SPECT Myocardial Perfusion Imaging Evaluated in New-Onset Heart Failure Patients

(North Billerica, MA, USA), an international company that develops medical imaging agents, reported that new data from a prospective, nonrandomized, multinational study that shows gated SPECT myocardial perfusion imaging (MPI) with Cardiolite (kit for the preparation of technetium Tc99m sestamibi for injection) had a 96% negative predictive value for diagnosing extensive coronary artery disease in patients hospitalized with their first episode of heart failure. The study findings were published in the January/February 2009 issue of The Journal of Nuclear Cardiology.

One of the most common causes of heart failure is CAD. Data from observational studies suggest that CAD is the underlying cause of up to 70% of patients with heart failure. MPI is often used to determine the presence and severity of physiologically significant CAD in patients with suspicious symptoms. This is the first study to explore myocardial perfusion imaging's diagnostic utility specifically in patients with new-onset heart failure.

"Because some patients with heart failure and extensive coronary artery disease may benefit from coronary revascularization and improve their quality of life and longevity, identifying the extent and severity of underlying CAD in these patients is a critical first step in the initial management of their care. As the first study to examine the utility of SPECT MPI for CAD detection in patients with new-onset heart failure, these results are very encouraging and point to gated SPECT as a potentially useful diagnostic modality for heart failure patients without angina or other clinical indicators of CAD,” said Prem Soman, M.D., Ph.D., F.R.C.P., associate director of nuclear cardiology, University of Pittsburgh Medical Center, Presbyterian University Hospital and lead author of The Investigation of Myocardial Gated SPECT Imaging in Heart Failure (IMAGING in HF) trial.

A SPECT scan is a nuclear imaging technique that involves injecting a radioactive liquid into the blood, then taking a series of images around the chest. A SPECT scan produces three-dimensional images that show how organs function. For myocardial perfusion imaging, SPECT remains the dominant modality at this time.

MPI is a noninvasive test that utilizes a small amount of radioactive material injected into the body to depict the distribution of blood flow to the heart. MPI is used to identify areas of reduced blood flow to the heart muscle to determine whether or not the heart is working correctly. Following the administration of the radiopharmaceutical, the heart rate is raised to induce myocardial stress, either by exercise or pharmacologically. Using SPECT technology, images of the heart muscle are then obtained and examined.

A normal stress SPECT MPI indicates a very low probability of extensive CAD in patients with heart failure, and therefore, invasive coronary angiography can be avoided. "These initial findings point to the need for further evaluation of the use of SPECT MPI for CAD detection in new-onset heart failure patients,” continued Dr. Soman.

The IMAGING in HF study was designed to explore the role of gated SPECT MPI using Cardiolite as an initial investigative strategy for diagnosing extensive CAD, which is potentially etiologically relevant to patients hospitalized with their first episode of heart failure. The observational study assessed 201 patients hospitalized with their first presentation of heart failure at 14 sites in the United States and the United Kingdom. All patients received a stress and rest SPECT MPI test using Cardiolite. Data were analyzed in a core laboratory and provided researchers with 99.5% interpretable stress images and 98.5% interpretable rest and stress images. Coronary arteriography was performed when clinically indicated.

SPECT MPI had 96% sensitivity, 56% specificity, and a 96% negative predictive value for the diagnosis of extensive CAD, defined conventionally as greater than or equal to 70% stenosis in two or more major epicardial coronary arteries, or greater than or equal to 70% in the left main coronary artery, proximal left anterior descending coronary artery, or single vessel disease with prior myocardial infarction or coronary revascularization. The diagnostic values of SPECT MPI for more limited CAD were 82% sensitivity, 57% specificity, and 75% negative predictive value. These definitions were used to differentiate heart failure patients with extensive, etiologically relevant CAD from those with more limited, coexisting CAD. The presence of extensive CAD indicates a causal relationship with heart failure and such patients are likely to benefit from coronary revascularization.

"The current professional society guidelines provide physicians with mixed direction regarding diagnostic procedures for patients with new-onset heart failure,” said James Udelson, M.D., lead investigator of the study and chief of cardiology at Tufts Medical Center (Boston, MA, USA). "These study findings build additional clinical evidence for the use of SPECT MPI with Cardiolite as a noninvasive procedure, prior to more invasive coronary angiography, to help physicians assess and select which patients would benefit most from revascularization.”

"Only 12% of patients had active anginal symptoms, making a CAD diagnosis difficult on clinical grounds, and increasing the importance of using imaging tests such as Cardiolite. These study findings further demonstrate the expanding role that SPECT imaging with Cardiolite plays in risk stratification for patients with their first episode of heart failure,” said Mark Hibberd, M.D. Ph.D., senior medical director, global medical affairs, Lantheus Medical Imaging.

Cardiolite is one of the world's most widely used cardiac imaging agents and has been used to image more than 40 million patients.

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