b'Arrest Characteristics and OutcomesSurvival outcomes differed markedly across etiology, presenting rhythm, and witness status categories.Patients with an arrest of presumed cardiac etiology had an unadjusted40% 37% 38% 36% 38%35%survival rate to hospital discharge32%of 9.3%. Survival rates were slightly30% 25% 27% 28%higher among patients with an arrest24% 22%caused by a respiratory mechanism20% 18% 19%or drowning (12.9 and 11.9%,13% 12% 14%respectively), whereas patients10% 9%with an overdose-related arrest had4%a survival rate of 18.0%. Survival0%Presumed CardiacRespiratory/ Drowning/ Drug Overdose Exsanguination/ Otherwas lowest among patients withEtiology Asphyxia Submersion Hemorrhagean arrest due to exsanguination orSustained ROSC Survived to admission Survived to dischargehemorrhage (4.2%) (Figure 17).Figure 17. Unadjusted survival outcomes by arrest etiology.Patients presenting with an initial shockable rhythm of ventricular fibrillation (VF) or ventricular tachycardia (VT) have a significantly higher chance of survival compared50% 46% 47%to those presenting with a non- 40%shockable rhythm, such as asystole36% 34% 33%or pulseless electrical activity (PEA)30% 29% 31%(Figure 18). Patients who presented in a shockable rhythm had a survival20% 16% 15% 16%to hospital admission rate of 47.0%,11%10%compared to 33.8% for those in PEA2%and 14.9% for those in asystole.0%VF/VT/ Asystole Idioventricular/ Unknown UnshockableSimilarly, patients presenting in aUnknown Shockable PEAshockable rhythm had a greaterSustained ROSC Survived to admission Survived to dischargechance of being discharged alive (28.8%), compared to 11.4% ofFigure 18. Unadjusted survival outcomes by presenting arrest rhythm.patients presenting in PEA and 2.5% of patients in asystole. Arrest witness status also has a significant impact on patient40% 38% 40% 37%outcomes, as witnessed arrests35%have more opportunity for bystander30%intervention and early delivery of care. Patients with a 911 Responder20% 18% 18%witnessed arrest had the highest16% 17%chance of survival to hospital10%discharge (18.2%), followed closely5%by those with a bystander witnessed arrest (15.6%). In contrast,0% Witnessed by 911 Responder Bystander Witnessed Unwitnessedunwitnessed events had a survivalSustained ROSC Survived to admission Survived to dischargerate of 4.6% (Figure 19).Figure 19. Unadjusted survival outcomes by arrest witness status.40 41'