Objective: The correlation between pre-revasculariza-tion measured coronary wedge pressure (CWP), angi-ographic collateral flow, necrosis, and microvascular obstruction (MVO), as assessed by the gold standard of cardiac magnetic resonance imaging (MRI), was evalu-ated in a group of patients with ST-segment elevation myocardial infarction (STEMI).

Methods: Forty-five consecutive patients with acute STEMI underwent pressure-wire based CWP mea-surement, followed by culprit artery revascularizati-on. Collateralization was evaluated according to the Rentrop grading system. Cardiac MRI was performed three-to-five days after the index event. Infarct size, MVO, intramyocardial oedema, and intramyocardial haemorrhage (IMH) were expressed as percentage of left ventricular mass.

Results: Significant negative correlations were identi-fied between mean CWP and necrosis (p=0.02), MVO (p=0.04), intramyocardial oedema (p=0.04), and IMH (p=0.05), respectively. ROC curve analysis showed a strong association between mean CWP and an extent of necrosis>20% of left ventricular mass (AUC=0.810, p=0.003), with an optimal cutoff value of 28.5mmHg. Mean CWP was positively correlated with Rentrop grade (p=0.04). In addition, collateral circulation was absent in 75% of patients with CWP <28.5mmHg and in only 40% of those with CWP ≥28.5mmHg. Necro-sis had a greater extent in patients with Rentrop gra-de <2 (15.79 vs. 8.89% in patients with Rentrop grade ≥2, p=0.08). No significant association was identified between collateralization grade and MVO (p=0.14), in-tramyocardial oedema (p=0.54), or IMH (p=0.90).

Conclusions: Pre-revascularization CWP was nega-tively correlated with necrosis, MVO, intramyocardi-al oedema, and IMH, as evaluated by cardiac MRI. A mean CWP <28.5 predicted an infarcted area >20% of left ventricular mass. Although CWP correlated positi-vely with the extent of collateralization, collateral grade by itself was not associated with the extent of MVO.