What is the recommended imaging protocol after Tenecteplase (tPA) administration for acute ischemic stroke?

Post-Tenecteplase Imaging Protocol for Acute Ischemic Stroke

After Tenecteplase (TNK) administration for acute ischemic stroke, a follow-up non-contrast CT scan should be performed at 24 hours to assess for hemorrhagic transformation before initiating or continuing antithrombotic therapy. 1

Initial Imaging Considerations

The imaging protocol after Tenecteplase administration follows similar principles to post-thrombolytic imaging in general:

• 24-hour follow-up imaging: A non-contrast CT (NCCT) scan is essential at 24 hours post-thrombolysis to:

  • Detect hemorrhagic transformation
  • Assess infarct evolution
  • Guide subsequent management decisions, particularly regarding antithrombotic therapy

• Earlier imaging if clinical deterioration: If the patient experiences neurological worsening after TNK administration, an immediate NCCT should be performed to rule out hemorrhagic transformation 1

Imaging Modality Selection

Non-Contrast CT (NCCT)

• Remains the standard follow-up imaging modality due to:
  • Widespread availability
  • Speed of acquisition
  • High sensitivity for detecting hemorrhage
  • Lower cost compared to MRI

MRI Considerations

• MRI with gradient-echo sequences is highly sensitive for detecting hemorrhage and may be considered if:

  • Clinical deterioration occurs and CT findings are equivocal
  • More detailed assessment of infarct evolution is needed
  • The patient has posterior fossa infarcts where CT has limited sensitivity 1

• MRI is superior to CT for demonstration of subacute and chronic hemorrhage and hemorrhagic transformation of acute ischemic stroke (Class IIa, LOE: B) 1

Special Considerations for Tenecteplase

While the general post-thrombolysis imaging protocol applies to Tenecteplase, there are some specific considerations:

1. Recanalization assessment: Tenecteplase has shown higher recanalization rates compared to alteplase in patients with large vessel occlusions 2. If the patient had a baseline vessel occlusion, consider:

   • CT angiography (CTA) or MR angiography (MRA) at 24 hours to assess recanalization status
   • This is particularly important for prognostication and understanding treatment efficacy

2. Hemorrhagic transformation risk: While studies suggest Tenecteplase may have a similar or potentially lower risk of symptomatic intracranial hemorrhage compared to alteplase 2, 3, vigilant monitoring remains essential

Practical Implementation

Timing of Follow-up Imaging

• Standard: 24 hours post-TNK administration
• Urgent: Immediately if neurological deterioration occurs

Imaging Protocol Algorithm

1. At 24 hours post-TNK:

   • NCCT as primary imaging modality
   • Consider adding CTA if baseline vessel occlusion was present

2. If clinical deterioration occurs:

   • Immediate NCCT to rule out hemorrhage
   • Consider MRI with gradient-echo and DWI sequences if CT is negative but clinical suspicion remains high

3. Additional imaging considerations:

   • For patients who underwent mechanical thrombectomy after TNK, follow the same 24-hour imaging protocol
   • For patients enrolled in clinical trials, adhere to trial-specific imaging protocols

Pitfalls and Caveats

• Contrast timing: If CTA is planned, ensure adequate renal function before administering contrast, especially in patients at risk for contrast-induced nephropathy 1

• Interpretation challenges: Early ischemic changes may be difficult to differentiate from hemorrhagic transformation. Having neuroradiology expertise available for image interpretation is valuable 1

• Microbleeds: The presence of a small number of microhemorrhages (<5) on gradient-echo MRI does not contraindicate continued antithrombotic therapy (LOE: B) 1

• Timing constraints: While additional imaging such as CTA or MRI provides valuable information, it should not unduly delay treatment decisions, especially in the acute setting 1