Door-to-Balloon Time Outperforms ST-Segment Elevation in Predicting the STEMI vs. NSTEMI Final Diagnosis

<b>Background:</b> The STEMI/NSTEMI classification guides management and quality metrics for acute myocardial infarction (AMI). We examined whether the final cath-lab diagnosis of STEMI versus NSTEMI correlates more closely with door-to-balloon (D2B) time than with either ST-segment elevation (STE) on pre-angiogram ECG or a culprit lesion with TIMI 0-1 flow. <b>Methods:</b> This retrospective study analyzed 410 patients with AMI from the DOMI-ARIGATO database who underwent coronary angiography. For each patient, we recorded FDx coded by the interventional cardiologist, D2B < 120 min versus > 120 min, STE criteria (Fourth Universal Definition), and angiographic TIMI 0-1 culprit. Predictors of FDx-STE discordance were evaluated with multivariable logistic regression. <b>Results:</b> Among 410 angiographed AMI patients (mean age 63 ± 13; 71% male), 165 (40.2%) received an FDx-STEMI and 245 (59.8%) an FDx-NSTEMI. D2B time showed 94% agreement with FDx (160/165 FDx-STEMI treated < 120 min; 225/245 FDx-NSTEMI treated > 120 min), exceeding concordance for STE (82%; <i>p</i> < 0.001) and TIMI 0-1 flow (75%; <i>p</i> < 0.001). FDx and STE diverged in 75 patients (18%): 60 rapidly treated STE-negative cases were labelled STEMI, whereas 15 delayed STE-positive cases were labelled NSTEMI. In regression analysis, D2B < 120 min remained the sole independent predictor of discordance (adjusted OR 6.7, 95% CI 3.5-13.8). <b>Conclusions:</b> In this registry, the cath-lab label "STEMI" showed the strongest correlation with meeting a 120 min benchmark, exceeding correlations for STE or angiographic occlusion. These findings suggest that quality-metric compliance, rather than electrocardiographic or anatomic criteria, predominantly drives final diagnosis.