Because children with an ASD often have no symptoms, the ASD may be first noticed during routine testing or medical check-ups. Most commonly, it is found when a physician uses a stethoscope to listen for a heart murmur. However, not all heart murmurs are signs of ASD. Therefore, the physician will often listen to the patient’s heart a number of times over a six- to 12-month period and may refer the patient to a cardiologist.

To help diagnose ASD, the cardiologist may first order an echocardiogram. This non-invasive test uses sound waves to track the structure and function of the heart. A moving image of the patient’s beating heart is played on a video monitor, where a physician can study the heart’s thickness, size and function. The image also shows the motion pattern and structure of the four heart valves, revealing any potential leakage (regurgitation). During this test, a Doppler ultrasound may also be done to evaluate blood flow. The echocardiogram, however, is limited because it cannot detect abnormal blood vessel connections from the lungs. An MRI is often ordered for this purpose (see below).

Other tests that might be ordered include:

• Chest x-ray. A diagnostic test that uses radiation to produce images of internal organs, structures and tissues. A chest x-ray may indicate an enlarged heart due to the increased blood flow. The test also may detect changes that can occur in the lungs due to ASD.
  
  
• Angiogram. In this test, a long, thin catheter is threaded through an artery into the heart, where it is used to inject special contrast dye that is visible under x-ray. This can help the physician trace the flow of the blood through the heart. Because of advancing MRI and ultrasound technology, this test is rarely used today, although catheter-based interventions remain an important part of therapy for ASDs.
  
  
• Magnetic resonance imaging (MRI). In this test, powerful magnets are used to create images of the heart on a screen, which can help the physician visualize the function of the heart. Researchers are also testing a newer diagnostic tool called an XMR. This test combines the MRI with a traditional x-ray to allow better visualization of the heart.