To analyze whether admission on weekends or public holidays (WHA) influences the management (performance of angioplasty, percutaneous coronary intervention [PCI]) and outcomes (in-hospital mortality) of patients hospitalized for acute coronary syndrome in the Spanish National Health System compared with admission on weekdays.

Retrospective observational study of patients admitted for ST-segment elevation myocardial infarction (STEMI) or for non–ST-segment elevation acute coronary syndrome (NSTEACS) in hospitals of the Spanish National Health system from 2003 to 2018.

A total of 438 987 episodes of STEMI and 486 565 of NSTEACS were selected, of which 28.8% and 26.1% were WHA, respectively. Risk-adjusted models showed that WHA was a risk factor for in-hospital mortality in STEMI (OR, 1.05; 95%CI,1.03-1.08; P < .001) and in NSTEACS (OR, 1.08; 95%CI, 1.05-1.12; P < .001). The rate of PCI performance in STEMI was more than 2 percentage points higher in patients admitted on weekdays from 2003 to 2011 and was similar or even lower from 2012 to 2018, with no significant changes in NSTEACS. WHA was a statistically significant risk factor for both STEMI and NSTEACS.

WHA can increase the risk of in-hospital death by 5% (STEMI) and 8% (NSTEACS). The persistence of the risk of higher in-hospital mortality, after adjustment for the performance of PCI and other explanatory variables, probably indicates deficiencies in management during the weekend compared with weekdays.