Myocardial sympathetic innervation imaging is considered experimental, investigational and unproven, including but not limited to patients with heart failure or left ventricular ejection fraction.
In a MedLine search through April 2013, the scientific literature on myocardial sympathetic innervation imaging consists of single-center studies. No randomized trials or larger multicenter trials have been identified.
In 2010, Jacobson et al. performed a prospective study known as the ADMIRE-HF (AdreView Myocardial Imaging for Risk Evaluation in Heart Failure). (4) The authors evaluated 961 patients with New York Heart Association (NYHA) functional class II/III heart failure (HF) and left ventricular ejection fraction (LVEF) < or = 35%. Iodine-123 meta-iodobenzylguanidine [(123)I-mIBG] imaging myocardial imaging (sympathetic neuronal integrity quantified as the heart/mediastinum (H/M) uptake ratio with 4 hour delayed planar images) and myocardial perfusion imaging were done. Subsequently, the subjects were followed for up to 2 years. The objective was to identify those patients with symptomatic HF who would most likely experience cardiac events.
The results were stated as, “A total of 237 subjects (25%) experienced events (median follow-up 17 months). The hazard ratio for H/M > or = 1.60 was 0.40 (p<0.001): the hazard ratio for continuous H/M was 0.22 (p<0.001). Two-year event rate was 15% for H/M > or = 1.60 and 37% for H/A <1.60; hazard ratios for individual event categories were as follow: HF progression, 0.49 (p=0.002); arrhythmic events, 0.37 (p=0.02); and cardiac death, 0.14 (p=0.00606). Significant contributors to the multivariable model were H/M, LVEF, B-type natriuretic peptide, and NYHA functional class. [(123)I-mIBG imaging also provided additional discrimination in analyses of interactions between B-type natriuretic peptide, LVEF, and H/M.”
Later in 2012, the same subjects from the ADMIRE-HF study were evaluated to determine if (123)I-mIBG had the same predictive value across the LVEF spectrum. (5) In systolic HF, both abnormal (123)I-mIBG imaging and reduced LVEF are associated with a higher risk of cardiovascular events. Of the 985 ADMIRE-HF patients, 901 were available for the laboratory-determined LVEFs, ranging from 20% to 58%. The study population mean age was 62 ± 12 years, 80% male, with the majority having NYHA functional class II HF. When comparing those patients with LVEF 35% and >35%, there was no evidence of effect modification of LVEF on the risk associated with love H/M ratio for death or arrhythmic event. The authors concluded additional prospective trials are required to determine the prospective value of (123)I-mIBG imaging for patients with HF and an LVEF > 35%.
A literature search was conducted by Treglia et al. in January 2013 to determine the clinical usefulness of (123)I-mIBG scintigraphy in evaluating the effectiveness of pharmacological treatments in patients with HF. (6) Thirty-three studies were located, with a total sample size of 1,124 patients with HF. The authors concluded that [(123)I-mIBG imaging was successfully used to assess changes in myocardial sympathetic innervation, or neuronal function, caused by several pharmacological interventions for patients with HF.
Clinical Trials for Myocardial Sympathetic Innervation Imaging:
There are no pending or future clinical studies listed in the ClinicalTrials.gov Database for trials to evaluate (123)I-mIBG imaging for patients with HF, congestive HF, LVEF or left ventricular remodeling conditions.
There is limited prospective or controlled evidence for (123)I-mIBG imaging to determine the predictive value for patients with HF or LVEF. The current evidence is insufficient to permit conclusions regarding the impact on health outcomes. Therefore, myocardial sympathetic innervation imaging is considered experimental, investigational and unproven.
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