Predictive Value of the Sequential Organ Failure Assessment Score for Mortality in a Contemporary Cardiac Intensive Care Unit Population

Abstract

Background: Optimal methods of mortality risk stratification in patients in the cardiac intensive care unit (CICU) remain uncertain. We evaluated the ability of the Sequential Organ Failure Assessment (SOFA) score to predict mortality in a large cohort of unselected patients in the CICU.

Methods and results: Adult patients admitted to the CICU from January 1, 2007, to December 31, 2015, at a single tertiary care hospital were retrospectively reviewed. SOFA scores were calculated daily, and Acute Physiology and Chronic Health Evaluation (APACHE)-III and APACHE-IV scores were calculated on CICU day 1. Discrimination of hospital mortality was assessed using area under the receiver-operator characteristic curve values. We included 9961 patients, with a mean age of 67.5±15.2 years; all-cause hospital mortality was 9.0%. Day 1 SOFA score predicted hospital mortality, with an area under the receiver-operator characteristic curve value of 0.83; area under the receiver-operator characteristic curve values were similar for the APACHE-III score, and APACHE-IV predicted mortality (P>0.05). Mean and maximum SOFA scores over multiple CICU days had greater discrimination for hospital mortality (P<0.01). Patients with an increasing SOFA score from day 1 and day 2 had higher mortality. Patients with day 1 SOFA score <2 were at low risk of mortality. Increasing tertiles of day 1 SOFA score predicted higher long-term mortality (P<0.001 by log-rank test).

Conclusions: The day 1 SOFA score has good discrimination for short-term mortality in unselected patients in the CICU, which is comparable to APACHE-III and APACHE-IV. Advantages of the SOFA score over APACHE include simplicity, improved discrimination using serial scores, and prediction of long-term mortality.

Keywords: Acute Physiology and Chronic Health Evaluation score; Sequential Organ Failure Assessment score; cardiac critical care; cardiac intensive care unit; critical care; intensive cardiac care unit; intensive care unit; mortality; risk prediction.

Figure 1

Distribution of day 1 Sequential Organ Failure Assessment (SOFA) scores, as a percentage of overall population, hospital survivors, and inpatient deaths. P<0.001 between groups.

Figure 2

Short‐ and intermediate‐term mortality as a function of day 1 Sequential Organ Failure Assessment (SOFA) score tertile. Tertile 1 includes patients with day 1 SOFA score <2, tertile 2 includes patients with day 1 SOFA score of 2 to 3, and tertile 3 includes patients with day 1 SOFA score ≥4. P<0.001 between groups. CICU indicates cardiac intensive care unit.

Figure 3

Short‐term mortality stratified by day 1 Sequential Organ Failure Assessment (SOFA) score. CICU indicates cardiac intensive care unit.

Figure 4

Short‐term mortality as a function of change in Sequential Organ Failure Assessment (SOFA) score from day 1 to day 2. Patients without a day 2 SOFA score are classified as “left cardiac intensive care unit (CICU) on day 1.” P<0.001 between groups.

Figure 5

Distribution of day 1 Sequential Organ Failure Assessment organ system subscores in the overall population, hospital survivors, and hospital nonsurvivors (P<0.001 between hospital survivors and hospital nonsurvivors).

Figure 6

Kaplan‐Meier survival curves for hospital survivors, by day 1 Sequential Organ Failure Assessment (SOFA) score tertile. Tertile 1 includes patients with day 1 SOFA score <2, tertile 2 includes patients with day 1 SOFA score of 2 to 3, and tertile 3 includes patients with day 1 SOFA score ≥4. P<0.001 between groups by log‐rank test.