The linear regression model was created to investigate a trend in quarter data of the percentage of young patients’ procedures. The Shapiro-Wilk test checked the normality of model residuals. To check heteroscedasticity, the Brown-Forsythe test was used to examine whether the upper half’s residuals had different variability than those in the lower half (median split). The Durbin-Watson test checked the autocorrelation of residuals.

Two-sided P-values <0.05 were considered statistically significant. All calculations were performed with JMP®, Version 14.2.0 (SAS Institute Inc., Cary, NC, USA).

RESULTS

The data of 237 747 patients with a diagnosis of myocardial infarction were collected in the ORPKI Registry between 2014 and 2017. In that group, 3 208 (1.3%) patients were under 40 years old (mean [SD] age, 34.5 [4.6] vs. 67.3 [11.3] years).

Young patients with myocardial infarction were more frequently men with significantly higher body weight than their older counterparts (Table 1).

Typical risk factors of coronary heart disease in young patients were slightly different from those in the older population, namely diabetes mellitus, arterial hypertension, and chronic kidney disease were less frequent in younger patients than in older patients. However, in the under-40 group, there was a significantly higher number of current smokers. Detailed data regarding the medical history of both groups of patients are presented in Table 2.

Based on patient characteristics on admission to the hospital (Table 3), young patients with AMI had significantly more often diagnosed STEMI with cardiac arrest during the index hospitalization. Even though the rate of direct transport to the primary Percutaneous Coronary Interventions (PCI) center was similar in both groups, time delays from the onset of symptoms to the treatment were lower in the younger group (Table 4).

Radial access was used more frequently in the group of young patients. Still, additional diagnostic devices including intravascular ultrasound (IVUS), optical coherence tomography (OCT), or fractional flow reserve (FFR) were used with similar frequency in both study groups. Moreover, the young patients had more frequently non-significant stenosis in coronary arteries and a single-vessel disease when significant lesions were diagnosed (Table 5).

During the PCI procedure, aspiration thrombectomy was used in the young patients twice as often as in their older counterparts (Table 6).

Moreover, the young patients received thrombolytic therapy more often, and new antiplatelet agents were used more frequently than in the older group. In more than half of the young patients, an infarct-related artery was the left anterior descending artery (LAD, Table 7).

Drug-eluting stents (DES) were used with similar frequency in both study groups, but bare-metal stents (BMS) were implanted more often in the older patients. On the contrary, bioresorbable vascular scaffolds (BVS) were more commonly chosen for the young patients (Supplementary material, Table S1). The percentage of patients with the final complete flow (TIMI grade 3 flow) in the infarct-related artery was similar in both groups. Even though the younger patients have higher body weight than the older ones, the total amount of contrast and total radiation dose during the procedures were lower in the under-40 group (Table 8).

The frequency of periprocedural complications during coronary angiographies and PCI procedures was relatively small and similar in both study groups (Supplementary material, Table S2).

DISCUSSION

According to our study, AMI in young patients seems to be a slightly different medical problem than in older patients. These differences could be observed in several distinct areas. When it comes to demographic data, a typical young patient with AMI is a smoking man. A similar observation was found in other studies [4–6]. Other specific AMI risk factors — like arterial hypertension, diabetes mellitus, or chronic kidney disease — are more often observed in older patients with AMI. Our results are concordant with the results of the study by Chhabra et al. [7]. As we know from previously published studies, the correlation of even one risk factor with the patient’s age may significantly affect his prognosis [12]. Apart from the abovementioned, a significant risk factor of AMI, especially in young patients, is familial hypercholesterolemia. Due to the nature of the data, it was not possible to assess this risk factor’s occurrence in our study population. Clinically, in young patients with AMI, STEMI is more prevalent [1]. It was also described that in young patients with AMI, significant coronary artery stenosis is observed more frequently in the LAD than in other arteries [8], which is concordant with our findings.

Unfortunately, because of the data characteristics (registry), it is impossible to distinguish between true atherosclerotic lesions and spontaneous coronary artery dissection (SCAD), which might be an underlying cause of AMI, especially in young women. Similarly, the domination of non-significant lesions and one-vessel disease in young patients was described previously in the Russian population [9]. Patients with non-significant lesions on coronary angiography, as well as with no evidence of atherosclerosis, but with the diagnosis of myocardial infarction (MINOCA, almost 35% of young patients in contrary to the older ones — 9%), are eventual candidates for extended diagnostic workup of coronary arteries, like IVUS or OCT. Unfortunately, this management was rarely reported in our registry (approx. 0.3%). Even though our patients’ groups had similar rates of periprocedural complications, the extended follow-up results may differ. As it was published previously, early coronary artery disease is strongly associated with AMI and death within 30 days of presentation in patients hospitalized for chest pain [10].

In comparison to older patients with AMI, in patients under 40 with this medical condition, the reason for their troponin elevation is more often not so obvious. Accurate differential diagnosis may require in this case the use of more sophisticated diagnostic tools. During long-term follow-up in young patients with AMI, the risk of myocardial ischemia recurrence may be higher when the underlying cause of ischemia is not thoroughly diagnosed. Close follow-up and post-hospital cardiac control, whose positive effects have been studied and described [13], seem to be particularly justified in the group of young patients with AMI.

CONCLUSION

AMI in young patients (defined as under 40 years old) is a different disease than in their older counterparts. Younger patients with AMI have distinct risk factors profiles and angiographic findings in coronary arteries. The primary prevention of AMI in young patients should mainly focus on smoking cessation. During coronary angiography, additional diagnostic tools, such as IVUS, OCT, or microvascular examination should be considered, as reasons other than atherosclerosis are particularly frequent in this group of patients.

Limitations

Despite a relatively large group of patients, the data acquisition methodology (the ORPKI registry) does not allow the collection of data regarding familial hypercholesterolemia or hyperuricemia, which may play a role in the development of coronary artery disease [11]. We could not perform a standardized analysis of patient angiography, so it was not possible to assess the role of muscle bridge in LAD stenosis and SCAD.

Supplementary material

Supplementary material is available at https://journals.viamedica.pl/kardiologia_polska.

Article information

Conflict of interest: None declared.

Open access: This article is available in open access under Creative Common Attribution-Non-Commercial-No Derivatives 4.0 International (CC BY-NC-ND 4.0) license, allowing to download articles and share them with others as long as they credit the authors and the publisher, but without permission to change them in any way or use them commercially. For commercial use, please contact the journal office at kardiologiapolska@ptkardio.pl.

How to cite: Zasada W, Bobrowska B, Plens K, et al. Acute myocardial infarction in young patients. Kardiol Pol. 2021; 79(10): 1093–1098, doi: 10.33963/KP.a2021.0099.

REFERENCES