What cardiac condition is indicated by a harsh systolic and diastolic murmur in a pediatric patient?

A patent ductus arteriosus (PDA) is characterized by a continuous "machine-like" murmur, which can often be described as a harsh sound that is present during both systole and diastole. This condition occurs when the ductus arteriosus, a blood vessel that connects the pulmonary artery and the aorta, fails to close after birth, resulting in abnormal blood flow between these two vessels.

In a PDA, blood flows from the higher pressure aorta into the lower pressure pulmonary artery, leading to increased pulmonary blood flow, which is responsible for the continuous murmur. This murmur is loudest at the left upper sternal border, often described as a "systolic and diastolic" murmur due to its continuous nature.

Other conditions, while they may present with murmurs, depict different characteristics. Aortic stenosis typically presents as a systolic ejection murmur with a specific "crescendo-decrescendo" pattern and does not usually have a diastolic component. A ventricular septal defect usually features a holosystolic murmur, where the sound occurs only during systole, and an atrial septal defect may present with a systolic ejection murmur due to