Out-of-hospital cardiac arrest (OHCA) is still a major challenge in medicine despite many efforts to improve outcomes. In patients with OHCA, the rate of the return of spontaneous circulation (ROSC) has been reported to be from 24 to 44% [
Most in-hospital deaths after ROSC are due to cardiac dysfunction and neurologic failure in postcardiac arrest syndrome, and early death is mainly due to cardiac dysfunction [
When ROSC is achieved, blood pressure and heart rate (HR) are usually measured immediately. HR, an essential vital sign that reflects hemodynamic stability, influences myocardial oxygen demand, coronary blood flow, and myocardial performance [
HR at the time of ROSC could be influenced by the
In children with OHCA, it has been reported that HR in the first hour after sustained ROSC was associated with survival to discharge [
Given that the cardiac dysfunction after ROSC showed significant morbidity and mortality [
We performed a secondary analysis of consecutive OHCA databases in a single ED from January 2008 to July 2014. The study facility was a 1250-bed urban tertiary academic hospital with an annual ED census of approximately 85,000. This study was approved by the Institutional Review Board (IRB) of Seoul National University Bundang Hospital and reported according to the STROBE (STrengthening the Reporting of OBservational studies in Epidemiology) guidelines for reporting observational trials [
Patients with cardiac arrest were managed based on the recommendations of the international guidelines during the study period [
When the prehospital EMTs notified the ED, the CPR team of the ED was activated. Details on the CPR team and resuscitation protocol in the ED have been presented previously [
Based on the OHCA registry in accordance with Utstein-style guidelines [
Bradycardia is defined as HR below 60 beats per minute and tachycardia is defined as HR above 100 beats per minute. Given those definitions and that symptomatic tachycardia generally involves rates over 150 beats/min [
Data were collected by trained research personnel using a standardized registry template form [
The HR of each patient was retrieved from the ECG taken at the time of ROSC. If the HR was not available from the ECG, the HR was retrieved from the vital signs recorded immediately after ROSC.
The primary outcome was the rate of sustained ROSC according to the HR groups. Sustained ROSC was defined according to the Utstein statement as the status in which chest compressions for 20 consecutive minutes are not required and signs of circulation persist [
The Chi-square test or Fisher’s exact test was used for comparisons of categorical variables and presented as numbers (percentages). Continuous variables were examined with the Kolmogorov–Smirnov test for the normality of the distribution and presented as medians (interquartile ranges). The analysis of variance or the Kruskal–Wallis test was used depending on the normality of the distribution. If the Kruskal–Wallis test showed statistical significance, Bonferroni correction was used for multiple comparisons.
Univariable logistic regression analysis was performed to investigate the association between the HR (as a continuous variable) at the time of ROSC and the probability of sustained ROSC. Multivariable logistic regression analysis was performed with the enter method, which brings all clinically relevant variables into the model, to determine the independent factors for outcomes including sustained ROSC, one-month survival, and six-month neurologic outcome. As a result, HR (bradycardia, normal HR, tachycardia, and extreme tachycardia), age, sex, witnessed arrest, public place, shockable initial rhythm, bystander CPR, total epinephrine dose, mean arterial pressure at the time of ROSC, no-flow time defined as time from collapse to the start of resuscitation attempts, and low-flow time defined as time from start of life support until the restoration of spontaneous circulation were included in the multivariable logistic regression analysis.
All tests were two-sided, and
During the study period, a total of 866 adult OHCA patients who presented to the ED were initially screened. Among these patients, 43 patients who achieved prehospital ROSC, 48 patients whose cause of cardiac arrest was trauma, 49 patients who were supported by ECLS devices, and 388 patients who did not achieve any ROSC were excluded. Among the remaining 338 patients, eight had no HR record because of brief ROSC (duration less than one minute). As a result, 330 OHCA patients who underwent CPR in the ED and had HR records after ROSC were included in the final analysis (Figure
Flowchart of the study population. ROSC, return of spontaneous circulation; ECLS, extracorporeal life support; HR, heart rate; brief ROSC, ROSC less than one minute of duration.
The median age of the patients was 72 (59–79) years, and 194 (58.8%) patients were males. HR was retrieved from the ECGs taken immediately after ROSC in 323 patients and from the vital signs in seven patients. The numbers of patients according to HR were 26 in the bradycardia group, 67 in the normal HR group, 176 in the tachycardia group, and 61 in the extreme tachycardia group. The mean arterial pressure at the time of ROSC was higher in the extreme tachycardia group than in the other groups. The total epinephrine dose was lower in the extreme tachycardia group compared to the other groups. The median low-flow time showed no significant difference between groups after Bonferroni correction. There was no significant difference among groups in terms of the age, gender, rates of witnessed arrest, public place, initial shockable rhythm, bystander CPR, and no-flow time (Table
Baseline characteristics and the outcomes of the patients.
Total | Bradycardia | Normal HR | Tachycardia | Extreme tachycardia | ||
---|---|---|---|---|---|---|
( | ( | ( | ( | ( | ||
Age (years) | 72 (59–79) | 73 (66–77) | 74 (62–79) | 72 (60–79) | 69 (49–76) | 0.094 |
Male | 194 (58.8) | 17 (65.4) | 44 (65.7) | 98 (55.7) | 35 (57.4) | 0.470 |
Witnessed arrest | 264 (80.0) | 20 (76.9) | 57 (85.1) | 141 (80.1) | 46 (75.4) | 0.565 |
Public place | 52 (15.8) | 5 (19.2) | 11 (16.4) | 23 (13.1) | 13 (21.3) | 0.451 |
Shockable initial rhythm | 41 (12.4) | 3 (11.5) | 7 (10.4) | 21 (11.9) | 10 (16.4) | 0.757 |
Bystander CPR | 105 (31.8) | 10 (38.5) | 18 (26.9) | 55 (31.3) | 22 (36.1) | 0.611 |
MAP at ROSC (mmHg) | 93 (68–114) | 81 (43–94) | 89 (67–105) | 89 (68–113) | 111 (85–137) | <0.001 |
HR at ROSC (beats/min) | 120 (98–144) | 47 (32–51) | 84 (76–94) | 124 (113–136) | 161 (155–175) | <0.001 |
No-flow time (min) | 4 (0–12) | 4 (1–14) | 5 (0–12) | 4 (0–11) | 1 (0–9) | 0.194 |
Low-flow time (min) | 26 (17–36) | 37 (18–46) | 27 (18–36) | 25 (17–34) | 24 (15–32) | 0.047 |
Total epinephrine dose (mg) | 3 (2–4) | 3 (2–7) | 4 (2–5) | 3 (2–4) | 2 (1–3) | <0.001 |
Sustained ROSC | 281 (85.2) | 18 (69.2) | 54 (80.6) | 149 (84.7) | 60 (98.4) | 0.002‡ |
One-month survival | 58 (17.8) | 4 (15.4) | 11 (16.1) | 26 (15.1) | 17 (27.9) | 0.153 |
Good neurologic outcome | 23 (7.0) | 2 (7.7) | 4 (6.0) | 5 (6.0) | 5 (6.0) | 0.965 |
Data are expressed as median (interquartile range) or number (%) as appropriate. Bradycardia, HR < 60 beats/min; normal, 60 ≤ HR ≤ 100 beats/min; tachycardia, 100 < HR < 150 beats/min; extreme tachycardia, HR ≥ 150 beats/min; HR, heart rate; CPR, cardiopulmonary resuscitation; MAP, mean arterial pressure; ROSC, return of spontaneous circulation.
In terms of the outcomes, the sustained ROSC was achieved in 60 of 61 patients (98.4%) in the extreme tachycardia group, and the rate of the sustained ROSC was highest in the extreme tachycardia group and lowest in the bradycardia group (Table
The probability of sustained ROSC according to heart rate. ROSC, return of spontaneous circulation.
In the multivariable logistic regression analysis, the extreme tachycardia group was independently associated with a high probability of sustained ROSC compared to the normal HR group (OR 11.297; 95% CI 1.350–94.527;
Multivariable logistic regression analysis for the outcomes.
Sustained ROSC | One-month survival | Six-month good neurologic outcome | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | ||||||
Heart rate group | |||||||||||
Bradycardia | 0.79 | (0.23–2.75) | 0.711 | 1.92 | (0.41–9.10) | 0.411 | 1.69 | (0.29–9.82) | 0.558 | ||
Normal HR | 1.00 | (Reference) | 1.00 | (Reference) | 1.00 | (Reference) | |||||
Tachycardia | 1.23 | (0.54–2.82) | 0.624 | 0.70 | (0.27–1.79) | 0.449 | 0.79 | (0.29–2.16) | 0.642 | ||
Extreme tachycardia | 11.30 | (1.35–94.53) | 0.025∗ | 0.82 | (0.27–2.49) | 0.724 | 0.92 | (0.28–3.08) | 0.896 | ||
Age, per 10 years | 0.85 | (0.66–1.11) | 0.230 | 0.82 | (0.66–1.02) | 0.079 | 0.80 | (0.63–1.02) | 0.073 | ||
Male | 0.73 | (0.34–1.57) | 0.427 | 2.15 | (1.02–4.55) | 0.045∗ | 3.45 | (1.56–21.50) | 0.009 | ||
Witnessed arrest | 2.15 | (0.91–5.11) | 0.083 | 1.30 | (0.49–3.46) | 0.605 | 0.96 | (0.34–2.65) | 0.929 | ||
Public place | 1.84 | (0.56–6.02) | 0.313 | 1.11 | (0.42–2.96) | 0.829 | 1.83 | (0.66–5.07) | 0.245 | ||
Shockable initial rhythm | 1.19 | (0.37–3.84) | 0.268 | 3.03 | (1.22–7.51) | 0.017∗ | 3.18 | (1.25–8.10) | 0.015 | ||
Bystander CPR | 1.67 | (0.67–4.16) | 0.268 | 1.81 | (0.76–4.34) | 0.182 | 1.87 | (0.71–4.91) | 0.205 | ||
Total epinephrine dose, per 1 mg | 0.89 | (0.75–1.05) | 0.152 | 0.69 | (0.52–0.92) | 0.011 | 0.77 | (0.57–1.04) | 0.083 | ||
MAP ≥ 80 mmHg at ROSC | 0.90 | (0.43–1.88) | 0.778 | 2.21 | (0.98–4.97) | 0.056 | 1.84 | (0.76–4.43) | 0.175 | ||
No-flow time, per 1 min | 1.02 | (0.98–1.06) | 0.395 | 0.95 | (0.91–1.00) | 0.057 | 0.94 | (0.89–0.99) | 0.042∗ | ||
Low-flow time, per 1 min | 0.99 | (0.97–1.02) | 0.716 | 0.95 | (0.91–0.98) | 0.005∗ | 0.94 | (0.91–0.98) | 0.007∗ |
Bradycardia, HR < 60 beats/min; normal, 60 ≤ HR ≤ 100 beats/min; tachycardia, 100 < HR < 150 beats/min; extreme tachycardia, HR ≥ 150 beats/min. ROSC, return of spontaneous circulation; OR, odds ratio; CI, confidence interval; HR, heart rate; CPR, cardiopulmonary resuscitation; MAP, mean arterial pressure.
The median NT-proBNP concentration in total patients was 1403 [277–4579] pg/mL. The NT-proBNP concentration was significantly lower in the extreme tachycardia group than in the normal HR group (874 [164–2902] pg/mL and 2277 [519–8743] pg/ml in the extreme tachycardia group and normal HR group, respectively;
In the present study, patients with extreme tachycardia (HR ≥ 150 beats/min) had the highest rate of sustained ROSC, and extreme tachycardia was an independent factor for the probability of sustained ROSC.
The myocardium is damaged by ischemia and reperfusion injury and electrical shock during cardiac arrest and resuscitation. It leads to reduced contractility and compliance of myocardium, and severe myocardial dysfunction has been reported to be associated with high mortality in the early postcardiac arrest period [
Myocardial dysfunction after cardiac arrest has been measured directly or indirectly using pulmonary artery catheterization, echocardiography, blood pressure, and several biomarkers such as troponin and NT-proBNP concentrations. Low cardiac output measured by pulmonary artery catheterization was common in patients after ROSC from cardiac arrest, but the association of cardiac output with outcomes was unclear [
In this study, extreme tachycardia was associated with the high probability of sustained ROSC. However, Redwood et al. reported that higher HR in acute myocardial ischemia was associated with increased myocardial infarct size in the experimental model, while reduced HR may show a beneficial effect because of the decrease in myocardial oxygen consumption and prolongation of total diastolic time which affects coronary collateral flow [
This difference could be explained by the
Although extreme tachycardia showed a high rate of sustained ROSC, it showed no association with the six-month good neurologic outcome. Nevertheless, HR is still important since early prognostication is valuable to the determination of the treatment and disposition plan for OHCA patients, and it is an easily and immediately measurable parameter. Based on the results of the present study, patients with extreme tachycardia after ROSC should be paid more attention in regard to postresuscitation care such as primary coronary intervention and targeted temperature management, while hemodynamic support should be continued for all patients including those without extreme tachycardia after ROSC.
This study has some limitations. First, this study was performed retrospectively in a single institution. Therefore, the results might not be generalizable to other institutions, so a multicenter study is warranted.
Second, echocardiography was not performed immediately after ROSC, so the exact cardiac function could not be investigated. Instead, NT-proBNP was used as an indicator of cardiac function.
Third, we analyzed HR only at the time of ROSC and did not analyze the change with time. Depending on cardiac function and type and dose of vasopressors and inotropes, HR could be different with time. However, although we mainly retrieved HR from the ECG taken immediately after ROSC, HR could be easily measured with cardiac monitoring. Therefore, it is worth noting that a simple HR measurement could be used as an independent predictor of sustained ROSC.
Extreme tachycardia (HR ≥ 150) at the time of ROSC is associated with a high probability of sustained ROSC in nontraumatic adult OHCA patients.
The data used to support the findings of this study have not been made available because the authors were not allowed to share the patients’ information.
The authors declare that they have no conflicts of interest regarding the publication of this article.