CT transcatheter aortic valve implantation planning (protocol)

At the time the article was created Jessica Hui Shi Ng had no recorded disclosures.

At the time the article was last revised Arlene Campos had no financial relationships to ineligible companies to disclose.

• TAVI planning (CT protocol)
• TAVI CT
• CT TAVI

The transcatheter aortic valve implantation or TAVI planning CT protocol is used to plan for transcatheter aortic valve implantation. CT allows for the assessment of the aortic root and valve annulus in order to select an appropriate valve size and location specific to the patient. An aortic angiogram is also performed in order to determine the suitability of iliofemoral access 1 .

NB: This article is intended to outline some general principles. Protocol specifics especially medications, contrast doses and decisions vs other cardiac acquisitions will vary subject to institutional protocols and patient factors as well as CT hardware and software.

The medication and contrast doses apply for cardiac CT examinations in adults.

On this page:

• Indications
• Technical requirements
• Patient preparation
• Technique
• Practical points
• Related articles
• References

• Cases and figures

Indications

The main indication for TAVI CT is severe aortic stenosis 2 . This can present as:

• rapid or irregular heartbeat
• chest pain
• shortness of breath
• heart palpitations

Purpose

The purpose of TAVI CT is to demonstrate the aortic valve filled with contrast without motion or step artifacts. The origins of the coronary arteries and entire aorta down to the femoral arteries should be opacified to allow for planning and measurements to be made.

This examination requires patients to maintain long breath holds and follow breathing instructions. A stable heart rate of around 60 bpm is ideal for capturing a motionless aortic valve.

Technical requirements

The minimal technical requirements for TAVI CT are the following 2 :

• 64-slice scanner
• detector element width ≤0.625 mm
• option of cardiac CT and ECG-gated triggering

Patient preparation

• patients should take their cardiac medications as usual
• no food 3-4 hours before the scan
• no caffeine for 12 hours
• instructions on how to breathe
• electrocardiogram signal need to be acquired

Technique

• patient position
  • supine with both arms above their head (as comfortable as possible)
  • ECG placement
  • ​100 kVp if patient’s weight ≤100 kg or BMI
  • ​ use automated current adjustment mode
  • aortic arch to femoral arteries
  • ​calcium score to include valve only
  • TAVI to include the entire heart
  • aortogram to include aortic arch to the femoral arteries
  • craniocaudal
  • contrast agents with high iodine concentrations (270-400 mg iodine/mL)
  • contrast timing
    • monitoring: ascending aorta
    • test bolus (test volume 10-20 mL at the same flow as the cardiac scan e.g. 5.0-6.0 mL/s)
    • bolus tracking
    • 50-70 mL contrast media at 5-7 mL/s
    • 30-40 mL contrast media at 4-5 mL/s (for longer bolus)
    • 50-80 mL saline chaser at 4-5 mL/s
    • inspiration
    • for breath-hold consistency, a medium-sized breath is easier to reproduce throughout the examination compared to sharp deep breaths
    • if the aortogram and TAVI scan are performed in one breath-hold, instruct the patient to let their breath out slowly if they run out of breath

    Practical points

    • setting the estimated heart rate as the patient's lowest heart rate will ensure the pitch is appropriate for imaging the patient's heart
    • calculating scan delay for a test bolus
      • as the time-enhancement curve will only begin recording after the scan delay.
      • the widely accepted formula for calculating the scan delay is 3 : peak contrast enhancement (time-enhancement curve) + scanner's diagnostic scan delay

      TAVI work up

      The workup is performed by either the radiographer, cardiologist, radiologist or a combination. Measurements are made for:

      • valve plane
        • the plane just inferior to the coronary cusps
        • the diameter of the aorta one slice below the valve plane
        • the circular diameter of the aorta one slice below the valve plane
        • from the origin of the right coronary artery to the valve plane
        • from the origin of the left main coronary artery to the valve plane
        • the diameter of the aortic valve leaflets
        • the largest point of the aortic bulge
        • one slice superior to the left and right sinus heights
        • just superior to the left and right coronary artery origins
        • where the aorta transitions to a straight wall
        • from the top of the left sinus to the valve plane
        • gives rise to the left main coronary artery
        • from the top of the right sinus to the valve plane
        • gives rise to the right coronary artery

        References

        • 1. Blanke P, Schoepf U, Leipsic J. CT in Transcatheter Aortic Valve Replacement. Radiology. 2013;269(3):650-69. doi:10.1148/radiol.13120696 - Pubmed
        • 2. Computed Tomography in the Evaluation for Transcatheter Aortic Valve Implantation. Cardiovascular Diagnosis and Therapy. 1(1):446-56. doi:10.3978/j.issn.2223-3652.2011.08.01
        • 3. Bae K. Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches. Radiology. 2010;256(1):32-61. doi:10.1148/radiol.10090908 - Pubmed