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IABP-SHOCK II Risk Score
Study Questions:
What is the utility of an easy-to-use, readily available risk prediction score for short-term mortality in patients with cardiogenic shock (CS), as derived from the IABP-SHOCK II (Intraaortic Balloon Pump in Cardiogenic Shock) trial?
Methods:
This is a substudy of the randomized IABP-SHOCK II trial. A model was developed on the randomized population of the IABP-SHOCK II trial (n = 600) using a stepwise multivariable Cox proportional hazards regression analysis with forward selection technique. Unselected extensive univariable testing was performed including all database variables potentially associated with mortality. Variables significantly related to mortality in univariable testing (p < 0.1) were further examined in multivariable analysis. Six independent variables remained statistically significantly associated with mortality, and constitute the risk score parameters.
Results:
Six variables emerged as independent predictors for 30-day mortality and were used as score parameters: age >73 years; prior stroke; glucose at admission >10.6 mmol/L (191 mg/dl); creatinine at admission >132.6 μmol/L (1.5 mg/dl); Thrombolysis In Myocardial Infarction flow grade after percutaneous coronary intervention <3; and arterial blood lactate at admission >5 mmol/L. Either 1 or 2 points were attributed to each variable, leading to a score in three risk categories: low (0-2); intermediate (3 or 4); and high (5-9). The observed 30-day mortality rates were 23.8%, 49.2%, and 76.6%, respectively (p < 0.0001). Validation in the IABP-SHOCK II registry population showed good discrimination with an area under the curve (AUC) of 0.79. External validation in the CardShock population (n = 137 patients) showed short-term mortality rates of 28.0% (score 0-2), 42.9% (score 3-4), and 77.3% (score 5-9; p < 0.001) and an AUC of 0.73. Kaplan-Meier analysis revealed a stepwise increase in mortality between the different score categories (0-2 vs. 3-4; p = 0.04; 0-2 vs. 5-9; p = 0.008).
Conclusions:
The authors concluded that the IABP-SHOCK II risk score can be easily calculated in daily clinical practice and strongly correlated with mortality in patients with infarct-related CS.
Perspective:
This study reports on the IABP-SHOCK II risk score, a simple tool that can be rapidly calculated in the catheterization laboratory setting and applied in clinical routine with good predictive ability. All variables are readily available by point-of-care testing and/or immediate blood gas analysis, such as glucose or blood lactate, and it may helpful for clinical decision making with respect to the selection of management strategies (e.g., deciding whether to implant a mechanical support device). It should be noted that a single score should not be the only variable for decision making, and must take into account other individual aspects, such as the patient’s comorbidities and neurological situation. Despite some limitations, the score might provide some assistance for the clinician, but needs validation in other cohorts.
Keywords: Acute Coronary Syndrome, Area Under Curve, Catheterization, Creatinine, Heart Failure, Intra-Aortic Balloon Pumping, Glucose, Myocardial Infarction, Percutaneous Coronary Intervention, Risk Factors, Shock, Cardiogenic, Stroke
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