Echo-related studies garner attention at the AHA Scientific Sessions
Research presented at the American Heart Association 2012 Scientific Sessions in Los Angeles highlights the important role of cardiovascular ultrasound in research and clinical practice.
Nanobubbles, ultrasound can deliver drugs to treat infective endocarditis
AHA Daily News: A combination of nano-sized bubbles and ultrasound can deliver drugs to treat infective endocarditis by disrupting the biofilm that typically shields infected cardiac tissue from antibiotics. ASE member Satoshi Nakatani, MD, PhD, professor in the department of functional diagnostics at Osaka University Graduate School of Medicine in Japan, explained “endocarditis is refractory to treatment due to a biofilm which protects the bacterial vegetation from antibiotics and other external materials. In humans, endocarditis is a lethal disease. We want antibiotics to penetrate into the bacterial vegetation more easily in order to reduce the time and difficulty of treatment. That is why we thought of ultrasound.”
The study was summarized in abstract “Sonoporation With Nano-Sized Bubble Liposomes may be a Useful Method of Drug Delivery to Vegetations: An Experimental Study Using Rats With Infective Endocarditis” (Abstract 12332) and presented as a poster on Sunday, November 4.
Ultrasound is used to facilitate delivery of drugs and genes through cellular membranes through sonoporation, in which acoustic energy delivered by ultrasound causes the formation of microbubbles at the cell membrane surface that cavitate and open microscopic pores and force outside material through the membrane and into the cell. The addition of microbubbles can dramatically increase sonoporation, but it can also cause unacceptable tissue damage.
Nakatani’s research group used nano-scale bubbles with an average diameter of less than 2 nanometers to minimize tissue damage. Aortic valves showing bacterial infection were removed from rats and fixed in a saline solution containing India ink as a marker. A control group received neither ultrasound nor nanobubbles. A second group received ultrasound only, and a third both ultrasound and nanobubbles. The India ink penetration score for the ultrasound-only group was 0.56, compared to 1.65 for those that also received nanobubbles. There was no penetration in the control group. “Aquatic pressure from the ultrasound disrupts the microbubbles and causes cavitation. We believe the same thing would happen if we used an antibiotic instead of India ink,” explained Nakatani.
MedPage Today: Research presented by ASE member Thomas Porter, MD, FASE of the University of Nebraska Medical Center in Omaha showed that while myocardial contrast echocardiography revealed more abnormal results in patients with suspected coronary artery disease, it couldn’t best conventional stress echocardiography for predicting event-free survival (EFS).
The study was designed to determine if the use of stress perfusion imaging would give better images than conventional stress wall motion imaging and would influence outcomes. It was summarized in abstract “Prospective Evaluation of Outcomes With Stress Perfusion Imaging Versus Stress Wall Motion Imaging During Dobutamine or Exercise Echocardiography” and presented during the Late-Breaking Clinical Trials II (LBCT.02) session on Sunday, November 4.
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). 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).
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. Potentially what we are seeing here is a test that can identify that high-risk patient and modify the outcome.”
ASE member Sharon Mulvagh, MD, FASE of the Mayo Clinic in Rochester, MN told MedPage Today that 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.” She pointed out that real-time echo has the advantage of being portable so that it can be used at bedside. Also, the results are more immediate. She also noted 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.”
Cardiac imaging management reduces unnecessary follow-up tests
: A utilization management program modeled on the American College of Cardiology Foundation’s Appropriate Use Criteria was shown to prevent unnecessary imaging exams and resulted in a 12 percent reduction in the likelihood of follow-up tests, including myocardial perfusion imaging and cardiac CT scans. The study “Utilization Management Reduces Repeated Outpatient Cardiovascular Imaging” (Abstract 14699) was presented as a poster on Sunday, November 4. ASE partnered with the ACC on the appropriate use criteria for echocardiography.
“While the reduction in follow-up tests is important on its own, we can extrapolate that unnecessary catheterizations, angioplasty procedures and heart bypass procedures were prevented as well,” Andrea DeVries, director of research operations for HealthCore, said in a press release.
Previous research places the rate of inappropriate cardiac imaging exams at approximately 15 percent. HealthCore analyzed information provided by AIM Specialty Health, a benefit management company, on a study group of 96,906 people who were members in WellPoint-affiliated health plans in Indiana, Ohio, Kentucky, Missouri and Georgia before and after a cardiac program was implemented in these states. The cardiac program reviews stress echocardiography, resting transthoracic echocardiography, transesophageal echocardiography, myocardial perfusion imaging, cardiac PET, cardiac CT, cardiac MRI and blood pool imaging. AIM’s medical necessity clinical guidelines were developed using the ACCF’s appropriate use criteria as a primary source, to help ensure that a requested cardiac procedure is appropriate for the patient.
HealthCore compared patients managed through the AIM cardiac management program to others who received no management from AIM. HealthCore followed the patients’ health data for up to 24 months after their initial diagnostic test. Researchers found that for every 100 index tests across the entire study population, the following domino effect of medical services occur within 12 months: 20 additional follow-up diagnostic tests, 10 catheterizations, three angioplasty procedures and one heart bypass surgery. The analysis also found that two out of every nine patients with a baseline diagnostic test had a follow-up test within 24 months; one out of six patients with a baseline diagnostic test had a follow-up test within one year. These follow-up tests were most likely to happen during the first month after the initial test.
Controlling for key factors, such as age, gender, member comorbidity, and cardiac risk, the utilization management program was associated with reduced volume of downstream cardiac imaging.
Study shows one third of repeat TTE studies at tertiary care center inappropriate; 70% were ordered by non-cardiologists
: A study designed to evaluate the application of the Appropriate Use Criteria (AUC) for Echocardiography published by the ACC, ASE and other societies in 2011, determined that one-third of repeat transthoracic echocardiography (TTE) tests in a tertiary care medical center were inappropriate according to the criteria. The study “Appropriate Use of Inpatient Repeat Echocardiography in a Tertiary Care Center” was presented as a poster on Sunday, November 4 (Abstract 19632).Anu Vellanki, MD, University of Massachusetts Medical School, and colleagues evaluated written requests for 500 consecutive inpatient TTEs over a 1-month period in 2012 and examined the echocardiography database to determine if a TTE had been performed within 1 year. Overall, 131 (26%) of the TTEs were repeat studies; 107 patients had a previous TTE repeated within the last 6 months, while 24 patients had a previous TTE in the last year. Per the AUC, forty-nine percent of the repeat echocardiograms were deemed appropriate, 34% inappropriate and 17% uncertain. The three main indications for inappropriate TTE were heart failure, syncope, and pericardial effusion. Thirty percent of the repeat TTEs were ordered by cardiologists and 70% were ordered by non-cardiology providers.
The study concluded that in an effort to reduce inappropriate, repeat TTEs, knowledge of prior TTE data and incorporation of AUC into order entry mechanisms should occur. “The entire clinical picture and knowledge of the presence and results of prior imaging should be taken account when contemplating repeat TTE,” said Dr. Vellanki. “In an effort to reduce inappropriate imaging, AUC criteria should be incorporated into order entry mechanisms in a fully functional electronic medical record in order to help guide providers decisions on ordering echocardiography in the inpatient setting.”