If you have a heart attack today your chances of surviving are much better than they would have been 50 years ago, thanks to medical advances. But on the flipside, more people are living with heart failure (HF) today than ever before.
"Heart failure is a huge and rapidly growing medical problem in the U.S. and developed countries ... healthcare providers are doing a good job of improving the outcomes of people who have heart attacks and they're now surviving, but they now have heart failure," Mark Hibberd, MD, PhD, senior medical director at Lantheus Medical (North Billerica, Massachusetts), told Diagnostics & Imaging Week.
And because there are many different causes of heart failure, it isn't always easy for the patient's doctor to figure out what the causes are, Hibberd said, and without that they can't prescribe the right kind of therapy.
"There are a significant number of patients with ischemic heart failure but no real clinical signs that they have the disease. It can be difficult for a clinician to figure that out by himself," Hibberd said.
Lantheus recently reported new data that shows gated single-photon emission computed tomographic (SPECT) myocardial perfusion imaging (MPI) with Cardiolite had a 96% negative predictive value for diagnosing extensive coronary artery disease (CAD) in patients hospitalized with their first episode of heart failure. The study findings were published in the January/February issue of The Journal of Nuclear Cardiology.
An imaging agent developed by Lantheus, Cardiolite is a radioactive technetium labeled myocardial perfusion tracer intended to provide physicians with prognostic information that can be helpful in making patient management decisions, according to the company. "It's become a very good way of showing how much of the heart is blocked," Hibberd said.
A SPECT scan is a nuclear imaging technique that involves injecting a radioactive liquid into the blood, then taking a series of pictures around the chest. A SPECT scan produces three-dimensional images that show how organs function.
MPI is a non-invasive test that uses a small amount of radioactive material (radiopharmaceutical) 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 properly. Following the administration of the radiopharmaceutical (in this case, the Cardiolite), 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, the company noted.
"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," said Prem Soman, MD, PhD, associate director of nuclear cardiology at the UPMC Presbyterian Hospital (Pittsburgh) and lead author of the Investigation of Myocardial Gated SPECT Imaging in Heart Failure (IMAGING in HF) trial. "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."
According to Lantheus, 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 U.S. and the United Kingdom. All patients received a stress and rest SPECT MPI test using Cardiolite. Data was 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 ? 70% stenosis in two or more major epicardial coronary arteries, or ? 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, co-existing CAD. The presence of extensive CAD indicates a causal relationship with heart failure and such patients are likely to benefit from coronary revascularization, Lantheus noted.
"If you have heart failure and a lot of blocked arteries you're in a very difficult situation because your heart isn't pumping properly and you're not receiving enough blood," Hibberd said.
In such cases, medicine is going to be of relatively limited value, Hibberd added, and the patient would benefit from coronary revascularization. He said that in the study, Cardiolite SPECT imaging was able to pick out the patients with the most severe disease. Patients with less severe blockages or no blockages may be better off with medicine than a revascularization procedure, he noted.
According to Lantheus, more than 5 million Americans are living with heart failure. CAD is one of the most common causes of heart failure, the company noted. MPI is often used to determine the presence and severity of physiologically significant CAD in patients with suspicious symptoms. Lantheus says IMAGING in HF is the first study to explore MPI's diagnostic use specifically in patients with new-onset of heart failure.
"The current professional society guidelines provide physicians with mixed direction regarding diagnostic procedures for patients with new-onset heart failure," said James Udelson, MD, principal investigator of the study and chief of cardiology at Tufts Medical Center (Boston). "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."