Background: Primary PCI is the main stain therapy of acute MI in Europe. Evaluation of ST-segment resolution (STR) is a simple tool to assess the quality of myocardial reperfusion after primary percutaneous coronary intervention (PCI). Cardiac MRI is the most adequate tool to judge the extent of myocardial injury and thus the quality of reperfusion.
Objectives: This study aims to correlate STR to the infarct size (IS) on the post angiographic CMR.
Methods: an observational retrospective single-center study was conducted in 189 patients who underwent primary PCI between 2014 and 2018. Patients were divided into 2 groups, successful myocardial reperfusion, characterized by a STR ≥ 70% (group 1) and failed myocardial reperfusion, characterized by STR < 70% (group 2). Univariate linear regression was used to assess the correlation between MRI parameters (area at risk – AAR, Infarct size – IS and Microvascular obstruction – MVO) and STR. Chi-square test was used to compare categorical variable, whereas comparison of between quantitative variable in the two groups was performed using an unpaired t-test. In both case we consider a p value < 0.05 significant.
Results: 49 patients were included in the final analysis. 13 in group 1 and 36 in group 2.
There was no difference in baseline characteristics between the two groups.
The comparison of MRI parameters between the two groups present no statistically significant difference. AAR [g]: Group 1 mean size was 19g and Group 2 was 22g (P=0.43); AAR [% of LV-mass]: Group 1 mean size was 16% and Group 2 was 18% (P=0.43); IS [g] for Group 1 was 14g and for Group 2 was 12g (P=0.48); IS [% of LV-mass] for Group 1 was 12% and for Group 2 was 14% (P=0.65); MVO [g] for Group 1 was 1.5g and for Group 2 was 3.9g (P=0.17).
Linear regression model between the AAR in g and the STR present a R2 < 0.001; AAR in % of LV-mass with STR presents a R2 =0.006; the myocardial IS in % of LV-mass and STR present a R2 = 0.006; the myocardial IS in gram present a R2 = 0.109 and finally MVO in gram with STR present a R2 = 0.028.
Conclusions: As no correlation between STR and the CMR parameters has been shown in this project, we conclude that, for this particular population, STR is not an adequate surrogate to assess the quality of myocardial reperfusion.