Validation of contrast enhanced cine steady-state free precession and T2-weighted CMR for assessment of ischemic myocardial area-at-risk in the presence of reperfusion injury.

The purpose of the study was to validate by histopathology, contrast enhanced cine steady-state free precession and T2-weighted CMR for the assessment of ischemic myocardial area-at-risk (AAR) in the presence of microvascular obstruction (MVO). Eleven anesthetized pigs underwent CMR 7 to 10 days post infarction. The area-at-risk was measured from T2-weighted fast spin echo (T2-STIR) and contrast-enhanced steady-state free precession magnetic resonance imaging (CE-SSFP) images using semi-automated algorithms based on a priori knowledge of perfusion territory. Also, late gadolinium enhancement (LGE) was performed to measure final infarct size (FIS). Histopathological comparison with Evans blue dye to define AAR and triphenyltetrazolium chloride to define FIS served as the reference. All infarcts demonstrated MVO on LGE images. Bland-Altman analysis showed no significant bias in AAR or myocardial salvage between T2-STIR and CE-SSFP or between CMR and histopathology. The mean differences ± 2SD from Bland-Altman analysis were: AAR: Evans Blue vs. T2-STIR [0.7%; + 13.5%; - 12.1%]; AAR: Evans Blue vs. CE-SSFP [0.1%; + 13.8%; - 13.7%]; AAR: T2-STIR vs. CE-SSFP [0.7%; + 6.2%; - 4.9%]; Salvage: Evans Blue - TTC vs. T2-STIR-LGE [0.8%; + 11.1%; - 9.6%]; Salvage: Evans Blue - TTC vs. CE-SSFP-LGE [0.1%; + 9.9%; - 9.6%]; Salvage: CE-SSFP-LGE vs. T2-STIR-LGE [0.7%; + 6.2%; - 4.9%]. Both T2-STIR and CE-SSFP sequences allow for unbiased quantification of AAR in the presence of ischemia/reperfusion injury when analysed by semi-automated algorithms. These experimental data, which was validated by histopathology, supports the use of CMR for the assessment of myocardial salvage during the subacute phase.