Which heart defect is characterized by a continuous machinery murmur?

The heart defect that is characterized by a continuous machinery murmur is the persistent ductus arteriosus. This condition occurs when the ductus arteriosus, which is a normal part of fetal circulation that connects the pulmonary artery to the aorta, fails to close after birth. As a result, blood flows continuously from the aorta into the pulmonary artery, leading to increased blood flow to the lungs.

The continuous murmur is due to the constant flow of blood through the PDA, and it is typically described as a "machinery-like" sound because of the ascending and descending components of the flow. This sound can often be heard best during the systolic phase and may continue into diastole, which distinguishes it from murmurs associated with other congenital heart defects such as ventricular septal defect or atrial septal defect, which typically produce different patterns of sound.

Understanding this characteristic murmur helps in the diagnosis of the persistent ductus arteriosus and highlights the unique hemodynamic changes that occur when blood flow is shunted inappropriately from the systemic circulation to the pulmonary circulation.