Objective ST-elevation myocardial infarction (STEMI) is frequently associated with reciprocal ST-segment depression in contralateral ECG leads. However, the relationship of the resolution of ST-segment depression (STD-R) with myocardial damage is unknown and the potential prognostic value incompletely understood. We sought to evaluate the association between STD-R and markers of myocardial injury as well as to determine the prognostic impact of STD-R in patients with acute reperfused STEMI.

Methods We enrolled 611 patients with STEMI in this multicentre cardiac magnetic resonance (CMR) study. STD-R, defined as either worsened (<0%), incomplete (0–50%) or complete (≥50%), was determined 90 min after primary percutaneous coronary intervention (PCI). Patients underwent CMR in median 3 (2–4) days after infarction. Major adverse cardiac events (MACE) were defined as a composite of death, reinfarction and new congestive heart failure within 12 months after enrolment.

Results Patients with worsened or incomplete STD-R (n=148 (24.2%)) had a significantly larger area at risk (42 (31–50) vs 37 (29–52) vs 34 (24–46) %LV, p=0.001), larger infarct size (20 (13–30) vs 17(10–26) vs 16 (8–24) %LV, p=0.003), larger extent of microvascular obstruction (0.6(0–3.4) vs 0.4 (0–2.4) vs 0.0 (0–1.4) %LV, p=0.003), and a lower LVEF (46 (39–54) vs 48 (40–56) vs 52 (45–58) %, p<0.001). MACE rate (n=37 (6%)) was significantly higher in patients with worsened (n=10 (19%)) or incomplete STD-R (n=7 (7%)) than in patients with complete STD-R (n=20 (4%), p<0.001). In multivariate Cox regression analysis, categorised STD-R emerged as an independent predictor of MACE at 12 months after adjusting for clinical variables (p=0.007).

Conclusions Patients with acute STEMI and worsened or incomplete STD-R after PCI show a more pronounced myocardial as well as microvascular damage as detected by CMR with subsequent independent prognostic information on MACE over a 12-month follow-up period.