Ambulatory 24-Hour BP Monitoring Best Predicts Mortality

April 19, 2018

The largest study ever conducted of ambulatory blood pressure (BP) monitoring (ABPM) has shown that measuring BP over a 24-hour period predicts all-cause and cardiovascular mortality much better than does office or clinic measurements.

"Our study suggests that more frequent use of 24-hour blood pressure measurement could improve the diagnosis and management of hypertension, which is the primary cause of premature death and disability worldwide," lead author, José Ramon Banegas, MD, Universidad Autónoma de Madrid, Spain, told Medscape Medical News.

The study also showed that masked hypertension, where BP is normal in the clinic but elevated out of the office, was linked to the highest risk for mortality but would never be identified by just measuring BP at the clinic. White coat hypertension, where BP is elevated in the clinic but not outside, was also associated with high risks.

"A hypertension diagnosis based exclusively on blood pressure readings in the clinic is no longer acceptable. There is no scientific or clinic justification for not using ABPM, which should be part of the evaluation and follow-up of most hypertensive patients," Banegas said.

The study is published in the April 19 issue of The New England Journal of Medicine (NEJM).

The researchers analyzed data from a registry of 63,910 adults recruited from Spanish primary care centers between 2004 and 2014. Patients were required to meet guideline-recommended indications for ABPM, which included suspected white coat hypertension, refractory or resistant hypertension, high-risk hypertension, and labile or borderline hypertension, as well as assessment of drug-treatment efficacy and study of the circadian BP pattern.

They had their BP measured in the clinic and again over 24 hours using ABPM devices.

During a median follow-up of 4.7 years, 3808 patients died of any cause, and 1295 of these patients died of cardiovascular causes. 

Results showed that 24-hour systolic BP was more strongly associated with all-cause mortality (hazard ratio [HR], 1.58 per 1-standard deviation increase in pressure) than the clinic systolic BP (HR, 1.02). Nighttime-alone and daytime-alone measurements had risks very similar to those of 24-hour BP.

Masked hypertension was more strongly associated with all-cause mortality (HR, 2.83) than was sustained hypertension (HR, 1.80) or white coat hypertension (HR, 1.79). Results for cardiovascular mortality were similar to those for all-cause mortality

"We know hypertension is a surrogate for mortality but this has only been validated for office blood pressure," coauthor Luis Miguel Ruilope, MD, Universidad Autónoma de Madrid, commented to Medscape Medical News.

"Our data shows ABPM is clearly much more informative of risk than office measurement," he added. "Previous data has suggested night-time blood pressure may be riskier but our data does not agree — it is the same as daytime and 24-hour measurements."

The other major finding was that masked hypertension had the highest risk of all, he added. "In our dataset, masked hypertension was present in 4% of the population studied, and when we add in masked uncontrolled hypertension (normal clinic but elevated ambulatory blood pressure in persons receiving antihypertensive medication) this rises to almost 10%," Ruilope added. "That is a lot of patients with elevated blood pressures not being picked up with office measurements."

Another coauthor, Bryan Williams, MD, University College London, United Kingdom, and chair of the ESC Council on Hypertension, told Medscape Medical News that this study "provides the most compelling evidence yet that there should be wider use of ABPM to confirm the diagnosis of hypertension and monitor the quality of blood pressure control."

"It also shows unequivocally that white coat hypertension is not benign and masked hypertension is perhaps an even higher-risk situation than we realized."

Williams says ABPM is not used often enough. "This is mainly because reimbursement rates are so low or nonexistent and the monitors are way overpriced relative to the cost of conventional monitors," he noted. "The cost needs to come down and this will drive more widespread use. I personally feel the monitors could be better designed to make them more appealing and user friendly."

Even so, he says wider use of ABPM would be more cost-effective in the medium term as "it is a better predictor of risk and better identifies people who really need treatment and those who don't."

The researchers are hoping the NEJM paper will have a major impact. Ruilope says that because of this large registry, ABPM is becoming more accepted in Spain, and now with the current publication he is hoping it will be used more frequently worldwide.

"The data is very compelling and cannot be ignored," Williams said. "We haven't changed the way we diagnose hypertension for more than 100 years — perhaps the time has come."

But he notes that there are still challenges in using ABPM to monitor treatment, for example, there are fewer data on optimal treatment targets.

He adds that for those not able to access ABPM, home BP monitoring might be a suitable alternative with two provisos: one, that the measurements of home BP must be made carefully and in standardized conditions, usually averaging the result of several measurements over a few days; and two, that there are not as much data on the predictive value of home values with respect to outcomes.

Gild for the Lily

An accompanying editorial in the NEJM was written by Raymond R. Townsend, MD, Perelman School of Medicine, University of Pennsylvania, Philadelphia.  

"The take-home message from this study is that ambulatory blood-pressure monitoring is a valuable tool in the assessment of the most important and treatable factor worldwide contributing to premature death and disability, namely blood pressure," he writes.

"It is hoped that the work of Banegas et al will serve as one more spur to manufacturers of ambulatory blood-pressure monitoring devices and to providers in this field…to initiate a registry in the United States."

To Medscape Medical News, Townsend added: "We've had enough information to support expanded use of ABPM for years and this study provides more gild for the lily. While it is used more in some European countries where it has government funding, it just isn't being done very much at all in the US, mainly because it is not reimbursed. This needs to change."

This study was supported by the Spanish Society of Hypertension, and by an unrestricted grant from Lacer Laboratories, Spain. Williams receives consulting fees from Vascular Dynamics, Relypsa, and Novartis and honoraria from Daiichi Sankyo, Boehringer Ingelheim, Servier, and Pfizer and has served as an advisor to HealthStats PTE, Singapore. Townsend reports grants from the National Institutes of Health and personal fees from Medtronic, AXIO, CLARUS Therapeutics, Continuing Medical Education, and UpToDate outside the submitted work.

N Engl J Med. Published April 19, 2018.  Abstract, Editorial

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