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Diagnostic Tests

Can you show me how a heart catheterization works?

A cardiac or right heart catheterization is a test which directly measures the pressures in the chambers of the heart and the pulmonary arteries. The test is performed by either a pulmonologist or a cardiologist who has advanced training in doing invasive procedures. Typically this test is performed in a special part of the hospital called a cardiac catheterization laboratory (cath lab) or an intensive care unit (ICU). The procedure is done under local anesthesia (numbing medicine at the site of the insertion of the catheter into the skin), and you may receive some medications to make you slightly sleepy, but you will remain awake.

The goal of this procedure is to insert a long catheter (a very thin tube about the width of a thick strand of spaghetti) with a pressure measuring device into one of the large veins of the body that drains into the right atrium. Veins that are typically used for catheter entry include the subclavian vein or internal jugular vein, both located in the neck, or the femoral vein, located in the groin. If the neck approach is used, the catheter travels into the large vein (superior vena cava) that drains the upper body and then on into the right atrium. If the groin approach is chosen, the doctor inserts the catheter into the femoral vein and then guides it through the large vein (inferior vena cava) that drains blood from the lower body and then on into the right atrium.

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Pressures are recorded at different points along the catheter's journey, including in the right atrium and right ventricle of the heart. The doctor advances the catheter from the right ventricle into the pulmonary arteries and moves it forward through the arterial branches until it can't be moved any further. A small balloon at the tip of the catheter prevents any damage to the vessels. When the catheter is as far along as possible, the balloon is inflated, thereby wedging the tip of the catheter at this point – called the "wedge" position. The pressures that are then recorded at the tip of the catheter accurately reflect the pressures on the left side of the heart and are important to help your doctor rule out left sided heart problems (like congestive heart failure or valvular heart disease) as a cause of your pulmonary hypertension.

With a catheter in the pulmonary arteries, medications such as nitric oxide, epoprostenol or adenosine, can be given as short-acting vasodilators (substances that dilate vessels). If the pulmonary vessels are able to dilate in response to the medication, then there is an immediate reduction in pressure and the pulmonary circulation is said to be "reactive." If a patient's pulmonary pressures become normal or near normal with these medications (see medication section), the patient is termed a "responder" to vasodilators. Additionally, with the catheter in this position, patients can be given a "fluid challenge" (meaning a specific amount of fluid in a short period of time) to see how the heart responds. Patients may also be asked to perform leg exercise with the catheter in place to see how the pressures respond to increased demands on the heart.

After the catheter is removed, bleeding is prevented by exerting pressure at the site of the vein puncture in either the groin or the neck. Typically, pressure is held for a longer period of time than when you have blood drawn from your arm. Some patients can go home after catheterization, but others may need to stay in the hospital with their catheter in place while they are started on medications to treat PAH.