Admission Predictors of In-Hospital Mortality and Subsequent Long-Term Outcome in Survivors of Ventricular Fibrillation Out-of-Hospital Cardiac Arrest: A Population-Based Study

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Abstract
Background: Survival following out-of-hospital cardiac arrest (OHCA) from ventricular fibrillation (VF) is poor and dependent on a rapid emergency response system. Improvements in emergent early response have resulted in a higher percentage of patients surviving to admission. However, the admission variables that predict both short- and long-term survival in a region with high discharge survival following OHCA require further study in order to identify survivors at subsequent highest risk. Methods: All patients with OHCA arrest in Olmsted County Minnesota between 1990 and 2000 who received defibrillation of VF by emergency services were included in the population-based study. Baseline patient admission characteristics in survivor and nonsurvivor groups were compared. Survivors to hospital discharge were prospectively followed to determine long-term survival. Results: Two hundred patients suffered a VF arrest. Of these patients, 145 (73%) survived to hospital admission (7 died within the emergency department) and 79 (40%) were subsequently discharged. Sixty-six (83%) were male, with an average age of 61.9 ± 15.9 years. Univariate predictors of in-hospital mortality included call-to-shock time (6.6 vs. 5.5 min, p = 0.002), a nonwitnessed arrest (75.4 vs. 92.4%, p = 0.008), in-field use of epinephrine (27.8 vs. 93.4%, p < 0.001), age (68.1 vs. 61.9 years, p = 0.017), hypertension (36.1 vs. 14.1%, p = 0.005), ejection fraction (32.4 vs. 42.4, p = 0.012), and use of digoxin (34.9 vs. 12.7%, p = 0.002). Of all these variables, hypertension [hazard ratio (HR) 4.0, 95% CI 1.1–14.1, p = 0.03], digoxin use (HR 4.5, 95% CI 1.3–15.6, p = 0.02), and epinephrine requirement (HR 62.0, 95% CI 15.1–254.8, p < 0.001) were multivariate predictors of in-hospital mortality. Nineteen patients (24%) had died prior to the survey follow-up. Five patients experienced a cardiac death, resulting in a 5-year expected cardiac survival of 92%. Multivariate variables predictive of long-term mortality include digoxin use (HR 3.02, 95% CI 1.80–5.06, p < 0.001), hypertension (HR 2.06, 95% CI 2.12–3.45, p = 0.006), and call-to-shock time (HR 1.18, 95% CI 1.01–1.38, p = 0.038). Conclusion: A combined police/fire/EMS defibrillation program has resulted in an increase of patients surviving to hospital admission after OHCA. This study confirms the need to decrease call-to-shock times, which influence both in-hospital and long-term mortality. This study also identifies the novel demographic variables of digoxin and hypertension, which were also independent risk factors of increased in-hospital and long-term mortality. Identification of these variables may provide utility in identifying those at high-risk of subsequent mortality after resuscitation.

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