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Figure 3 Intracoronary hyperemic pressure measurements at baseline and during dobutamine challenge. The graph shows the recorded electrocardiogram (EKG), aortic pressure (Pa), and intracoronary pressure distal to the myocardial bridge (Pd) as well as the instantaneous pressure gradient resulting from the difference between the two pressures. These tracings are shown as recorded at baseline and during dobutamine challenge (note the differing scaling of the pressure tracings). The overshooting of Pd over Pa noted during dobutamine challenge contributes to the characteristic negative systolic and positive protodiastolic pressure gradients, which mimic the Doppler flow velocity pattern described previously (1,9). At baseline mean fractional flow reserve (FFR) was 0.90 and diastolic FFR was 0.87; during dobutamine challenge mean FFR was 0.80 and diastolic FFR was 0.72.