Acute myocardial infarction in young adults: features of pathogenesis, disease course and justification of strategy for prevention of complications

We retrospectively and prospectively studied 835 patients with acute myocardial infarction (AMI) under the age of 45 and older. Depending on age, patients were divided into two groups: < 45 years and ≥ 45 years. In 189 patients under 45 years of age, the main risk factors leading to the development of ST-elevation myocardial infarction were male sex (OR 6.58; 95 % CI (2.64–16.41), smoking (OR 2.02; 95 % CI (1.44–2.82) and family history of premature coronary artery disease (OR 1.75; 95 % CI (1.21–2.54). According to coronary angiography, AMI patients under 45 years of age in most cases showed no hemodynamically significant coronary vessels damage and had a different course of AMI caused by other reasons – aneurysms of the coronary arteries, muscle bridges, coronary spasm, spontaneous dissections. It was found that 10 % of young patients who did not have obstructive lesions of coronary vessels, according to magnetic resonance imaging (MRI) had focal myocarditis. However, it is noted that in patients under 45 years of age, the presence of familial hypercholesterolemia (FH) may affect the development of AMI. Thus, according to the DLCNS criteria, FH was more frequently reported in young patients than in patients older than 45 years (7.34 % vs 1.32 % (p<0.05)). Hospital course of AMI in young adults was more favorable, with fewer complications. Data from studies of flow-dependent vasodilation have shown that young patients have worse endothelial function on the 1st day of AMI (p=0.043), but better recovery of it in the dynamics of observation. However, in young patients, early (day 7, p=0.029) and late (day 90, p=0.041) left ventricular dilatation was more commonly reported compared with older patients. According to the MRI data on day 1 and in the dynamics (90 days), it was found that, despite the higher prevalence of AMI, young patients have better recovery of contractile myocardial function. The arrhythmogenic substrate (according to late ventricular potential) for life-threatening arrhythmias was more commonly recorded in the older age group at the beginning of the development of AMI, but it was detected with the same frequency in both groups during prolonged observation (6–12 months). Despite better survival and fewer complications during long-term follow-up (4.9 years on average), the greatest impact on the development of the combined endpoint (cardiovascular death / recurrent myocardial infarction / stroke) and death from any cause was made by the patients’ age up to 35 years (best prognosis), concomitant hypertension (worsens prognosis) and low left ventricular ejection fraction (increases complications). The study indicates the possibility of implementing a secondary prevention system in AMI patients of young age through careful (active) observation and control of adherence to treatment and the adequacy of its implementation.