IJCS | Volume 32, Nº2, March/April 2019

168 Figure 2 - Bias risk of selected studies. Lei & Bin Differences of risk factors in young AMI patients Int J Cardiovasc Sci. 2019;32(2)163-176 Review Article analysis. No significant differences were observed in the analysis (p = 0.07), as there were no obvious differences between young and older AMI patients regarding LVEF values. Three studies 10,14,15 reported chest pain in AMI patients (figure 6), and heterogeneity was observed regarding the outcome (p = 0.01, I 2 = 77%). Thus, the random-effect model was used to perform the analysis. No significant differences were found between the two groups (p = 0.13). There were no obvious differences regarding the incidence of chest pain between young and older AMI patients. Three studies 13,15,17 reported all-cause mortality in AMI patients (figure 6), with lowheterogeneity being observed in the studies (p = 0.65, I 2 = 0%); thus, the fixed-effect model was used to perform this analysis. Significant differences were observed in the analysis (OR = 0.09, 95% CI: 0.07 to 0.12). When compared with older AMI patients, young AMI patients had obviously a lower rate of all-cause mortality (6.43% vs 41.57%). Five studies 11,14-17 compared the outcome of coronary angiography (CA) between young and older AMI patients. Significant differences were observed between the two groups (figure 7). Compared with older AMI patients, single-vessel disease was more prevalent in young AMI patients (OR = 2.48, 95% CI: 1.87 to 3.29). A total of 42.86%of young AMI patients had single-vessel disease, which was more prevalent than that in older AMI patients (18.71%). Whilemultiple-vessel disease was more common in older AMI patients (OR = 0.42, 95% CI: 0.28 to 0.61), with 38.77%of older AMI patients exhibiting multiple-vessel disease, which was a higher incidence than that in young AMI patients (34.28%). Moreover, we compared the coronary artery disease location in young and older AMI patients, which included left Anterior descending artery (LAD), right coronary artery (RCA) and left circumflex artery (CX). No significant differences were observed in the coronary artery disease location of LAD (p = 0.22), RCA (p = 0.36) and CX arteries (p = 0.11) between young and older AMI patients. Discussion The incidence of AMI in young individuals was once as low as 2-6%, 4 but it has been increasingly rising. 14 Young AMI patients differed from older AMI patients in several ways including risk factors, clinical, coronary angiographic characteristics and prognosis. 8 Yunyun et al. 12 said that AMI tend to occur suddenly in young patients; most young people do not experience a warning before its onset, and the first occurrence often leads to a large infarction size. 18,20 . Zimmerman et al., 21 reported that males show an absolute predominance among young AMI patients; however, there is a tendency for the incidence of myocardial infarction to be equal in both sexes with increasing age. In our meta-analysis, male patients were predominant among young AMI patients,