Notes on CTCA.docx
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Notes on Cardiac CT (RCR guidelines on CTCA and Contrast)
· Heart rate should be below 65bpm for the scan (reduces artefacts on
images) - LOWER THRESHOLD?
· Scanner uses prospective ECG gating (points of cardiac rest, usually middiastole/end-systole, are used for images)
· 20G right arm cannula is preferred (avoids artefacts from undiluted contrast
in the left brachiocephalic vein where it crosses the midline)
· Indications for CTCA: Investigation of coronary artery disease
· Clinical Referral letter – should detail any contraindications to beta blockers,
GTN or contrast
o Contrast - History of allergy, recent contrast administration, use of
metformin and renal function
o Beta-blockers - Asthma, Severe AS, Restrictive physiology (?), 2nd/3rd
degree heart block, history of transient LoC or those taking verapamil (risk
of ventricular standstill + cardiac arrest)
o GTN - Sildenafil and other phosphodiesterase inhibitors (risk of profound
hypotension). Use in caution with SBP < 90, and severe AS.
Before/Aftercare
· Patient care/checks before
o Why CTCA is being performed
o List of current medications
o BMI calculation
o Blood pressure and heart rate
o Relevant past medical history
· Patient care/checks after the scan:
o Communication: Light-headedness on sitting/standing up immediately
after.
o Waiting: Monitoring for contrast reactions - 15 minutes before leaving, or
30 minutes if increased risk of contrast reaction
Drugs
Metoprolol
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· IV use (first line) - Starting dose 5mg over 1 minute, followed by saline flush.
Re-administration of the same dose every 2-3 minutes until HR < 65 BPM.
o BNF max dose is 15mg, but higher doses (30mg, 50mg) have been used.
· Oral use - 2 regimes. Both are followed by titrated IV metoprolol.
o 50-100 mg 1hr prior to CTCA
o 50mg 12hr prior, followed by 50mg 1hr before the scan.