Out-of-hospital cardiac arrest (OHCA) outcomes vary throughout North America. Most notably, a 2008 Resuscitation Outcomes Consortium (ROC) analysis revealed a fivefold variation in survival to hospital discharge, with Birmingham, Alabama, having the lowest survival rate at 3%.1 Since then, studies have shown that bystander cardiopulmonary resuscitation (B-CPR) and bystander automated external defibrillator (B-AED) use are particularly low in communities like Birmingham, which have high minority populations and low socioeconomic characteristics.2, 3 A lack of bystander interventions may be a significant contributor to the disparities in OHCA outcomes.
The goals of this analysis were to examine recent outcomes of OHCA in Birmingham and understand trends in bystander response. We hypothesize that survival following OHCA has not improved in Birmingham since the original ROC publication in 2008, and that layperson B-CPR and B-AED use are critical deficiencies in the Birmingham OHCA system of care.
We performed a retrospective observational analysis using the Cardiac Arrest Registry to Enhance Survival (CARES) dataset for Birmingham from 1/1/2020–12/31/2022. Birmingham did not participate in CARES prior to January 2020. All adult (age ≥18 years) non-traumatic emergency medical services (EMS) treated OHCA of presumed cardiac etiology within the city of Birmingham were included. Events occurring in nursing home/healthcare facilities or prisons, those witnessed by EMS, and those missing survival outcomes were excluded. This analysis was IRB approved and the data can be made available upon written approval by Birmingham Fire and Rescue.
The primary outcomes were survival with favorable neurologic outcome, defined as a cerebral performance category (CPC) score of 1 or 2 at hospital discharge, and B-CPR participation and B-AED application rates. We compared OHCA characteristics by year using the Chi-Square test or one-way ANOVA test. The average B-CPR rate in Birmingham was compared to the published average national B-CPR rate from CARES4 using the one-sample proportions test. Incidence rates were calculated using the 2022 U.S. Census data.
A total of 524 records met inclusion criteria with 7 (1.3%) surviving with favorable neurologic outcome (Table). The median age was 61 years (IQR 47,72), 40.6% were female, and 78.2% were of Black race. Most OHCA occurred at home (84.5%), 67.6% were unwitnessed, and 85.5% were found in non-shockable rhythms. The B-CPR rate was stable from 2020 to 2022. The overall B-CPR rate of 15.5% was ~2.6x below the national average (40.8%),4 p< 0.001. When evaluating only bystander witnessed events, the B-CPR rate increased to 28.8% but still below then national average (p = 0.002). The overall B-AED rate was 0% indicating no cases of layperson AED application over the study period.
Table.
Out-of-hospital cardiac arrest characteristics and outcomes by year in Birmingham, Alabama
| Variable | 2020 n=189 | 2021 n=175 | 2022 n=160 | Overall n=524 | P value |
|---|---|---|---|---|---|
| Annual Incidence per 100,000* | 96.0 | 88.9 | 81.3 | 88.7 | <0.001 |
| Age, median [IQR] | 63 [50,76] | 62 [48,71] | 60 [47,72] | 61 [47,72] | 0.228 |
| Female Gender, n (%) | 73 (38.6) | 67 (38.3) | 73 (45.6) | 213 (40.6) | 0.306 |
| Black Race, n (%) | 139 (73.5) | 139 (79.4) | 132 (82.5) | 410 (78.2) | 0.117 |
| Location, n (%) | |||||
| Home | 158 (83.6) | 155 (88.6) | 130 (81.3) | 443 (84.5) | 0.163 |
| Public | 31 (16.4) | 20 (11.4) | 30 (18.8) | 81 (15.5) | |
| Witnessed Status, n (%) | |||||
| Unwitnessed | 137 (72.5) | 120 (68.9) | 97 (60.6) | 354 (67.6) | 0.058 |
| Bystander Witnessed | 52 (27.5) | 55 (31.4) | 63 (39.4) | 170 (32.4) | |
| Initial Rhythm, n (%) | |||||
| Asystole | 111 (58.7) | 100 (57.1) | 98 (61.3) | 309 (59.0) | 0.115 |
| Idioventricular/PEA | 41 (21.7) | 46 (26.3) | 36 (22.5) | 123 (23.5) | |
| Unknown Unshockable | 7 (3.7) | 2 (1.1) | 7 (4.4) | 16 (3.1) | |
| Ventricular Fibrillation | 16 (8.5) | 20 (11.4) | 17 (10.6) | 53 (10.1) | |
| Ventricular Tachycardia | 7 (3.7) | 5 (2.9) | 0 (0) | 12 (2.3) | |
| Unknown Unshockable | 7 (3.7) | 2 (1.1) | 2 (1.3) | 11 (2.1) | |
| Initial Rhythm Status, n (%) | |||||
| Non-shockable | 159 (84.1) | 148 (84.6) | 141 (88.1) | 448 (85.5) | 0.523 |
| Shockable | 30 (15.9) | 27 (15.4) | 19 (11.9) | 76 (14.5) | |
| Bystander CPR, n (%) | 29 (15.3) | 27 (14.4) | 25 (15.6) | 81 (15.5) | 0.997 |
| Bystander CPR for only bystander witnessed OHCA, n (%) | 16 (30.8) | 16 (29.1) | 17 (27.0) | 49 (28.8) | 0.904 |
| Bystander AED application, n (%) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 1.000 |
| Sustained ROSC, n (%) | |||||
| No | 143 (75.7) | 124 (70.9) | 131 (81.9) | 398 (76.0) | 0.201 |
| Outcome | |||||
| Died in the field | 74 (39.2) | 45 (25.7) | 64 (40.0) | 183 (34.9) | 0.077 |
| Died in the ED | 77 (40.7) | 80 (45.7) | 56 (35.0) | 213 (40.6) | |
| Died in the hospital | 32 (16.9) | 46 (26.3) | 36 (22.5) | 114 (21.8) | |
| Survived with unfavorable neurologic outcome | 3 (1.6) | 2 (1.1) | 2 (1.3) | 7 (1.3) | |
| Survived with favorable neurologic outcome | 3 (1.6) | 2 (1.1) | 2 (1.3) | 7 (1.3) |
Note: IQR = interquartile range; OHCA = out-of-hospital cardiac arrest; PEA = pulseless electrical activity; CPR= cardiopulmonary resuscitation; AED = automated external defibrillator; ROSC = return of spontaneous circulation; ED = emergency department.
study population excludes EMS-witnessed and nursing home/healthcare facility events.
Our analysis shows OHCA survival in Birmingham has not improved since the original ROC report published more than 15 years ago.1 The overall survival rate with favorable neurological outcomes in this three-year cohort was 1.3%, which is among the lowest documented in the U.S. It is important to note that our study excluded EMS-witnessed events, as our focus was on examining layperson bystander response. However, when we included EMS-witnessed events (n = 59) in the overall denominator, the rate of favorable neurological survival remained low (1.7%).
The strikingly poor bystander response rates are likely driving factors behind this survival disparity. Bystander CPR in Birmingham was found to be ~2.6x below the national average and nearly three quarters of bystander witnessed OHCA did not receive B-CPR prior to EMS arrival. With nearly 85% of OHCA occurring at home, family members appear to be facing barriers to bystander response. Further work is needed to understand the bystander experience in Birmingham, and targeted community interventions to overcome modifiable barriers to B-CPR are needed. Additionally, local use of telecommunicator CPR protocols should be explored.
Another alarming finding is the lack of B-AED application. Among the 524 OHCAs, none had an AED applied by a bystander. This may be partly attributed to most OHCA occurring at home. However, it is noteworthy that 81 OHCA occurred in public locations without the application of an AED. Further research is needed to understand AED availability and community barriers to B-AED application. It is worth noting that the current rate of non-shockable rhythms (85.5%) limits the utility of AEDs in many cases. We suspect this high rate of non-shockable rhythms is, at least in part, due to the infrequent B-CPR resulting in the degradation of a shockable rhythm into a non-shockable state.5
Limitations of our analysis include its retrospective design, single location with a relatively small sample size, and overlapped with the COVID-19 pandemic. The OHCA incidence, characteristics, bystander response rates, outcomes may have been influenced by the pandemic. Continued data surveillance is warranted.
In conclusion, survival following OHCA in Birmingham remains rare, and B-CPR participation and B-AED use represent critical gaps in the local OHCA system of care. Community-focused initiatives are needed to enhance bystander response and improve OHCA survival in this at-risk location.
Sources of Funding
This work was funded by an NHLBI grant (K23 HL166692) awarded to Dr. Coute.
Footnotes
Disclosures
HLK: none; BHN: received consultant fees for statistical analysis related to this work; JDR: none; WCF: none; EAJ: None; RAC: NIH/NHLBI K23 HL166692.
References
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