This is not an artical directly related to ONLY HCM, it is a general article.
Lisa

Which is More Important - the Upper or Lower BP Number?

Summarized by Robert W. Griffith, MD
April 11, 2003


When told they have high blood pressure, people usually want to know what sort of health risks they face, and how serious it is. Which number is more important, the upper (systolic) or the lower (diastolic) measurement? Or is the difference between the two numbers (the pulse pressure, or PP) or the average of the two (the mean arterial pressure, or MAP) more important in predicting the risk of heart attack, etc? After all, the correct use of available safe and effective drugs to control blood pressure depends on the risks shown by the actual readings. A recently reported analysis has helped to clear this up.

What was done

Harvard scientists used the results of two large clinical studies to analyze the usefulness of different blood pressure readings for determining the likelihood of a cardiovascular event (such as heart attack, a stroke, sudden heart death, or the need for a coronary bypass or angioplasty).

The trials were the Physicians' Health Study (22,000 men followed for 13 years) and the Women's Health Study (40,000 women followed for 6 years).

Separate analyses were done for the men and women. Estimates of what was called 'relative risk reduction' were made; these expressed the reduction in how likely a cardiovascular event might occur, depending on stepwise reductions in systolic blood pressure (SBP) and diastolic blood pressure (DBP).

What was found

The known risk factors for cardiovascular disease (diabetes, smoking, overweight, and so on) were present equally in both the men and women participants, except for a higher level of exercise and alcohol intake in the men, and a slightly higher body mass index (BMI, a measure of overweight) in the women.

In both men and women, lower levels of blood pressure predicted lower rates of cardiovascular events, without an obvious plateau - that is to say, a point where lowering the blood pressure further didn't improve the risk.

In men, benefits were seen with the lowering of both systolic and diastolic blood pressure values, although the effect was less clear at lower DBP levels. In women, only the lowering of SBP was associated with the reduction in risk.

These findings suggest that the systolic is more important than the diastolic pressure for predicting cardiovascular problems in both men and women, and that it's even more important in women.

Further analyses showed that the mean arterial pressure (MAP) was equivalent to the SBP in predicting risk, while the pulse pressure (PP) was about as useful as the DBP. In other words, there's no clear advantage to making these additional calculations.

How does treatment improve the risk?

The scientists who analyzed these results found that a reduction of 20 mm Hg in both SBP and DBP lowered the risk of a cardiovascular event in the next 5 years by 62% in men, and by 54% in women. If the SBP was reduced by only 5 mm Hg and the DBP by 20 mm Hg, the risk reductions were 49% for men and only 18% for women; but with an SBP reduction of 20 mm Hg and a DBP reduction of only 5 mm Hg, the risks reductions were 42% for men and 54% for women.

The detailed analyses given in the publication will clearly be very useful to clinical researchers investigating the effectiveness of new blood pressure drugs. For most of us, however, the 'take-home message' is that women must pay more attention to treating their raised systolic blood pressure, while men should watch both their upper and lower numbers, if they want to minimize their risks of the ill effects of hypertension.

Source

Development of predicative models for long-term cardiovascular risk associated with systolic and diastolic blood pressure. RJ. Glynn, GJ. L'Italien, HD. Sesso, et al., Hypertension, 2002, vol. 39, pp. 105--110