Clinical Original
The universal classification is an independent predictor of long-term outcomes in acute myocardial infarction

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Abstract

Background

The long-term outcomes of patients with acute myocardial infarction (AMI) according to the universal classification (UC) are unknown. We investigated whether the outcome of these patients is better predicted by the UC than the ST-segment classification (STC).

Methods

We conducted a retrospective study of 348 consecutive patients with AMI with mean follow-up of 30.6 months. The primary outcome was major adverse cardiovascular events (MACE) [composite of all causes of death and AMI].

Results

The study included ST-segment elevation (STEMI)=168 (48%), non-ST-segment elevation (NSTEMI)=180 (52%), Type 1=278 (80%), Type 2=55 (15.8%), Type 3=5 (1.4%), Type 4a=2 (0.6%), Type 4b=5 (1.4%), and Type 5=3 (0.9%). During follow-up, 102 (29.3%) patients had MACE, 80 (23%) patients died, and 31 (8.9%) had an AMI. The adjusted risk of MACE was similar for NSTEMI and STEMI (HR 1.26, 95% CI 0.77–2.03, P=.35) but was significantly lower for patients with Type 2 AMI as compared to Type 1 (HR 0.44, 95% CI 0.21–0.90, P=.02). The UC, peak troponin levels, discharge glomerular filtration rate <60 ml/min per 1.73 m2, and thrombolysis in myocardial infarction risk score were independent predictors of MACE (all, P<.05).

Conclusions

The UC is an independent predictor of long-term outcomes in AMI patients compared to the STC. Type 2 AMI has less than half the risk of MACE as Type 1 AMI. Future studies should report outcomes of AMI patients according to the UC types.

Introduction

The universal classification (UC) of acute myocardial infarction (AMI) aims to facilitate cross-study analysis and interpretation with emphasis on cardiac troponin (cTn) as the preferred biomarker [1]. The UC groups the AMI according to clinical and pathophysiologic characteristics in Types 1 to 5, as described in the Methods section (Fig. 1). However, it is unknown whether the long-term outcomes of AMI patients are different using the UC compared to the traditional electrocardiographic (ECG) based ST-segment classification (STC).

Section snippets

Study population

This is a retrospective cohort study of 348 consecutive patients from a single tertiary hospital with a discharge diagnosis of AMI from December 31, 2004, until December 31, 2006, who met the study criteria. Patients were followed for a minimum of 24 months for clinical outcomes until December 31, 2007. We performed a retrospective classification of AMI based on the 2007 Universal Definition consensus document [1].

Inclusion and exclusion criteria

We included male and female patients, age >30 years old, who met the UC criteria

Baseline characteristics

The study population consisted of 348 patients with AMI, including STEMI=168 (48.3%), NSTEMI=180 (51.7%), Type 1=278 (79.9%), Type 2=55 (15.8%), Type 3=5 (1.4%), Type 4a=2 (0.6%), Type 4b=5 (1.4%), and Type 5=3 (0.9%). The underlying etiology of patients with Type 2 AMI included coronary artery spasm=3 (5.4%), coronary embolism=1 (1.8%), anemia=18 (32.7%), arrhythmias=9 (16.4%), hypertension=23 (41.8%), hypotension=6 (10.9%), and more than one cause=5 (9%). The general demographic, clinical,

Discussion

We observed a lower incidence of Type 1 AMI (79.9% vs. 88.5%) but a higher incidence of Type 2 (15.8% vs. 1.6%) compared to rates reported by Melberg et al. [4]. Patients with Type 1 AMI have more than twice the risk of MACE than Type 2 patients despite having similar rates of CVRF, CAD, PVD, ejection fraction (EF), three-vessel CAD, and receiving similar CVPM at discharge. The significant differences at baseline between Type 1 and Type 2 patients are higher peak CK, CK-MB, and cTn levels. This

Limitations

This is a retrospective cohort study of 348 patients with AMI admitted to a single tertiary hospital with potential for selection, referral, and overrepresentation bias. Therefore, the results may not be directly generalizable to other regions. Second, we performed a retrospective definition of AMI based on the 2007 UC consensus document, which may be a source of misclassification bias despite our best efforts to minimize it. Third, we could have underestimated the rate of all causes of death

Conclusion

This is the first study to demonstrate that the UC is an independent predictor and has better discrimination of long-term outcomes of patients with AMI compared to the STC. Type 2 AMI has less than half the risk of MACE as Type 1 AMI at 30.6 months of follow-up. The UC, peak cTn levels, discharge GFR <60, and TIMI risk score are independent predictors of MACE and all causes of death. In contrast, the STC and peak MB levels are independent predictors of recurrent nonfatal AMI. Future studies

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