Chapter 85 Cardiac Catheterization
Cardiac catheterization is an invasive procedure used to measure the intracardiac pressure of the heart chambers and the great vessels, as well as oxygen saturation. In addition, angiography is performed when contrast or dye is injected to outline the anatomic details of any cardiac malformation. A radiopaque catheter is inserted percutaneously through a large-bore needle into a large artery, such as the femoral artery. Measurements of chamber pressures, oxygen saturation, cardiac output, and shunt flow, as well as pulmonary vascular resistance, are obtained and recorded (Box 85-1). In children, cardiac catheterization is used primarily to accurately diagnose complex cardiac defects.
Box 85-1 Normal Heart Chamber and Great Vessel Pressures and Oxygen Saturations
Heart Chamber and Great Vessel Pressures
The pressures in the systemic circuit, or on the left side of the heart, are normally higher than those in the pulmonary circuit, or on the right side of the heart.
• Superior vena cava mean pressure: 3 to 5 mm Hg
• Right atrium mean pressure: 3 to 5 mm Hg
• Right ventricle systolic/diastolic pressure: 25/3 mm Hg
• Pulmonary artery systolic/diastolic pressure: 25/10 mm Hg
• Left atrium mean pressure: 8 mm Hg
Oxygen Saturation Levels
It is normal for oxygen in the blood to be extracted by the tissues so that blood returns to the right side of the heart with an oxygen level about 30% lower than the level when it entered the left atrium from the lungs. Blood entering the left atrium is less than 97% to 100% saturated because there is mixing with blood passing through pulmonary arteriovenous and other small shunts.
• Right atrium saturation: 65% to 75%
