Background and purpose
The Observatoire Régional Breton sur l’Infarctus (ORBI) risk score is a prognostic model developed from large, consecutive STEMI cohorts to estimate the probability that a patient will develop in-hospital cardiogenic shock after reperfusion with primary percutaneous coronary intervention (pPCI). It was constructed and described together with the RICO (obseRvatoire des Infarctus de Côte-d’Or) network, reflecting real-world French registry practice and contemporary STEMI systems of care.
Unlike generic severity scores, the ORBI score focuses on a single, high-impact complication: cardiogenic shock that emerges after presentation and initial management, among patients who were not in shock at the outset in the derivation framework. That distinction matters clinically: the score is meant to complement—not replace—bedside assessment, echocardiography, invasive hemodynamics when indicated, and guideline-directed STEMI therapy.
Clinical problem: shock after successful or attempted reperfusion
ST-segment elevation myocardial infarction results from acute coronary occlusion and myocardial jeopardy. Primary PCI restores antegrade flow in the infarct-related artery and improves outcomes, yet a subset of patients deteriorates hemodynamically during hospitalization. Late or recurrent shock is associated with substantial morbidity, need for vasoactive drugs and mechanical circulatory support, longer intensive care, and higher mortality. Early recognition of patients at elevated modeled risk allows teams to align monitoring intensity, escalation triggers, and resource planning (for example, early heart-team discussion and shock pathways) without waiting for overt collapse.
The ORBI score addresses that need by combining presentation features (age, hemodynamics, rhythm/arrest history, infarct territory, glycemic stress, Killip class, system delay) with angiographic results (culprit vessel location and final TIMI flow). In practice, it is most often applied once pPCI has been completed and core angiographic data are available, though some items are known at admission.
Derivation population and what the score estimates
The score was derived in patients with STEMI treated by pPCI, emphasizing a cohort without cardiogenic shock at initial assessment (consistent with the original publication and public calculator materials). The outcome of interest is in-hospital cardiogenic shock occurring during the index admission—not 30-day mortality alone, not reinfarction in isolation, and not a composite tailored to outpatient risk.
Because the model is cohort-derived, reported risk bands describe observed incidence in the derivation set (and have been contextualized alongside external validation). Any patient-level probability should be interpreted as epidemiologic context that must be integrated with the current examination, labs, imaging, and trajectory.
Variables and why they matter
Each component captures pathways linked to larger infarct burden, more extensive ischemia, microvascular dysfunction, arrhythmic instability, or multivessel jeopardy—processes that predispose to pump failure and shock after reperfusion.
Age greater than 70 years
Advanced age is associated with reduced reserve, more prevalent comorbidity, and often smaller vessel caliber and more complex disease. In the ORBI weighting, older age contributes fixed points, reflecting higher modeled shock risk independent of other factors.
Prior stroke or transient ischemic attack
Cerebrovascular disease marks systemic atherosclerosis and may correlate with autonomic, renal, or medication-related vulnerabilities. It also hints at baseline cerebrovascular reserve issues that complicate hypotensive states should shock develop.
Presentation with cardiac arrest
Arrest (typically ventricular fibrillation or pulseless ventricular tachycardia in this context) signals extreme electrical instability and global ischemic stress. Even after return of spontaneous circulation, myocardial stunning, right ventricular involvement, and post-resuscitation physiology can evolve into shock hours later.
Anterior myocardial infarction
Anterior STEMI usually implies left anterior descending territory jeopardy and often a larger absolute mass of left ventricular myocardium at risk. That anatomic pattern is a classic driver of reduced output and shock when reperfusion is incomplete or when there is extensive microvascular injury.
First medical contact-to-pPCI delay greater than 90 minutes
Prolonged ischemic time permits greater myocardial necrosis before reperfusion. Delay also selects for patients with more turbulent presentations, inter-hospital transfers, or system-level bottlenecks—contexts where shock may appear after initial stabilization.
Killip class on admission (I, II, or III in the score)
Killip classification summarizes hemodynamic and pulmonary congestion severity at presentation. Higher Killip class (II versus I, III versus II) indicates greater baseline circulatory stress. The ORBI score assigns progressively more points across these classes. Patients presenting in Killip IV physiology (cardiogenic shock) were not the target of the derivation framework for this outcome definition.
Heart rate greater than 90 beats per minute on admission
Tachycardia may reflect pain, anxiety, fever, anemia, or arrhythmia—but in STEMI it often mirrors sympathetic drive and hemodynamic compensation for reduced stroke volume. Persistent tachycardia after initial care can foreshadow failure to stabilize.
Systolic blood pressure below 125 mm Hg with pulse pressure below 45 mm Hg
This combined hemodynamic criterion identifies relatively low systolic perfusion pressure together with a narrow pulse pressure (systolic minus diastolic), a pattern consistent with reduced stroke volume or vasoconstriction with limited cardiac output reserve. In the published calculator implementation, meeting both conditions triggers additional points; if either systolic pressure is adequately preserved or pulse pressure is wider, this item does not contribute.
Glycemia greater than 10 mmol/L (180 mg/dL) on admission
Stress hyperglycemia is common in acute MI and may mirror higher catecholamine tone, diabetes (diagnosed or undiagnosed), or acute metabolic derangement. Elevated admission glucose has been associated with worse cardiovascular outcomes in multiple ACS populations; here it functions as a simple dichotomous stress marker in the score.
Culprit lesion involving the left main coronary artery
Left main or equivalent jeopardy threatens a very large myocardial territory. Even with restored TIMI flow, stunning, residual ischemia, and the potential for multivessel compromise can precipitate shock. This item carries one of the largest point increments in the score.
Post-pPCI TIMI flow less than grade 3
TIMI flow grades describe antegrade perfusion in the infarct-related artery after intervention. Less than TIMI 3 indicates incomplete microvascular-level reperfusion despite the procedure. It is strongly associated with larger infarcts, arrhythmia, and hemodynamic deterioration—hence a substantial point burden in the ORBI model.
Point weights (sum all applicable items)
The public ORBI calculator maintained by the investigators uses the following integer weights (an early iteration included hypertension; that item was removed from the web tool in January 2018 and should not be counted in current applications):
| Variable | Points |
|---|---|
| Age > 70 years | 2 |
| Previous stroke or TIA | 2 |
| Presentation with cardiac arrest | 3 |
| Anterior MI | 1 |
| First medical contact-to-pPCI > 90 min | 2 |
| Killip I / II / III | 0 / 2 / 6 |
| Heart rate > 90/min on admission | 3 |
| SBP < 125 mm Hg and pulse pressure < 45 mm Hg | 4 |
| Admission glucose > 10 mmol/L (> 180 mg/dL) | 3 |
| Culprit left main | 5 |
| Post-pPCI TIMI flow < 3 | 5 |
Total points are summed without an upper bound imposed by the arithmetic; clinically, most patients fall within a finite range determined by how many high-weight items are present.
Risk bands and how to use them
Investigators published discrete risk bands tied to the observed incidence of in-hospital cardiogenic shock in the derivation cohort:
- Low (0–7 points): lowest reported shock incidence in the derivation description.
- Low-to-intermediate (8–10 points): intermediate incidence versus the lowest band.
- Intermediate-to-high (11–12 points): higher incidence; warrants heightened vigilance and often intensive monitoring pathways.
- High (≥13 points): highest reported incidence; signals proactive shock-oriented care planning even if the patient is currently stable.
These bands are descriptive strata, not automatic rules for device implantation, transfer, or medication choices. A low score does not eliminate the possibility of shock, and a high score is not a standalone mandate for any one intervention. Serial reassessment after major events (repeat ischemia, bleeding, sepsis, arrhythmia, or new valve disease) is essential because the score reflects the indexed presentation and procedure snapshot rather than dynamic physiology over subsequent days.
Practical documentation and communication tips
When documenting, record the exact thresholds used (for example, first medical contact time, TIMI grade after pPCI, and whether left-main disease was the infarct-related culprit). If systolic or diastolic pressures needed for pulse pressure are missing, teams should document why and avoid over-interpreting a partial calculation. Similarly, glucose should be tied to a defined draw (admission versus emergency department versus intensive care) for consistency with how the variable was intended.
For handoffs, pairing the ORBI band with a brief statement of current perfusion (mental status, urine output trend, lactate if measured, echo findings) preserves clinical context better than reporting the integer total alone.
Limitations and scope
The score is validated for a specific population (STEMI treated with pPCI, without shock at presentation in the derivation design) and a specific outcome (in-hospital cardiogenic shock). It should not be extrapolated to NSTEMI, fibrinolysis-only pathways, chronic coronary disease, or patients already in frank shock at arrival. Calibration can shift across countries, eras of door-to-device performance, and revascularization adjuncts.
Angiographic elements require catheterization laboratory data; in settings where immediate transfer for PCI is planned but not yet completed, only a partial score can be estimated. Finally, like all regression-derived tools, the ORBI score encodes associations from its training cohorts; it does not establish causality for individual items and should not be used to justify withholding guideline-indicated care.