Infarct characteristics and outcome of patients with transient ST-segment elevation myocardial infarction compared to ST-segment and non-ST-segment elevation myocardial infarction
Authors: Demirkiran A , Hoeven N , Janssens G , Lemkes J , Everaars H , Ven P , Cauteren Y , Leeuwen M , Nap A , Bekkers S , Royen N , Smulders M , Rossum A , Robbers L , Nijveldt R 
Published: November 2020

Abstract

Background
Up to one out of four patients with signs of ST-segment elevation myocardial infarction (STEMI) express complete normalization of ST elevation before primary revascularization procedure. This condition is commonly referred to as “transient ST-segment elevation myocardial infarction” (TSTEMI) and recent data suggests that this group of patients may have favorable outcome compared to STEMI patients. However, it is currently unknown how these patients compare to both STEMI and non-ST-segment elevation myocardial infarction (NSTEMI) patients with respect to infarct size characteristics and outcome.

Objective
This study aims to explore cardiac magnetic resonance (CMR) derived scar tissue and 1-year outcome in patients with TSTEMI by comparison to STEMI and NSTEMI.

Methods
Patients with STEMI were enrolled from two prospective studies (n=170); the patients with TSTEMI were recruited from the TRANSIENT trial (n=141); the patients with NSTEMI were prospectively and consecutively collected from local registries of Amsterdam UMC (n=57) and Maastricht UMC (n=51). All patients underwent CMR examination 2–8 days after the index event. Cine imaging was done for volume and function assessment. Late gadolinium enhancement imaging was performed to identify infarct size (in grams) and the presence of microvascular obstruction (MVO). All CMR images were processed in a single core laboratory (Amsterdam UMC). Clinical outcome after 1 year was measured by the incidence of major adverse cardiac events (MACE), defined as recurrent myocardial infarction (MI), revascularization and all cause death.

Results
The TSTEMI group demonstrated the lowest end-systolic left ventricular volume and highest left ventricular ejection fraction across the groups (overall p&lt;0.001). Although there was a remarkably lower infarct size in TSTEMI patients compared to STEMI (1.41g [0.00–3.91] vs 13.48g [5.31–26.81], p&lt;0.001), there was only a trend towards lower infarct size compared to NSTEMI patients (1.41g [0.00–3.91] vs 2.13g [0.00–8.64], p=0.06). Whilst MVO was observed less frequently in TSTEMI compared to STEMI patients (5 (4%) vs 53 (31%), p&lt;0.001), no significant difference was seen between TSTEMI and NSTEMI patients (5 (4%) vs 5 (5%), p=0.72). Multivariable linear regression analysis identified infarct type, smoking, peak troponin-T and pre-PCI TIMI flow as predictors for infarct size (p=0.03, p=0.03, p&lt;0.001 and p&lt;0.001, respectively). One-year mortality rate was low in all 3 MI types (TSTEMI 3 (2.2%), NSTEMI 3 (3.1%), 4 (2.4%), log-rank test p=0.91). However, there was a significant difference in MACE at 1 year across the 3 MI types (TSTEMI 18 (13.2%), NSTEMI 19 (19.4%), STEMI 11 (6.7%), overall p&lt;0.01).

Conclusion
In comparison to NSTEMI and STEMI, TSTEMI yielded favorable cardiac left ventricular function and scar mass. However, this did not lead to benefit in short term (1-year) outcome; further studies are needed with longer follow-up.

Funding Acknowledgement
Type of funding source: Other. Main funding source(s): European Association of Cardiovascular Imaging (EACVI) Research Grant