Why can some congenital heart defects first be discovered through a heart murmur?

Some congenital heart defects are first discovered through a heart murmur because structural abnormalities—such as holes in the heart (septal defects) or malformed valves—create turbulent blood flow as blood moves through the chambers, valves, or nearby vessels.123

When blood flows through these irregular pathways, it produces audible, prolonged swishing or hissing noises known as heart murmurs, which can be detected by a physician during auscultation using a stethoscope. In many children and adults, the presence of a congenital heart disease is identified for the first time when such a murmur is heard, as these lesions are rarely signaled by disturbances in heart rate or rhythm.1245

While some murmurs are innocent and harmless, abnormal murmurs are pathological and serve as a critical diagnostic indicator for underlying structural issues. Once a murmur is detected, further diagnostic tools like an echocardiogram are typically used to confirm the specific nature of the defect.23