A blood pressure measurement has two readings: the systolic and the diastolic pressures. Systole is the contraction of the heart that pumps the blood into the main arteries, and diastole is the relaxation phase, in which the heart fills up again with blood entering from the veins and the lungs. (Refer back to figure 2 in chapter 3 for an illustration.) during diastole, valves close to stop the blood in the arteries rushing back into the heart, and the arteries tense, exerting a further pressure on the blood inside them, so that it continues on its way.
Pressures are measured in millimeters of mercury (mm Hg). The systolic pressure is the pressure exerted on the blood in systole, the normal being around 110-130 mm Hg, and the diastolic pressure, measured during diastole, is around 60-80 mm Hg. Blood pressures are noted down as the systolic/diastolic reading, for example, 125/80 mm Hg.
As blood pressure rises, so does the risk of a heart attack. The British Regional Heart Study revealed that at a systolic pressure equal to or higher than 148 mm Hg, the heart attack risk was twice normal. There was a raised risk, too, if the resting diastolic pressure was, on repeated measuring, above 93 mm Hg, but even those with diastolic pressures above 72 mm Hg appeared to carry some extra risk. This result was similar to those in studies conducted in the U.S., which suggest that the lower the diastolic blood pressure, the better it is for the heart.
*29\86\8*
