Several diagnostic tests can be used to help the physician to diagnose cardiac tamponade and rule out other conditions. Tests typically include:

• Echocardiogram. This test uses sound waves to visualize the structures and functions of the heart. It may reveal a buildup of fluid in the pericardium, abnormal heart movements (a “swinging heart”) and/or a dilated vena cava. Echocardiograms can also be used to exclude other possible causes for the symtoms, including tumors, constrictive pericarditis, cardiomyopathy and blood clots. In addition, a Doppler ultrasound may be done to measure blood flow. This test may show insufficient diastolic (relaxation) activity in the right atrium and right ventricle. It may also reveal heart valve obstruction or leakage as the cause of the bulging neck veins.
  
  
  
  
  
• Electrocardiogram (EKG). A recording of the heart’s electrical activity as a graph on a moving strip of paper or video monitor. The test, in the presence of cardiac tamponade, often exhibits low electrical voltage.
  
  
  
  
  
• Chest x-ray. The x-ray may show an enlarged cardiac “silhouette” due to an excessive volume of pericardial fluid, especially when more than 200 milliliters of fluid has built up in the pericardium.