Home-based BP Measures Should Drive Treatment Decisions

Naomi Deirdre Fisher, MD * Director, Hypertension Service and Hypertension Specialty Clinic, Brigham and Women’s Hospital * Associate Professor of Medicine, Harvard Medical School
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Time and data have proven that out-of-office blood pressures are the ones on which to base treatment decisions.

Dr Naomi Fisher, director of the hypertension service at the Brigham and Women’s Hospital talks in more detail about the where, how, and when of optimal blood pressure monitoring.

The following transcript has been edited for length and clarity.

Patient Care: I was interested in the American Heart Association, American Medical Association, Target:BP program to help practices improve their blood pressure control rates. There is a lot of focus on the very basic core competency of accurate blood pressure measurement, whether that's in the office or having patients do it at home. Is there really a real problem with accurate blood pressure measurement?

Dr Fisher: Yes, without accurate, proper blood pressure measurement, we can't possibly provide good care for our patients. For better or worse, the blood pressure reading is the outcome that we're measuring and that we’re guiding all of our therapy by. So, I think the issue of measurement has a lot of facets. We understand pretty well “why”—why we have to measure. Let’s talk about where we have to measure it. And then I'd like to talk about "how" and then I'd like to talk about "when."

But the where—for decades patients come into the doctor's office, they get their blood pressure measured—160 over 105. The doctor says you have high blood pressure and starts a medicine. They come back in 3 months, their blood pressure still high. The doctor may say, why don't you take a few more months to try and lose weight; they come back again, may still be high. That's kind of the way it's been working. We understand well now that it's blood pressures out-of-office that are much more important to capture. These are the blood pressures that really predict target organ damage, risk of having a heart attack or a stroke, or going into heart failure, or developing blindness or kidney disease or cognitive decline. There are so many ill effects of high blood pressure. And many studies have shown us that it's the out-of-office blood pressures that really matter. So, we have to change our focus from in-office blood pressures to out-of-office and home blood pressures. And they can be done with home blood pressure monitoring or with ambulatory 24-hour blood pressure monitoring. There are some new techniques in the office that also help to eliminate the white coat effect. That's a really big deal, for example, too.

So before I leave the “when,” do you have any comments on that? And then we can go on to “how,” where we get measurement mistakes.

Patient Care: The approaches seems very simple to us lay people who just write about this for a living, you go in, you get the patient to sit still, put their feet on the ground, you don't talk to them. But I guess that in the space of a day, with 15 people in the waiting room, doing it [measuring BP] quickly and accurately at the same time, is a challenge.

Dr Fisher: Right, right. So we can talk about the technique now about measuring blood pressure. And you're right, it's a big challenge. And I think whether you're measuring a blood pressure at home, or whether you're measuring it in the office, often it's a medical assistant who does it, it really has to be done correctly.

I always cite Murphy's law when I talk about measuring blood pressure, because anything that can go wrong will. Patients can have just had a cigarette or a cup of coffee within a half hour before getting their blood pressure. Maybe they just ran up the stairs. They maybe have to go to the bathroom, it's really good to have an empty bladder before blood pressure is measured. And very often they're brought in from the waiting room into the MA’s little suite to have their blood pressure measured, and they're sent into the PCP office. But they ideally should be seated for several minutes and come to a full rest. There's generally not time for that in an office flow. But of course, it can happen at home. So patients should be seated resting feet flat on the floor. It's really important if the arm is at the level of the heart, and not too low, not too high. It's very important that the cuff is a reliable one. This is not a case where a generic is a good product necessarily. We need something that's been validated by biomedical engineers. The cuff has to fit well--it can't be too tight and it can't be too loose. And we can't talk during the blood pressure measurements because all of these things affect what the blood pressure is. So yes, you're right.

And then the last facet I want to talk about is “when” to measure blood pressures because when patients start measuring their blood pressures at home, sometimes we doctors receive pages and pages of what looked like random blood pressure's faxed in to us. We don't know what to make of them or how to make any decisions. So there is actually a proper algorithm that's been developed by the American Heart Association. After a patient has been titrated, a drug dose has been changed, we recommend that there, they wait to get into steady state for a week or two, and then measure their blood pressure according to a very specific algorithm, measuring it twice a day, in the morning, and in the evening, always before their pills. And that way we can calculate a weekly average.

Patient Care: How are patients doing with that on average?

Dr Fisher: I would say that almost all of my patients have a home blood pressure cuff and use a home blood pressure cuff because without that, I'm really really hamstrung. And with good education, they do well, it's really the onus is on us as physicians to explain the importance to patients. But this is this is a team approach, we really have to get patients engaged and involved, understand why they have to measure their blood pressure and how to do it well.

Patient Care: I did a small slideshow, I think I might have gotten the information also from Target:BP a while back, and it suggested the number of millimeters off the measurement could be for various reasons—the patient has legs crossed, patient has his arms crossed, you're talking. It was pretty dramatic if I remember correctly.

Dr Fisher: Yes, there is the chart from American Heart, I know the one to which you are referring. It’s a little bit overdramatized because—it’s 10 points plus 10 points plus 10 points. It looks like your blood pressure could be overshot by 100. That's not always so additive, but it's referring to particular studies which have shown how dramatic each of these offenses in technique can be.