Determining microvascular obstruction and infarct size with steady-state free precession imaging cardiac MRI

Abstract

Purpose: In cardiac MRI (cMRI) injection of contrast medium may be performed prior to the acquisition of cine steady-state free precession (SSFP) imaging to speed up the protocol and avoid delay before late Gadolinium enhancement (LGE) imaging. Aim of this study was to evaluate whether a condensed clinical protocol with contrast cine SSFP imaging is able to detect early microvascular obstruction (MO) and determine the infarct size compared to the findings of LGE inversion recovery sequences.

Materials and methods: The study complies with the Declaration of Helsinki and was performed following approval by the ethic committee of the University of Erlangen-Nuremberg. Written informed consent was obtained from every patient. 68 consecutive patients (14 females/54 males) with acute ST-elevation myocardial infarction (STEMI) treated by percutaneous coronary revascularization were included in this study. CMRI was performed 6.6±2 days after symptom onset and MO and infarct size in early contrast SSFP cine imaging were compared to LGE imaging.

Results: MO was detected in 47/68 (69%) patients on cine SSFP and in 41/68 (60%) patients on LGE imaging. In 6 patients MO was found on cine SSFP imaging but was not detectable on LGE imaging. Infarct size on cine SSFP showed a strong agreement to LGE imaging (intraclass correlation coefficient [ICC] of 0.96 for enddiastolic, p<0.001 and 0.96 for endsystolic, p<0.001 respectively). Significant interobserver agreement was found measuring enddiastolic and endsystolic infarct size on cine SSFP imaging (p<0.01).

Conclusions: In patients after STEMI infarct size and presence of MO can be detected with contrast cine SSFP imaging. This could be an option in patients who are limited in their ability to comply with the demands of a cMRI protocol.

Fig 1. Typical MO appearance on early cine SSFP imaging at the same slice position during the cardiac cycle (A-E).

Fig 2. Bland-Altman plot for ES infarct size indicate that differences between the tests are consistent and the majority of them are within the 1.96 SD intervals.

Fig 3. Bland-Altman plot for ED infarct size indicate that differences between the tests are consistent and the majority of them are within the 1.96 SD intervals.

Fig 4. Cine and LGE imaging after 6 and 14.5 minutes respectively.

Both images (A and B) show a well demarcated hyperintense midventricular inferolateral myocardium with a subendocardial located crescent shaped hypointensity representing myocardial infarction with MO (arrows: MO size, dotted arrows: infarct size).

Fig 5. Bland-Altman plot for MO indicates that differences between the tests are consistent and the majority of them are within the 1.96 SD intervals.

Fig 6. Comparison between MO on early cine SSFP and LGE.

A) Cine imaging performed 4 minutes after contrast medium injection. Midventricular subendocardial MO reaching from septal, anteroseptal to anterior. B) LGE imaging 16.5 minutes after contrast medium injection. Hyperenhanced midventricular septal, anteroseptal to anterior myocardium with less MO compared to cine imaging (arrows: MO size, dotted arrows: infarct size).

Fig 7. Comparison between MO on early cine SSFP and LGE.

A) Cine imaging performed 4 minutes after contrast medium injection. A demarcated crescent shaped hypointensity representing MO in the midventricular inferior myocardium. B) LGE imaging 19 minutes after contrast medium injection. Hyperenhanced midventricular inferior myocardium missing MO at an identical slice position compared to cine imaging (see arrows for comparison).

Fig 8. MO with different imaging methods.

Early enhancement 9 min after contrast agent: A) Cine SSFP B) IR GE imaging and C) PSIR. Late enhancement 23 min after contrast agent: D) Cine SSFP E) IR GE imaging and F) PSIR. Note the comparable extent of MO with SSFP and IR imaging at each time point, but the greater extent of MO at early imaging (A-C) compared to late imaging (D-F).