Fractional flow reserve in patients with prior myocardial infarction

Background-Fractional flow reserve (FFR), an index of coronary stenosis sev erity, can be calculated from the ratio of hyperemic distal to proximal cor onary pressure. An FFR value of 0.75 can distinguish patients with normal a nd abnormal noninvasive stress testing in case of normal left ventricular f unction. The present study aimed at investigating the value of FFR in patie nts with a prior myocardial infarction. Methods and Results-In 57 patients who had sustained a myocardial infarctio n greater than or equal to6 days earlier, myocardial perfusion single photo n emission scintigraphy (SPECT) imaging and FFR were obtained before and af ter angioplasty. The sensitivity and specificity of the 0.75 value of FFR t o detect flow maldistribution at SPECT imaging were 82% and 87%. The concor dance between the FFR and SPECT imaging was 85% (P <0.001). When only truly positive and truly negative SPECT imaging were considered, the correspondi ng values were 87%, 100%, and 94% (P<0.001). Patients with positive SPECT i maging before angioplasty had a significantly lower FFR than patients with negative SPECT imaging (0.52<plus/minus>0.18 versus 0.67 +/-0.16, P=0.0079) but a significantly higher left ventricular ejection fraction (63 +/- 10% versus 52 +/- 10%, P=0.0009) despite a similar degree of diameter stenosis (67 +/- 13% versus 68 +/- 16%, P=NS). A significant inverse correlation was found between LVEF and FFR (R=0.29, P=0.049). Conclusions-The present data indicate (1) that the 0.75 cutoff value of FFR to distinguish patients with positive from patients with negative SPECT im aging is valid after a myocardial infarction and (2) that for a similar deg ree of stenosis, the value of FFR depends on the mass of viable myocardium.