Who benefits most from mild therapeutic hypothermia in coronary intervention era? A retrospective and propensity-matched study

Abstract

Introduction: The aim of the present study was to investigate the impact of the time interval from collapse to return of spontaneous circulation (CPA-ROSC) in cardiac arrest patients and the types of patients who will benefit from therapeutic hypothermia.

Methods: Four hundred witnessed adult comatose survivors of out-of-hospital cardiac arrest of cardiac etiology were enrolled in the study. The favorable neurological outcome was defined as category 1 or 2 on the five-point Pittsburgh cerebral performance scale at the time of hospital discharge. A matching process based on the propensity score was performed to equalize potential prognostic factors in the hypothermia and normothermia groups, and to formulate a balanced 1:1 matched cohort study.

Results: The rate of favorable neurological outcome was higher (P < 0.05) in the hypothermia group (n = 110) than in the normothermia group in patients with CPA-ROSC of 15 to 20 minutes (64% vs. 17%), 20 to 25 minutes (70% vs. 8%), 25 to 30 minutes (50% vs. 7%), 35 to 40 minutes (27% vs. 0%) and 40 to 45 minutes (29% vs. 2%). A similar association was observed in a propensity-matched cohort, but the differences were not significant. There was no significant difference in the rate of favorable neurological outcome between the hypothermia-matched group and the normothermia-matched group. In the patients whose CPA-ROSC was greater than 15 minutes, however, the rate of favorable neurological outcome was higher in the hypothermia-matched group than in the normothermia-matched group (27% vs. 4%, P < 0.001). In multivariate analysis, the CPA-ROSC was an independent predictor of favorable neurological outcome (every 1 minute: odds ratio = 0.89, 95% confidence interval = 0.85 to 0.92, P < 0.001).

Conclusions: The CPA-ROSC is an independent predictor of neurological outcome. Therapeutic hypothermia is more beneficial in comatose survivors of cardiac arrest with CPA-ROSC greater than 15 minutes.

Figure 1

Flow diagram of study patients and outcomes. ROSC, return of spontaneous circulation.

Figure 2

Rate of favorable neurological outcome. The rate of favorable neurological outcome (FR) by the time interval from collapse to return of spontaneous circulation (CPA-ROSC) every 5 minutes in (a) the hypothermia group and (b) the normothermia group. *The rate of FR in the hypothermia group was higher than that in the normothermia group (P < 0.05). ^†There was a trend toward a higher rate of FR in the hypothermia group than in the normothermia group (0.05 <P < 0.10).

Figure 3

Time interval from collapse to return of spontaneous circulation predicting favorable neurological outcome. Receiver-operating characteristic curves for predicting a favorable neurological outcome in (a) the hypothermia group and (b) the normothermia group. CPA-ROSC, time interval from collapse to return of spontaneous circulation.

Figure 4

Distribution of propensity scores. Distribution of propensity scores (a) in the hypothermia and normothermia groups and (b) in the matched hypothermia-M and normothermia-M groups.

Figure 5

Rate of favorable neurological outcome in the propensity-matched cohort. Plot representing the rate of favorable neurological outcome (FR) against the time interval from collapse to return of spontaneous circulation (CPA-ROSC) every 5 minutes in (a) the propensity-matched hypothermia-M group and (b) the normothermia-M group.