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Medical memo: Blood pressure and the heart: Lower is better

Medical memo

Blood pressure and the heart: Lower is better

First it happened with cholesterol. When the statin drugs became available around 1990, doctors first concentrated on lowering elevated blood cholesterol levels into the normal range. As they observed important benefits, they began to treat patients who had atherosclerosis despite “normal” cholesterol levels. Again, the drugs produced major reductions in the risk of heart attack and cardiac death.

As studies have continued to accumulate, the goals for LDL (“bad”) cholesterol have continued to drop, at least for the patients at the highest risk. Whereas LDL levels of 130 mg/dL are still considered desirable for healthy people, levels below 70 mg/dL are considered optimal for those with acute coronary artery disease (heart attack or unstable angina).

Blood pressure is every bit as important as cholesterol in contributing to heart attack and stroke. As with cholesterol, the higher the reading, the greater the risk. New evidence, in fact, suggests that risk begins to rise with systolic readings above just 115 mm Hg, a level universally considered “normal.”

As a result of this evidence, the Seventh Report of the Joint National Committee on the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) developed a new blood pressure classification system in 2003.

JNC 7 also issued new treatment goals. They called for both lifestyle modification and medication to achieve blood pressure readings of 140/90 or lower for average patients, but they set a goal of 130/80 or lower for patients with diabetes or chronic kidney disease.

These guidelines are extremely important, especially since only 27% of America’s 65 million hypertensive patients are being treated adequately. But although JNC 7 set lower goals for diabetics and patients with kidney disease, it did not establish special goals for patients with coronary artery disease. If the findings of a more recent study hold up, that’s likely to change.

Beginning in 1991, the CAMELOT Study evaluated 1,997 patients with angiographically proven coronary artery disease but normal blood pressure readings, which averaged 129/78. The patients all received medical care according to their individual needs; 95% of them took aspirin and 53% took a statin drug. About three-fourths of the patients also received a beta blocker, and about a third took a diuretic. In addition, each volunteer was randomly assigned to receive antihypertensive therapy with 10 mg amlodipine (Norvasc, a calcium-channel blocker), 20 mg enalapril (Vasotec, an ACE inhibitor), or a placebo. The researchers tracked the patients for an average of 2 years, collecting information on cardiovascular events, hospitalizations, and deaths. In addition, 274 patients underwent intravascular ultrasounds to measure cholesterol-laden plaques before and after treatment.

Both amlodipine and enalapril lowered blood pressure by an average of about 5 mm Hg systolic and 3 mm Hg diastolic. These reductions may seem small, especially in patients already receiving aggressive multidrug therapy. Still, amlodipine reduced cardiovascular events by 31%, a statistically significant result.

Enalapril produced a 15% reduction, which did not meet the test for statistical significance. But both drugs produced similar trends toward protection against heart attack, stroke, and death, and both halted the growth of plaques as measured by intravascular ultrasound. Both drugs were well tolerated.

Although the CAMELOT Study is important, it is a relatively small and short-term investigation. Still, earlier studies suggest that systolic blood pressures of about 120 mm Hg may be best for patients with coronary artery disease. More research is needed before sweeping new guidelines are adopted, but if current trends are confirmed, blood pressure goals for patients at risk will mirror those for cholesterol: Down is up.

Last updated:	August 21, 2006