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Treatment

Why do I need this catheter? Where does it go? Can't they just give that drug by mouth or through my vein?

Some PAH patients are on a therapy called a prostacyclin. Prostacyclins are found naturally in the body and have several functions in the blood vessels of the lung. As related to PAH, two important effects of prostacyclins include vasodilation and remodeling.


Vasodilation can be important when it occurs, but may not happen in everyone treated with prostacylins. When vasodilation does occur, it is probably due to relaxation of the muscle around the smaller pulmonary arteries. This leads to lower pulmonary vascular resistance and may allow the blood flow through the pulmonary arteries to increase. Patients show a considerable amount of variation in the degree and timing of vasodilation they experience with prostacyclins.


Even when vasodilation is minimal or delayed, however, there are several other beneficial effects of prostacyclins in PAH, and these effects may end up being even more important over time. One of the most significant effects is called "remodeling," meaning a change in the shape or structure of the blood vessels. This happens via reduction of smooth muscle cells in the walls of the pulmonary arteries. Also important are prostacylins' effects on inhibition of platelet aggregation (clumping), which may lead to a decreased tendency to form clots in the pulmonary arteries.


There are six forms of prostacyclin currently available in this country for PAH patients. One medication is called iloprost (Ventavis®) and this is an inhaled medication that is described in a separate section. The other two prostacyclins are intravenous epoprostenol (Flolan® and room temperature stable Veletri®) and treprostinil in intravenous (Remodulin®®), subcutaneous (Remodulin®), inhaled (Tyvaso®®) and pill (Orenitram®) forms. More discussion of these different options is found under additional treatment-related questions in this section.


Epoprostenol requires that you have a catheter placed under your skin into one of your major veins. Typically, the subclavian vein is the site for this catheter. The subclavian vein lies underneath your clavicle (the bone between your shoulder and your neck) and carries blood returning from your arms and head to your heart. Treprostinil also can be delivered through this sort of intravenous catheter (called a central line or central catheter), but it also can be delivered as an inhaled medication or under your skin directly (this is called subcutaneous or sub-Q administration).


Epoprostenol and treprostinil (as intravenous therapies) must be administered by continuous infusion into the bloodstream. Continuous in this case means 24 hours a day, 7 days a week without interruption. It can not be given once a day or a few times a day like some other medications because of the way it is broken down in the body. It is metabolized (broken down into smaller molecules) quickly, and therefore, without a continuous infusion, the levels of the medication in the bloodstream would not be high enough to have an effect. We describe this as the medication having a very short "half-life". Epoprostenol gets broken down so quickly that it can be dangerous for patients to be disconnected from their continuous infusion for even very short periods of time. This is less of a concern with treprostinil because it lasts a little longer, but the medicine still must be given as a continuous infusion.


In order to ensure secure venous access, a special catheter must be used. If you have ever been in the hospital, you've probably had an intravenous (IV) line placed in your arm. These are placed in the superficial veins of your arms to infuse fluids and medications into the bloodstream. However, these small, peripheral IV lines usually last only a few days. Therefore, they are not practical to use for a medication like a prostacyclin that you will be receiving around the clock indefinitely. In addition, medications like prostacyclins can be irritating to small veins, and a small vein could only be used for a short time.


Therefore, in order to infuse a prostacyclin chronically, you need an IV line that is more permanent and secure (eg. you really don't want this to fall out or get damaged). This special catheter is called a central venous catheter (CVC). The central veins in your body are the large veins that are the last veins that carry blood just before it enters the heart. A CVC is a long catheter with one end on your skin (so it can be accessed) and the other end in one of these central veins. The catheters are usually placed by surgeons or interventional radiologists, and this may be done either as an office procedure or during one of your hospitalizations.


Although chronic intravenous therapy with prostacyclins has been an enormous advance in medical therapy, it still has many drawbacks. The catheters themselves can become infected, patients still have to be continuously connected to a pump, and there can be problems if the catheter kinks or becomes disconnected. Prostacyclins should also not be stopped abruptly (ie if the catheter kinks or becomes disconnected) as this might cause rebound pulmonary hypertension (where your PA pressures rise rapidly and to high levels once the medication is stopped).