BP Beat-to-Beat and the Drugs That Reduce Variability

Henry R. Black, MD


December 22, 2011

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Hi. I am Dr. Henry Black. I am a clinical professor of Internal Medicine at the New York University School of Medicine, a member of the Center for the Prevention of Cardiovascular Disease, and Immediate Past President of the American Society of Hypertension.

Ambulatory blood pressure monitoring and home blood pressure monitoring have become particularly interesting in the past several years. [We have always had the idea] that your [provider's] office blood pressure did not really reflect your outcomes. The office blood pressure was simply a small sample of many, many readings. But as ambulatory blood pressure monitoring has become more available and even recommended recently by the United Kingdom group, the question is, what can we learn from ambulatory blood pressure monitoring? When you look at these ambulatory blood pressure tracings, it is clear that there is a fairly wide difference between blood pressures from beat to beat. This is not surprising. Even though we only have maybe 60 or 80 beats, we can learn a lot about how much blood pressure is reduced during the day, how much it is reduced during the 24-hour period, and how much is reduced at night.

We can also learn something else, which is, how much does blood pressure vary from beat to beat on the recording? One of the things we have seen is that people who have wide blood pressure variability tend to have a higher [cardiovascular] risk. Whether this is sympathetic stimulation or parasympathetic failure to control, this does seem to increase [cardiovascular] risk.

Now, a very interesting clinical trial was conducted in France and 4 other countries to look at how various agents reduce blood pressure variability.[1] This was a small substudy of a larger trial, with about 400 participants overall. The investigators compared amlodipine, a dihydropyridine calcium channel blocker; a long-acting form of indapamide; an angiotensin receptor blocker, candesartan; and placebo over a 3-month period. Ambulatory blood pressure monitoring was done.

These investigators found that all the drugs lowered 24-hour blood pressure, and all of them lowered daytime blood pressure. Most of them lowered nighttime blood pressure as well, but there was a real difference between what happened to blood pressure variability, tending to favor amlodipine, which lowered blood pressure variability at all 3 time periods, and the long-acting indapamide, which did it during the daytime and at 24 hours. Candesartan, the angiotensin receptor blocker, while lowering blood pressure, did not reduce blood pressure variability compared with the placebo group.

Whether this means we ought to be favoring an agent that does this remains to be seen. We do not know the mechanism, nor do we know the outcomes until we have looked at this in a formal, long-term study. But it gives us one more thing to think about. When I do ambulatory blood pressure monitoring, I always look at the standard deviation in the systolic and diastolic blood pressure, and if the standard deviation is much above 12% or 13%, that indicates excess blood pressure variability and a source of potential concern.

We need to do a lot more, of course. We need to look at combination therapies. We need to look at whether we should take some of these medications at night. We have many, many different ways to do this. Ambulatory blood pressure monitoring has now given us an insight into other ways to look at blood pressure rather than simply how much it lowers blood pressure in the office. I look forward to more data on this subject. Thank you very much.