmedblogs.blogspot.com/2016/12/masked-hypertension.html/​ for a study and review of masked hypertension

--and, what about the non-dippers, who have abnormally high nocturnal blood pressures?

    --several studies have found that those with normal ABPM results may still be at increased cardiovasc risk if they do not have the normal nocturnal “dipping”, that there is a continuum of adverse cardiovascular events as night-time hypertension increases (from non-dippers to reverse dippers). The high levels of non-dipping in the above study may reflect the fact that women with pre-eclampsia do have increased sympathetic tone. they also have increase sensitivity to angiotensin II

    ​--and, since ABPM is necessary to detect non-dippers, this becomes yet another incentive for more aggressive ABPM testing 

So, this study reinforces the utility of ABPM measurement in women with severe pre-eclampsia, who are at high risk of sustained hypertension. The data are abundantly clear that ABPM is a better predictor of clinical events than clinic BP (see Clement study and graph below, for example, which actually found that clinic BP had actually no clinical predictive value, only ABPM). What does this mean?

    --the largest hypertensive group in the above study (masked hypertension) had normal blood pressure measurements in the office, further indicating the lack of sensitivity of office measurements for detecting hypertension

    --masked hypertension (patients with lower clinic BP than outside BP​) may reflect something big and important. Is their life at home really more stressful than a clinic visit? Or at work? Or in their neighborhood/community? Seems like these issues should be explored

    --should we routinely be doing ABPM on everyone?? I doubt that is feasible… but perhaps in high risk people (other cardiovasc risk factors, family history of hypertension, etc)?? or maybe these folks should have their blood pressure checked occasionally at home (home-based BP is more predictive than clinic-based, though not great studies to support this. See http://gmodestmedblogs.blogspot.com/2016/04/home-blood-pressure-monitoring.html  ).

-- perhaps we should check those with white-coat hypertension who are also at higher risk later for sustained hypertension (as are those with masked hypertension)

--i do not mean to say that office-based blood pressure measurement has no utility. it is clear from many studies that when done in a standardized way (see http://gmodestmedblogs.blogspot.com/2017/09/the-most-important-hypertension-blog.html ), it is associated with future cardiovasc outcomes. but, it is both much less sensitive and specific than ABPM, per many studies. and, per my brief review, these monitors are actually not so expensive to be prohibitive (around $1500 for monitors with printout of results).

--another issue: what should we do with abnormal ABPM results? S​hould everyone with masked or white-coat hypertension be treated?? i am not aware of studies showing clinical efficacy of this. But I would suggest at this point that we inform the patient of their higher risk of CVD, and use abnormal results to reinforce strongly nonpharmacologic therapy: weight loss if appropriate, diet (eg DASH or Mediterranean) and exercise​

Clement DL. New Engl J Med 2003; 348:2407

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