Role of stress in dynamic single-photon emission computed tomography with myocardial perfusion reserve determination in assessing the severity of coronary artery stenosis

Abstract

Aim. To assess the role of global and selected scintigraphic scores of myocardial perfusion, blood flow and reserve in the anatomical and functional significance of coronary artery (CA) stenosis.Material and methods. The double-blind comparative study included 23 patients (mean age 61,2±6,8 years, 12 (52%) women, 11 (48%) men). All patients underwent stress dynamic single-photon emission computed tomography (SPECT) with adenosine triphosphate (ATP) (140 µg/kg/min in 6 minutes). Myocardial perfusion disorders were assessed by a semi-quantitative method, the total Summed Stress Score (SSS), the Summed Rest Score (SRS), and the Summed Difference Score (SDS) were determined. Global (g) and regional (r) myocardial perfusion (MP) were evaluated; myocardial perfusion reserve (MPR) was calculated as the ratio of MP at stress and at rest. Coronary angiography (CAG) was performed within 1 week after SPECT, the amount of CA narrowing was evaluated by diameter. Stenoses >50% were considered anatomically significant. The assessment of the fractional flow reserve (FFR) was performed by the ratio of the mean intracoronary pressure at the CA ostia to the pressure distal to the stenosis at the ATP infusion peak. FFR ≤0,80 was considered a sign of hemodynamically significant stenosis. Results. Neither regional nor global scintigraphic scores reflecting myocardial perfusion showed statistical significance as markers of CA stenosis >50%. Among perfusion markers, only SSSg (>4) showed good sensitivity and specificity in the diagnosis of hemodynamically significant (FFR ≤0,80) stenoses (AUC 0,76; p=0,002; sensitivity 81,8%, specificity 83,3%). The following regional flow scores allowed identification of hemodynamically significant CA: stress MPr ≤0,54 ml/min/g (AUC 0,8; p=0,0003; sensitivity 57%, specificity 92%) and MPR ≤1,5 (AUC 0,86; p< 0,0001; sensitivity 71,4%, specificity 92,8%).Conclusion. It is proved that global and regional scintigraphic scores of MP and MPR are sensitive and specific markers of hemodynamically significant (FFR ≤0,80) coronary stenosis. It can be more useful for localization diagnosis of the lesion than standard SPECT.