Which condition is characterized by the presence of a continuous murmur in infants?

The presence of a continuous murmur in infants is most commonly associated with patent ductus arteriosus (PDA). In PDA, the ductus arteriosus, which is a normal fetal blood vessel that connects the pulmonary artery to the aorta, fails to close after birth. This results in continuous flow of blood from the aorta into the pulmonary artery, leading to increased pulmonary blood flow.

The murmur associated with PDA is typically described as "machinery-like" and is heard throughout the cardiac cycle, both during systole and diastole. This characteristic sound reflects the continuous nature of the blood flow through the patent ductus arteriosus. As the ductus remains open, the hemodynamic changes induced by the shunting can lead to various clinical manifestations, including heart failure if significant.

In contrast, ventricular septal defect and atrial septal defect are typically associated with systolic murmurs or fixed splitting of the second heart sound, rather than continuous murmurs. Hypertrophic cardiomyopathy features a different kind of murmur related to dynamic obstruction and is characterized by a systolic ejection murmur.

Thus, the continuous murmur is a key differentiating factor for patent ductus arteriosus, making it the