LOS ANGELES -- Although a real-time cardiac imaging tool revealed more abnormal results in patients with suspected coronary artery disease, it couldn't beat conventional stress echocardiography for predicting event-free survival (EFS), researchers found.
Among more than 2,000 patients, abnormal real-time myocardial contrast echocardiography studies were more frequent than abnormal conventional stress echo studies (P<0.001), and were more frequently abnormal in a multivessel territory (P<0.005), Thomas Porter, MD, from the University of Nebraska Medical Center in Omaha, and colleagues reported at the American Heart Association meeting.
But overall EFS in those with positive or negative studies did not differ between real-time contrast echo and conventional echo, they said. Among patients with abnormal real-time echo test results, EFS was achieved by 209 of 224 patients over a median of 4.55 years, while 288 of 309 patients who had abnormal conventional stress echo achieved EFS (P=0.88).
The study was designed to determine if the use of real-time myocardial contrast echo would give better images than conventional stress echo and would influence outcomes, Porter told MedPage Today.
A total of 2,063 patients with intermediate pre-test probability undergoing either dobutamine or exercise stress echo were prospectively randomized to real-time contrast echo or conventional echo as their imaging modality.
Patients randomized to real-time had slightly lower ejection fraction and higher frequency of prior revascularization (P<0.005 for both).
A continuous intravenous microbubble infusion (Definity, Lantheus Medical) was used for all real-time studies to examine myocardial perfusion and wall motion. The same contrast agent was used for conventional echo only when endocardial border delineation was inadequate, which was the case in 46% of all studies.
Real-time echo was performed with real-time pulse sequence schemes with a mechanical index of less than 0.25 and a frame rate of 20 to 25 Hz.
The studies were interpreted immediately by either an experienced reviewer in perfusion imaging, or four Level III reviewers with basic training in perfusion imaging.
Follow-up was available in 2,014 patients with a mean age of 59. More than half of the patients were women.
"Both groups with normal tests had greater than 95% EFS at 3 years," Porter said. "The abnormal studies also had significant adverse outcomes, as you would expect, but it was the same for conventional and real-time myocardial contrast echo. If either study indicated abnormal tests, there were similar adverse events in both groups."
Only one patient had an anaphylactic reaction to the contrast agent, and he was treated with epinephrine, Porter explained.
In terms of the readers, the predictive value of a positive study for both imaging exams was significant for the experienced readers, but not for Level III reviewers, the group reported.
Porter said his next step would be to "explore using real-time myocardial contrast echo to identify patients at greatest risk, probably those who have abnormal wall motion at rest." The goal would be to identify these patients and then determine if intervention could improve outcomes.
"We have seen studies that show that revascularization isn't that effective when done routinely," he said. "Potentially what we are seeing here is a test that can identify that high-risk patient and modify the outcome."
The study results showed that both the older and new imaging modalities are "equally valuable in predicting death and nonfatal myocardial infarction based on whether there is a normal or abnormal test," commented Sharon Mulvagh, MD, from the Mayo Clinic in Rochester, Minn.
Mulvagh pointed out to MedPage Today that real-time echo does have the advantage of being portable so that it can be used at bedside. Also, the results are more immediate.
She also pointed out that patients who had a resting defect on real-time myocardial contrast echo were more likely to have a poorer outcome. "These are your higher-risk patients where, perhaps, you might be able to make a difference," she added.
Porter disclosed commercial interests with GE Healthcare, Philips Research North America, Lantheus Medical Imaging, Astellas Pharma, Philips Healthcare, NuvOx Pharma, and Acusphere. Co-authors reported no conflicts of interest.
Mulvagh disclosed commercial interests with Lantheus Medical Imaging, GE Healthcare, and Astellas Pharma.
- Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner