Pulse pressure is the difference between the systolic and diastolic pressure readings.
It is measured in millimeters of mercury. It represents the force that the heart generates
each time it contracts. If resting blood pressure is 120/80 millimeters of mercury, pulse pressure
is 40.
Calculation Formally it is the systolic pressure minus
the diastolic pressure. Theoretically, the systemic pulse pressure
can be conceptualized as being proportional to stroke volume, or the amount of blood ejected
from the left ventricle during systole and inversely proportional to the compliance of
the aorta. The aorta has the highest compliance in the
arterial system due in part to a relatively greater proportion of elastin fibers versus
smooth muscle and collagen. This serves the important function of damping the pulsatile
output of the left ventricle, thereby reducing the pulse pressure. If the aorta becomes rigid
in conditions such as arteriosclerosis or atherosclerosis, the pulse pressure would
be very high. Systemic pulse pressure = Psystolic - Pdiastolic
= 120mmHg - 80mmHg = 40mmHg Pulmonary pulse pressure = Psystolic - Pdiastolic
= 25mmHg - 10mmHg = 15mmHg Values and variation
Low Pulse Pressure A pulse pressure is considered abnormally
low if it is less than 25% of the systolic value. The most common cause of a low pulse
pressure is a drop in left ventricular stroke volume. In trauma a low or narrow pulse pressure
suggests significant blood loss. If the pulse pressure is extremely low, i.e.
25 mmHg or less, the cause may be low stroke volume, as in Congestive Heart Failure and/or
shock. A narrow pulse pressure is also caused by
aortic valve stenosis and cardiac tamponade. High Pulse Pressure
High values during or shortly after exercise Usually, the resting pulse pressure in healthy
adults, sitting position, is about 30-40 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 aerobic exercise, the systolic pressure progressively increases
while the diastolic remains about the same. In some very aerobically athletic individuals,
for example distance runners, 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. Individuals with larger BMIs due to increased
muscle mass have also been shown to have lower diastolic pressures and larger pulse pressures.
Consistently high values If the usual resting pulse pressure is consistently
greater than 100 mmHg, the most likely basis is stiffness of the major arteries, aortic
regurgitation, arteriovenous malformation, hyperthyroidism or some combination. While
some drugs for hypertension have the side effect of increasing resting pulse pressure
irreversibly, other hypertension drugs, such as ACE Inhibitors, have been shown to lower
pulse pressure. A high resting pulse pressure is harmful and tends to accelerate the normal
aging of body organs, particularly the heart, the brain and kidneys. A high pulse pressure
combined with bradycardia and an irregular breathing pattern is associated with increased
intracranial pressure and should be reported to a physician immediately. This is known
as Cushing's triad and can be seen in patients after head trauma related to intracranial
hemorrhage or edema. Examples:
Atherosclerosis Arteriovenous fistula
Chronic aortic regurgitation Thyrotoxicosis
Fever Anemia
Pregnancy Anxiety
Heart block Aortic dissection
Endocarditis Raised intracranial pressure
beri beri hyperkinetic heart syndrome
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%. Heightened pulse pressure is also a risk factor for the development of
atrial fibrillation. The authors of the meta-analysis 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. Self measurement
Pulse pressure readings can be taken on a home blood pressure monitoring device. These
devices display systolic and diastolic blood pressure, from which pulse pressure can be
calculated, and pulse rate readings. Monitoring at home will measure true pulse and blood
pressure and is helpful to a medical provider in interpreting in-office results and/or progression
of disease processes. Treatment
If the patient suffers from elevated pulse pressure, treatment may include medications
that address this factor, such as an angiotensin-converting enzyme inhibitor.
Effect of folic acid A 2005 study found that 5 mg of folate daily
over a three-week period reduced pulse pressure by 4.7 mm of Hg compared with a placebo,
and concluded that folic acid is an effective supplement that targets large artery stiffness
and may prevent isolated systolic hypertension. See also
Blood pressure Mean arterial pressure
Cold pressor test Hypertension
Prehypertension Antihypertensive
Patent ductus arteriosus References