Young and older patients with acute myocardial infarction: differences in risk factors and angiographic characteristics.

OBJECTIVE

Although coronary artery disease mainly affects older individuals, the incidence of myocardial infarction (MI) among younger adults (<55 years) has increased during the past decade. Young and older MI patients have different underlying pathophysiologic characteristics, atherosclerotic plaque morphology, and risk factor profiles.

METHODS

We studied 977 patients (≤55 years old: 322, >55 years old: 655) who were hospitalized for MI in the previous 5 years. Patients' baseline characteristics and daily habits were recorded. Angiographic characteristics and vascular lesions were detected, and further examinations, including flow-mediated dilation (FMD), pulse wave velocity (PWV), and central augmentation index (AIx), were performed. Biomarkers of inflammation (Interleukin-6, Tumor-Necrosis factor-a, Intercellular Adhesion Molecule 1, and Osteopontin) were also tested.

RESULTS

The median age in the younger age group was 49 years [interquartile range (IQR: 44-53)] and 66 years (IQR: 61-73) in the older age group. Arterial hypertension was less prevalent in the young compared to the elderly with MI (47.4% vs. 76.2%, p < 0.01). The younger counterparts presented significantly lower rates of diabetes mellitus (19.3% vs. 30.6%, p < 0.01), dyslipidemia (59% vs. 70.8%, p < 0.01), and atrial fibrillation (2.6% vs. 9.7%, p < 0.01) and were more casual smokers (49.3% vs. 23.8%, p < 0.01) compared to older patients with MI. In terms of arterial stiffness, lower PWV [7.3 m/s (IQR: 6.5-8.4 m/s) vs. 9 m/s (IQR: 8-10.8 m/s), p < 0.01] and AIx (20.5 ± 10.8 vs. 25.5 ± 7.8, p < 0.01) were recorded in the young compared to the elderly with MI. Concerning angiographic characteristics, younger patients were more likely to have none or single-vessel disease (55.6% vs. 45.8%, p < 0.02), whereas the older participants more frequently had three or more vessel disease (23.5% vs. 13.6% in the young, p < 0.02). Although significant disparities in blood test results were detected during the acute phase, the great majority of young MI patients were undertreated.

CONCLUSION

Younger patients with MI are more likely to be smokers with impaired PWV measures, present with non-obstructive or single-vessel disease, and often remain undertreated. A better knowledge of the risk factors as well as the anatomic and pathophysiologic processes in young adults will help enhance MI prevention and treatment options in this patient population.