Why Are There Widened Pulse Pressures With a PDA?

Patent ductus arteriosus (PDA) is a heart defect that is present at birth. At first, it may not cause any problems except for a heart murmur, or it may cause severe problems. If left untreated, it will lead to complications.

Anatomy

• The fetus has an extra blood vessel called the ductus arteriosus that connects the aorta and the pulmonary artery of the heart. According to the Mayo Clinic, the ductus usually closes within the first two to three days after birth, but sometimes, especially in premature babies, it remains open. "Patent" is another word for open.

Physiology

• As explained on the National Heart Lung and Blood Institute website, blood is normally pumped from the left ventricle to the aorta and then distributed to the rest of the body. In the case of a PDA, some of the blood is diverted back through the PDA to the pulmonary artery. It then goes back to the lungs, then the left side of the heart, and then to the aorta and PDA again. Some of the blood meant for the rest of the body is continually flowing through the heart chambers, which can lead to heart failure.

Consequences

• The difference between the two numbers in a blood pressure reading is called the pulse pressure. As stated in the textbook "Moss and Adams' Heart Disease in Infants, Children, and Adolescents," the high volume of blood flowing through the heart with a PDA causes a high systolic pressure (the first number), and the rush of blood through the PDA causes a low diastolic pressure (the second number). This large gap is called a widened pulse pressure.