Pulse pressure

Pulse pressure is the difference between systolic and diastolic blood pressure. It is measured in millimeters of mercury (mmHg). It represents the force that the heart generates each time it contracts. Resting blood pressure is normally approximately 120/80 mmHg, which yields a pulse pressure of approximately 40 mm Hg.

Causes

High

High sodium intake may cause high pulse pressure.

Calculation

Pulse pressure is the (higher) systolic blood pressure minus the (lower) diastolic blood pressure.

The systemic pulse pressure is approximately proportional to stroke volume, or the amount of blood ejected from the left ventricle during systole (pump action) and inversely proportional to the compliance (similar to Elasticity) 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 ( max pump pressure) output of the left ventricle, thereby reducing the initial systolic pulse pressure but slightly raising the subsequent diastolic phase (a period rather similar to Dwell time). If the aorta becomes rigid because of disorders such as arteriosclerosis or atherosclerosis, the pulse pressure would be very high because the aorta becomes less compliant due to the formation of rigid lesions to the (otherwise flexible) aorta wall.
* Systemic pulse pressure (SPP) (usually measured at upper right arm artery) = P_systolic - P_diastolic
:e.g. normal 120mmHg - 80mmHg = 40mmHg
: low 107mmHg - 80mmHg = 27mmHg
: high 160mmHg - 80mmHg = 80mmHg
* Pulmonary pulse pressure (PAP) (Heart-Lung), is normally significant lower than systemic blood pressure due to the higher compliance of the pulmonary system compared to systemic circulation. It is measured by right heart catheterization or may be estimated by transthoracic echocardiography (TTE) Normal pulmonary artery pressure is between 8mmHg -20 mm Hg at rest.
: e.g. normal 15mmHg - 8mmHg = 7mmHg
: high 25mmHg - 10mmHg = 15mmHg

Values and variation

Low (narrow)

The most common cause of a low (narrow) pulse pressure is a drop in left ventricular stroke volume.
In trauma, a low or narrow pulse pressure suggests significant blood loss (insufficient preload leading to reduced cardiac output).

A narrow pulse pressure is also caused by aortic valve stenosis and cardiac tamponade.

Systemic

A pulse pressure is considered abnormally low if it is less than 25% of the systolic value. 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 cardiogenic shock.

High (wide)

From 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 systemic vascular resistance drops during exercise. In healthy individuals the pulse pressure will typically return to normal within about 11 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 systemic vascular resistance of the muscle arterioles in response to the exercise (a greater proportion of red versus white muscle tissue). Individuals with larger BMIs due to increased muscle mass (bodybuilders) have also been shown to have lower diastolic pressures and larger pulse pressures.

Consistently high

If the usual resting pulse pressure is consistently greater than 100 mmHg, the most likely basis is stiffness of the major arteries, aortic regurgitation (a leak in the aortic valve), arteriovenous malformation (an extra path for blood to travel from a high pressure artery to a low pressure vein without the gradient of a capillary bed), hyperthyroidism or some combination. (A chronically increased stroke volume is also a technical possibility, but very rare in practice.) While some drugs for hypertension have the side effect of increasing resting pulse pressure irreversibly, other antihypertensive 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 increased intracranial pressure.

Some common causes of widening pulse pressure :

* Anemia
* Aortic dissection
* Atherosclerosis
* Arteriovenous fistula
* Chronic aortic regurgitation
* Aortic root aneurysm
* Aortic root dilation
* Beri beri
* Distributive shock
* Endocarditis
* Fever
* Heart block
* Increased intracranial pressure
* Patent ductus arteriosus
* Pregnancy
* Thyrotoxicosis

Clinical signficance

Heart disease

A meta-analysis study conducted in 2000, suggested that a high pulse pressure is an important risk factor for heart disease. The study, 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.

Psychotic disorders

In a large study (N=1289) among patients with psychotic disorders researchers found that, when controlling for patients' age and cardiovascular disease status, body mass index (BMI) and employment status predicted the likelihood of having elevated pulse pressure. Further, it was also found that elevated pulse pressure was (above 60 mm/Hg) mainly associated with the physical domains of functioning such as mobility and self-care.

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 can be helpful to a medical provider in interpreting in-office results and 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 (ACE inhibitor).

See also

* Mean arterial pressure
* Cold pressor test
* Hypertension
* Prehypertension
* Antihypertensive
* Patent ductus arteriosus

References

{{DEFAULTSORT:Pulse Pressure
Medical signs
Cardiovascular physiology