Pulse pressure

A pulse pressure is considered abnormally low if it is less than 25% of the systolic value.[2] If the pulse pressure is extremely low, i.e. 25 mmHg or less, it may indicate low stroke volume, as in congestive heart failure.[3]

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.[8]

A narrow pulse pressure is also caused by aortic stenosis.[3]

For most individuals, during aerobic exercise, the systolic pressure progressively increases while the diastolic pressure remains about the same, thereby widening the pulse pressure. These pressure changes facilitate an increase in stroke volume and cardiac output at a lower mean arterial pressure, enabling greater aerobic capacity and physical performance. The diastolic drop reflects a reduced systemic vascular resistance of the muscle arterioles in response to the exercise.[9]

A pulse pressures of 50 mmHg or more can increase the risk of heart disease, heart rhythm disorders, stroke and other cardiovascular diseases and events. Higher pulse pressures are also thought to play a role in eye and kidney damage from diseases such as diabetes.[3] If the usual resting pulse pressure is consistently greater than 100 mmHg, potential factors are stiffness of the major arteries, aortic regurgitation (a leak in the aortic valve), or arteriovenous malformation, among others.[3] While some drugs for hypertension have the side effect of increasing resting pulse pressure, other antihypertensive drugs, such as hydrochlorothiazide, have been shown to lower pulse pressure.[10] A high pulse pressure combined with bradycardia and an irregular breathing pattern is associated with increased intracranial pressure, a condition called Cushing's triad seen in people after head trauma with increased intracranial pressure.[11]

Common causes of widening pulse pressure include:[3]

• Anemia
• Aortic dissection
• Atherosclerosis
• Arteriovenous fistula
• Chronic aortic regurgitation
• Aortic root aneurysm[12]
• Aortic root dilation[12]
• Beri beri
• Distributive shock
• Endocarditis
• Fever
• Heart block
• Increased intracranial pressure[11]
• Patent ductus arteriosus
• Pregnancy
• Thyrotoxicosis

Awareness of the effects of pulse pressure on morbidity and mortality is lacking relative to the awareness of the effects of elevated systolic and diastolic blood pressure. However, pulse pressure has usually been found to be a stronger independent predictor of cardiovascular events, especially in older populations, than has systolic, diastolic, or mean arterial pressure.[3]

A meta-analysis in 2000 showed that a 10 mmHg increase in pulse pressure was associated with a 20% increased risk of cardiovascular mortality, and a 13% increase in risk for all coronary end points. The study authors also noted that, while risks of cardiovascular end points do increase with higher systolic pressures, at any given systolic blood pressure the risk of major cardiovascular end points increases, rather than decreases, with lower diastolic levels.[13] This suggests that interventions that lower diastolic pressure without also lowering systolic pressure (and thus lowering pulse pressure) could actually be counterproductive. Increased pulse pressure is also a risk factor for the development of atrial fibrillation.[14]

A 2001 randomized, placebo-controlled trial of 1,292 male veterans, compared the effects of hydrochlorothiazide (a thiazide diuretic), atenolol (a beta-blocker), captopril (an ACE inhibitor), clonidine (a central α2-agonist), diltiazem (a calcium channel blocker), and prazosin (an α1-blocker) on pulse pressure and found that, after one year of treatment, hydrochlorothiazide was the most effective at lowering pulse pressure, with an average decrease of 8.6 mm Hg. Captopril and atenolol were equal as least effective, with an average decrease of 4.1 mm Hg. Clonidine (decrease of 6.3 mm Hg), diltiazem (decrease of 5.5 mm Hg), and prazosin (decrease of 5.0 mm Hg) were intermediate.[10]

Diastolic blood pressure falls during the early stages of sepsis, causing a widening of pulse pressure. If sepsis becomes severe and hemodynamic compromise advances, the systolic pressure also decreases, causing a narrowing of pulse pressure.[15] A pulse pressure of over 70 mmHg in patients with sepsis is correlated with an increased chance of survival. A widened pulse pressure is also correlated with an increased chance that someone with sepsis will benefit from and respond to IV fluids.[16]