Infarct size by SS-SSFP vs. IR-GRE: influence of imaging time after contrast administration and infarct age, and implications for clinical trials
Journal of Cardiovascular Magnetic Resonance volume 16, Article number: P183 (2014)
Myocardial late gadolinium enhancement (LGE) imaging is conventionally acquired using a gradient-echo inversion recovery (IR-GRE) sequence 15-20 min after contrast administration. However, this method can be limited by poor breath holding or arrhythmias. Free-breathing single shot steady state free precession (SS-SSFP) sequence is an alternative LGE imaging technique which can overcome some of the IR-GRE limitations but at the expense of lower resolution. The ideal imaging timing for LGE SS-SSFP, and whether it can be used interchangeably with IR-GRE has not yet been established. The aim of our study was to investigate acute and chronic infarct size: 1) Comparing LGE by SS-SSFP vs. IR-GRE at 15 min. 2) Comparing LGE SS-SSFP imaging at 5 vs. 10 vs. 15 min after contrast administration vs. IR-GRE at 15 min.
36 patients were prospectively recruited for CMR day 2 and 3 months following reperfused STEMI. IR-GRE images were acquired 15 minutes following gadolinium contrast administration (Gadovist 0.1 mmol/kg). Free-breathing SS-SSFP images were obtained 5, 10 and 15 min following contrast. LGE was calculated and infarct size was expressed in grams. Agreement between the 2 sequences was assessed by the Bland Altman method. Differences between time following contrast for both acute and chronic infarct size were assessed using paired t-tests. All patients provided informed written consent and the study was approved by the regional ethics committee.
When imaging 15 min after contrast administration, there was a significant difference in acute infarct mass using SS-SSFP vs. GRE-IR (p = 0.006), whilst there was no difference in chronic infarct mass (p = 0.54) (Table 1). Bland Altman agreement with IR-GRE was best for chronic infarct (chronic infarct bias -0.81 g, acute infarct bias -7.08 g). When imaging using SS-SSFP in acute infarct at multiple time points, there was no difference between imaging at 5 or 10 min (p = 0.13), but there was a significant difference between 10 and 15 min (p = 0.02) and 5 and 15 min (p = 0.01) (Table 2). When imaging LGE with SS-SSFP in chronic infarct at multiple time points, the only significant difference was noted between 5 and 15 min (p = 0.04) (Table 2).
Our study demonstrates both acute and chronic infarct size with SS-SSFP changes significantly between 5 vs. 10 vs. 15 min, demonstrating that the time of imaging after contrast administration is important for this sequence too. The ideal timing for imaging acute and chronic infarct size by SS-SSFP and IR-GRE are different. In particular, when imaging at 15 min after contrast, LGE by SS-SSFP can underestimate acute infarct size. In chronic infarctions time after contrast injection for LGE by SS-SSFP seems less critical but infarct size at 15 min best correlated with LGE by IR-GRE. LGE by SS-SSP offers a valid alternative in clinical practice for the (visual) assessment of myocardial infarction but in clinical trials it should not be used interchangeably with LGE IR-GRE
This work was funded by the NIHR Bristol Cardiovascular Biomedical Research Unit.
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McAlindon, E., Lawton, C., Ahmed, N. et al. Infarct size by SS-SSFP vs. IR-GRE: influence of imaging time after contrast administration and infarct age, and implications for clinical trials. J Cardiovasc Magn Reson 16 (Suppl 1), P183 (2014). https://doi.org/10.1186/1532-429X-16-S1-P183