Acute Myocardial Infarction in Libyan Patients below 45 Years of Age

Prevalence and Risk Factors

Abstract

Background and Aims: 

Acute myocardial infarction (AMI) below 45 years of age constitutes a specific subset of population having different risk factors and clinical features as compared to older patients. The aim of the study was to assess the frequency and risk factors of AMI in patient's ≤45 years of age.

Patients and Methods: 

A cross-sectional retrospective study was conducted involving 187 patients with clinical diagnosis of AMI. They were studied for risk factors, clinical characteristics, coronary angiographic finding and in-hospital outcome during January 2015 and December 2015 at Benghazi medical center, Benghazi - Libya.

Results: 

Out of total 187 AMI patients studied, there were 41 (22%) young patient ≤45 years of age. Risk factors was studied, smoking was found in 63.4% of young patients, 44% were had history of dyslipidemia, 14% had history of alcohol drinking and 12% had family history of coronary artery disease. In young AMI patients, anterior wall STEMI was the most common site and single vessel disease was the most common finding in coronary angiography. However, 13% of patients have normal or non-obstructive coronary lesions. Arrhythmia (24%) and heart failure (17%).

Conclusion: 

In our young AMI patients, smoking was the single most important modifiable risk factor, other conventional risk factors are less strongly associated than older patients. Our young patients tend to have less extensive coronary artery lesions. The presence of normal or non-obstructive coronary lesions would suggest possibility of different mechanism of myocardial necrosis.

INTRODUCTION

Acute myocardial infarction (AMI) in young adults is relatively low when compared with older population.[¹] The prevalence of young patients of less than 45 years of age among AMI patients is variable depending on the population studied and generally ranges from less than 2 to 10%.^[2–5] It has been observed that there is high prevalence of current smoking, hyperlipidemia, obesity, and family history of coronary artery disease (CAD) among young ACS patients and the clinical outcome in this group of ACS patients is better than older population.^[6–9] Most of the studies involving young ACS patients are reported from Western countries and presently, there is no contemporary data on the prevalence, risk factors, clinical characteristics, and outcome of such patients in the developing countries and even in Libya. Thus. The aim of this study was to assess the prevalence and risk factors of AMI patients ≤45 years of age from Libya.

PATIENTS AND METHODS

We included in our study all AMI patients younger than or equal 45 years of age who were admitted to cardiac care unit at Benghazi medical center from 01/01/2015 to 31/12/2015, and discharged with the diagnosis of AMI according to accepted WHO criteria[¹⁰] (i.e. a) typical symptoms of chest pain lasting for more than 20 minutes. b) ST-segment elevation/depression or new LBBB on ECG tracings, and c) rise and fall of serum cardiac biomarkers such as creatine-kinase MB fraction (CK-MB) and troponi).

Data collection

Data on the following variables were collected: a) demographic characteristics: 1) age and gender, 2) history of heart disease: previous angina or infarct, angioplasty and (CABG), 3) coronary artery diseases risk factors: history of tobacco smoking, arterial hypertension, diabetes mellitus, dyslipidemia, positive family history of CAD and alcohol consumption, 4) AMI data including (type of AMI, time of hospital arrival and use of thrombolytic treatment), 5) diagnostic and therapeutic procedures performed during the CCU stay including (transthoracic echocardiography, stress ECG, diagnostic coronary angiography and revascularization procedures either PCI or CABG), 6) medication administered in CCU, and 7) complications that developed in the CCU.

Statistical analysis

Statistical analysis was performed using the SPSS software (Chicago, Illinois; Version 15.0) was used for all statistical analyses. P value of < 0.05 was considered significant. Data are presented as percentages for discrete variables and as mean ± standard deviation and/or median for continuous variables. Differences in baseline characteristics between age groups were compared using unpaired t-test and Fisher's exact test.

RESULTS

During the study period (from 01-01-2015 to 31-12-2015), there were a total of 187 patients with AMI, 41 (22%) of the patients were ≤ 45 years of age and 146 (78%) were older than 45 years of age (P = 0.003), the mean age was 42 ± 3.2 vs. 61 ± 5.0 years in young and old patients, respectively. The percentage of AMI in young patients to the total number of patients described in [Figure 1]. The frequency of AMI increased with age, the youngest AMI patient was age 32 years old and the oldest was 85 years; [Figure 2 and Figure 3]. The occurrence of AMI in total number of patients was more frequent in men. More men were seen in the younger age group, 33 (80%) of young patients were male compared with 111 (76%) in old patients above 45 years, both variables showed significant statistical difference (P = 0.004). Percentage of female patients with AMI increased in older age group compared to younger patients (24 vs. 19.5%, respectively, P = 0.003).

Figure 1: Frequency of acute myocardial infarction in total patient's cohort

Figure 2: Frequency of acute myocardial infarction in young patients ≤45years

Figure 3: Distribution of AMI according to patients' gender

Risk factors of AMI in both age groups

Smoking was the most frequent risk factor in young patients with AMI, being documented in current smokers (65 vs. 41%) and ex-smokers (20 vs. 13%) in young and old adults, respectively (P =0.001).

The second common risk factor of AMI in young patients was history of dyslipidemia being found in (49.5%) compared to (27%) in old patients (P =0.001).

Alcohol drinking was found in (14.6 vs. 7.5%) in young and old patients, respectively (P = 0.001).

Positive family history of CAD (9.7% vs. 3.4%) in young and old patients, respectively (P = 0.003). In comparison to young AMI patients, older patients had higher frequencies of traditional risk factors like diabetes (44% vs. 63%, P =0.002) and arterial hypertension (27% vs 55%, P =0.003) in young and old patients, respectively. Comparative analysis of both groups revealed that the prevalence of the various risk factors showed statistically significant differences [Table 1].

Table 1: Risk factors of acute myocardial infarction in both age groups

Clinical presentation

Chest pain was the most frequent symptom at hospital admission in both age groups, which were presented in patients (88% vs. 82%) with typical description of ischemic type of chest pain in young and old patients respectively; P = NS.

AMI characteristic

The distribution of STEMI and Non-STEMI was not significantly different between young and older patients 33 (80.5%) of young patients showed STEMI whereas this proportion compared to 116 (79%) in patients older than 45 years; P = NS. The most frequent location of the infarct in the younger group of patients was anterior STEMI in 15 patients (46%), followed by the inferior STEMI in 10 patients (30%), lateral STEMI in 5 patients (15%) and 3 patients presented with new LBBB (9%). The frequency of occurrence in older patients group showed 69 patients (60%) in anterior infarcts compared to inferior STEMI (40 patients, 34%) and lateral STEMI (7 patients, 6%), both variables showed significant statistical difference [Table 2].

Table 2: Distributions of acute myocardial infarction according to electrocardiographic changes

Treatment and complications

Coronary angiographic procedures were carried out in 23 (56%) of young patients and 69 (47.2%) of old patients. Young patients showed less diffuse atherosclerotic lesions as compared to patients of the older age group, in young patients, 39% showed one coronary vessel involvement, 26% two vessel and three-vessel CAD was seen in 22%. The proportion of young patients with normal coronary arteries was 13%. Older patients showed increase in percentage of double vessel involvement in comparison to younger age group and absences of normal coronary arteries on diagnostic coronary angiography post AMI. Single vessel disease was found in (32%), double vessel disease (54%) three vessel disease (14%). Therapeutic percutaneous coronary intervention either by coronary balloon or stents insertion performed in (46 vs. 31%, P = 0.04) of young and old AMI patients, respectively, and the remaining patients were treated medically. Primary percutaneous coronary intervention (PCI) was performed within 24 hours in one young patient (2.4%), he was suffering from extensive anterior STEMI and ventricular arrhythmias and there were no documented cases in older age group. Of the 41 young patients with AMI, 30 patients (73%) received intravenous thrombolytic therapy while in older group thrombolysis was performed only in (55%, P = 0.003). During their admission and stay in the CCU, young patients developed arrhythmias more than old patients (24% vs. 9%) young and old patients, respectively (P = 0.003). Conversely heart failure occurred more frequently in the old patients (22% vs 17.1% in old and young patients, respectively, P = 0.004).

DISCUSSION

In this study, 22% of patients with AMI in Benghazi were ≤45 years of age. In the Global Registry of Acute Coronary Events (GRACE) study, the prevalence of young ACS patients was 6.3%;[¹¹] in the Thai ACS Registry, it was 5.8%;[¹²] and in Spain registry, it was 7%.[¹³]. The proportion of AMI patients under the age of 45 years in Benghazi is considerably higher than other society that's possibly because the changes in life style and smoking habits of Libyan people. Furthermore, the small sample size of this study effect on total percentage of AMI patients and this study doesn't reflect the total number of AMI in young Libyan patients because it is limited to only one center.

Our study showed that AMI in young patients occurred typically in men, 33 (80%) males and 8 (20%) females with male to female ratio was 4:1 comparable with Italian and USA studies in which females were 8% and 19%, respectively.[²³⁴] It is assumed that exposure to endogenous estrogens during the fertile period of life delays the manifestation of atherosclerotic disease in women, before menopause the CHD event rate in women is low and predominantly attributed to smoking. Furthermore, oestrogens have a regulating effect on several metabolic factors, such as lipids, inflammatory markers and the coagulation system. Smoking adversely affects all phases of atherosclerosis given that it hastens thrombotic process, instigates endothelial dysfunction, augments pro inflammatory effects, and induces coronary vasoconstriction even in patients with normal coronary vasculature In this study smoking was found to be the main risk factor in young patients with AMI was affecting 63.4% of young patients and 41.1% in older age group. Cigarette smoking is a well-known risk factor for the development of CAD in young patients. Numerous studies have highlighted elevated rates of tobacco use among very young patients who present with AMI, with percentages ranging from 62% to 90%[¹⁴¹⁵¹⁶].

The results of the Lipid Research Clinics Trail[¹⁷] demonstrated a direct association between the plasma lipoprotein profile, the cholesterol levels and the morbidity and mortality from coronary atherosclerosis. Hyperlipidemia, which is very common in young adults with AMI as per earlier studies[¹⁸¹⁹²⁰]. The prevalence of a history of dyslipidaemia's in young patients with AMI varies from 12% to 80%. In our study the rate was (43.9%) compared to older patients (17.8%),

Unfortunately, in our study, family history of CAD not assessed in all AMI patients, because lack of data in patients records, positive family history of CAD recorded in 9.7% of young patients and only in 3.4% of older group.

In agreement with international studies and reports, the present study has also shown that older patients had an increased frequency of traditional risk factors like diabetes, arterial hypertension. Diabetes mellitus was found to be an important risk factor for coronary disease. In our study the prevalence was (63% vs. 44%) in old and young patients respectively.[²¹²²] Variety of mechanisms may contribute to the increase in CHD risk in patients with diabetes, include endothelial dysfunction, platelet activation and coagulation abnormalities in addition to the effects on blood pressure and lipid metabolism.[²³]

In our study, the rate of use of thrombolytic therapy in young patients was higher than in old age group. The possible reason for the less frequent use of thrombolytic therapy in older patients, is a result of an increase in medical contraindications for this type of therapy in old patients. Only 23 (56%) of young patients underwent diagnostic coronary angiography following AMI, compared to 69 (47%) in older patients. The present findings of predominantly single vessel disease in young patients and multivessel disease in older patients is in accord with international studies.[¹⁴¹⁵²⁴] The predilection for involvement of the left anterior descending artery followed by the right coronary and left circumflex arteries has been noted in other reports of young patients[²⁴²⁵]. On the other hand, most of the older patients had more than one coronary vessel disease and this is possibly due to comorbid diseases like diabetes, arterial hypertension, atherosclerosis and chronic renal impairment.

In our study, the prevalence of arrhythmias among young patients is greater than that found in older patients, was (24% vs. 9%) of young and old patients respectively. The occurrence of heart failure post AMI was slightly greater than that noted in other international studies there were 17% in young patients, this percentage increases significantly when we analyze data from the group of older patients 22%^[26.27]

This study is subject to the usual limitations associated with a retrospective design which is deficit to control group. Because of the low incidence of AMI in young people, the sample size of this study was small. We report only in-hospital outcome, which may be inadequate to assess the true burden of premature coronary disease in Benghazi, also mortality rate of AMI patients is not accurately recorded. Cocaine and other substance abuse deserve more attention and should be asked at hospital admission. The risk of overweight or high body mass index is an important risk factor for CAD which was not documented in our medical records.

In conclusion, AMI in young people has risk factors and clinical features that are different from those in older patients. Smoking was the most common risk factor of AMI followed by dyslipidemia, alcohol consumption and family history in young adults. Acute anterior STEMI owing to occluded left anterior descending artery was most frequent type. The majority of the young patients had single vessel disease while two vessel involvement was common finding in old patients which was seen on coronary angiography. The cessation of smoking would play a major role in preventing MI in young adults. Also, health education about hazard of smoking is an important to prevent AMI in young.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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