Routine heart scans for patients referred to cardiac clinics with chest pain could reduce heart attack rates, research suggests. The scans would help doctors to make better treatment decisions which could ultimately save lives, researchers say.
The SCOT-HEART study, led by the University of Edinburgh, tracked 4,000 patients who were referred with symptoms of angina – a condition that restricts the blood supply to the heart. Half of the patients were given a cardiac CT – computerised tomography – scan in addition to standard diagnostic tests. Researchers found that around a quarter of patients had their diagnoses reclassified after receiving the scan, prompting new treatments in many cases. The study also found that the number of heart attacks that occurred in patients who had received the scan dropped by around a third in the subsequent twenty months of follow-up.
"Our findings are encouraging. However, the overall rate of heart attacks was low and we need to follow them for longer to confirm whether the technology helps to save lives in the long-term," David Newby, British Heart Foundation professor of cardiology, Centre for Cardiovascular Science said.
In a separate study, researchers are to investigate whether giving the scans to all patients who arrive at hospital emergency departments with chest pains can also help to cut heart attack rates. The £2m study will be led by researchers at the University of Edinburgh and NHS Lothian. The RAPID-CTCA trial plans to test whether the scans can detect patients at risk of a heart attack more effectively than current procedures.
At the moment, heart patients are given an angiogram, which checks the blood flow through their heart to identify any obstructions that could pose a heart attack risk. Cardiac CT scans enable doctors to look at the blood vessels within the heart more easily. They are around an eighth of the cost of an angiogram and are safer for patients.
Researchers aim to recruit 2,500 patients for the trial, which includes Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth Hospitals NHS Trust and the University of Sheffield.
A study by researchers at Duke University Medicine has found that although a new type of CT scan initially costs slightly less than the traditional stress test to diagnose blocked coronary arteries in patients with chest pain, its lower cost did not translate into medical care savings over time.
An earlier study presented by another Duke researcher found that CTA and stress testing had statistically equal patient outcomes, although CTA exposed patients to less radiation relative to some of the alternatives.
"Together, these presentations reveal a truer picture of the value of CT angiography: not significantly better than functional testing at saving lives or reducing complications for heart artery blockage, but also not significantly worse, and with comparable costs out to three years," said Dr Daniel Mark, professor of medicine in the Duke Clinical Research Institute (DCRI) and the Duke Heart Centre, and lead author of the financial analysis.
More than 4m people a year in the US develop symptoms of chest pain that could be heart-related, and cardiologists have long sought a non-invasive way to see inside the arteries of these patients to determine whether they have life-threatening coronary blockage.
For the past 60 years, the primary way to get such information has been invasive angiography – heart catheterisation. The benefits of catheterisation include the ability to see severe heart artery blockage that requires either surgery or stenting. But many patients are given this test and found not to have any blockage of consequence, or blockage that could be treated with medications.
The most common way that doctors now decide whether to do a heart catheterisation in a patient with chest pain is to first perform a stress test, typically taking pictures of the heart muscle and its blood flow patterns under stress, usually with ultrasound or with radioactive tracers. The stress test provides what is called "functional" information, quite different from the anatomic information available from both invasive and CT coronary pictures. However, functional testing does not show the heart arteries directly and does not allow doctors to decide if stenting or bypass is needed.
Over the past 15 years, researchers and engineers have developed an additional test, using CT scanners to take pictures of the heart arteries without anything more invasive than an intravenous injection of X-ray contrast. These have produced pictures that are approaching the quality of those seen with invasive angiography.
CT coronary angiography has therefore been greeted by some heart specialists as a breakthrough test, allowing the inside of the heart arteries to be seen clearly with much lower risk. What has not been clear before now is whether skipping the functional testing and going directly to CT angiography would provide patient outcomes that are better, worse or the same as using a functional test and basing the decision to use invasive catheterisation upon finding stress induced abnormalities.
The results of the PROMISE study provide those answers. The main findings from the study found no statistical difference between the two diagnostic tests on the risk of serious events such as heart attacks, hospitalisations, unstable angina or death. Costs of the test were also quite similar. But the CTA testing strategy resulted in a trend for additional costs during the first 90 days after testing, driven mainly by the use of more procedures to unblock arteries and despite reduced use of additional non-invasive testing.
"Despite some fair differences in the prices of these diagnostic tests, there was not a statistical difference between the costs over three years of follow-up," Mark said. "Prior to this, there were no reliable clinical trial data, so these data provide tremendous value when viewed from the perspective of how little was known in 2009, when PROMISE was funded by the National Heart Lung and Blood Institute to settle this question."
"Coronary CT angiography may not be quite the hoped-for holy grail of cardiology, but its more liberal use following the standards set in PROMISE will not hurt patients and will not cause a major additional cost burden on the health care system. That is extremely important information to have," Mark said.
The other study by Dr Pamela Douglas, the Ursula Geller professorship for research in cardiovascular diseases at Duke University, found that patients with symptoms of heart disease have similar outcomes in terms of death and major cardiac conditions regardless of whether they undergo a functional stress test or a CT scan, but the scan may be better at ruling out the need for subsequent tests and procedures in patients who are free of heart disease.
The PROMISE trial is the first-ever randomised controlled trial to compare clinical outcomes in patients receiving functional stress testing or computed tomographic angiography to check for signs of cardiovascular disease. It also provides the first data to inform clinical guidelines on the use of these tests, according to the authors.
The study included a total of 10,003 patients who visited 193 health centres in the US and Canada. Participants had no prior diagnosis of coronary artery disease but had new symptoms that made physicians suspect they might have heart disease. Nearly all had at least one cardiovascular risk factor such as high blood pressure, diabetes or a history of smoking.
Half were randomly selected to receive a heart CT scan, which generates 3-D images of the heart’s arteries that doctors can use to assess the degree of narrowing. The rest received a functional test – either an exercise electrocardiogram, stress echocardiography or nuclear stress test – which are used to track the heart’s response to stress using electrical signals, sound waves or imaging. All of these tests have been in common use for a decade or more but functional tests and CT scans have never before been compared head-to-head in terms of clinical outcomes.
The study showed no differences between patients receiving a heart CT scan and those receiving functional heart tests in terms of the study’s primary endpoint, a composite rate of death, heart attack, major procedural complications or hospitalisation for chest pain. At least one of these outcomes occurred in roughly 3% of patients in both groups during more than two years of follow-up. However, some secondary endpoints, including the level of radiation exposure and the rate of subsequent procedures that did not reveal significant heart disease, favoured computed tomographic angiography.
Authors said these results are important because current clinical guidelines leave the selection of tests for patients reporting symptoms such as chest pain or shortness of breath – which constitutes at least 4m patients in the US each year – largely up to physician and patient preference.
"Until this study, we have essentially been guessing on decisions about which initial test to use for this huge population of patients who need evaluation for cardiovascular symptoms," Douglas said. "Our study shows that the prognostic outcomes are excellent and are similar regardless of what type of test you use, but there are some indications that computed tomographic angiography might be the safer test with fewer catheterisations without obstructive disease and lower radiation exposure when compared to nuclear testing."
A key strength of the study is that it offers a reflection of current medical practice, rather than an idealised view. "Unlike most trials where medical care is very tightly controlled, this study was designed to represent real world care," Douglas said. "The health centres that collected the data were responsible for interpreting the tests and doing appropriate patient follow-up. Because this was such a community-based, real-world setting, the study really tells us a lot about clinical practice and how patients are being cared for in the US now."
The 3% rate of death, heart attack, major procedural complications or hospitalisation for chest pain seen in both groups was lower than expected, especially considering the fact that most study participants had two or more significant heart disease risk factors, were middle aged or older and symptomatic. The relative benefit of CT angiography compared to functional testing held steady across different patient subgroups as defined by age, gender, race and cardiovascular risk factors. Although there was a significantly lower rate of death and non-fatal heart attacks after one year of follow-up in patients receiving a heart CT scan, for reasons that are unclear, this difference was not sustained in the second year, study authors said.
"The event rate in itself is intriguing, because no previous studies have closely tracked and adjudicated the rate of adverse events in this patient population," Douglas said. "These outcomes are so good given widespread use of medications like statins and aspirin. It does raise the question of whether we can identify a group of people who actually do not need to be tested."
After their initial non-invasive test, about 10% of study participants underwent at least one cardiac catheterisation procedure, a more invasive procedure in which an interventional cardiologist threads a catheter into the heart through an artery to assess narrowing in the arteries and, if needed, open the arteries with a balloon or stent. The rates of patients undergoing catheterisation that failed to identify substantial narrowing were significantly higher in the patients receiving functional testing, at 4.3%, compared to 3.4% in the patients who had received a CT scan. In addition, at three months patients receiving heart scans received significantly lower radiation exposure than patients who were given a nuclear stress test as their first diagnostic test.
Douglas said the bottom line for patients is that if the primary concern is avoiding serious adverse heart problems such as death, heart attack or hospitalisation, heart CT scans and functional tests are both excellent options. For lower-priority concerns such as avoiding subsequent tests and procedures or avoiding radiation exposure, heart CT scans appear to be a slightly better option. Douglas said the team plans to further investigate outcomes for different subgroups of patients to determine whether different groups might benefit from different testing approaches.
[link url="http://www.ed.ac.uk/news/2015/ctscans-160315"]University of Edinburgh material[/link]
[link url="http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(15)60291-4/abstract"]The Lancet article summary[/link]
[link url="http://corporate.dukemedicine.org/news_and_publications/news_office/news/tests-to-diagnose-coronary-artery-disease-come-with-similar-costs"]Duke University material[/link]
[link url="http://corporate.dukemedicine.org/news_and_publications/news_office/news/tests-to-diagnose-coronary-artery-disease-come-with-similar-costs"]New England Journal of Medicine abstract[/link]
[link url="http://www.acc.org/about-acc/press-releases/2015/03/14/12/00/heart-ct-scans-show-slight-benefits-over-functional-tests-for-heart-disease?w_nav=S"]American College of Cardiology material[/link]
[link url="http://www.nejm.org/doi/full/10.1056/NEJMoa1415516#t=articleTop"]New England Journal of Medicine article[/link]