Background: Early risk stratification in cardiogenic shock (CS) is crucial for guiding therapy. While the SCAI shock classification at ICU admission is widely used, dynamic biomarkers such as lactate may provide additional prognostic value, as recently emphasized by the Society for Cardiovascular Angiography & Interventions Foundation.1 We evaluated whether lactate trajectories during the first hours after ICU admission improve prediction of 30-day mortality compared with SCAI classification.
Methods: MIRACLE (Multimodal phenotyping in acute cardiac failures) is an ongoing, multicenter observational study. We included prospectively collected cases up to October 2025 (n = 311) amended by retrospective consecutive cases from 2018-2023 at the University Hospital Freiburg - Bad Krozingen, excluding SCAI A, uncertain etiology, pulmonary embolism, or predominant infectious/septic shock (final n= 471). Lactate trajectories within the 2, 4, and 8 hours after ICU admission were categorized as: Clearance (≥50% decrease or <2 mmol/L), Partial Clearance (10-50% decrease), and No Clearance (<10% decrease). Associations with 30-day mortality were assessed using Cox proportional hazards models adjusted for age, sex, and prior cardiac arrest. Model performance was evaluated using Harrell’s C-index. Sensitivity analyses were performed in patients with SCAI ≥C and by prior cardiac arrest.
Results: Absence of lactate clearance was consistently associated with higher 30-day mortality across all investigated timepoints. At 4 hours, patients with No Clearance had substantially higher risk compared with those showing Clearance (HR 2.33, 95% CI 1.58-3.44; p<0.001). Higher SCAI stages at 4 hours were also associated with increased mortality (SCAI E vs B: HR 4.29, 95% CI 1.38-10.21; p=0.01). Age and prior cardiac arrest remained independent predictors. When lactate trajectories and SCAI stage at 4 hours were combined in a multivariable model, the C-index was higher than for either marker alone (combined model C-index 0.76). Among the evaluated timepoints, 4-hour assessment performed best. Sensitivity analyses in patients with SCAI ≥ C and in subgroups defined by prior cardiac arrest yielded comparable effect sizes.
Conclusions: Early lactate trajectories, within the first hours of ICU admission, provide important prognostic information in CS and could be used as a valuable addition to SCAI classification. These interims analyses suggest that a 4-hour assessment may offer a better prognostic window than ICU admission alone, potentially enhancing early risk-adapted therapeutic decisions.
- Naidu SS, Nathan S, Basir MB, Baran DA, Marbach JA, Grines CL. SCAI Door to Lactate Clearance (SCAI DLC) Cardiogenic Shock Initiative: Definition, Hypothesis, and Call to Action. J Soc Cardiovasc Angiogr Interv. Published online September 2025:103996. doi:10.1016/j.jscai.2025.103996
