The difference between systolic and diastolic pressure is called pulse pressure.


Pulse pressure has diagnostic value only if it is used together with other data (systolic and diastolic pressure, heart rate etc.). Used alone it can cause confusion. For example, a person with a blood pressure of 120/80 mmHg and a person with a blood pressure of 140/100 have the same values for the pulse pressure (40 mmHg) but their conditions are completely different: the first person has a normal blood pressure and the second one has hypertension which requires treatment.


Certain conditions (aortic valve disorders, severe anemia and hyperthyroidism) can increase your pulse pressure. The most important cause of elevated pulse pressure is stiffness and reduced elasticity of the aorta, the largest artery in the body. This may be due to high blood pressure or fatty deposits on the walls of the arteries (atherosclerosis). As the pulse pressure is higher, the stiffer and more damaged the vessels are thought to be. Pulse pressure can be used for choosing proper medication for treating high blood pressure because different medicines act differently on the pulse pressure.


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 sinus tachycardia), reflecting increased sympathetic nervous system activity and the body's response to low stroke volume and low cardiac output.