Medical Intensive Care Unit Overflow Into the Cardiac Intensive Care Unit: Insights From CCCTN Registry.

Background: Cardiac intensive care units (CICUs) typically manage critically ill patients with acute cardiovascular (CV) conditions but may serve patients with non-CV critical illness when medical ICU (MICU) beds are unavailable.

Objectives: The purpose of this study was to characterize the clinical profiles and outcomes of "MICU overflow" admissions to the CICU.

Methods: We used the Critical Care Cardiology Trials Network registry to compare CICU admissions without acute or major cardiac issues (MICU overflow) vs those with acute CV illness.

Results: Among 19,912 CICU admissions (2018-2023), 923 (4.6%) were MICU overflow, ranging from 0% to 26% across centers. MICU overflow admissions had higher median Sequential Organ Failure Assessment scores than CV admissions (5 vs 3; P < 0.001) and more commonly presented with respiratory failure (50.5% vs 24.6%; P < 0.001) and noncardiogenic shock (30.9% vs 8.0%; P < 0.001). MICU overflow status was associated with similar ICU mortality (adjusted OR: 1.13; 95% CI: 0.90-1.43; P = 0.28) but higher hospital mortality (adjusted OR: 1.80; 95% CI: 1.48-2.19; P < 0.001) vs CV illness. In units where the CICU team managed all admissions, ICU mortality was higher among MICU overflow admissions than CV admissions (adjusted OR: 1.35; 95% CI: 1.02-1.80; P = 0.04), whereas in CICUs where off-unit MICU teams managed MICU overflow admissions, this mortality imbalance was not present (adjusted OR: 0.72; 95% CI: 0.47-1.11; P = 0.14; P interaction = 0.02).

Conclusions: MICU overflow admissions constitute a meaningful proportion of the CICU population and present with more multisystem disease and experience higher hospital mortality compared with acute CV admissions, underscoring the need for multidisciplinary CICU teams with broad critical care expertise.