An arteriovenous (AV) fistula serves as a lifeline for many individuals undergoing dialysis, creating a direct connection between an artery and a vein, typically in the arm. This surgically created access allows for efficient blood flow during hemodialysis treatments. However, a serious complication known as AV fistula thrombosis can occur, which involves the formation of a blood clot within this specialized vessel, significantly hindering its ability to function for dialysis.
Understanding AV Fistula Thrombosis
AV fistula thrombosis occurs when a blood clot, or thrombus, forms inside the surgically created connection between an artery and a vein. This clot obstructs normal blood flow, potentially leading to a complete blockage.
When a fistula thromboses, it can no longer be used for dialysis, a life-sustaining treatment for patients with end-stage renal disease. This necessitates alternative, often temporary, vascular access, which carries its own risks. Understanding this complication is important for patients and their caregivers.
Factors Contributing to Thrombosis
Several factors can contribute to a blood clot forming within an AV fistula. Stenosis, or the narrowing of the blood vessel, is a primary cause. This narrowing often occurs at the venous anastomosis, where the artery and vein are joined, due to neointimal hyperplasia, a thickening of the vessel wall.
Patient-related factors also increase thrombosis risk. These include hypercoagulable states, which promote blood clotting. Low blood pressure (hypotension) can reduce blood flow through the fistula, leading to stasis and increasing clot formation. Dehydration can also thicken blood, making it more prone to clotting.
Repeated punctures for dialysis can damage the vessel wall, leading to stenosis. External compression on the fistula, such as from tight clothing or sleeping positions, can impede blood flow. Underlying health conditions like heart disease or uncontrolled blood pressure may also contribute to a higher risk by affecting overall circulatory health.
Recognizing the Signs
Recognizing the signs of AV fistula thrombosis is important for preserving its function. A common sign is the loss of a “thrill” or “bruit” in the fistula. A thrill is a vibrating sensation felt over the fistula, while a bruit is a whooshing sound heard with a stethoscope, both indicating active blood flow.
If the fistula has clotted, these sensations will be absent or diminished. The affected limb may also show swelling, pain or tenderness over the site, and a purplish discoloration. The skin over the fistula may feel cooler to the touch due to reduced blood flow. Any of these changes warrant immediate medical attention to assess the fistula’s condition.
Treatment Options
When AV fistula thrombosis occurs, several medical interventions aim to restore blood flow and preserve the access for dialysis. One common approach is thrombectomy, which involves physically removing the blood clot. This can be performed surgically, with an incision to extract the clot, or mechanically, using specialized catheter-inserted devices.
Another treatment option is thrombolysis, which involves injecting clot-dissolving medication, such as tissue plasminogen activator (tPA), directly into the fistula. This medication breaks down the clot. Following clot removal or dissolution, angioplasty is often performed to address any underlying stenosis that may have contributed to the thrombosis. This procedure involves inflating a balloon within the narrowed vessel to widen it, and sometimes a stent may be placed to keep the vessel open.
The goal of these treatments is to restore the fistula’s patency. Prompt treatment is important for a successful outcome and to prevent the need for a new vascular access site. The success rate for endovascular approaches to thrombosed fistulas is high, ranging from 80% to 90%.
Strategies for Prevention
Preventing AV fistula thrombosis involves patient self-care and professional oversight. Maintaining adequate hydration helps prevent blood from becoming too thick and prone to clotting. Avoiding tight clothing, jewelry, or anything that could compress the arm with the fistula is also advised to ensure uninterrupted blood flow.
Protecting the fistula from injury, such as avoiding blood pressure measurements or blood draws in the fistula arm, is key. Regular assessment by healthcare professionals, including physical examination and monitoring blood flow during dialysis, can help detect early signs of dysfunction. Prompt treatment of any infections near the fistula site can prevent inflammation and potential clotting. Adherence to medical advice regarding blood pressure management and prescribed medications, including antiplatelet drugs when indicated, also contributes to long-term fistula patency.