Increased Pulse Pressure
The pulse pressure is the difference between systolic and diastolic pressures and reflects cardiac output. The systolic pressure rises in exercise, fever and conditions such as hyperthyroidism. Attention to the pulse pressure is important in head injuries, because a widening pulse pressure may indicate rising intracranial pressure from edema or bleeding. Aortic regurgitation
may cause a widened pulse pressure. When the aortic valve is damaged, some aortic blood flows backwards at diastole, lowering the diastolic pressure. The left ventricle now pumps more blood during systole, raising the systolic pressure.
In patent ductus arteriosus,
the connection between the pulmonary artery and aorta remains open in the adult. In the fetus, the ductus arteriosus carries blood from the pulmonary artery to the aorta, bypassing the lungs, which are inactive. If the ductus fails to close at birth, blood is shunted from the high-pressure aorta back into the pulmonary artery. The result is high output heart failure (the left ventricle is pumping two or more times the normal cardiac output). A continuous “machinery” murmur is heard over the pulmonary area.
Decreased Pulse Pressure
A narrowed pulse pressure is seen in conditions such as hypovolemic shock and cardiac tamponade. It is sometimes seen in heart failure from increased peripheral resistance and in severe aortic stenosis from decreased stroke volume.