WHAT IS A NORMAL BLOOD PRESSURE?

Ask any doctor and I bet he can give you the answer in a flash, but what I'm curious about is what "the real normal blood pressure value or range is", in individuals.

The CAMELOT Study, also known as the Comparison of Amlodipine vs Enalapril to Limit Occurrences of Thrombosis, was published yesterday in the Journal of the American Medical association (JAMA). Done by researchers led by Dr. Steven Nissen of the Cleveland Clinic, it is an international multicenter, double-blind, placebo-controlled randomized trial involving 100 study sites in North America and Europe.

The study compared cardiovascular treatment using amlodipine, which is a calcium channel blocker (amlodipine) and enalapril, which is an ACE inhibitor, with placebo in coronary artery disease (CAD) patients with normal blood pressure.

I won't bore you with the technical details and will just tell you that the researchers found out that amlodipine given to CAD patients and those with normal blood pressure resulted in reduced adverse cardiovascular events, compared to those given enalapril and placebo. So, in brief, the CAMELOT study promotes the use of amlodipine over enalapril in CAD patients with normal or high blood pressure. You can read the full text of the study of the study here.

Great, good news. Another medal of praise for Pfizer, which sponsored this study, and issued the statement that, "the final decision on content was exclusively retained by the authors." [NYTImes Health] I can't wait to hear this being discussed in the next medical convention.

But that is not entirely what this post is all about.

In the discussion part of the study, Dr. Nissen and his co-researchers said:

The blood pressures in the current trial are, to our knowledge, the lowest ever studied in a major trial of antihypertensive drug therapy, averaging only 124 mm Hg during active treatment.

In CAMELOT, although initial blood pressures appeared "normal," a 5/3-mm Hg decrease in blood pressure during amlodipine treatment was accompanied by a 31% relative reduction in morbidity.

Although we cannot directly attribute the observed reduction in cardiovascular events to blood pressure reduction, these findings suggest the possibility that current target levels for blood pressure are too high for patients with established CAD. Our findings support the hypothesis that, even within the normal range, blood pressure represents a continuous risk factor for adverse cardiovascular outcomes.

[JAMA, Vol. 292 No. 18, Nov 10, 2004]

That's what so interesting about this study. All 1,991 subjects had CAD but at the same time had normal blood pressure. They were all considered high-risk patients because of CAD, but their blood pressures were normal based on current medical standards. And still, thefindings of the study showed a significant "31% relative reduction in morbidity" using amlodipine.

Gina Kolata, science and health writer for the New York Times put it more accurately:

Although the study was modest in size, with 1,991 patients, all with normal blood pressure, experts said its surprising result reopened this longstanding question: How low should blood pressure go?

The question takes on special urgency because millions of Americans have heart disease severe enough to cause the adverse symptoms.

The patients in the study were at high risk for adverse events, Dr. Nissen said, but their blood pressure was considered so well controlled that researchers had not previously asked what would occur if it went lower. Their starting pressure, he said, "was 10 millimeters lower than anyone has studied."

[NYTImes Health]

In my opinion, it seems in people with heart pathologies like CAD, blood pressure standards might not be as rigid as we, doctors, were once taught. 120/80 may be normal for the general population, but in CAD patients, a new set of blood pressure values might be needed. We might be missing the picture that these set of people might have new definitions and values for the classification of "normal blood pressure."

I agree with most that the study is an eye-opener and confirms to us the fact that blood pressure control remains an important part of the treatment process of cardiovascular conditions.

In practice, I have seen a few patients who exhibit symptoms of hypertension (high blood pressure) at 120/80. These patients, mostly women, have their 'normal' blood pressure at 90-100/70-80 mmHg. Unfortunately, because of lack of funds and interest, no study has been done locally to explore the details of this occurrence.

This makes me echo what Dr. Peter Libby of the Harvard Medical School asked when informed of the results of the CAMELOT study:

"Is average blood pressure optimal for our species?" [NYTimes Health]