17.91% initial nonshockable out-of-hospital cardiac arrest patients convert into a shockable rhythm during resuscitation.
•Spontaneous conversion to a shockable rhythm does not necessarily have a favourable prognosis.
•25 min is a reasonable cut-off point to distinguish between early and late conversion.
•Early conversion into a shockable rhythm resulted in a better prognosis.
•Late conversion into a shockable rhythm was not significantly different from nonconversion group.
AbstractBackgroundThe prognostic significance of conversion into a shockable rhythm in patients who experienced out-of-hospital cardiac arrest (OHCA) with an initially nonshockable rhythm is controversial, perhaps due to the timing of rhythm conversion not being considered previously. We aimed to compare the different prognoses of patients with OHCA and early and late conversion of their rhythm into a shockable rhythm.
MethodsThis was a single-centre retrospective cohort study. We enrolled patients with OHCA who were sent to a medical centre in central Taiwan from 2016 to 2020. Patients <18 years old, those with cardiac arrest due to trauma or a circumstantial cause, and those for whom resuscitation was not attempted were excluded. Patients were divided into two groups in accordance with presentation with an initially shockable rhythm. Those with an initially nonshockable rhythm were divided into three subgroups: early-conversion, late-conversion, and nonconversion groups. The primary outcome was the neurological functional status upon discharge from hospital.
ResultsA total of 1645 patients with OHCA were included: initially shockable rhythm group, 339; early conversion group, 68; late-conversion group, 166; and nonconversion group, 1072. After adjustment, multivariate logistic regression revealed that a favourable neurological outcome was more common in the early conversion group than the nonconversion group (odds ratio [OR] 2.4; 95% confidence interval [CI], 1.1–5.3; p = 0.035), whereas the late-conversion group did not significantly differ from the nonconversion group (OR 0.5; 95% CI, 0.1–1.5; p = 0.211). The proportions of sustained return of spontaneous circulation and survival to discharge were also higher in the early conversion group than the late-conversion group (OR 2.9 95% CI 1.6–5.5, p = 0.001 and OR 4.5, 1.8–11.0, p = 0.001, respectively).
ConclusionIn patients who experience OHCA and have an initially nonshockable rhythm, early conversion into a shockable rhythm resulted in a better prognosis, whereas late conversion was not significantly different from nonconversion.
KeywordsShockable rhythm
Out-of-hospital cardiac arrest
Rhythm conversion
Favourable neurological outcome
AbbreviationsOHCAOut-of-hospital cardiac arrest
EMSemergency medical service
CPRcardiopulmonary resuscitation
VFventricular fibrillation
VTventricular tachycardia
EMTemergency service technician
AEDautomated external defibrillator
PCIPercutaneous coronary intervention
ROSCreturn of spontaneous circulation
TTMtarget temperature management
CPCCerebral Performance Category
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