Contributions of Cardiac PET/CT to Better Assess the Cardiovascular Risk

Imaging of myocardial perfusion with SPECT, SPECT/CT and PET/CT is widely used for the detection of flow-limiting epicardial lesions and risk stratification of patients with suspected or known CAD. While regional reductions in radiotracer uptake during stress as compared to rest identify flow-limiting effects of the most advanced focal epicardial lesions, the haemodynamic significance of less severe obstructive CAD lesions in multivessel disease or the presence of subclinical and nonobstructive CAD may be missed. The concurrent ability of PET/CT to determine regional myocardial blood flow (MBF) in ml/g/min at rest and during pharmacologically induced hyperaemic flows allows the calculation of the myocardial flow reserve (MFR). Adding the hyperaemic MBF and MFR to the conventional visual analysis of myocardial perfusion (1.) signifies reductions in coronary vasodilator capacity, as functional precursor of the CAD process, and determines its response to preventive medical intervention, (2.) provides important prognostic information in subclinical – and clinically manifest CAD, as well as in cardiomyopathy, (3.) improves the identification and characterisation of the extent and severity of CAD burden; and (4.) contributes to denote the flow-limiting effect of single lesions in multivessel CAD. The diagnostic scope of PET/CT, however, extends beyond myocardial flow to the identification of hibernating stunning myocardium in ischaemic cardiomyopathy, cardiac sarcoid involvement, and inflammatory coronary plaque burden. It is anticipated that with the advent of PET/MRI (magnetic resonance imaging) further advances and refinement in the comprehensive assessment of cardiovascular pathology will ensue.