Plasma osmolality predicts clinical outcome in patients with acute coronary syndrome undergoing percutaneous coronary intervention.

Aims: The impact of plasma osmolality on clinical outcome in acute coronary syndrome (ACS) patients has not been investigated so far.

Methods: In a retrospective analysis, we included 985 patients with ACS undergoing percutaneous coronary intervention (PCI). Plasma osmolality was calculated using concentrations of sodium, plasma glucose, and blood urea nitrogen at admission. Patients were stratified by quartiles (Q) of admission osmolality, clinical outcome was compared between those groups. The primary endpoints were in-hospital, 30-day, and 1-year mortality.

Results: Univariate analysis in the Cox proportional-hazards model revealed significantly higher rates of in-hospital death for patients with osmolality in Q4, as compared to patients with osmolality in Q1-3 (HR 5.4, 95% CI 3.3-9.0, p<0.01). After adjustment for confounding baseline variables, osmolality in Q4 was associated with 2.8-fold hazard of in-hospital death (HR 2.75, 95% CI 1.35-5.61, p=0.005). Upon multivariate analysis, admission osmolality in Q4 vs. Q1-3 was associated with higher mortality rates after 30 days (HR 2.53, 95% CI 1.23-5.21, p=0.012) and 1 year (HR 1.73, 95% CI 1.02-2.91, p=0.04). Moreover, we performed landmark analysis in order to exclude critically ill patients, which revealed similar adjusted rates of death beyond 30 days to 1 year (HR 1.21, 95% CI 0.55-2.66, p=0.642).

Conclusions: Using the 4th quartile of plasma osmolality at admission as a natural cut-off point, osmolality in Q4, as compared to Q1-3, was significantly predictive of short term but not long-term outcome in ACS patients undergoing coronary stenting. Our data suggest osmolality to be an independent, feasible, and cost-effective tool for rapid risk stratification in ACS patients.