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|Newsletters: Preserving and Creating Vascular Access: The Interventional Radiologist at Work|
Preserving and Creating Vascular Access: The Interventional Radiologist at Work
Elvira Lang, MD Director, Cardiovascular/Interventional Radiology, Beth Israel Deaconess Medical Center
If access is an issue for you, don’t miss the promising new solutions Dr. Lang describes in the article below. Dr. Lang has 21 years experience in cardiovascular/interventional radiology. In addition to her practice at Beth Israel Deaconess in Boston, she is an Associate Professor of Radiology and Medicine at Harvard Medical School. Dr. Lang’s talk from last year’s Oley conference is available from the Oley Videotape Library.
Most readers are probably already familiar with an interventional radiologist. For those who aren’t, interventional radiologists are physicians who perform minimally invasive surgery by using x-rays or other imaged guidance to advance their instruments within the body through small skin openings. Imaged guidance can help HomePEN consumers preserve their access by allowing the interventional radiologist to accurately assess the status of the consumer’s venous system and that of any indwelling catheters. Tunneled catheters can be placed de novo (from scratch), or if catheters are not functioning, they can be redirected, cleaned, and liberated from fibrin sheaths. If needed, patency of veins can be restored to permit the placement of a new catheter. Following is a brief description of how interventional radiologists preserve and create vascular access.
Occasionally the tips of catheters, particularly those that have been placed without imaged guidance, may “slip up” into one of the jugular veins, or be misplaced — leaving their tip in an undesirable location. In these instances, the interventional radiologist can approach the venous system from the femoral vein (in the groin) and advance a small catheter to the tip of the tunneled line, snare it with a lasso-device and pull it towards the desired location (see photos below).
Catheters that have become occluded can be treated by injecting a clot-dissolving agent, such as tissue plasminogen activator (t-PA), or can be cleared by mechanical means, such as with a small brush. When a fibrin sheath forms around the tip of the catheter it can adhere to the wall of the superior vena cava, and make it difficult for the consumer to aspirate blood or infuse through the catheter. Traditionally, these fibrin sheaths have been addressed by gaining access from the femoral vein, and stripping the fibrin sheath off with a snare.
We have recently developed a less invasive method to restore patency, which involves placing an “internal lasso” through the hub of the tunneled catheter that breaks the fibrin sheath apart when it exits the catheter. Provided they are not infected, tunneled catheters can also be exchanged for new catheters using a guidewire technique.
Narrowed Blood Vessels
Occasionally, catheters induce intimal hyperplasia at their tips: a build-up of tissue arising from the vessel wall which can lead to some narrowing. Consumers who have had repeat central access, or are on dialysis, are more likely to develop such central stenoses. These stenoses can progress to the point where they occlude the vessels, preventing access, and can also cause swelling of the upper extremities, such as in the neck or face.
Stenoses can be treated by balloon angioplasty. Occasionally it is necessary to place a metallic meshwork (a “stent”) to keep the area of dilated stenosis open. If a clot has developed in the narrowed area, the interventional radiologist can treat it by infusing a clot-dissolving agent. When stenosis or thrombosis persists over an extended time, the occlusion can become very difficult to treat. Commonly, however, we are still able to cross blockages with catheters and guidewires and then proceed with clot-dissolving agents, angioplasty and/or stenting. Even some chronic occlusions may clear up with the infusion of clot-dissolving agents.
An additional “specialty of the house” at the Beth Israel Deaconess Medical Center is sharp recanalization of chronic vein occlusions. In these cases, a special needle system is used to create a new channel through very firm blockages. This is performed when all other traditional means with catheters and guidewires fail in restoring vascular patency. With an assembly of devices invented for this purpose several years ago, we perform the following procedure: The area of occlusion is approached with catheters coming from both ends (typically one upper extremity and one lower extremity approach). After ensuring that both ends are aligned in a straight passageway, a 21g needle is advanced through a protective catheter and very carefully probed under imaged guidance until it enters the adjacent patent vessel. From there on, standard catheter guidewire techniques can be used, and stenting is typically required. This method is particularly beneficial for creating new venous access, when practically all access would be lost otherwise.
When angioplasty or stenting is performed, it is not uncommon for a touch-up to be necessary within one year. In response to these procedures, the vessels may develop some exuberant formation of intimal hyperplasia, which itself can be treated with angioplasty and possibly some additional stenting.
The great advantage of the interventional approach is the availability of multiple devices and experience that can draw from applications in other regions of the body. So, if there is a special problem arising that needs fixing, experienced interventionalists typically can “invent a solution while you wait.”
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