11 May 2009

Another blow to the 'Lower Is Better' craze

Low BP associated with increased risk for stroke and heart attack

Researchers found a J-curve relationship between cardiovascular events and blood pressure (BP) at above and below reference levels.

Data results from the American Society of Hypertension 24th Annual Scientific Meeting and Exposition, San Francisco Marriott, San Francisco, CA, May 6 – Saturday, May 9, 2009, show that patients with coronary artery disease who also have low blood pressure are at higher risk for stroke and heart attack.

Researchers examining results from the TNT study analyzed 10,001 patients with coronary artery disease. Patients were assigned to either 10 mg of atorvastatin daily (n=5,006) or 80 mg atorvastatin daily (n=4,995). The primary endpoint was a composite of death from coronary disease, nonfatal MI (heart attack), resuscitation following cardiac arrest and fatal or nonfatal stroke.

Among the 10,001 patients, 982 (9.82%) reached the primary endpoint during the 4.9 follow-up period.

The researchers reported a J-shaped curve relationship between systolic or diastolic BPs both above and below reference BP ranges (130 to 140 mm Hg for systolic, 70 to 80 mm Hg for diastolic) and major cardiovascular events, despite a reduction in LDL levels.

According to the study results, there was a 3.1-fold increase in the risk for major cardiovascular events in patients with a systolic BP of 110 mm Hg and a 3.3-fold increased risk in the group with a diastolic BP of 60 mm Hg.

Following application of a nonlinear Cox model, the lowest event rates were associated with a systolic BP of 140.6 mm Hg and diastolic BP of 79.8 mm Hg for diastolic BP.

Franz Messerli, MD, director of the hypertension program at Saint Luke’s-Roosevelt Hospital in New York, said in an interview:
“There is no question that a lot of patients are not controlled at present, but the dictum that lower is better is not true in all patients and particularly not true in patients with manifest coronary artery disease . . . In patients with coronary artery disease, you really have to be careful.”
This means that the current 'healthy' guidelines on BP - the 'optimal' level of 120/80 may need rethinking.


gharkness said...

If I read this correctly, the subtitle is misleading. It should say: "Low BP associated with increased risk for stroke and heart attack for patients who have coronary artery disease AND are treated with atorvastatin."

To conclude that naturally occurring low blood pressure would pose the same risk is unfounded - even dangerous - at this time.

It's reasonable to think that many people only read the headline and the subtitle of articles like this, and can easily make erroneous conclusions based on what they read. It seems to me that it would be more reasonable to qualify the study's conclusion in either the title or subhead so as to not mislead people.

Trinkwasser said...

Interesting, as always.

One wonders if it was the low BG per se or the medications used to attain it which were causual.

Either way as with LDL the existence of yet another J curve is a data point.

Barry Groves said...

G Harkness

Yes, the subtitle could say that.

What we have is a a study of people who are already at high risk of a heart attack or a stroke as they have confirmed coronary artery disease.

Such patients are routinely given drugs such as beta blockers and/or ACE inhibitors to lower their blood pressure, as well as statins.

What this study suggests is that such treatment might not be a good idea.

Perhaps I should have added that to my original post

Alicia Vincent said...

Speaking of blood pressure medications...my father-in-law almost lost his life due to the overzealous efforts by his generalist to control his supposedly high bp. He is 76 and had been taking bp medication for years...one day after getting good and irritated after a long wait in the doctor's waiting room (he is the impatient type)...his doctor got a reading of 160 for his bp. The good Dr. promptly added a second medication. Several weeks later, my father in law was admitted to the emergency room with sky-high potassium and a heartrate of 26 bpm. He almost died. That's an example of the treatment being worse than the disease if I ever heard one!

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Barry Groves said...

Then again, if you just learn to relax, there is no need for drugs - 'natural' or otherwise which cost nearly a dollar a day. Eating properly helps as well.

My BP is usually around 115 /62, but my resting* systolic can occasionally read up to 135. If I have the same test in the doctor's surgery, it is usually around 145.(*There is no point taking readings if you are stressed, been walking, or talking, or doing anything other than being totally relaxed. This is why a reading in a doctor's surgery is really not all that useful.)

What I have noticed - and what is widely recognised - is that a one-off reading isn't worth much. To determine a realistic BP profile requires readings for several days, and on all four limbs. Diagnosis on less than that is completely unreliable.

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