Background: Left ventricular (LV) thrombus formation is a severe complication after acute ST-segment elevation myocardial infarction (STEMI). However, the incidence and determinants of LV thrombus formation are still a matter of controversy. We aimed to assess the incidence of early LV thrombus formation as detected by cardiac magnetic resonance (CMR) imaging and its determinants in a large contemporary cohort of STEMI patients treated with primary percutaneous coronary intervention (PPCI).

Methods: This observational study included 530 consecutive STEMI patients treated with PPCI. Contrast enhanced CMR was performed at a median of 3 days (interquartile range 2-4 days) after PPCI for the evaluation of LV thrombus formation, LV function and infarct severity including infarct size (IS) and microvascular obstruction (MVO).

Results: LV thrombi were detected in 3.2% of the overall cohort (n=17). In all patients presenting with LV thrombus, left anterior descending artery (LAD) was identified as culprit lesion. Accordingly, the incidence of LV thrombi in anterior STEMI patients (n=247) was 6.9%.

The occurrence of thrombi was significantly associated with reduced LV ejection fraction (LVEF) (p<0.001), larger LV end-diastolic volume (LVEDV) (p<0.001) and LV end-systolic volume (p<0.001), larger areas of MVO (p=0.003) and larger IS (p<0.001). Furthermore, increased levels of peak high sensitivity cardiac Troponin T (p<0.001) were significantly related to LV thrombi.

After multivariable analysis, only LVEF (odds ratio (OR): 0.91, 95% confidence interval (CI) 0.87-0.96; p=0.001) and LVEDV (OR: 1.02, 95% CI 1.01-1.03; p=0.004) emerged as independent predictors of LV thrombus formation.