Imaging Agent Helps Identify Risk of Heart Failure

 

May 19, 2010

May 19, 2010 – A new study shows a single photon emission computed tomography (SPECT) imaging agent can identified symptomatic heart failure patients most likely to experience cardiac events.

Results from the ADMIRE-HF (AdreView Myocardial Imaging for Risk Evaluation in Heart Failure) trial were published in the May 18 issue of the Journal of the American College of Cardiology. The prospective study evaluates cardiac sympathetic nerve imaging using the SPECT imaging agent Iobenguane I 123 Injection (also called 123I-mIBG or by its trade name AdreView).

According to the study, the drug imaging results produced a model with four independent variables contributing to the prediction of the primary outcome events.

"Increased cardiac sympathetic activity is a prominent feature of heart failure and is associated with progressive deterioration and remodeling of the myocardium, inexorable decline in left ventricular function, and worsening symptoms," said professor Roxy Senior, M.D., director of cardiac research at Northwick Park Hospital, an author of the study. "Our results suggest that in appropriately selected patients with heart failure, the 123I-mIBG imaging procedure can alert clinicians to the potential need for considering additional treatments."

The ADMIRE-HF Trial
ADMIRE-HF consisted of two identical open-label phase III clinical studies evaluating the cardiac sympathetic nerves at the cellular level. The studies were conducted in 96 centers in North America and Europe. Nine hundred sixty-four patients were included. They had New York Heart Association (NYHA) Class II (83 percent) and Class III (17 percent) heart failure (66 percent ischemic, 34 percent nonischemic) and left ventricular ejection fraction (LVEF) less than or equal to 35 percent. They underwent early (15-minute) and late (four-hour) planar and SPECT myocardial imaging. Patients were then observed every six to seven weeks over the course of two years to monitor for occurrence of cardiac events. The composite endpoint was the time to first occurrence of NYHA heart failure class progression, a potentially life-threatening arrhythmic event, or cardiac death, as determined by an independent adjudication panel.(1)

The researchers used the heart/mediastinum ratio (H/M) to assess the functionality of the sympathetic nerves. H/M is a ratio of the nerve function in the heart compared to that of a reference background region in the mediastinum (the mass of tissues and organs between the two pleural sacs, which separate the heart from the lungs). The study was designed to demonstrate that if the cardiac nerves are damaged or reduced in number, as reflected by reduced 123I-mIBG uptake in the heart, the patient is at increased risk for heart failure progression, arrhythmic events, and cardiac death.(1)

The primary analysis employed a Cox proportional hazards model to compare outcomes in subjects with H/M of less than 1.6 and greater than or equal to 1.6 on late planar imaging. A multivariable Cox proportional hazards analysis incorporated imaging and clinical variables into a prediction model for adverse cardiac events.(1)

"Using imaging tests are consistent with current trends toward gaining improved and earlier understanding of heart disease at a molecular level and may enable preventive management strategies," said Arnold F. Jacobson, M.D., Ph.D., head, Cardiac Center of Excellence, GE Healthcare. “This testing method is not new, however ADMIRE-HF is the first large-scale multicenter prospective validation of the potential prognostic power and provides data that clinicians may be able to use to improve current practice."

Trial Results
The evaluable efficacy population consisted of 961 patients. During the median follow-up period of 17 months, first cardiac events were observed in 237 patients (25 percent); these included 163 cases of heart failure progression, 50 arrhythmic events, and 24 cardiac deaths. The risk of cardiac events (the trial's primary endpoint) was significantly lower for patients with an H/M greater than or equal to 1.6, with a hazard ratio (HR) of 0.4 (97.5 percent confidence interval [CI]: 0.25 to 0.64; p < 0.001). A Cox proportional hazards analysis based on a continuous numerical H/M (i.e., rather than on separating patients according to H/M greater than or equal to 1.6 or less than 1.6) revealed an even lower HR of 0.22 (97.5 percent CI: 0.10 to 0.47; p < 0.001).(1)

Survival analysis revealed two-year event rates of 15 percent for patients with an H/M greater than or equal to 1.6, compared to 38 percent for patients whose H/M was below 1.6. Hazard ratios for individual events, based on an H/M threshold of 1.6, were as follows: heart failure progression, 0.49 (95 percent CI: 0.32 to 0.77; p = 0.002); arrhythmic events, 0.37 (95 percent CI: 0.16 to 0.85; p = 0.37); and cardiac death, 0.14 (95 percent CI: 0.03 to 0.58; p = 0.006).(1)

A multivariate analysis of the pooled ADMIRE-HF data using only the planar 123I-mIBG imaging results produced a model with four independent variables contributing to the prediction of the primary outcome events. These included late H/M, LVEF, NYHA functional class, and plasma B-type brain natriuretic peptide (BNP).(1)

In subanalyses, the H/M provided significant information to complement BNP – a frequently used marker of prognosis in heart failure patients – for identifying patients at the highest risk for cardiac events and cardiac death. The two-year cardiac event rate for patients with BNP above the median of 140 ng/l was 42 percent, but among patients with H/M greater than or equal to 1.6, the rate was 20.5 percent. Whereas there were no cardiac deaths among the 57 patients with BNP greater than 140 ng/l and H/M greater than or equal to 1.6, there were 42 cardiac deaths among the 406 patients (10.3 percent) with above-median BNP and H/M less than 1.6.(1)

The AdreView Imaging Agent
AdreView (Iobenguane I 123 Injection) is a molecular imaging agent. GE Healthcare began developing AdreView in 2004, and the agent was granted orphan-drug status by the Food and Drug Administration (FDA) in December 2006. In September 2008, AdreView was approved by the FDA for the detection of primary or metastatic pheochromocytoma or neuroblastoma as an adjunct to other diagnostic tests. In the United States, it is not currently approved for use in cardiac imaging.

AdreView is approved in Germany, France, Great Britain, Spain, Belgium, Holland, Denmark, and Norway for the functional assessment of the cardiac sympathetic innervation.

For more information: www.gehealthcare.com

References:
1. Jacobson AF, Senior R, Cerquiera M.D., et al. “Myocardial iodine‐123 meta‐iodobenzylguanidine imaging and cardiac events in heart failure: results of the prospective ADMIRE‐HF (AdreView Myocardial Imaging for Risk Evaluation in Heart Failure) study.” Journal of the American College of Cardiology. In press
2. “American Heart Association Heart Disease and Stroke Statistics,” 2009 update

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