Supported by a growing base of clinical studies, cardiac CT angiography (CCTA) has shown its utility in improving cardiac patient management and ruling out heart disease with greater than 99 percent accuracy, while also offering fiscal benefits that can be found by limiting unnecessary diagnostic cardiac catheterization procedures on low- to intermediate-risk patients presenting with acute chest pain.
It’s no wonder CCTA system installations have surged in recent years, in university hospitals and medical centers as well as in community hospitals and outpatient imaging center settings. There were approximately 4.3 million CTA procedures performed in 2007, according to IMV Medical Information Division.
Diagnostically, CCTA is a good fit for patients with low to intermediate likelihood of coronary artery disease (CAD) with atypical chest pain and/or prior equivocal or non-diagnostic other tests (e.g. stress testing, nuclear myocardial perfusion imaging). It also has proved valuable in the detection and exclusion of obstructive CAD, the severity of stenosis, as well as plaque volumes, composition and remodeling.
Clinical evidence suggests CCTA will revolutionize patient management for the treatment of heart disease. However, the future implications of the procedure remain unclear as CMS noted in its final ruling that “questions remain on the indications of use.”
CCTA in clinical practice
One question that has been answered is whether there is enough evidence to justify incorporating CCTA into clinical practice for assessing heart disease. The answer is unanimous and unequivocal—absolutely. “If used appropriately, CCTA is an extremely beneficial tool in clinical practice,” says U. Joseph Schoepf, MD, cardiac radiologist, Medical University of South Carolina (MUSC). “The main reason is that it has an extremely high negative predictive value—almost 100 percent.”
From the patient viewpoint, the value is in replacing one invasive procedure, invasive coronary angiography, with a non-invasive one. For the institution, value is gained by inserting CT into the clinical algorithm for patients with suspected CAD. A substantial number of patients with normal arteries can be eliminated from the cath lab schedule, creating a much more specific selection of patients who need interventional procedures meaning time can be more cost-effectively spent on the more lucrative coronary interventions. For the healthcare system, significant cost-savings can be realized by ruling out CAD with a test (i.e. CCTA) that typically runs at one-third of the cost of diagnostic coronary catheterization. “Thus, if patient management is based on CTA’s exceedingly high negative predictive value, this test can be beneficial on many levels,” Schoepf adds.
CCTA offers a financial incentive for institutions operating a CT scanner and a cath lab to use the procedure to fill the schedules with patients who are reasonably expected to need an intervention, Schoepf says.
He is among researchers at MUSC who have developed a dual-source CT scanner technique using the Somatom Definition from Siemens Medical Solutions, enabling a comprehensive diagnosis of heart disease based on a single CT scan.
Normally, heart disease is difficult to diagnose because it not only requires a detailed view of structures like heart valves and blood vessels, but also blood flow to the heart muscle. By adding two x-ray spectrums with varying degrees of energy, researchers have gained a static image of the coronary arteries and the heart muscle, and thus the ability to map blood distribution and pinpoint areas of decreased blood supply. The technique, which requires only a single CT scan within a breath-hold of 15 seconds or less, brings better accuracy for detecting coronary stenosis, Schoepf says.
“We have gained the ability to better see those lesions and grade them, differentiating between lesions that are non-obstructive versus those lesions that cause significant decrease in blood supply,” he says. “This is revolutionary because you historically needed a combination of tests—invasive coronary angiography and myocardial perfusion imaging—to determine the significance of the lesion and its affect on blood supply,” he notes. “Now, we bring them together into one single, non-invasive test, which bodes well for the work up of patients with suspected CAD.”
By dropping the use of beta blockers, they also have seen improvements in workflow—now cardiac CT is like a regular CT scan. “It can