Cardiac CT
Your doctor has referred you for a CT Coronary Angiogram (Cardiac CT). The aim of this scan is to take images of the blood vessels around your heart. However, this is often challenging to do because the heart is constantly moving as it beats. In order to maximise our chances of taking clear, diagnostic images, we will need your heart rate to be low and steady (ideally below 60 beats per minute). To help achieve this, there are some specific preparation instructions that you will need to follow.
Preparation for the Scan
- This will help to lower your heart rate. Your referring doctor can prescribe this for you, after they have checked you for any contraindications.
- Do not have anything to eat 4 hours prior.
- Keep well hydrated the day before and morning of the scan (water only 4 hours prior).
- No caffeinated products 12 hours prior (coffee, tea, energy drinks, cola, chocolate, etc.).
- No physical exercise 24 hours prior.
- No Viagra 24 hours prior.
- You will be required to have a recent renal function blood test if you are over 70 years old or a Diabetic.
On the Day
- Arrive 40 minutes prior to your scan time.
- A trained nurse or radiographer will go through a brief medical history questionnaire with you and obtain consent for the scan. They will also take some heart rate and blood pressure measurements, as well as record your height and weight.
- If your heart rate is slow and steady, you will most likely be taken into the CT straight away for the scan, which takes 15-20 minutes. A nitroglycerine spray will be given under the tongue just before scanning. You will be given an injection of Iodine Contrast during the scan, which highlights your blood vessels on the images.
- If your heart rate is high, then we will need to give you extra Beta Blocker medication to bring your heart rate down. This can take up to 2 hours, so please make sure you factor this in when planning the rest of your day. If we cannot get your heart rate below an acceptable level, then we may have to abort the scan as the images won’t be diagnostic.
- You may feel lightheaded and dizzy after the exam as a result of the Beta Blockers. This will pass and should not affect you significantly, however it is advisable that you arrange for someone to drive you home afterwards if possible.
Contraindications
- Mobitz I / II AV block
- Complete heart block
- Severe LV dysfunction / Cardiac failure
- Severe CAL / Brittle asthma
- Hypotension
- Severe Aortic Stenosis
Preloading by Referrer
This option is preferable to ensure the patient’s heart rate is low and steady when they arrive for their scan.
- Metoprolol 50mg bd x 1-3 doses (after ECG)
- Patient to take the night before the scan
Beta Blocker Administration on the Day of Scan
- Heart Rate < 50 bpm: Scan
- Heart Rate 50-55 bpm: 25mg Metoprolol and Scan
- Heart Rate 55-65 bpm: 50mg Metoprolol, check in 45 minutes and redose if indicated
- Heart Rate > 65 bpm: 100mg Metoprolol, check in 45 minutes and redose if indicated
Maximum 250 mg Metoprolol. Keep checking BP.
If heart rate 60-65 bpm after redosing, use IV Metoprolol 5mg over 1-2 minutes to a max of 20mg.
If heart rate > 65 bpm after redosing, abort scan and rebook for another day.
Reduce Beta Blocker Dosage in:
- Elderly
- 1st Degree AV Block
- LBBB
- Other rate slowing agents – CCB’s, digoxin, amiodarone
If you have any questions regarding charges or would like to know more information, please contact our friendly staff on admin@wollongongdiagnostics.com.au or corrimal@wollongongdiagnostics.com.au or call us on (02) 4249 2710.