CHICAGO—Evaluation of acute chest pain in the emergency department (ED) setting with stress myocardial perfusion imaging (MPI) results in a lower one-year cardiac event rate and at lower costs compared with exercise treadmill testing, according to a scientific poster presented March 25 at the 61st annual American College of Cardiology (ACC) Scientific Session.
Proper triage with acute chest pain in the emergency department is critical for delivering cost-effective care. While stress MPI is one of several recognized techniques for evaluating acute chest pain for those who have a non-diagnostic electrocardiogram for ischemia, little is known about its impact as a primary diagnostic tool in a real-world ED setting.
John J. Mahmarian, MD, chief of nuclear cardiology and CT services at Methodist DeBakey Heart & Vascular Center in Houston, and colleagues sought to examine the relative value of stress MPI vs. exercise testing in patients admitted to the ED with acute chest pain of uncertain etiology. They used U.S. commercial and Medicare health plan claims data.
In the study, the researchers analyzed a retrospective claims database of adults (18 years or older) who had either an exercise test or a stress MPI study on the same day or one day after admission to the ED between Jan. 1, 2007 to Dec. 31, 2009.
The index date was defined as the date of the first diagnostic test. Patients were observed for one year before the index date and one year after the index date or until death, if sooner. Patients were excluded if they had any diagnosis or procedure codes for pregnancy, labor or delivery at any time.
The two primary outcomes were cardiac events (defined as hospitalization for coronary angiography or coronary revascularization or coronary artery disease (CAD, MI and death) and healthcare costs (total all-cause cost and acute coronary syndrome-related costs, including services for acute myocardial ischemia).
The pre-match sample included 31,080 patients (12,925 exercise testing and 18,155 MPI). The total post-match sample included 22,794 patients (11,297 exercise testing and 11,397 MPI). In the post-match sample, there were 8,524 low-risk ACS patients (4,262 exercise testing and 4,262 MPI), 3,902 intermediate-risk ACS patients (1,951 exercise testing and 1,951 MPI), and 9,936 high-risk ACS patients (4,968 exercise testing and 4,968 MPI).
During the one-year post-test period, exercise testing patients had a higher cardiac event rate than MPI patients. The one-year cardiac events were 14.5 percent in the exercise testing arm and 10.1 percent in the MPI arm. Compared with MPI, the exercise arm had a higher percentage of cardiac events for coronary angiography (3.5 vs. 3.1 percent); CAD (12.5 vs. 9 percent); MI (7.8 vs. 7.1 percent); heart failure (7.3 vs. 3.7 percent); and death (5 vs. 1.8 percent). There was the same percentage of events for coronary revascularization at 2.2 percent.
Moreover, MPI patients had an improved clinical outcome over exercise testing patients across all three ACS risk groups. The advantage of MPI over exercise testing was greatest for high-risk ACS patients (24.8 vs. 18 percent).
The pre-test healthcare costs were defined as the cost of care provided within the 12 months before the index diagnostic test. “Although statistically significant, the pre-test total all-cause costs (mean) for exercise testing and MPI patients were quantitatively similar (exercise testing, $13,651 vs. MPI, $15,045),” the study authors reported.
The post-test healthcare costs were defined as the cost of care provided within the 12 months after the index diagnostic test. Mean all-cause costs during the post-test period were significantly greater than MPI patients (exercise testing, $26,743 vs. MPI, $19,656). For the exercise testing arm, mean all-cause costs increased 96 percent between the pre-test and post-test periods, and for the MPI arm, mean all-cause costs increased 31 percent between the pre-test and post-test periods.
A “similar significant pattern” was observed across all ACS risk groups, according to Mahmarian and his colleagues. “Mean all-cause cost differences with exercise testing were higher than mean all-cause costs than MPI patients during the post-test period. ACS-related costs during the post-test period also were significantly higher for the exercise testing arm, compared with the MPI arm, and across all ACS groups:
- All patients: exercise testing, $3,373 vs. MPI, $2,035;
- Low-risk ACS: exercise