Fig. 1

Study enrollment. OHCA data divided into three groups by initial ECG waveform at EMS arrival. Abbreviations: OHCA, out of hospital cardiac arrest; ECG, electrocardiogram; EMS, emergency medical service; ROSC, return of spontaneous circulation; PAD, public access defibrillation; response interval, call 119 to EMS contact with patient; unknown, first rhythm other than VF; pVT, PEA, asystole. VF, ventricular fibrillation; pVT, pulseless ventricular tachycardia; PEA, pulseless electrical activity. CPC, cerebral performance category