Background: The extent of myocardial salvage after primary percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI) is variable and can not be predicted on the basis of vessel patency. The aim of this study was to evaluate the tissue salvage and the microvascular integrity after successful intervention in AMI by coronary blood flow velocity and sestamibi perfusion imaging.
Methods: Twenty-two patients (17 m, 5f; mean age 57 +/- 14 yrs.) undergoing primary PTCA and stent implantation for AMI were studied. 99mTc Sestamibi was injected intravenously before intervention and single photon emission computed tomography (SPECT) was performed immediately after successful reperfusion to determine the area at risk before PTCA due to the minimal 99mTc Sestamibi redistribution. Sestamibi SPECT was repeated 3 days and 6 months after AMI. Area at risk (%) was determined automatically by myocardial perfusion tomography (PERFIT) with the use of a multistage, 3D iterative inter-subject registration of patient images to normal templates (2SD) and myocardial salvage was calculated. Coronary flow velocity was measured using a Doppler-tipped guidewire in the infarct-related artery after successful completion of primary PTCA and in an angiographically normal reference vessel. Absolute coronary flow reserve (CFR) and relative CFR (rCFR) were calculated using hyperemic to basal average peak velocity.
Results: Despite successful reperfusion of the target vessel (TIMI grade III flow) CFR and rCFR remained impaired (1.8 +/- 0.9 and 0.77 +/- 0.21). Area at risk decreased significantly from 21 +/- 9% to 9 +/- 10% (p < 0.05) corresponding to 11 +/- 8% myocardial salvage. Acute CFR and rCFR showed no correlation with the area at risk before and after primary PTCA. The increase of CFR within 6 months correlated with the myocardial salvage (p < 0.05).
Conclusions: Despite successful primary PTCA in AMI, CFR and rCFR often remain impaired because of a significant loss of microvascular integrity. The long-term success of primary PTCA can be assessed by myocardial salvage and the change of CFR which might be a useful parameter for additional reperfusion strategies such as glycoprotein IIb/IIIA receptor inhibition.