In-hospital cardiac arrest (IHCA) is associated with high mortality and serious neurological sequelae. Although medical alert systems have evolved, the ability of these systems to influence changes in IHCA incidence and aetiology remains limited.

Retrospective observational cohort study.

A single tertiary hospital in South Korea, covering tertiary care levels.

A total of 1994 adult patients (≥18 years) who experienced 2121 episodes of IHCA between January 2011 and December 2019. Patients with out-of-hospital cardiac arrest, those aged ≤18 years and those with do-not-resuscitate orders were excluded. The mean age of patients was 63.0 years (SD, 14.6); 64.1% were male.

Not applicable.

The incidence and temporal trends of IHCA were stratified by aetiology (cardiac vs non-cardiac). Additional analyses examined changes in arrhythmic versus non-arrhythmic causes over time using Poisson regression.

Cardiac arrhythmia was the most common cause of IHCA (314 of 2121, 14.8%; incidence: 0.42/1000 admissions), including ventricular tachycardia (n=86), ventricular fibrillation (n=87) and Torsades de Pointes (n=79). Respiratory failure was the second most common cause (266 of 2121, 12.5%; incidence: 0.36/1000 admissions). The incidence of IHCA due to respiratory failure in 2011 was 0.63/1000 admissions, which decreased to 0.20/1000 admissions by 2019 (β=0.883, 95% CI 0.842 to 0.926, p for trend 0.007; Poisson p

IHCA causes have shown significant temporal shifts. Arrhythmia has become the leading cause of IHCA, with incidences remaining stable, whereas a marked decrease has been observed in respiratory-related IHCA. Therefore, enhanced in-hospital cardiac monitoring systems are required for early detection.