Risk score may help predict mortality in cardiogenic shock patients

Researchers in Germany have developed a risk prediction score that strongly correlated with mortality in patients who suffer from cardiogenic shock following an acute MI.

They used a stepwise multivariable regression analysis to develop the score and identified six variables that were independent predictors of 30-day mortality.

The 30-day mortality rates were 23.8 percent in the low risk group, 49.2 percent in the intermediate risk group and 76.6 percent in the high risk group.

Lead researcher Janine Pöss, MD, of the University Heart Center Lübeck in Germany, and colleagues published their results online in the Journal of the American College of Cardiology on April 10.

For this analysis, the researchers evaluated the IABP-SHOCK II study, a randomized trial that found patients with acute MI-related cardiogenic shock had similar short- and long-term outcomes whether they underwent intra-aortic balloon pump (IABP) support or had no IABP support.

They defined cardiogenic shock as hypotension, pulmonary congestion and signs of end-organ hypoperfusion. They added that cardiogenic shock is the most common in-hospital cause of death among patients with an acute MI.

After the researchers identified the six variables that were significantly associated with mortality, they developed a scoring system that attributed one or two points to each variable. The six variables that were independent predictors for 30-day mortality were: age older than 73 years old, prior stroke, glucose level at hospital admission greater than 191 mg/dL, creatinine level at admission greater than 1.5 mg/dL, Thrombolysis in Myocardial Infarction (TIMI) flow grade of less than 3 after PCI and arterial blood lactate at admission greater than 5 mmol/L.

Patients in the low risk group had a score of 0 to 2, patients in the intermediate risk group had a score of 3 or 4 and patients in the high risk group had a score of 5 to 9.

The mean age of the 480 patients was 70, and 69 percent were men. All of the patients had infarct-related cardiogenic shock.

Of the patients, 49 percent were at low risk, 37.7 percent were at intermediate risk and 13.3 percent were at high risk.

The researchers validated the score in 98 patients enrolled in the IABP-SHOCK II registry and found it had good discrimination with an area under the curve of 0.79. They also performed an external validation by analyzing data on 137 patients with infarction- related cardiogenic shock who underwent primary PCI in the multicenter, observational CardShock trial. They found that the score had an area under the curve of 0.73.

The analysis had a few limitations, according to the researchers, including small sample sizes in the main study and the validation cohorts. They also excluded some patients because they had missing data regarding the score variables, although they noted that the event rates were similar in the included and excluded groups. In addition, researchers in the IABP-SHOCK II and the CardioShock studies did not use a core laboratory to assess TIMI flow after PCI.

“The IABP-SHOCK II risk score is a simple tool that can be rapidly calculated in the catheterization laboratory setting and applied in clinical routine,” the researchers wrote. “It might therefore serve for identifying patients for future clinical trials and, more importantly, it might help stratify patients according to their risk for short-term mortality and thus facilitate clinical decision making.”