CT Coronary Angiography

CT Coronary Angiography (CTCA) is a non-invasive imaging alternative for the evaluation of coronary artery disease. In appropriately selected patients, studies with satisfactory image quality have a sensitivity for the detection of haemodynamically significant coronary stenosis of greater than 95%. In a small proportion of patients, CTCA does not provide satisfactory images, and further investigation may be required.

As CTCA utilises intravenous contrast and radiation to generate images, it should only be performed where potential benefits outweigh the risks of contrast and radiation exposure.

Indications for CTCA:

Patients with atypical chest pain at intermediate risk for coronary artery disease

Patients with inconclusive stress test results

Patients with at least intermediate risk for coronary artery disease, but no documented coronary artery disease

Detection and evaluation of suspected coronary artery anomalies

CTCA is not appropriate for:

Initial evaluation of symptomatic patients suspected of having coronary artery disease. These patients would typically still require and should be referred for a standard coronary angiogram.

Patients meeting any of the following the criteria should be discussed with a cardiologist prior to referral:

Impaired renal function

Allergy to intravenous contrast

Irregular or rapid heart rates

Known coronary artery disease (including previous bypass grafting, angioplasty or stenting) or extensive coronary calcification (older males with significant risk factors)

Risk stratification prior to non-cardiac surgery

Any patient <40 years of age

Are there any medical conditions that preclude patients from having CT Coronary Angiography?

CTCA should not be performed on patients who are or might be pregnant. Patients with pacemakers, defibrillators and arrhythmias may also be unsuitable. CTCA does require administration of intravenous contrast so is contraindicated without further discussion in patients with chronic renal insufficiency (a current creatinine level is required for all patients) or contrast allergy.

What preparation is required?

Patients are asked to withhold Cialis, Viagra and Levitra for 36hrs prior to the scan, and not to take drinks containing caffeine or alcohol on the day of the scan. Prior to the scan patients will be asked to read and sign an information and consent form.

How is the scan performed?

CTCA is an ECG gated contrast enhanced CT scan through the heart. Patients will be asked to lie on the scanner table. ECG leads will be attached to their chest and intravenous access will be obtained (usually via an antecubital fossa vein) for contrast injection. Immediately prior to the coronary scan patients may be given sublingual nitroglycerine. Patients will need to be able to hold their breath for up to 15 seconds while the coronary scan is acquired.

What are the risks?

There is a small risk of side effects and complications related to intravenous contrast administration including contrast allergy. Allergic reactions are usually mild (such as itch or a rash). Rarely severe reactions occur (<1 in 10,000).

CTCA exposes the patient to ionising radiation. The effective dose on the Siemens Definition scanner used is in the range of 4 to 6 mSv. This is in comparison to the effective dose from a chest x-ray of 0.1mSv, conventional coronary angiography of 2-2.5mSv, and annual natural background radiation of about 2mSv. The risk of cancer from exposure to 1mSV of radiation is about 1 in 17 000. This compares to a natural incidence of cancer of about 57 in 17 000.

In a small proportion of patients CTCA does not provide satisfactory images, and further investigations may be required.

How much does the examination cost?

The cost is $1870 (GST inclusive). Health insurance may not cover the full cost of the examination and reimbursement may vary depending on whether referral is via a GP or specialist. Each patient should confirm their level of coverage with their insurer in advance of their appointment.

How long before the scan results are available?

The images acquired as part of CTCA include the equivalent of a limited range CT chest. A CT chest report will be issued on the day of the scan. Analysing the coronary artery images using a dedicated workstation and software (Siemens Circulation) is more time consuming and as a result, a final report including the angiogram report will be issued separately once the analysis is completed.

Important note regarding incidental findings:

Non-cardiac incidental findings are detected in 25%-60% of coronary angiogram scans, with pulmonary nodules being amongst the most common. All patients should be aware that further investigation and follow-up of incidental findings might be required.

How to refer for CTCA:

Download the specific CCTA referral form

Complete and fax the referral form back to CHRISTCHURCH RADIOLOGY GROUP (at St Georges Radiology) on 03 355 2173.

Radiology and/or cardiology staff will review the form and contact the patient to discuss a convenient appointment.

 

Dr Ross Keenan

June 2008