AHA: New imaging agent may shed light on cardiac sympathetic nerves

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Research presented at the American Heart Association (AHA) scientific sessions last week based on the subanalysis from the ADMIRE-HF phase III clinical trial suggested that imaging of the cardiac sympathetic nerves using the molecular imaging agent 123I-meta-iodobenzylguanidine (123I-MIBG, AdreView, GE Healthcare) may be useful in the assessment of risk for cardiac arrhythmias and cardiac death.

Lead investigator Arnold F. Jacobson, MD, PhD, head of the Cardiac Center of Excellence at GE Healthcare said that “the measure used to evaluate the functionality of the nerves is the heart/mediastinum ratio (H/M).” This is a ratio of the nerve function in the heart compared to a reference background region in the mediastinum.

The study was designed to demonstrate that if the cardiac nerves are damaged or reduced in number, as reflected by reduced radiotracer uptake in the heart (H/M less than 1.60), the patient is at increased risk for heart failure progression, arrhythmic events, and cardiac death.

Of the 961 New York Heart Association (NYHA) class II (83 percent) and III (17 percent) heart failure (66 percent ischemic, 34 percent non-ischemic) subjects, 905 had complete clinical data and measurements of plasma norepinephrine concentrations and B-type natriuretic peptide (BNP).

During median follow-up of 17 months, 8.3 percent died; 51 deaths were adjudicated as cardiac and 24 as non-cardiac, according to the researchers.

“The study demonstrated that age, BNP and H/M ratio were three consistent contributors to prediction models of death in NYHA class II and III heart failure patients with left ventricular ejection fraction (LVEF) of less than or equal to 35 percent," Jacobson said.

Imaging of myocardial sympathetic innervation was also used to predict arrhythmic events in heart failure patients. In a 17-month follow-up of 961 subjects, 86 (9 percent) experienced arrhythmic events (45 implantable cardioverter-defibrillator (ICD) activations; 22 sudden cardiac deaths (SCD); 12 self-limited sustained ventricular tachycardia; six resuscitated cardiac arrests; one resuscitated cardiac arrest with later SCD).  

“Cardiac imaging may help identify both NYHA Class II and III heart failure patients with extremely low two-year risk of arrhythmic events and others with a higher than average likelihood of fatal and non fatal-arrhythmias, suggesting a potential role for this procedure in decisions regarding ICD therapy,” Jacobson concluded.

ADMIRE-HF is the combination of two identical Phase III clinical trials, MBG311 and MBG312, which were conducted in 96 centers in North America and Europe, according to GE.