Stress imaging versus fractional flow reserve: what comes first—the chicken or the egg?

Performance of positron emission tomography (PET), magnetic resonance imaging (MRI), and single-photon emission computed tomography (SPECT) for diagnosing fractional flow reserve (FFR)-defined significant coronary artery disease (CAD) on a per-patient level. A 67-year-old male who underwent multiple diagnostic tests because of stable angina serves as a graphical summary of the PACIFIC 2 study (Driessen et al.3). The final diagnosis is made using invasive catheter coronary angiography that showed a significant stenosis of the mid-portion of the left descending artery (left panel, arrowhead). After insertion of a pressure wire, the pressures distal (Pd) to the stenosis and in the aorta (Pa) were recorded under hyperaemia, and the FFR (Pa/Pd) was 0.68, which was consistent with a significant flow reduction, and perfectly correlated with the anteroseptal perfusion defects on stress PET (middle left panel), MRI (middle right panel), and SPECT (right panel). These defects were reversible, as both resting MRI and SPECT perfusion showed no defect. Furthermore, there was no scar on late gadolinium-enhanced (LGE) MRI. The lower part of the figure reports the respective diagnostic values (sensitivity, specificity, and accuracy) of these tests in the PACIFIC 2 study for FFR-defined significant coronary artery disease (i.e. either FFR ≤0.80 or FFR ≤0.75) in symptomatic patients with prior myocardial infarction and/or percutaneous coronary intervention on a per-patient basis.