An arteriovenous (AV) fistula is a surgically created connection between an artery and a vein, typically in the arm. This procedure provides a robust and reliable point of access for hemodialysis, a treatment that filters waste and excess fluid from the blood when kidneys no longer function adequately. Regular self-assessment of the AV fistula is important for monitoring its health and longevity. Early detection of potential issues helps maintain the fistula’s function.
What Bruit and Thrill Signify
A thrill is a distinct, palpable vibration that can be felt over a functioning AV fistula, generated by the turbulent flow of blood as it moves from the high-pressure artery into the lower-pressure vein. A bruit is the characteristic whooshing or rumbling sound heard with a stethoscope over the fistula, also resulting from turbulent blood flow. The continuous presence of both a thrill and a distinct bruit indicates a properly functioning AV fistula. These are positive indicators of adequate blood flow and patency.
Performing the Assessment
Assessing your AV fistula for thrill and bruit involves both touch and sound. To feel for the thrill, gently place your fingertips over the area where your fistula is located. You should feel a continuous vibration, which some describe as a buzzing or purring sensation. Start by feeling at the anastomosis, where the artery and vein were joined, as this is typically where the thrill is strongest. Gradually move your fingertips along the course of the vein toward your shoulder, observing how the strength of the thrill changes. A healthy thrill should feel soft and continuous, gradually diminishing in intensity as you move away from the anastomosis.
To listen for the bruit, use the diaphragm of a stethoscope and place it directly over the fistula, typically at the anastomosis. You should hear a characteristic whooshing or rumbling sound. A normal bruit is usually low-pitched and continuous, audible throughout both the systolic and diastolic phases of the heartbeat. Move the stethoscope along the entire length of the fistula.
Interpreting Your Findings
A healthy AV fistula will exhibit a strong, continuous thrill that feels like a steady vibration under the skin. When auscultated with a stethoscope, a normal fistula produces a low-pitched, continuous whooshing or rumbling bruit. These findings indicate that there is good blood flow and the fistula remains open and functional. The presence of both a clear thrill and bruit confirms the patency necessary for effective hemodialysis.
Changes in these findings can signal potential problems. The complete absence of a thrill or bruit suggests that blood flow has stopped, possibly due to a clot. A thrill or bruit that is weak or intermittent may indicate a narrowing of the vessel, known as stenosis, or reduced blood flow. A high-pitched or whistling bruit, or one heard only during systole, can also point to significant narrowing within the fistula.
If the thrill or bruit feels pulsatile but lacks continuity, it might suggest an obstruction upstream or issues with the inflow of blood. Other local signs such as swelling, redness, or warmth around the fistula site could indicate an infection or a hematoma. Any new or worsening pain or tenderness at the fistula site also warrants attention.
When to Seek Medical Attention
Contact your healthcare provider or dialysis center if you notice a sudden absence of the thrill or bruit in your AV fistula. Any significant change in the quality of the thrill or bruit, such as it becoming weak, intermittent, or high-pitched, also requires immediate medical evaluation. New or worsening pain, swelling, redness, or warmth at the fistula site are concerning signs that should be reported.
Bleeding from the fistula site that does not stop with direct pressure also warrants attention. Symptoms such as numbness, tingling, or coldness in the hand or arm connected to the fistula may indicate a condition where blood is diverted away from the extremity. Seeking timely medical advice for these symptoms is important to prevent serious complications and preserve the long-term function of your fistula.