Background:Two-dimensional (2D) and three-dimensional (3D) speckle tracking echocardiography (STE) after ST-elevation acute myocardial infarction (STEMI) can predict the prognosis. This study investigated the clinical significance of a serial 3D-STE can predict the prognosis after onset of STEMI.Methods and Results:This study enrolled 272 patients (mean age, 65 years) with first-time STEMI treated with reperfusion therapy. At 24 h after admission, standard 2D echocardiography and 3D full-volume imaging were performed, and 2D-STE and 3D-STE were calculated. Within 1 year, 19 patients who experienced major adverse cardiac events (MACE; cardiac death, heart failure requiring hospitalization) were excluded. Among the 253 patients, 248 were examined with follow-up echocardiography. The patients were followed up for a median of 108 months (interquartile range: 96–129 months). The primary endpoint was the occurrence of a MACE; 45 patients experienced MACEs. Receiver operating characteristic curves and Cox hazard multivariate analysis showed that the 2D-global longitudinal strain (GLS) and 3D-GLS at 1-year indices were significant predictors of MACE. The Kaplan-Meier curve demonstrated that a 3D-GLS of >−13.1 was an independent predictor for MACE (log-rank χ2=165.5, P<0.0001). The deterioration of 3D-GLS at 1 year was a significant prognosticator (log-rank χ2=36.7, P<0.0001).Conclusions:The deterioration of 3D-GLS measured by STE at 1 year after the onset of STEMI is the strongest predictor of long-term prognosis.