Tests such as SPECT, PET and MRI offer noninvasive alternatives for diagnosing patients with suspected coronary artery disease (CAD). Some recent evidence tilts in favor of these advanced imaging modalities, particularly when a multistep strategy is applied to diagnose the presence of CAD. By ruling out low-risk patients, these screening tools may help to eliminate unnecessary treatments and their associated costs.
CAD is the most common form of heart disease in the U.S., according to the Centers for Disease Control and Prevention. The American Heart Association estimated that CAD led to 1.4 million hospitalizations in 2004, with a cost of more than $44 billion. One study placed the prevalence of CAD among the general population in Europe at 7.3 percent (Eur Heart J 2000;21:45-52).
Physicians may choose from a variety of strategies to assess patients who present with suspected CAD. In some circumstances, they may employ invasive coronary angiography as an initial diagnostic strategy. In others, they may first order noninvasive imaging tests, such as SPECT and PET, to try to determine a patient’s risk. In either case, they may be guilty of inappropriate use if they put low-risk patients through an unnecessary invasive procedure or if they call for a multitude of additional tests that add little diagnostic value. Both scenarios add costs and hold potential risks for patients, making the need to identify cost-effective imaging strategies all the more critical.
Expected Cost & Quality-adjusted Life Years at Different Levels of CAD Prevalence
|Diagnostic Strategy||Cost $||QALY|
|Prevalence = 2% (20/1,000 patients have CAD)|
|CTA then SPECT (dominant ICER)||2,382||0.8648|
|Prevalence = 30% (300/1,000 patients have CAD)|
|CTA then SPECT (dominant ICER)||2,483||0.8373|
|CAD = coronary artery disease; Ex = exercise; ICER = incremental cost-effectiveness ratio; QALY = quality-adjusted life years|
|Source: J Am Coll Cardiol Img 2011;4:549-556|
Convincing with EVINCI
The prevalence of significant CAD in patients who present with chest pain symptoms is lower than was previously thought, according to researchers of the European EVINCI (EValuation of INtegrated Cardiac Imaging) study. EVINCI enrolled 695 patients in nine European countries who had a 60 percent average probability of having CAD. Preliminary results from the study, which was designed to spell out the most cost-effective strategy for diagnosing patients with suspected CAD, showed that invasive angiography can be avoided in as many as 75 percent of the study participants. Researchers unveiled their findings June 26 at the study group’s final meeting in Madrid.
As part of the study protocol, patients underwent noninvasive diagnostic tests, mostly using cardiac imaging, and catheterization, if appropriate. Coronary angiography and functional measurements were used as a reference to define the presence, extent and functional relevance of the disease. The strategies were then compared for diagnostic accuracy, actual cost for each procedure, as well as social costs such as missed work and potential risks.
Previous studies have relied on data from only one or two centers, says EVINCI’s principal investigator Danilo Neglia, MD, PhD, director of the Cardiac PET/CT and Multimodality Cardiovascular Imaging Program at the CRN Institute of Clinical Physiology in Pisa, Italy. The three-year study included both an imaging data bank and a biological data bank that contains blood samples.
“We have two major objectives,” Neglia says. “First is to compare different anatomo-functional imaging strategies for their accuracy and cost-effectiveness to identify patients with significant CAD.” The second is to build a predictive model using clinical and biological data to better define the individual probability of disease, which could inform patient selection.
According to preliminary results, the actual prevalence of significant CAD was 25 percent. Final results are expected to show that use of noninvasive imaging will reduce costs by keeping 75 percent of patients with suspected CAD from having to undergo invasive procedures.
SPECT, PET & combos
For noninvasive assessments, EVINCI researchers used multi-slice CT and radionuclide imaging—either SPECT or PET—to measure