An external automatic device to detect ventricular fibrillation

An analysis of a micro-processor-based system to detect cardiac arrest rhythms was made in a series of 84 cardiac arrests in 78 patients. The ECG was sensed using 2 external ECG/defibrillator pads applied to the chest wall. In 5 arrests, the initial rhythm was continuous electrical pacing in addition to the cardiac arrest and these were not included in the analysis. Of the remaining 79 arrests there were 15 in which the initial rhythm was ventricular fibrillation and 14 were correctly detected by the system (sensitivity 93%). In the remaining 64 arrests the initial rhythm was not ventricular fibrillation and 62 were correctly identified (specificity 97%). A high specificity is required in any device employing automatic detection of ventricular fibrillation. Continuous electrocardiographic recordings of the cardiac arrests were analysed every 8 to 18 s: of 223 sections showing ventricular fibrillation, 165 were correctly determined by the system, i.e. sensitivity 74%, where the rhythm was not ventricular fibrillation, of the 5002 sections 4953 were correctly detected by the system, i.e. specificity 99%. The percentage accuracy of detection of ventricular fibrillation varied from 25-100% (mean 81%) and for detection of non-ventricular fibrillation from 57-100% (mean 99%) in every 8 to 18 s section of ECG tracing per cardiac arrest episode. Thus the automatic detection of cardiac arrest rhythms is feasible with a high degree of accuracy.