Pulse pressure
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Pulse pressure is the change in blood pressure seen during a contraction of the heart.
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[edit] Calculation
Formally it is the systolic pressure minus the diastolic pressure.[1]
It can be calculated by 
(stroke volume/compliance).
[edit] Values and variation
Usually, the resting pulse pressure in healthy adults, sitting position, is about 40 mmHg. The pulse pressure increases with exercise due to increased stroke volume, healthy values being up to pulse pressures of about 100 mmHg, simultaneously as total peripheral resistance drops during exercise. In healthy individuals the pulse pressure will typically return to normal within about 10 minutes.
For most individuals, during exercise, the systolic pressure progressively increases while the diastolic remains about the same. In some very aerobically athletic individuals, the diastolic will progressively fall as the systolic increases. This behavior facilitates a much greater increase in stroke volume and cardiac output at a lower mean arterial pressure and enables much greater aerobic capacity and physical performance. The diastolic drop reflects a much greater fall in total peripheral resistance of the muscle arterioles in response to the exercise (a greater proportion of red versus white muscle tissue).
[edit] Low values
If the usual resting pulse pressure is measured as less than 40 mmHg, the most common reason is an error of measurement. If the pulse pressure is genuinely low, e.g. 25 mmHg or less, the cause may be low stroke volume, as in Congestive Heart Failure and/or shock, a serious issue. This interpretation is reinforced if the resting heart rate is relatively rapid, e.g. 100-120 (in normal sinus rhythm), reflecting increased sympathetic nervous system activity.
[edit] High values
If the usual resting pulse pressure is consistently greater than 40 mmHg, e.g. 60 or 80 mmHg, the most likely basis is stiffness of the major arteries, aortic regurgitation (a leak in the aortic valve), an extra path for the blood to travel from the arteries to the veins, hyperthyroidism or some combination. (A chronically increased stroke volume is also a technical possibility, but very rare in practice.) Some drugs for hypertension have the side effect of increasing resting pulse pressure irreversibly. A high resting pulse pressure is harmful and tends to accelerate the normal ageing of body organs, particularly the heart, the brain and kidneys. A high pulse pressure combined with bradycardia is associated with increased intracranial pressure and should be reported to a physician immediately.
[edit] Relationship to heart disease
Recent work suggests that a high pulse pressure is an important risk factor for heart disease. A meta-analysis in 2000, which combined the results of several studies of 8,000 elderly patients in all, found that a 10 mm Hg increase in pulse pressure increased the risk of major cardiovascular complications and mortality by nearly 20%[2]. The authors suggest that this helps to explain the apparent increase in risk sometimes associated with low diastolic pressure, and warn that some medications for high blood pressure may actually increase the pulse pressure and the risk of heart disease.
