The Role of Diagnostic Imaging in Identifying Appropriate Strategies for Heart Failure Management

Purpose: The aim of this study was to determine whether regional sympatheticactivity is independently predictive of adverse cardiac events (CE) in heartfailure (HF) patients, and whether 123I-mIBG SPECT imaging can perform thisrole.Methods: Twenty-two clinically diagnosed HF patients were recruited into thisstudy. The subjects underwent myocardial perfusion SPECT and cardiacsympathetic imaging with 123I-mIBG. Early (at 15 min post-injection) anddelayed (four hours post-injection) planar and SPECT scintigraphy wasperformed. Visual and semi-quantitative analysis was conducted on theseimages, and global (from planar imaging) and regional (from SPECT imaging)uptake and washout indices obtained. The patients were clinically followed upfor up to two years and the CEs in these patients were recorded. Theoccurrence of CE was then correlated with the various demographic, clinical,scintigraphic and biochemical parameters. Results: The occurrence of CE in HF was independent of the patients''demographics or the cause of HF. Left ventricular ejection fraction (LVEF) hadno concordance with CE, however a decrease of 5% or more in LVEF was asignificant predictor of CE (p = 0.011). Genetic biomarkers were also unable topredict CE. Global or regional uptake had limited ability to predict CE, where asregional washout from inferior (p = 0.005) and lateral (p = 0.085) walls werestatistically significant predictors of CE. A high washout of 40% or more from vithe peri-infarcted and non-infarcted segments on MPS was also a significantpredictor of CE (p = 0.035).Conclusion: HF is a complex, multi-factorial progressive disease that appears tobe regional to begin with, but then progressively involves the whole heart. Therole of the autonomic nervous system, especially the sympathetic nervoussystem, is central to the clinical course of the disease, especially the incidenceof sudden cardiac death (SCD). 123I-mIBG provides a valuable tool in not justimaging the global sympathetic innervation of the heart, but also in assessingthe regional distribution. This allows earlier diagnosis and stratifications ofpatients at risk of cardiac events, in particular SCD. While previous reportsindicate that delayed washout offers identification of risk, the key marker isregional washout of 123I-mIBG from non-infarcted myocardium.