Pre-perfusion coronary wedge pressure and microvascular obstruction in anterior ST elevation myocardial infarction (STEMI): An analysis from the EUROICE study.

BACKGROUND

Microvascular injury (MVI), commonly assessed on cardiac magnetic resonance (CMR) as microvascular obstruction (MVO), is frequently observed in patients with ST-elevation myocardial infarction (STEMI) despite timely primary percutaneous coronary intervention (PPCI), and is key to adverse left ventricular (LV) remodelling and poor outcomes. Established invasive indices, such as the index of microvascular resistance (IMR), are obtained after reperfusion and therefore do not capture microvascular compromise present during coronary occlusion. Coronary wedge pressure (CWP), obtained during balloon occlusion, is a simple invasive marker of microvascular function, but its clinical value remains uncertain.

OBJECTIVES

To determine whether pre-reperfusion CWP, coronary flow pressure index (CFPI) and related pressure-derived indices are associated with (i) the presence of CMR-defined MVO and (ii) MVO extent in anterior STEMI patients treated with selective intracoronary hypothermia (SIH). Secondary objectives were associations with intramyocardial haemorrhage (IMH) and myocardial salvage index (MSI).

METHODS

In this EUROICE substudy, distal coronary pressure was recorded during culprit LAD occlusion in patients randomised to selective intracoronary hypothermia. Systolic, diastolic and mean CWP, CFPI and outflow time (τ) were derived. CMR at 2-7 days quantified MVO, intramyocardial haemorrhage (IMH) and myocardial salvage index (MSI). Associations were analysed using Spearman correlation, parsimonious multivariable logistic regression, and receiver operating characteristic analysis.

RESULTS

Of 94 patients randomised to selective intracoronary hypothermia, 82 had paired pre-reperfusion physiology and CMR data available, of whom 65 had interpretable coronary pressure traces. Mean wedge pressure was 21.4 ± 11.0 mmHg, CFPI 0.24 ± 0.11, and τ 5.2 ± 2.6 s. MVO was present in 64% of patients (mean extent 2.7 ± 4.6% of LV mass). Lower CWP and CFPI were associated with MVO presence and extent (CFPI ρ = -0.33, p = 0.008), whereas τ was not. Lower CWP and CFPI were inversely related to IMH, but not to MSI. In complete-case multivariable models, lower CFPI remained associated with MVO presence (adjusted OR 0.91 per 0.01 increase, 95% CI 0.86-0.97, p = 0.002), as did lower mean CWP (adjusted OR 0.91 per 1 mmHg increase, 95% CI 0.85-0.97, p = 0.003). CFPI showed moderate discrimination for MVO, with an AUC of 0.74 (95% CI 0.61-0.87), while mean CWP showed similar discrimination, with an AUC of 0.74 (95% CI 0.61-0.86).

CONCLUSIONS

Lower CWP before reperfusion and CFPI during balloon occlusion were associated with greater MVO and IMH on early CMR in anterior STEMI. These indices support the feasibility of pre-reperfusion physiological phenotyping to aid on-table microvascular risk stratification.