Diltiazem versus metoprolol for atrial fibrillation with rapid ventricular rate in ICU patients using target trial emulation

Atrial fibrillation with rapid ventricular rate is common and difficult to manage. The evidence for the effectiveness of intravenous rate-controlling drugs is limited. In this study, MIMIC-IV was used to simulate the target trial, comparing "diltiazem initiation" with "metoprolol initiation": patients were enrolled with the first administration as T0, excluding those with concurrent initial medications, missing baseline heart rate, non-rapid ventricular rate, and insufficient observation window; missing data were imputed, and propensity score weighting was used to balance covariates. The primary outcome was achievement of heart rate < 110 beats/min within the first hour after T0; the secondary outcomes were recorded additional AF-related medication within 6 h after T0, in-hospital death, and ICU stay days. A total of 1492 cases were included (321 cases of diltiazem and 1171 cases of metoprolol), and the absolute SMD after weighting was close to 0. Diltiazem initiation was associated with a lower probability of achieving the primary outcome (OR = 0.67, 95% CI 0.51-0.88) and a higher probability of requiring additional medication within 6 h (OR = 2. 63, 95% CI 1. 98-3. 49); there was no significant difference in in-hospital death (OR = 0. 88, 95% CI 0. 66-1. 17) and ICU stay days (MD = -0. 41 days, 95% CI -1. 42 to 0. 61). The subgroup directions were consistent, and the interaction P for mechanical ventilation was 0. 057. Overall, metoprolol initiation was associated with a higher probability of early rate control and a lower probability of short-term additional AF-related medication in the overlap population, although these findings should be interpreted as hypothesis-generating because of residual confounding and limitations of structured electronic health-record data.