QUESTIONS & ANSWERS: GLOSSARY

Blood pressure

The pressure in the arteries is generated by the heart and evened out between the beat ("systole") and the pause between beats ("diastole") by a combination of resistance at the tissues of the body and the elasticity of the arteries. The pressure is measured in "millimetres of mercury (mmHg)", ie the height of a column of mercury that exactly balances the pressure in the artery. This can be determined by varying the pressure in a cuff around a limb and finding out at what pressure blood is allowed through. The normal blood pressure (BP) is 120/80mmHg. If a too high BP is maintained (hypertension) there are adverse consequences for which the British Heart Foundation can provide further information. These adverse consequences include an increased likelihood for developing coronary heart disease (CHD).

The coronary arteries supply blood to the heart muscle and come off the main artery (the aorta). The flow of blood through the coronary arteries depends in a complex manner on the blood pressure to push the blood through the resistance of the vessels in the heart wall. This resistance is so high during systole that coronary blood flow stops. Most of the blood gets to the heart muscle during diastole. This is the reason why, when there is a very severe acute problem with coronary blood flow, "aortic balloon pumping" is used to increase diastolic blood pressure, while decreasing systolic blood pressure to relieve the heart itself.

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