A simple MR algorithm for estimation of myocardial salvage following acute ST segment elevation myocardial infarction

To assess myocardial salvage in acute ST segment elevation myocardial infarction (STEMI) by using contrast-enhanced CMR.

Forty-four consecutive patients (38 male; mean age 59 ± 10 years) with a first acute STEMI underwent acute percutaneous coronary intervention with successful restoration of TIMI grade 3 flow. CMR was performed 2 ± 1 days after reperfusion on a standard 1.5 T MR Scanner that included a steady-state free precession cine imaging for LV function and an inversion-recovery fast low angle shot (TR 8 ms, TE 4 ms, FA 25°) sequences for late gadolinium enhancement (LGE) following the injection of 0.2 mmol/kg BW gadodiamide. The myocardium at risk (MR) was approximated by the volume of myocardium exhibiting LGE and/or impaired wall motion. The myocardial salvage index (MSI) was calculated as the volume of the MR minus the volume of LGE divided by the volume of the MR. Reperfusion therapy was rated successful with an ST elevation resolution (STR) ≥70% and was considered inadequate below 70%.

Infarct size (LGE) was 17 ± 13% of LV mass, the mean STR was 53.4 ± 28.3%, and the MSI was 10.9 ± 6.2%. There was a good correlation between the MSI and the STR (r = 0.695, P < 0.0001). Thirty patients had an STR below 70%, and 14 patients had an STR greater than 70%. The MSI was greater in patients with a STE resolution of more than 70% (12 ± 11 vs. 6 ± 3%, P < 0.0001).

A simple MR algorithm based upon the relationship of functional impairment, which includes myocardial stunning, to the extent of LGE (infarct necrosis) is in accordance with STR as a clinical marker of successful reperfusion in acute myocardial infarction.