Inpatient myocardial perfusion imaging characteristics of patients admitted with suspected type 2 myocardial infarction. (2nd May 2022) - Swinn, T
Abstract: Funding Acknowledgements: Type of funding sources: None. Background: ESC defines a type 1 myocardial infarction (T1MI) as "MI caused by atherosclerotic coronary artery disease and usually precipitated by atherosclerotic plaque disruption" and type 2 myocardial infarction (T2MI) as "ischaemic myocardial injury in the context of a mismatch between oxygen supply and demand". In practice it can be difficult to differentiate between MI types and the role of myocardial perfusion imaging (MPI) in making this distinction remains unclear. Purpose: To establish whether suspected T2MI has different characteristics on MPI compared to suspected T1MI. Methods: All inpatient MPI scans at our institution between 01/03/2018 and 28/02/2020 were retrospectively reviewed. Patients were excluded if they had a previous diagnosis of coronary artery disease, an invasive coronary angiogram prior to MPI, or a maximal troponin T < 14ng/l. Diagnoses were categorised based on review of scan request information. Echocardiography images were reviewed if within 30 days of MPI. Results: 58 patients were included: 28 with suspected type 2 MI and 30 with suspected type 1 MI (mean age 70 vs. 75). There was no statistically significant difference in maximal troponin T between groups (T2MI 394.0 ng/l, T1MI 415.6 ng/l; p=0.90). 50% T2MI patients and 53% T1MI patients had a territorial defect on MPI (fully reversible defect 25% vs. 17%, partially reversible defect 7% vs. 33%, irreversible defect 14% vs. 3% for T2MI vs T1MI respectively). 25% T2MI patients had an area >10% LV myocardium volume showing reversibility, compared with 33% T1MI (p=0.49). Both groups had similar proportions of left ventricular (LV) impairment (both had 65% of patients with normal LV ejection fraction) and prevalence of regional wall motion abnormalities ((RWMA) 39% for T2MI, 35% for T1MI, p=0.76) on echocardiography. Conclusions: A clinically significant proportion of the suspected T2MI group had territorial ischaemia. Additionally, both patient groups demonstrated similar proportion of patients with reversible ischaemia and of LV systolic dysfunction. Therefore differentiation between T2MI and T1MI can be challenging both clinically and with MPI. Prospective studies are required to establish the optimal methods for making the distinction between types of MI.