Re: “Factors associated with favorable outcomes in cardiac arrest and target temperature management” by Kimura et al

Dear Editor-in-Chief,

I read with great interest the article titled “Factors associated with favorable outcomes in cardiac arrest and target temperature management” by Kimura et al. (2023). In this article, the authors did not find a statistical association between Δ-temperature (defined as the difference between initial presenting temperature and target temperature) and both mortality and neurological outcomes. Although the authors expressed that the pulseless electrical activity (PEA) was the most common initial rhythm in both in-hospital and out-of-hospital cardiac arrests (IHCA and OHCA) in the study population, they did not include the initial rhythm in the regression analysis for predictors of mortality and worse neurological outcome. Instead of specific initial rhythm classification, they classify rhythm as “shockable” and “nonshockable” in regression analysis, and they did not find any statistical difference affecting neurological outcome depending on this grouping. On the other hand, the initial rhythm detected at the time of monitoring is closely related to mortality and neurological outcomes in the cardiac arrest victims (O'Horo et al., 2012).

The initial rhythm can provide information about the patient's arrest time and the underlying etiological factor. The initial rhythm not only predicts the chance of recovery of spontaneous circulation but also determines the neurological recovery that can be obtained from the target temperature management. Especially in OHCA victims, every clinical finding obtained by the medical stuff at the scene may have an impact on the patient's survival. For these reasons, the initial rhythm should be taken into consideration at the time of first intervention, should be noted in the medical reports and should guide further clinical management.

Nonshockable rhythms are known as PEA and asystole. Shockable initial rhythm was found to be closely related to better survival in cardiac arrest victims (O'Horo et al., 2012). Both PEA and asystole have lower survival rates than shockable initial rhythms. Besides this, a subgroup of sudden cardiac arrest victims with an initial rhythm as PEA may have better survival rates. Predictors of a better survival from PEA were expressed as young age, witnessed status, public location, and preexisting COPD/asthma (Holmstrom et al., 2023). It should be also kept in mind that a major proportion of atraumatic, witnessed cardiac arrests with an initial rhythm of PEA and younger than 65 years of age have been reported to be related to massive pulmonary embolism (Courtney et al., 2001). A treatment strategy with clot-targeted thrombolytic administration and following therapeutic hypothermia can be a life-saving option with better survival and even better neurological outcomes (Çoner et al., 2018). As a conclusion, an initial rhythm of PEA in young patients with witnessed sudden cardiac arrest should be managed different from remaining nonshockable rhythms.