Cardiac CT imaging

Coronary heart disease is the leading cause of death in Australia and is caused by a slow build up of fatty deposits on the inner walls of the coronary arteries, which supply blood to the heart muscles. Known as atherosclerosis, when these fatty plaques become significant enough to reduce blood flow to the heart muscles you could get angina (chest pain) or have a heart attack. Plaque build up in arteries begins when people are young and could be well advanced by middle age.

Cardiac CT is a non-invasive examination that characterises the heart and coronary arteries as an alternative to more invasive cardiac catheterisation, which remains the gold standard for assessing coronary artery disease. South Coast Radiology is the only private radiology service in the Gold Coast–Tweed Valley region that offers a comprehensive cardiac imaging service. We provide two key cardiac CT tests – CT coronary angiography (CTCA) and coronary artery calcium scoring (CACS).

 

CT Coronary Angiography

CT Coronary Angiography (CTCA) uses advanced CT technology to obtain high-resolution, 3D images of the moving heart and great vessels that flow in and out of the heart. This new, non-invasive test is used to diagnose coronary artery disease.

Previously, functional cardiac assessment such as stress echocardiography and nuclear medicine were used to indirectly assess coronary artery disease. Cardiac catheterisation and angiography is used to directly assess coronary artery disease and remains the gold standard. However, CTCA provides an alternative to invasive cardiac catheterisation. The test is faster (< one minute), presents less risk and discomfort for patients and has a reduced recovery time.

CTCA has developed rapidly. From the early days of quantifying calcium in the coronary arteries, the technique can now demonstrate coronary artery disease with good reliability and accuracy.

The Medical Services Advisory Committee (MSAC) recently performed a lengthy and rigorous assessment of CTCA for safety, effectiveness and economic consideration. The result – CTCA has been proven to be the most cost-effective test for investigation of coronary artery disease, in a number of clinical circumstances.

At South Coast Radiology, we use a 64-slice CT scanner, which produces the fast, high-resolution images needed for CTCA. A number of our radiologists have specialist accreditation awarded by the Conjoint Committee for the Recognition of Training in CT Coronary Angiography. These radiologists are onsite for all components of the examination, including consulting the patient, observing the acquisition of images and intervening as required, and then interpreting the study from raw data.

In fact, Medicare has implemented a robust credentialing system to support CTCA implementation and will only rebate examinations performed and reported by radiologists accredited to perform CTCA, using a minimum 64-slice CT scanner.

Contraindications for CTCA include:

  • Impaired renal function (due to IV contrast load)

  • Allergy to intravenous x-ray contrast medium
  • Irregular or rapid heart beat rates – a regular, slow heart rate is required

Medicare might not provide a rebate for patients with known coronary artery disease, including prior bypass grafting, angioplasty or stenting, and patients with extensive coronary calcification. A coronary artery calcium score is routinely performed prior to CTCA.

CTCA demonstrates heart anatomy and the degree of any coronary artery stenosis, which is classified as soft and/or calcified plaque. South Coast Radiology radiologists are working with local cardiologists to ensure the data produced correlates with current standards of coronary catheter angiography. Interventional procedures, such and angioplasty, cannot be performed during CTCA.

As with any x-ray examination the benefit of having CTCA has to be weighed against the small potential risk of exposure to ionising radiation. For CTCA we use Toshiba’s SURE Exposure™, which will ensure optimum image quality at minimum patient dose, by adjusting the tube current during scanning, which could total dose by up to 40% per patient. Our staff will ensure each patient receive the lowest radiation dose possible to gain the high-quality images needed for diagnosis.

South Coast Radiology performs CTCA at our Pindara Private Hospital location, where our staff have performed more than one thousand CTCA and developed extensive technical expertise.

 

Before CTCA

For CTCA, patients must have slow and stable heart beat of 65 bpm or less. If the heart rate at the time of scan is more than 65 bpm, the images obtained may have substantial motion artefact. Patients with a resting heart rate greater than 65 bpm need to take medication to slow the heartbeat, prior to study. A patient will be given a suitable beta-blocking medication if this medication is needed.

After consultation between radiologists and cardiologists, our radiologists recommend that doctors prescribe Metoprolol 50mg, twice a day for two days prior to a CTCA study. Metoprolol is a short-acting beta blocker, which will lower the heart rate to less than 65 beats per minute. You will need to determine if it’s safe, before prescribing this medication. If you have further questions about this medication, please contact our senior radiology nurse, at our Pindara rooms, on 5597 0677.

 

During CTCA

While CTCA itself is not painful, an injection of a small dose of x-ray contrast through an arm vein, to enhance visualisation of the coronary arteries. The patient will feel a sharp prick, similar to when blood is taken. Because the contrast media shows the blood flow in organs and soft tissues, it provides further information about the problem area. However, some people might be allergic to the contrast media. After the contrast agent is injected, a patient might feel flushed, or experience a metallic taste in the mouth.

Please advise our staff before CT if your patient:

  • Has asthma
  • Is allergic to seafood of shellfish
  • Has had a previous allergic reaction to contrast media
  • Is taking medication for Type 2 Diabetes
  • Has renal failure

Large deposits of calcification in the coronary arteries might obscure the lumen of the artery. At South Coast Radiology, we perform coronary artery calcium scoring (CACS), at no additional charge, prior to CTCA to determine whether the coronary arteries are heavily calcified. The radiologist will review the CACS first to ensure CTCA will be of value.

Medicare will provide a rebate for patients covered under Medicare criteria for CTCA, if a specialist doctor refers the patient. South Coast Radiology will bulk bill those patients. All other patients will be billed at $450 for CTCA.

 

After CTCA

Generally, a patient can resume usual activities and normal diet immediately after the CTCA.

One of our radiologists will interpret the CTCA and provide a comprehensive report about the findings. We will advise the patient to return to the referrer to discuss CTCA results. Processing and reporting of the CTCA could take up to two hours.

If you are a registered a referrer you can access your patient’s digital x-rays, scans and reports through our secure online archival system, or view the films we provide. For more information about registering to access patient images visit the Access Medinexus Portal section. <3.1 for referrers>.

Any hardcopy images and report can generally be delivered to the referrer, by lunchtime on the next working day. If the patient needs to be reviewed on the day of the CTCA, the patient can wait for the films and we will fax or email the results to the referring doctor.

 

Coronary artery calcium scoring – CACS

South Coast Radiology is the only private radiology service at the Gold Coast offering a comprehensive cardiac imaging service.

Coronary artery disease is a leading cause of death in Australia, so finding which patients are at risk of coronary artery disease, is an important consideration. Calcium in the coronary arteries almost always indicates arterial disease or atherosclerotic plaque, but bears relationship to plaque stability or instability. Cardiac risk factors and insulin resistance contribute to coronary artery calcification.

Coronary artery calcium scoring (CACS) is a non-invasive test that estimates the amount of coronary artery plaque, by assessing the extent of coronary artery calcification using high-resolution 64-slice CT. While a calcium score of ‘zero’ does not rule out arterial disease, there is a low likelihood of significant coronary blockage. A high calcium score correlates with a moderate to high risk of a coronary event, or heart attack, within two to five years.

CACS has a high negative predictive value (up to 98%), which means if your calcium score is low then this correlates very well with you having a low risk of coronary artery disease. Coronary artery calcium scanning is not as useful in patients who have a low or very high risk, or in those with known coronary artery disease.

Possible reasons for requesting CACS include:

  • Screening asymptomatic patients
  • Screening patients with intermediate risk of coronary artery disease
  • Presence of one risk factor such as hypertension
  • Strong family history of early coronary artery disease

Patients with diabetes or chronic kidney disease could have high calcium scores, which might not correlate with significant coronary artery disease.

At South Coast Radiology we routinely use CACS, at no additional charge, on each patient prior to CT coronary angiography to determine whether the coronary arteries are heavily calcified. If the calcium score is high, calcium might obscure the coronary arteries. The radiologist will review the CACS before staring CT coronary angiography.

South Coast Radiology performs CACS at our Pindara Private Hospital practice, where staff have performed more than one thousand CACS studies and developed extensive technical expertise.

 

Before coronary artery calcium scoring

Medicare does not provide patients with a rebate for CACS. Patients having a CACS during a CTCA will not be charged extra. There is no specific patient preparation for CACS.

 

During coronary artery calcium scoring

No x-ray contrast in injected during this test.

Our staff will ensure that all patients receive minimal radiation dose during an examination. The dose for CACS varies depending on factors such as patient size and body shape, but is relatively low.

 

After coronary artery calcium scoring

While the scan is completed in less than one minute, patients need to remain lying for around 15-20, with an overall appointment time of 30 minutes. Complex data sets are processed into 3D images after the scan, which is time consuming. Generally results will not be available immediately.

One of our radiologists will interpret the CACS and provide a comprehensive report about the findings. We will advise the patient to return to the referrer to discuss CACS results.

Processing and reporting of images could take up to two hours. If you are a registered a referrer you can access your patient’s digital x-rays, scans and reports through our secure online archival system, or view the films we provide. For more information about registering to access patient images visit the Access Medinexus Portal section.

If the patient needs to be reviewed on the day of the CACS, the patient can wait for the films and we will fax or email the results.