Getting a crisp, clear picture of certain areas of the heart, particularly to find a blood clot in the left ventricle, can be a challenge. A new study provides guidance on when to use echocardiography contrast agents to improve those images.

Lantheus Medical Imaging (North Billerica, Massachusetts) reported results of a 600-patient study that reinforces the use and impact of its contrast agent, Definity, specifically in hospitalized and critically ill cardiac patients.

"This study found that physicians' ability to help patients was positively impacted by use of Definity," Mark Hibberd, MD, senior medical director for global medical affairs at Lantheus, told Medical Device Daily. "In technically difficult cases, it improves clinical diagnoses, improves resource utilization and decision-making."

Up to 15% of routine echocardiograms have incomplete endocardial resolution. That figure reaches up to 30% for patients in the ICU. And although there are many studies on the benefits of contrast echocardiography to assess left ventricular function, very little data is available on the impact of contrast agents relative to patient management, which is what this study sought to accomplish.

The study results closely follow news that the American Society of Echocardiography (ASE; Morrisville, North Carolina) last fall issued a consensus statement on when and how ultrasound contrast agents should be used to enhance the diagnostic capability of ECG (MDD, Nov. 13, 2008).

The new study, which appears in the Journal of the American College of Cardiology, was a prospective, single-center, cohort study of some 632 patients. It found the use of Definity in technically difficult cases improves endocardial visualization and significantly impacts cardiac diagnosis.

The study found that when contrast echocardiography was used, additional diagnostic procedures were avoided in 32.8% of patients and drug management was altered in 10.4%, with a total impact (procedures avoided, change in drugs, or both) observed in 35.6% of patients.

The patient population was recruited specifically from hospitalized patients and a significant portion of those were from the intensive care unit.

"The study found that Definity decreased the number of uninterpretable studies from 11.7% to 0.3% and the number of technically difficult studies decreased from 86.7% to 9.8%," Hibberd said. "In some cases, when you do an echo exam, depending on the clinical question, you can see clearly enough without contrast because echo windows are clear enough that answer the questions being asked by doctor. However, there are roughly 20%, by published estimates, of echo studies that don't provide clear crisp images. In those situations it's not possible to be confident about results."

Hibberd explained that physicians often don't know that they'll have a difficult time until the echo test gets under way. But there are categories of patients for which you can predict the need for contrast, such as patients with lung disease, chest wall deformities and for those who are obese.

"Another situation where you could often expect to have to use contrast is in the ICU setting because when an echo study is done, you need patients' cooperation to roll around," he said. "In the ICU, you can't do that with patients, so you just have to take images as is and they are quite poor without contrast."

A technically difficult study was defined as a one in which greater than two myocardial segments were not visualized at baseline from any imaging window. Quality of the studies, number of left ventricular (LV) segments visualized, estimated left ventricular ejection fraction (LVEF), the presence, absence or suspicion of apical thrombus and management decisions were compared before and after contrast in the study.

Since its launch in 2001, Definity has been used in more than 2 million patients. The current study may be the largest to evaluate use of contrast in this particular indication.

"Most of these studies are much smaller because the coordination involved in speaking with the many referring physicians is a great challenge," Hibberd said.

He said that results of another ongoing study started in 2008, Contrast Echocardiography REgistry for Safety Surveillance (CaRES), are due to be published next month. CaRES is a 1,000-patient, multi-center, Phase IV observational registry that will further evaluate the safety profile of Definity.

"It's close to completion and I can say, as an interim evaluation, we're very pleased with the safety profile in this registry," Hibberd said.

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