CT can clearly show detailed anatomy and image plaque, unlike nuclear imaging, angiography or electrocardiograms, as in this 3-D reconstruction from a Toshiba 256-slice CT scanner.
CT can show anatomical features that are not evident on other chest pain diagnostic modalities, such as this image showing a coronary aneurysm.
With a growing problem of overcrowded emergency departments, coronary computed tomography angiography (CCTA) may be a solution to address the management of chest pain patients. CCTA is increasingly recognized as an accurate, noninvasive tool to safely assess coronary artery disease. Advocates for the modality say it leads to earlier identification and management of obstructive coronary artery disease (CAD), rapid early discharge, improved flow of overcrowded emergency departments and reduced costs.
The National Center for Health Statistics reports there were 4.5 million visits in 2004 to U.S. emergency departments for cardiovascular disease. Of these, 1.6 million patients were hospitalized with a primary or secondary diagnosis of an acute coronary syndrome (669,000 for unstable angina and 896,000 for myocardial infarction). It is estimated the cost of evaluating these patients is more than $12 billion a year.
James Min, M.D., FACC, FSCCT, director of cardiac imaging research and co-director of cardiac imaging, Cedars-Sinai Heart Institute, Los Angeles, and president of the Society of Cardiovascular Computed Tomography (SCCT), is a big proponent of using CCTA to noninvasively evaluate symptomatic patients. CCTA can clearly identify if a patient has significant coronary disease and exclude from further testing those who do not, which will save money, Min said during a session at the American College of Cardiology (ACC) 2011 meeting in April.
When multislice CT was introduced in the last decade (16-slice in 2002 and 64-slice in 2005), Min said it generated enthusiasm to move CCTA forward as a primary diagnostic test. Min said CCTA’s ability to both exclude and identify obstructive or severe CAD suggests the technology can identify patients who would best benefit from medical versus coronary artery bypass grafts or interventional procedures.
Studies such as CORE 64 and ACCURACY, and the CONFIRM registry of more than 727,000 patients who underwent CTA, show the technology has a 99 percent negative predictive value. He said this is evidence CCTA can help cut costs by eliminating the need for additional diagnostic testing, especially diagnostic catheterization angiography.
Min said multiple studies of CCTA show its cost-effectiveness in appropriately selected patients with a low to intermediate probability of CAD. Min was involved with a 2008 study comparing one-year costs associated with patients who underwent CCTA and single photon emission computed tomography (SPECT) myocardial perfusion imaging. Min found CCTA is a cost-saving technique that reduces healthcare costs in a substantial proportion of patients who present with an intermediate probability of CAD. The study found no major differences in outcomes in detecting coronary disease in chest pain patients. In addition, he said the baseline cost of nuclear imaging was higher than CT.
Patients in the study without known CAD underwent multi-detector CT as an initial diagnostic test. This was compared with those who underwent myocardial perfusion SPECT. The CCTA patients incurred lower healthcare costs with similar rates of myocardial infarction and CAD-related hospitalization.
A 2007 study by the University of South Alabama College of Medicine found using CCTA as a gate-keeper for catheterization reduced costs by $1,454, a savings of nearly 50 percent. The researchers concluded that even if some patients who would have received medical management rather than catheterization end up getting scanned, the overall savings would still be substantial because so much is saved by reducing catheterizations.
In a 2008 Harvard University study  of women with low risk of a heart attack who came to the emergency room with acute chest pain, CCTA was about $410 less expensive than the standard-of-care using blood and stress tests. Joseph Ladapo, M.D., Ph.D., lead author of the study, said CCTA is more efficient than a stress test in the identification of CAD, leading to faster patient discharge.
However, Min said there are many variables in both patients and imaging modalities, especially with changes in imaging technologies. He said there are no black-and-white answers to what is the best imaging modality or the most cost-effective and that larger clinical and cost-effectiveness studies are needed.
“The cost efficiencies of diagnostic imaging tests are changing, given the multitude of factors that contribute to costs,” Min said.
Mainstream media reports in recent years have raised both the public’s and lawmakers’ awareness of ionizing radiation from CT scans. However, experts say CT dose is being reduced and there is a question of whether the risk of CT dose is acceptable when comparing patient outcomes to other diagnostic modalities.
The end result of dose-lowering techniques and new advancements is that CT radiation dose is going down, said Suhny Abbara, M.D., director, cardiovascular imaging section, director of education, cardiac MRI and CT program, Massachusetts General Hospital, Boston. “The radiation dose has decreased dramatically over the past 10 years,” he said, during a presentation at ACC 2011.
At Mass General, Abbara said the average CCTA dose in 2005 was 12.4 mSv, but today that average has dropped to 3.6 mSv. He believes it will be possible by 2020 to perform a CTA exam with a dose of about 1 mSv, which is about equal to current chest X-ray.
CT system temporal resolution is also improving, which he said would lead to new uses for CT. Abbara believes it will be possible to accurately evaluate heart valves, endocarditis and to image tissue blood flow. He said CT will be able to gather physiological information such as perfusion with adenosine stress tests similar to nuclear imaging scans. CT will also be used to evaluate infarct scars and tissue viability.
Abbara believes new types of CT, such as photon-counting CT and laser X-rays, may enhance images of soft tissue with more contrast and better image quality.
“Radiation-intensive imaging will continue to face headwinds,” said Jagat Narula, M.D., Ph.D., FACC, FRCP, medical director of the Memorial Heart and Vascular Institute (MHVI), Long Beach Memorial Medical Center, Long Beach, Calif., during ACC 2011. However, he said the key elements in the future will be outcomes and cost-effectiveness of an imaging modality in comparison to rival technologies. Comparative effectiveness will likely determine reimbursements and which modality becomes the gold-standard in specific applications, such as diagnostic angiography.
1. Rosamond W, Flegal K, Furie K, et al. “Heart disease and stroke statistics—2008 update: A report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee.” Circulation 2008;117:e25-146.
2. Healthcare Cost and Utilization Project Web site. Rockville AHRQ, 2007; http://www.hcup.ahrq.gov, Accessed Sept. 18, 2010.
3. Min JK, Kang N, Shaw LJ, Devereux RB, Robinson M, Lin F, Legorreta AP, Gilmore A. “Costs and clinical outcomes after coronary multidetector CT angiography in patients without known coronary artery disease: comparison to myocardial perfusion SPECT.” Radiology. Oct. 2008. 249(1): 62-70.
4. Joseph A Ladapo. “Cost-effectiveness of coronary MDCT in the triage of patients with acute chest pain.” AJR Am J Roentgenol. 191:455-63. 2008
5. Jason H. Cole, Vance M. Chunn, J. Andrew Morrow, Ralphy S. Buckley, Gerry M. Phillips. “Cost implications of initial computed tomography angiography as opposed to catheterization in patients with mildly abnormal or equivocal myocardial perfusion scans.” Journal of Cardiovascular Computed Tomography, July 2007, Volume 1, Issue 1, July 2007, Pages 21-26