Young patients with acute myocardial infarction (AMI) are a specific subset of a population with different risk factor profiles, clinical presentations, and prognosis as compared to older AMI patients. Higher prevalence of current smoking, hyperlipidemia, and family history and favorable outcome are evidenced in young AMI patients. Better understanding of the disease-related features might lead to further improvements in the management of this patient population. The present review thus focuses on the prevalence, risk factors, presenting symptoms, potential underlying pathogenesis, coronary angiographic features, therapy, and prognosis of young patients with AMI.
Young adults aged <45 years represent a relatively small portion of those having acute myocardial infarction (AMI) and account for only 3%–10% of the total. However, they are an important group to examine with regard to risk factor modification and secondary prevention. AMI in young patients has some important different characteristics from that in older patients. The majority of sufferers are men; however, an increasing prevalence is being observed among women. Coronary angiography (CAG) studies performed in young AMI patients have revealed a relatively high incidence of normal coronary arteries, nonobstructive coronary lesions, and single-vessel coronary artery disease. Risk factor analysis in young patients with AMI has identified a high prevalence of current smoking, hyperlipidemia, and family history compared with that found in older patients; however, the most important modifiable risk factor is smoking. Other conventional risk factors are less strongly associated as in older patients. Overall, the young patients with AMI have a more favorable outcome prognosis.
Recent studies have shown a significant rise of AMI prevalence in younger age. This review focuses on the prevalence, risk factors, potential underlying pathogenesis, diagnosis, therapy, and prognosis in young patients with AMI.
Two to ten percent of AMI patients are <45 years old. The majority of sufferers are male; however, an increasing prevalence is being observed among females, accounting for 25% AMI patients <45 years old.
Young AMI patients have a different risk factor profile compared with older patients, characterized by a high prevalence of current smoking, hyperlipidemia, and family history of premature coronary artery disease and are less likely to have a history of hypertension and hypercholesterolemia. Al-Khadra reported that the smoking rate is as high as 76.9% in young male AMI patients. Singh et al. showed that smoking was present in 64.86% of male and 0% of female AMI patients; a family history of coronary artery disease was present in 54.05% of male and 23.07% female AMI patients, and hyperlipidemia was documented in 48.64% of male and 38.46% of female AMI patients. Obesity affects 35%–58% of young patients with AMI. However, other classical risk factors are seen less frequently such as type 2 diabetes mellitus which affects only 3%–5% of young patients with AMI. A variety of other possible contributing factors include substance abuse, environmental influence, and oral contraceptive use in young AMI patients.
Compared to older patients young patients with AMI have a more favorable prognosis. Rathod et al. analyzed 3618 ST-elevation myocardial infarction (STEMI) patients in London between January 2004 and September 2012 (367 were aged ≤45 years; 3251 were aged >45 years). The study revealed that in-hospital major adverse cardiac events (MACEs) rates tended to be lower and the 30-day MACE rate was significantly lower (2.7% vs. 6.9%; P = 0.008) in young AMI patients compared to older AMI patients. Long-term follow-up mortality rates and MACE rates were also significantly lower in young AMI patients compared with older AMI patients (2.7% vs. 12.5%; P < 0.0001 and 12.8% vs. 22.9%; P < 0.0001, respectively). Jing et al. reported that despite a 5-fold lower long-term mortality than older AMI patients; young AMI patients had significantly greater risk of long-term mortality than an age-matched background population. Although AMI prevalence is lower in young women than in young men , young female AMI patients have worse pre-event health status, more comorbidity, and higher in-hospital or long-term mortality as compared with young male AMI patients. Sadowski et al. reported that 12-month mortality was significantly higher in young female STEMI patients than in young male STEMI patients (10.8% vs. 3.0%; P = 0.003). Dreyer et al. showed that young female AMI patients had more comorbidities and significantly lower generic mean health scores compared with young male AMI patients (short form-12 physical health = 43 ± 12 vs. 46 ± 11 and mental health = 44 ± 13 vs. 48 ± 11). Their disease-specific health status was also worse, with more angina (Seattle angina questionnaire measures = 83 ± 22 vs. 87 ± 18), worse physical function (physical limitation = 78 ± 27 vs. 87 ± 21), and poorer quality of life (55 ± 25 vs. 60 ± 22, P < 0.0001 for all). Dreyer also revealed that young female AMI patients have a higher 30-day all-cause readmission rate than young male AMI patients (15.5% vs. 9.7%, P < 0.0001).
The main cause of AMI in young adults is atherosclerosis, usually affecting one coronary artery, and accounts for 80% of cases.[30] The most frequent mechanisms of cases without significant atherosclerosis are as coronary artery embolism (5%), thrombosis (5%), anomalies (4%), and inflammation or spasm of the vessel. In addition, a variety of other possible contributing factors, such as vasospastic tendencies, coronary artery anomalies, spontaneous coronary artery dissection, hypercoagulable state, Vitamin B12 deficiency, coronary microvascular dysfunction and a history of Kawasaki disease, have also been implicated for the pathogenesis of AMI in young patients without significant atherosclerosis.
Clinical presentation and comorbidities features
Chest pain is the leading symptom for young AMI patients and these patients are less likely to have previous myocardial infarction, myocardial revascularization, or to have left ventricular systolic impairment or renal impairment . Gupta et al. revealed that comorbidities were more prevalent in women as compared with men including congestive heart failure, hypertension, renal failure, chronic obstructive pulmonary disease, and diabetes mellitus. Dyslipidemia, however, was more prevalent in men than women.
Depressive symptoms
A high rate of lifetime history of depression and depressive symptoms at the time of an AMI was observed in young AMI patients. Smolderen et al. showed that more women than men experienced depressive symptoms (39% vs. 22%, P < 0.0001) at the time of admission for AMI. Moreover, young AMI patients with depressive symptoms had higher levels of stress and worse quality of life than young AMI patients without depressive symptoms (P < 0.001).
Sexual function impairment
Valued sexuality serves as an important index for quality of life before and after AMI in young adults. Lindau et al. prospectively analyzed 2802 patients (67.4% women) and found that impaired sexual activity and incident sexual function problems were more prevalent and common among young patients after AMI. In addition, they also observed that more than half of the women had sexual function problems in the year after AMI and women were more likely to develop incident sexual function problems than men after AMI. Despite the high prevalence of sexual function problems, particularly among women, few participants searched for medical help from physicians in an effort to resume sex after an AMI.
It is important to note that physicians are less likely to consider cardiac cause and may misdiagnose chest pain complaint for other diseases in young age group. In addition, young AMI patients have different risk factor profiles, clinical presentations, and prognoses when compared with older AMI patients. Thus, it is important to identify this patient cohort and make efforts to educate young AMI patients on the importance of smoking cessation and lifestyle modification to effectively control hyperlipidemia and other potential risk factors found in these patients.
Single vessel disease, the left anterior descending artery-related infarcts, anterior wall AMI, thrombectomy use, and procedural success were significantly more common in young AMI patients compared with older AMI patients whereas the right coronary artery-related infarcts, left main complex disease, and multi-vessel disease were less common [Table 1]. Moreover, the shorter (24.4 mm vs. 24.7 mm, P = 0.018), larger (3.5 mm vs. 3.3 mm, P < 0.001), and fewer number of (1.4 vs. 1.5, P = 0.002) stents were more frequently used in young AMI patients during the index PCI. Although there was no significant difference in preprocedure TIMI flow 0, young AMI patients had a higher incidence of postprocedure TIMI flow.
Since there are increased trends in the frequencies of comorbidities and in-hospital or long-term mortality for women hospitalized with AMI in the past decade, young female AMI patients justified special care to improve the outcome. Moreover, impaired sexual activity and incident sexual function problems are prevalent and more common among young women than men in the year after AMI. Therefore, efforts should be made to improve the sexual function in young AMI patients. A recent study showed that attention to modifiable risk factors and physician counseling are effective strategies to improve outcome in young AMI patients.
AMI carries significant morbidity, psychological effects, and financial constraints for the affected person and the family when it occurs at a young age. Young AMI patients present with different risk factors and CAG features when compared with older AMI patients. Further investigations are needed to identify the biological, clinical, and social factors that contribute to the development of AMI in young patients.