1Universitäts-Herzzentrum Freiburg / Bad Krozingen Klinik für Kardiologie und Angiologie Bad Krozingen, Deutschland; 2Institut für Medizinische Biometrie und Statistik Freiburg im Breisgau, Deutschland
Background: The greyzone fibrosis (GZF), consisting of myocardial fibrosis and viable myocardium, has been described as a risk factor for arrhythmias after myocardial infarction (MI) and can be detected via cardiac magnetic resonance (CMR). Yet, data about the correlation between the amount of GZF and long-term clinical parameters are scarce. The purpose of this study was to quantify GZF and to evaluate its predictive capabilities for two-year MI-free survival and one-year improvements in ejection fraction.
Methods Candidates for participation in the study were all patients who had suffered a myocardial infarction between september 2014 and november 2019 and subsequently received an CMR before discharge and a second CMR on average after 6 months. Image analysis was performed with a dedicated post-processing workstation (cvi42, Circle Cardiovascular Imaging Inc., Bellevue WA, USA). Late gadolinium enhancement (LGE) was quantified in both, grey zone only in the follow-up CMR after resolution of the initial infarct edema. Left-ventricular ejection fraction (LVEF) was measured in both CMR. High-sensitivity cardiac troponin T (hs-cTnT) levels were measured at admission as well as 8, 16 and 24 hours after percutaneous coronary intervention (PCI). Follow-up telephone visits were conducted annually for up to 8 years.
For two year MI-free survival, univariable cox regression models were conducted and Harrels’s C and Royston and Sauerbrei's D were calculated as discrimination measures and compared across different potential predictors. For one-year improvements in ejection fraction, linear regression models were conducted and the coefficients of determination R2 were calculated and compared.
Results: 176 patients (18.2% female, 63.3 + 11.4 years) with acute myocardial infarction (114 with ST-segment elevation myocardial infarction, 62 with non-ST-segment elevation myocardial infarction) were included in this study. During the follow-up period of 1308 + 320 days 6 patients died (3.4%) and 7 patients suffered a second myocardial infarction (4.0%).
LGE measurements were associated with better predictive capabilities regarding
MI-free survival (Harrell’s C of 0.714 and 0.708 of LGE volume and LGE mass, respectively) compared to GZF (0.590 and 0.571). hs-cTnT also performed better (Harrell’s C of 0.648) than GZF. As an univariable predictor for MI-free survival, only hs-cTnT reached significance (p<0.05).
With regard to one-year improvements in ejection fraction, hs-cTnT and LGE measurements were acceptable predictors for an improvement in ejection fraction (p<0.05), but GZF measurements were not suitable as predictors (p>0.5).
Conclusions: The GFZ, examined in CMR, has a worse prediction compared to hs-cTnT and LGE for patients after acute MI regarding the endpoint MI-free survival. Furthermore, GZF is not suitable as a predictor of improvement of LVEF. Therefore, routine determination of the GFZ can be dispensed with.