title: A rule for early outcome classification of out-of-hospital cardiac arrest patients presenting with ventricular fibrillation.
abstract: The aim of the study was to develop a scoring system for outcome classification at the start of prehospital first tier resuscitation for patients with cardiac arrest from ventricular fibrillation (VF). We studied a consecutive sample of 100 out-of-hospital cardiac arrest patients, presenting with VF of presumed cardiac etiology on arrival of the first tier (in a two-tiered urban Emergency Medical Services system). The number of patients discharged was 29 ('survivors') and 71 died ('non-survivors'). The electrocardiography (ECG) tracings recorded during resuscitation using a semi-automatic defibrillator were retrospectively analysed. For each patient, VF amplitude in mV (VF_a) and the number of base-line crossings per second (VF_blc) were calculated. Fisher's linear discriminant analysis was applied to discriminate between survivors and non-survivors using the variables VF_a, VF_blc and age. Patients were classed as potential survivors or non-survivors using a survival index = 0.6*(VF_a) + 0.4*(VF_blc)-4.0. If for a given patient the survival index is < 0, he is classified in the non-survivor group, if the survival index is > 0, he is classified in the survivor group. Using this index 79% of the survivors and 70% of the non-survivors could be classified correctly. Adding age to the formula increased the correct classification of survivors to 86 and 73% for the non-survivors. The survival index provides a research tool for the discrimination between potential survivors and non-survivors, which opens the possibility for the development of alternative treatment protocols in cardiac arrest.
authors.affiliation: Department of Intensive Care, University Hospital Antwerp-UIA, Belgium.
authors.forename: K G
authors.initials: KG
authors.lastname: Monsieurs
authors.forename: H
authors.initials: H
authors.lastname: De Cauwer
authors.forename: F L
authors.initials: FL
authors.lastname: Wuyts
authors.forename: L L
authors.initials: LL
authors.lastname: Bossaert
mesh_terms: D000368:Aged; D000465:Algorithms; D016887:Cardiopulmonary Resuscitation; D016002:Discriminant Analysis; D004554:Electric Countershock; D004562:Electrocardiography; D005260:Female; D006323:Heart Arrest / Q000209:etiology / Q000401:mortality* / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011379:Prognosis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014693:Ventricular Fibrillation / Q000150:complications / Q000401:mortality* / Q000628:therapy