Out-of-Hospital Cardiac Arrest in the Young: A 23-Year Middle Eastern Experience.

BACKGROUND: Worldwide, limited data are available about young patients (≤40 years) who present with out-of-hospital cardiac arrest (OHCA). We compared demographic characteristics, clinical presentation, and outcome in younger patients (≤40 years) versus older patients (>40 years) with OHCA.
MATERIALS AND METHODS: This was a retrospective analysis of a registry of patients hospitalized with OHCA over a 23-year period (1991-2013) in Hamad Medical Corporation, Doha, Qatar.
RESULTS: Of 1146 patients admitted to our institution with OHCA, 159 patients (13.9%) were 40 years of age or younger. Compared to the older group (>40 years), younger group patients were more likely to be males (84.9% vs. 71.5%; P = 0.001) and to be smokers (27.7% vs. 19.7%; P = 0.012). They are less likely to have diabetes (6.3% vs. 49.2%; P = 0.001), hypertension (8.3% vs. 49.9%; P = 0.001), prior myocardial infarction (3.1% vs. 23.4%; P = 0.001), or chronic renal disease (0% vs. 8.5%; P = 0.001). There was no significant difference in ejection fraction, ST-elevation myocardial infarction (13.2% vs. 15.7%; P = 0.41), utilization of inotropes (36.5% vs. 44%; P = 0.08), or utilization of reperfusion therapy (thrombolytic: 16.4% vs. 12.2%, P = 0.14, and percutaneous intervention: 6.3% vs. 5.3%, P = 0.60, for the younger and older groups, respectively); on the other hand, younger patients were more likely to receive antiarrhythmic medications (33.3% vs. 21.2%; P = 0.001). Inhospital mortality was lower in the younger group (52.1% vs. 68.3%; P = 0.001) even after adjustment for baseline variables.
CONCLUSION: In the Middle East it is not uncommon to present with OHCA in young age. These patients are predominantly males, more likely to present with arrhythmia and they have a better survival rate. Copyright:

INTRODUCTION

Out-of-hospital cardiac arrest (OHCA) is one of the leading causes of death in the United States. Annually, more than 300,000 deaths due to OHCA are reported.[123] Despite the significant advancement in the management of cardiac diseases, the mortality rate has changed only minimally over the past three decades. However, limited data are available about OHCA in the young.[3]

Between 2000 and 2009 in Melbourne, Australia, the incidence of OHCA in <40 years of age was 13%. They found that survival-to-hospital discharge rates from OHCA due to a “presumed cardiac” precipitant in young adults are much better than older adults; however, all-cause OHCA survival was similar.[4]

We aimed to study this age group (≤40 years) in regard to demographic data, clinical presentation, and prognosis in the Middle East population.

MATERIALS AND METHODS

Study population

The state of Qatar is located in the Middle East and has an estimated population of 2,045,239 in 2013. The male-to-female ratio is 3 to 1. Around 70% are younger than 40 years of age. The majority of the population is from Eastern Asia (>50%).

The Heart Hospital and the Cardiology Department Database at Hamad General Corporation were used for this study. Data on all patients admitted to Hamad General Hospital with cardiac illnesses were maintained electronically in the department. The Hamad Medical Review Board approved the investigation before data analysis. Data were collected from the hospital clinical records according to predefined criteria on the past medical history and clinical findings during the index admission. These records have been coded and registered at the cardiology department since January 1991.

Informed consent was waived by the Institutional Review Board, Medical Research Center, Hamad Medical Corporation. All patients' information and records were anonymized and de-identified before analysis.

Definitions

OHCA was defined as the absence of signs of cardiac circulation that happened outside the hospital setting. The study population consisted of adult patients who had an OHCA and were successfully resuscitated with the return of spontaneous circulation. Only those with OHCA of presumed cardiac etiology and admitted to the department of cardiology were included in this study. Patients with OHCA who died at the scene, during transportation to the hospital, in the emergency room before admission to the cardiac unit, or were dead on arrival were excluded, along with those who had OHCA secondary to noncardiac causes.

All patients hospitalized after sustaining OHCA within the 23-year period from January 1991 to 2013 were retrospectively identified. Patients then subclassified into two groups – Group 1: ≤40 years of age (the younger group) and Group 2: more than 40 years of age.

Statistical analysis

Data were presented as the mean ± standard deviation and median with interquartile range for interval variables and as the frequency and percentage for categorical variables. Baseline demographic characteristics, past medical history, clinical presentation, medical therapy, cardiac procedures, and clinical outcomes were compared between the OHCA (≤40 years) and OHCA (>40 years) groups using independent Student's t-tests and Chi-squared tests for interval and categorical variables, respectively. Variables influencing inhospital mortality were assessed using univariate logistic regression.

Risk factors along with other modified variables significant at the univariate level were considered for multivariate logistic regression analysis. Adjusted odds ratios, 95% confidence intervals, and P values are reported for predictors. All P values are the result of two-tailed tests and values of 0.05 were considered to be statistically significant. The Statistical Package for the Social Sciences version 19.0 software (SPSS Inc., Chicago, IL, USA) was used for the analysis.

RESULTS

Of 1146 patients admitted to our institution with OHCA, 159 patients (13.9%) were 40 years of age or younger.

Demographic and clinical characters

Compared to the older group (>40 years), younger group patients were more likely to be males (84.9% vs. 71.5%; P = 0.001) and to be smokers (27.7% vs. 19.7%; P = 0.012). They are less likely to have diabetes (6.3% vs. 49.2%; P = 0.001), hypertension (8.3% vs. 49.9%; P = 0.001), prior myocardial infarction (3.1% vs. 23.4%; P = 0.001), or chronic renal disease (0% vs. 8.5%; P = 0.001). The baseline demographic and clinical characteristics for both the groups are summarized in Table 1.

Table 1

Demographic and clinical characteristics

Variable	OHCA with age ≤40 years (n=159; 13.9%)	OHAC with age >40 years (n=985; 86.1%)	P
Gender (male)	135 (84.9)	704 (71.5)	0.001
Smoking	44 (27.7)	194 (19.7)	0.02
DM	10 (6.3)	485 (49.2)	0.001
Hypertension	13 (8.2)	492 (49.9)	0.001
Cholesterol	7 (4.4)	65 (6.6)	0.29
Family history	5 (3.1)	14 (1.4)	0.12
Previous MI	5 (3.1)	230 (23.4)	0.001
Chronic renal failure	0 (0)	84 (8.5)	0.001

DM: Diabetes mellitus, MI: Myocardial infarction, OHCA: Out-of-hospital cardiac arrest

The younger group was less likely to complain of dyspnea preceding the OHCA compared to the elder group (5.7% vs. 27.1%; P = 0.001). However, angina, dizziness, palpitation, and unwitnessed cardiac arrest were similar in both the groups as preceding symptoms [Table 2].

Table 2

Comparison of preceding cardiac symptoms between the groups

Variable	OHCA with age ≤40 years (n=159; 13.9%)	OHAC with age >40 years (n=985; 86.1%)	P
Angina	42 (26.4)	297 (30.2)	0.34
Dyspnea	9 (5.7)	267 (27.1)	0.001
Dizziness	5 (3.1)	30 (3.0)	0.95
Palpitations	7 (4.4)	37 (3.8)	0.69

OHCA: Out-of-hospital cardiac arrest

Investigations and treatment

There was no significant difference in ST-elevation myocardial infarction (13.2% vs. 15.7%; P = 0.41), ejection fraction, utilization of inotropes (36.5% vs. 44%; P = 0.08), or utilization of reperfusion therapy (thrombolytic: 16.4% vs. 12.2%, P = 0.14, and percutaneous intervention: 6.3% vs. 5.3%, P = 0.60, for the younger and older groups, respectively) [Table 3].

Table 3

Medical therapy initiated on hospital admission

Variable	OHCA with age ≤40 years (n=159; 13.9%)	OHAC with age >40 years (n=985; 86.1%)	P
Antiarrhythmics	53 (33.3)	209 (21.2)	0.001
Beta-blockers	35 (22)	181 (18.4)	0.28
Calcium channel blockers	1 (0.6)	45 (4.6)	0.02
ACEI/ARB	30 (18.9)	190 (19.3)	0.90
ASA	76 (47.8)	585 (59.4)	0.006
Clopidogrel	27 (17)	196 (19.9)	0.39
GP2b3a	2 (1.3)	19 (1.9)	0.56
Heparin or LMWH	57 (35.8)	373 (37.9)	0.63
Inotropes	58 (36.5)	433 (44)	0.08
Diuretics	20 (12.6)	283 (28.7)	0.001
Thrombolytic treatment	26 (16.4)	120 (12.2)	0.14
PCI	10 (6.3)	52 (5.3)	0.60
Shockable rhythm	23 (14.5)	183 (18.6)	0.21
STEMI	21 (13.2)	155 (15.7)	0.41

OHCA: Out-of-hospital cardiac arrest, STEMI: ST-elevation myocardial infarction, ACEI/ARB: Angiotensin-converting enzyme inhibitor/angiotensin-receptor blocker, LMWH: Low molecular weight heparin, PCI: Primary percutaneous intervention, ASA: Acetylsalicylic acid

Regarding the medications administered, there was no significant difference in beta-blockers (22% vs. 18.4%; P = 0.28), angiotensin-converting enzyme/angiotensin-receptor blockers (ACEI/ARBs) (18.9% vs. 19.3%; P = 0.9), clopidogrel, heparin, or inotropes. However, the younger group was less likely to receive aspirin, calcium channel blockers, and diuretics. On the other hand, younger patients were more likely to receive antiarrhythmic medications (33.3% vs. 21.2%; P = 0.001).

Mortality

Inhospital mortality was lower in the younger group (52.1% vs. 68.3%; P = 0.001; P = 0.001) which was statistically significant and even after adjustment for baseline variables [Table 4].

Table 4

Multivariate logistic regression analysis for inhospital mortality

Variable	Adjusted OR	95% CI	P
Age ≥40 years	1.62	1.10-2.40	0.02
Gender male	0.81	0.58-1.14	0.23
Smoking	0.70	0.53-0.98	0.04
DM	1.60	1.20-2.17	0.003
HTN	0.77	0.57-1.05	0.09
CRF	2.38	1.30-4.40	0.006
Old MI	1.0	0.71-1.41	0.99

OR: Odds ratio, CI: Confidence interval, DM: Diabetes mellitus, MI: Myocardial infarction, HTN: Hypertension, CRF: Cardiorespiratory fitness

Trends

During the 23-year study period, although the absolute number of both groups patients with OHCA increased over time [Figure 1a and b], the incidence per 100,000 population actually decreased [Figure 2]. This is explained by the fact that although the population of Qatar has nearly tripled since 2001 (600,000 population in 2001 and 2 million in 2013),[5] this growth is largely due to the coming of a young healthy workforce to the state of Qatar. Moreover, this is a preselected group of healthy individuals who had undergone preemployment health screening before arrival in the country.

Figure 1

(a): Growth of Qatar population, (b) out-of-hospital cardiac arrest in the young

Figure 2

Out-of-hospital cardiac arrest in the young – temporal trend corrected to 100,000 population

DISCUSSION

Clinical characteristics

It is well established that the incidence of cardiac arrest increases dramatically with increasing age in both men and women, although the incidence of sudden death is higher in men than in women[6] with men being 2–3 times more likely to experience sudden cardiac arrest than women. Consistent with previous studies, we observed a significant male predominance among the younger group with OHCA. They were more smokers than the older group. This can be explained by that they are young, free of limiting diseases and less life.

Presentation and treatment

The low percentage of using aspirin in the younger group (47.8%) along with a higher percentage of using antiarrhythmic medication can suggest an arrhythmic nature of cardiac arrest in the younger group. However, the older group also had a low percentage of using aspirin which may be explained by the high risk of bleeding in the older group.

We noticed also that there is a low percentage of beta-blocker and ACEI/ARB usage in both the groups; this is likely due to postcardiac arrest borderline/low blood pressure as both the groups had a high percentage of using vasopressors as well.

Outcome

Mortality following cardiac arrest is multifactorial. Younger age, fewer risk factors, fewer comorbidities and less ischemia are all contributors to a better prognosis. In our study, we found that patients with OHCA younger than 40 years old had a better survival rate than the older group even after adjustment of variable factors. These data were correlated with data from the nationwide Danish Cardiac Arrest Registry (2001–2011), which found that working-age patients and early senior patients had better survival in 30 days compared to late senior patients with OHCA.[7]

Limitations

The study data are limited to a single tertiary hospital in the Middle East and reflect a regional sample of patient population limited to this center. Furthermore, in our study, the limitations are inherent in all studies of observational design. The accuracy of the findings of the study depends on the accuracy of the collected data, which are difficult to verify in a retrospective manner. Because of the retrospective nature of the study, missing observations could not be used in multivariate analysis, and this may have affected the results.

During the 20 years of the study, there was a 4-fold increase in the population of the state of Qatar mainly because of the inflow of workforce of young healthy males, which may have influenced the referral pattern.

CONCLUSION

Young age group (<40 years of age) who presented with OHCA was observed to be common in the Middle East. Those patients are predominantly males, they are more likely to present with arrhythmia, and they have a better survival rate comparing to the older group.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.