Congenital heart defects causing acyanotic congestive heart failure usually involve which mechanism?

Congenital heart defects leading to acyanotic congestive heart failure typically involve left to right shunts. In these defects, blood flows from the left side of the heart, where the pressure is higher, to the right side, where the pressure is lower. This shunting occurs through anatomic defects like atrial septal defects or ventricular septal defects, allowing oxygen-rich blood to mix with oxygen-poor blood.

The result is an increased volume of blood returning to the right side of the heart and subsequently to the lungs, leading to congestion and the characteristic symptoms of heart failure. Since the primary blood flow remains in the systemic circulation, the patient does not experience cyanosis, which is why these conditions are classified as acyanotic heart defects.

Other mechanisms, such as obstructive lesions, right to left shunts, or mixed lesions, can cause problems but are more associated with different presentations, such as cyanotic congenital heart disease, where the mixing leads to reduced oxygen saturation in the arterial blood, resulting in cyanosis.