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LEADING cardiologists have called for zero radiation diagnostic tests in preference to radiation-based investigations because of the risk of cancer.
Professor Richard Harper, emeritus director of cardiology at MonashHeart, Monash Medical Centre in Melbourne, and Dr John Rivers, chairman of St Andrew’s Medical Institute (SAMI) in Brisbane, both said echocardiogram stress tests should replace nuclear stress tests because they provide similar diagnostic information without the radiation.
Statistics provided by Medicare show that, in Australia, the number of diagnostic imaging services with a nuclear stress test component has risen from 52 195 in 2000 to 82 581 in 2010, with a total of 774 892 performed in the past 10 years.
The experts’ comments follow the publication of a study which found a dose-dependent relationship between exposure to low-dose ionizing radiation from cardiac imaging and therapeutic procedures and the subsequent risk of cancer.(1)
The study, published in the Canadian Medical Association Journal, found that for every 10 milliSieverts (mSv) of radiation, there was a 3% increase in risk of age- and sex-adjusted cancer over a follow-up period averaging 5 years.
The study involved 82 861 patients who had an acute myocardial infarction and no history of cancer. Of these, 77% underwent at least one cardiac imaging or therapeutic procedure involving low-dose ionizing radiation, such as nuclear scans, diagnostic cardiac catheterisation and percutaneous coronary intervention.
The cumulative exposure to radiation from cardiac procedures was 5.3 mSv per patient-year, of which 84% occurred during the first year after the heart attack. A total of 12 020 incident cancers were diagnosed during the follow-up period.
The authors said even moderate levels of exposure were associated with an increased risk of cancer.
“We should at least consider putting into place a system of prospectively documenting the imaging tests and procedures that each patient undergoes, and estimating his or her cumulative exposure to low-dose ionizing radiation,” they said.
Professor Harper said there had always been an unspoken suspicion among cardiologists that sufficient exposure to cardiac procedures involving radiation could increase a patient’s risk of cancer and that the study was the first to provide evidence this could be the case.
Dr Rivers, SAMI’s chief investigator for a Queensland government-funded project to improve clinical outcomes for cardiology patients, including systems to reduce radiation dose, said there was no doubt patients with acute coronary artery problems are generally required to undergo procedures such as angiography and angioplasty.
“The area that requires more thought is routine use of radiation-based investigations,” he said.
He advocated echo stress testing first and then ultrasound, saying nuclear stress testing should only be used if no information was derived from these tests.
There had been huge growth in cardiac imaging, with nuclear cardiac perfusion scans in the United States growing from less than 3 million in 1990 to 9.3 million by 2002, he said.
The introduction of computed tomography coronary angiography (CTCA) and routine uses of CT scans for other testing had been a major contributor to increased radiation dose, he said.
Dr Rivers said SAMI was developing benchmarks for radiation doses for cardiac procedures and had been in discussion with the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) about national benchmarks.
“Our research shows that measuring the dose and reporting that back to clinicians is quite a powerful tool for getting them to reduce the dose,” he said.
“We also need to look at the cumulative dose [of radiation]. A patient doesn’t have one test; they often have multiple and repeat investigations and no system tracks their total dose.
“And the age at which the radiation dose is received may also be important. We should be extra vigilant with young patients.”
ARPANSA recently launched its Australian Clinical Dosimetry Service, to provide an independent, national approach to promoting safety and quality in radiotherapy for cancer patients.(2)
Professor Harper said the study was a good wake-up call for cardiologists to limit their cardiac procedures.
He reiterated a call he made recently, in a viewpoint in the eMJA, for nuclear stress tests to be eliminated and the Medicare item number abolished.(3)
He said there should be greater reliance on the standard electrocardiogram (ECG) stress test, with echo stress tests used when patients had a resting ECG abnormality or were unable to exercise.
“Diagnostic” coronary angiography by non-interventional cardiologists should also be eliminated and CTCA use limited, Professor Harper said.
– Cathy Saunders
Photo courtesy of St Andrews War Memorial Hospital, Brisbane
1. CMAJ 2011. doi:10.1503/cmaj.100463.
2. Australian Clinical Dosimetry Service .
3. eMJA Rapid Online Publication – 14 Dec 2010.
Posted 14 February 2011
At the very least all these investigations should be made arm’s length.
The cardiologist seeing a patient should not be allowed to send the patient to his/her own echo/angiogram imaging centre under Medicare rules especially if there is financial interest for the cardiologist. In America, where this is allowed (they are trying to change this), health costs have sky-rocketed due to self-referral.
If you really want to reduce health costs, arm’s length referral is the best way of weeding out such unethical practices. By the way, it appears some cardiologists are attempting to control CT coronary angiography for themselves as well. I would much prefer if something like that be arm’s length referred, eg, patient goes to another independent cardiologist to perform or to a radiologist or nuclear med physician, which then prevents over-investigation since no financial self-interest is involved in the referral.
Interesting dynamics in interventional Cardiology…. Once upon a time, the Cardiologist (physician) was the gategeeper to C-T surgery – there was some sort of arm’s length referral for procedures. Now the interventional Cardiologist refers their own patient to themselves for invasive investigations and interventions. Isn’t there are least the APPEARANCE of a financial interest here?
As a hospital-based cardiologist I can tell you that none of my registrars and few consultants know how much radiation is involved with a CT, Cath or nuclear scan. Ask them!
The whole underlying tone is that of bias whether it be financial or academic. Dr Harper’s push for FFR is well known (eMJA Rapid Online Publication — 14 Dec 2010). No mention is made on the catheter extra time and radiation FFR would place on the patient. Screening fluoroscopic guidance for the FFR wires is not negligible, as the article seems to imply. The cost of each wire ($1300) is also nothing to be sneezed at. It seems quite ironic that he wishes to use the “radiation scare” card when the FFR involves the patient having an invasive procedure (groin puncture, small risk of stroke/AMI) as well as more time in the catheter suite with screening radiation used to guide the wires. I’ve had IV adenosine before and it’s no fun, let me tell you, which his procedure requires.
While Dr Harper is a well known respected cardiologist, a statement on any financial interests in the company that makes these wires needs to be addressed first.
This is crazy. The article that this pertains to does not even adjust for likely confounders like smoking, obesity, genetic risk for cancer……the original article is hence flawed. For an Emeritus Prof to say that Nuclear Cardiac Tests should be banned is extrapolating a potentially biased article, and then to other subgroups where the external validity of this article is lacking!!! I am shocked.
Radiation should definitely be rationalised – but it should be remembered that it is NOT just nuclear tests that deal with radiation – CTCA IS radiation (4-10mSv), standard angiography (2-6mSv) IS radiation and of comparable dose (Nuclear Stress generally 7-15mSv, Thallium is higher 22mSv).
Newer nuclear cameras give the ability to reduce radiation to below other radiation utilising tests, so to ban them is biased – perhaps there is an alternative reason for the call for a ban.
Sure echo is radiation free. It is also very user dependent.
Great study and comments, however Professor Harper’s interventional underwear may be peeping through. Why focus on non interventional radiation. 63.9% of exposure was from cardiac catheterisation, 36% from thallium.
When there is no evidence that routine PCI lowers mortality in NSTEMI and when the mortality benefit of primary PCI in STEMI over non streptokinase thrombolysis is only 1% in absolute terms, then a 3% excess (relative) in cancer becomes an issue that maybe should be discussed when ‘informed’ consent is obtained. It is also important to consider that the great majority of cancers are likely to appear much later so this data may just represent the tip of the iceberg.
We also should be focussing on stable angina where there is no evidence of mortality benefit from intervention. Diagnosis can be established in a high percentage of cases without radiation. Treatment can and should proceed without angiography or PCI which should be considered only after failed medical treatment or where very high risk indicators are present.
At the very least thallium scans should not be requested by non specialists and a second opinion from a non interventional specialist should be obtained before stenting is considered.
It is more important to stop imaginative cardiac tests.
But only if our learned legal people understand. If at all.
One has to point out a significant financial bias. Cardiologists are in charge of echos, whereas nuclear stress tests are the domain of nuclear radiologists. Hence a significant financial bias in the push for more echos!
Also, availability is a significant problem with echos, whereas at our centre we can often get nuclear stress tests within 2-3 days. Standard ECG stress tests have inadequate sensitivity, at below 80%, versus higher than 90% for nuclear and stress echos.