Should a temporal artery biopsy or a PET-CT scan of the head and neck be performed in a patient with a recent subclavian artery stent and on prasugrel?

From the Guidelines

For a patient with a recent subclavian artery stent who is on prasugrel, a PET-CT scan of the head and neck is the preferred diagnostic approach over a temporal artery biopsy. This recommendation is based on the high sensitivity and specificity of PET-CT in detecting vascular inflammation in conditions like giant cell arteritis, as demonstrated in several studies, including those published in the Journal of the American College of Radiology 1. The use of PET-CT avoids the significant bleeding risks associated with temporal artery biopsy in patients on dual antiplatelet therapy like prasugrel. Discontinuing prasugrel prematurely, within the first 3-6 months after stent placement, significantly increases the risk of major adverse cardiac events, including stent thrombosis and death.

Given the patient's recent subclavian artery stent placement and ongoing prasugrel therapy, the non-invasive nature of PET-CT makes it an attractive alternative for diagnosing vasculitis without interrupting antiplatelet therapy. Studies have shown that FDG-PET/CT can detect vascular wall inflammation with high accuracy, and its prognostic value, particularly in assessing the risk of ischemic complications, makes it a valuable tool in managing patients with suspected large vessel vasculitis 1.

Key considerations include:

• The sensitivity and specificity of FDG-PET/CT for diagnosing large vessel vasculitis, which ranges from 75% to 90% and from 81% to 98%, respectively 1.
• The potential for false-negative results with temporal artery biopsy, as high as 61% in some cases, which can lead to underdiagnosis of vasculitis 1.
• The importance of not interrupting prasugrel therapy in the first few months after stent placement to prevent stent thrombosis and other major adverse cardiac events.
• The role of PET-CT in providing prognostic information and guiding treatment decisions in patients with large vessel vasculitis.

Overall, the benefits of using PET-CT for diagnosing vasculitis in this patient outweigh the risks, particularly considering the potential complications of temporal artery biopsy in the setting of dual antiplatelet therapy.

From the Research

Diagnostic Approaches for Giant Cell Arteritis

In a patient with a recent subclavian artery stent and on prasugrel, considering the diagnosis of giant cell arteritis (GCA), the choice between a temporal artery biopsy (TAB) and a PET-CT scan of the head and neck depends on several factors, including the clinical presentation, the need for rapid diagnosis, and the potential for large vessel involvement.

Temporal Artery Biopsy (TAB)

• TAB is considered a gold standard for diagnosing GCA, especially when clinical suspicion is high and the patient has not been on glucocorticoids for an extended period 2.
• However, TAB may not always be positive in patients with GCA, particularly if the disease involves larger arteries or if the patient has already started glucocorticoid therapy 3.

PET-CT Scan

• PET-CT scans, particularly those using 18F-FDG, have shown promise in diagnosing GCA by visualizing inflammation in the large arteries, including the aorta and its branches 4, 5.
• The sensitivity and specificity of PET-CT for GCA diagnosis can be high, especially when using specific scoring methods and when patients have not been on glucocorticoids for an extended period 4.
• PET-CT can also detect involvement of the temporal, occipital, and vertebral arteries, which might not be apparent through TAB alone 5.
• In patients with suspected GCA and a negative TAB, PET-CT can be particularly useful for assessing large vessel involvement and guiding further management 6.

Considerations for the Patient with a Subclavian Artery Stent

• Given the patient's recent subclavian artery stent placement and the use of prasugrel, an antiplatelet agent, there might be an increased risk of bleeding with a TAB.
• A PET-CT scan might offer a less invasive alternative for assessing the presence of GCA, especially if there is suspicion of large vessel involvement or if the patient is already on glucocorticoids.

Decision Making

• The decision between TAB and PET-CT should be based on the individual patient's clinical presentation, the urgency of diagnosis, and the potential risks and benefits of each procedure.
• Consultation with specialists, including rheumatologists and radiologists, can help in making an informed decision about the most appropriate diagnostic approach for the patient.