STEP-PRESS is a predefined exploratory observational substudy nested within the STEPCARE trial. The study will evaluate whether early low pulse-pressure burden after out-of-hospital cardiac arrest is associated with early mortality and selected biomarker outcomes. Pulse pressure will be calculated as systolic blood pressure minus diastolic blood pressure using recorded STEPCARE blood-pressure values. The primary exposure is cumulative hours with pulse pressure below 40 mmHg during the first 12 hours after randomization. The primary outcome is all-cause mortality from the 12-hour landmark to day 7.

STEP-PRESS is a predefined exploratory observational substudy nested within STEPCARE, an international, multicenter, randomized factorial trial of intensive-care strategies after out-of-hospital cardiac arrest. STEPCARE is registered as NCT05564754. The STEPCARE biomarker substudy is registered as NCT06471972.

STEP-PRESS will use data collected within the STEPCARE trial and applicable substudy approvals. No additional intervention, patient contact, or deviation from STEPCARE clinical management is planned for STEP-PRESS.

The source population will consist of randomized STEPCARE participants, excluding consent withdrawals. Pulse pressure will be calculated as systolic blood pressure minus diastolic blood pressure using recorded STEPCARE blood-pressure values. The primary exposure is cumulative low pulse-pressure burden, defined as the number of hours during 0 to 12 hours after randomization in which interpolated pulse pressure is below 40 mmHg.

The primary analysis population will be restricted to participants alive 12 hours after randomization, without mechanical circulatory support initiated before or within 24 hours after randomization, and with at least three valid recorded blood-pressure observations during 0 to 12 hours after randomization.

The primary outcome is all-cause mortality from the 12-hour landmark to day 7. Key secondary outcomes include mortality in a 24-hour landmark analysis, neurological biomarker endpoints, 30-day mortality, 6-month survival, and 6-month functional outcome. Six-month poor functional outcome will follow the parent STEPCARE definition of modified Rankin Scale score 4 to 6.

All STEP-PRESS objectives are associational. The substudy is not designed to test whether modifying pulse pressure improves outcomes.

Inclusion Criteria:

• Randomized in the STEPCARE trial.
• Out-of-hospital cardiac arrest.
• Stable return of spontaneous circulation, defined in the parent STEPCARE protocol as at least 20 minutes without chest compressions.
• Unconsciousness after sustained return of spontaneous circulation, defined as not being able to obey verbal commands, or intubated and sedated because of agitation.
• Eligible for intensive care without restrictions or limitations.
• Included in STEPCARE within the parent-trial inclusion window.
• For STEP-PRESS analyses, availability of recorded STEPCARE blood-pressure data sufficient to calculate pulse pressure for the relevant analysis population.
• For the primary STEP-PRESS analysis population: alive 12 hours after randomization, without mechanical circulatory support initiated before or within 24 hours after randomization, and with at least three valid recorded blood-pressure observations during 0 to 12 hours after randomization.

Exclusion Criteria:

• Withdrawal of consent for use of STEPCARE trial data.
• Trauma or hemorrhage as the presumed cause of cardiac arrest.
• Suspected or confirmed intracranial hemorrhage.
• On extracorporeal membrane oxygenation before STEPCARE randomization.
• Pregnancy.
• Previously randomized in the STEPCARE trial.
• For STEP-PRESS primary and 24-hour landmark analyses: mechanical circulatory support initiated before or within 24 hours after randomization.
• For endpoint-specific analyses: missing data required to define the relevant exposure, outcome, or biomarker endpoint.

Randomized STEPCARE participants with available trial data for STEP-PRESS analyses. The STEP-PRESS source population consists of randomized STEPCARE participants excluding consent withdrawals. The primary analysis population is restricted to participants alive 12 hours after randomization, without mechanical circulatory support initiated before or within 24 hours after randomization, and with sufficient valid blood-pressure observations during 0 to 12 hours after randomization.

STEP-PRESS will use deidentified or pseudonymized data from the parent STEPCARE trial according to STEPCARE governance procedures. Individual participant data sharing is determined by the STEPCARE sponsor and trial governance, not by the STEP-PRESS substudy investigators alone. Therefore, the IPD sharing plan for this substudy is currently undecided.