Cardiac catheterization is the insertion of a catheter into a chamber or vessel of the heart. Although it is more invasive than tests such as the echocardiogram, in some animals it may be necessary to perform this procedure for both diagnosis and treatment of the underlying disease. In this procedure, the animal is anesthetized and a small cut is made in the skin, allowing the insertion of the catheter into a blood vessel (artery or vein). The catheter is then guided through the vessel into one of the chambers of the heart. The location of the catheter in the heart can then be seen using a specialized form of X-ray (fluoroscopic radiography). Pressure and other information is recorded in the various heart chambers and adjacent blood vessels, which can be helpful in making a diagnosis or monitoring the success of treatment. In addition, dye can be injected through the catheter to show the path of the blood through the pumping heart, outlining the heart chambers and associated blood vessels. Administration of dye through the catheter is called angiography or angiocardiography, and is very useful in identifying abnormal heart structures (Ventricular Septal Defects or Pulmonic Stenosis). Some procedures to repair structural problems (closure of septal defects, balloon dilation of pulmonic stenosis and cardiac pacemaker implantation) use cardiac catheterization to access specific areas of the heart.