The aim of this study was to investigate the relationship between coronary wedge pressure (CWP), measured as a marker of pre-procedural microvascular obstruction, and left ventricular remodelling in high-risk ST-segment elevation myocardial infarction (STEMI) patients. Pre-revascularization CWP was measured in 25 patients with high-risk anterior STEMI. Left ventricular volumes and ejection fraction were echocardiographically measured at discharge and at follow-up. A 20% increase in left ventricular volumes was used to define remodelling. Patients with CWP ≤ 38 mmHg were characterized by late ventricular remodelling. Patients with CWP > 38 mmHg developed a progressive remodelling process which was associated with a significant 60 months increase in left ventricular volumes (P = 0.01 for end-systolic volume and 0.03 for end-diastolic volume) and a significant decrease in left ventricular ejection fraction (P = 0.05). A significant increase in both left ventricular end-systolic (P = 0.009) and end-diastolic volume (P = 0.02) from baseline to 60 months follow-up was recorded in patients with extracted thrombus length ≥2 mm. Pre-revascularization elevated CWP was associated with increased left ventricular volumes and decreased ejection fraction at long-term follow-up. CWP was a predictor of severe left ventricular enlargement, besides extracted thrombus quantity.