Background:
Patients presenting with suspected myocardial infarction without obstructive coronary artery disease (MINOCA) represent a heterogeneous clinical group. Cardiovascular Magnetic Resonance (CMR) helps clarify the underlying etiology, which can include Tako-Tsubo syndrome (TTS), myocardial infarction without obstructive coronary disease (true MINOCA) and myocarditis. Myocardial strain assessed by feature tracking (FT‑CMR) provides quantitative measures of ventricular and atrial function without the need for contrast. While global longitudinal strain (GLS) is a well-established prognostic marker in heart failure and coronary artery disease, its prognostic role in MINOCA remains unclear.
Purpose:
To evaluate (1) baseline functional impairment in the acute phase across CMR-defined MINOCA subtypes, and (2) the prognostic value of FT-CMR-derived strain parameters and left ventricular ejection fraction (LVEF) for predicting long-term major adverse cardiovascular events (MACE).
Methods:
This retrospective study included 216 patients who underwent CMR within 5 days of presentation for suspected MINOCA. Based on tissue characterization, patients were categorized TTS, myocarditis and true MINOCA, or other/indeterminate diagnoses. CMR was used to quantify LVEF, GLS, global circumferential strain (GCS), and global radial strain (GRS). In addition, left atrial strain parameters were measured, including reservoir, conduit, and booster function. The primary endpoint was MACE defined as myocardial infarction, new onset of heart failure and all-cause death. Kaplan–Meier survival analysis, incidence rates, and Cox regression were used to assess outcomes. Median follow-up was 96 months, totaling 1569.2 patient-years.
Results:
Strain parameters measured in the acute phase (within 5 days of presentation) showed significant differences across etiologies (GLS p < 0.001; GCS p < 0.001; GRS p = 0.017). Tako-Tsubo syndrome patients had the most impaired strain and lowest EF, while myocarditis showed relatively preserved function. True-MINOCA cases demonstrated only mild dysfunction related to the affected area.
During follow-up, 62 patients (28.7%) experienced MACE. TTS patients had the highest event rate (IRR 1.95; 95% CI 1.14–3.39; p = 0.012), while myocarditis had the lowest (IRR 0.37; 95% CI 0.12–0.91; p = 0.027). Despite these early differences in myocardial function, strain parameters and LV-EF measured in the acute phase were not predictive of long-term MACE in the overall cohort (all p > 0.).
Conclusion:
MINOCA subtypes show distinct patterns of myocardial dysfunction in the acute phase, detectable by FT-CMR. Although strain is prognostic in heart failure and coronary artery disease, acute-phase strain did not predict long-term MACE in MINOCA. These findings suggest that non-contrast strain imaging in the acute phase may aid in diagnostic differentiation by adding incremental value and could help in the development of machine learning algorithms leveraging the differences to achieve higher precision in diagnostic accuracy. However, the utility of strain parameters for long-term risk stratification in this population appears to be limited.
