How Do PET Myocardial Blood Flow Reserve and FFR Differ?

PURPOSE OF REVIEW: This review discusses similarities and differences between cardiac positron emission tomography (PET), absolute myocardial blood flow, and flow reserve with invasive fractional flow reserve (FFR). RECENT FINDINGS: Fundamentally, cardiac PET measures absolute myocardial blood flow whereas FFR provides a relative flow reserve. Cardiac PET offers a non-invasive and therefore lower risk alternative, able to image the entire left ventricle regardless of coronary anatomy. While cardiac PET can provide unique information about the subendocardium, FFR pullbacks offer unparalleled spatial resolution. Both diagnostic tests provide a highly repeatable and technically successful index of coronary hemodynamics that accounts for the amount of distal myocardial mass, albeit only indirectly with FFR. The randomized evidence base for FFR and its associated cost effectiveness remains unsurpassed. SUMMARY: Cardiac PET and FFR have been intertwined since the very development of FFR over 25 years ago. Recent work has emphasized the ability of both techniques to guide revascularization decisions by high-quality physiology. In the past few years, cardiac PET has expanded its evidence base regarding clinical outcomes, whereas FFR has solidified its position in randomized studies as the invasive reference standard.