IJCS | Volume 32, Nº1, January/ February 2019

78 Figure 5 - Flow diagram illustrating a potential algorithm for use of viability imaging. – With permission from Mc Ardle et al., Can J Cardiol 52 CABG: coronary artery bypass grafting; CAD: coronary artery disease; CRT: cardiac resynchronization therapy; EF: ejection fraction; ICD: implantable cardiac defibrillator; LV: left ventricle; MRI: magnetic resonance imaging; NYHA: New York Heart Association; PCI: percutaneous coronary intervention; SPECT: single-photon emission computed tomography. † Denotes the required indications for 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging in Ontario. Erthal et al. Myocardial viability: from PARR-2 to IMAGE HF - current evidence and future directions Int J Cardiovasc Sci. 2019;32(1)70-83 Review Article evidence of reducedMIBG uptake reflecting the high SN signal. The PARAPET study (Prediction of ARrhythmic Events with Positron Emission Tomography) has shown that sympathetic denervation measured by 11 C-meta- hydroxyephedrine (HED), a PET tracer able to quantify sympathetic denervation, could predict sudden cardiac death independently of ejection fraction and infarct size. 61 A novel F-18 PET tracer (LMI1195) is under initial evaluation and may be able to also measure myocardial innervation. 62–64 Its main advantage over HED is its longer half-life, which could enable wide distribution and hence potential for wider use of SN function imaging in the future. Conclusion Although the value of viability imaging may have been called into question by the STICH trial, several studies have reinforced the relationship between the extent of hibernating myocardium and improvement in patient outcome, left ventricular ejection fraction and quality of life if nutrient flow can be restored with revascularization. In general, there is accepted utility in using viability imaging in patient populations where decisions for revascularization are most difficult. Ongoing trials will further enable the identification of which patients most benefit from viability imaging and by which methods. Can biomarkers be used to guide