In-Hospital Versus Out-Of-Hospital Non-ST-Segment-Elevation Myocardial Infarction (NSTEMI)

Findings of the RHESA Study

Studies on acute myocardial infarction (AMI) have focused on ST-segment-elevation myocardial infarction (STEMI) and found that 5–7% of cases occur in the hospital setting (1, 2). Compared to patients with out-of-hospital STEMI, patients with in-hospital STEMI are older, more frequently have chronic comorbidities, and show a higher risk of complications and mortality in the hospital (1, 3). It remains unclear whether these differences also apply to non-ST-segment-elevation myocardial infarction (NSTEMI). We set out to answer this question.

Methods

We used data for the period 2013–2019 from The Regional Myocardial Infarction Registry of Saxony–Anhalt (RHESA). AMI was defined based on the Third Universal Definition of Myocardial Infarction from the European Society of Cardiology (ESC). We excluded patients who did not survive until hospital admission, as treatments and 30-day mortality could not be assessed in this case, as well as those with previous AMI, since we were interested only in risk factors associated with the first occurrence of NSTEMI. We compared patients’ characteristics, treatment, and outcomes between in-hospital and out-of-hospital NSTEMI. A literature review was conducted to identify (using a directed acyclic graph, not shown) the minimum set of covariables that had to be adjusted for in the logistic regression analysis to assess the association between NSTEMI type and 30-day mortality.

Results

We identified 2123 cases of NSTEMI in our sample, of which 14% occurred in the hospital setting. Compared to patients with out-of-hospital NSTEMI, patients with in-hospital NSTEMI were more commonly older over 75 years of age and had higher proportions of heart failure, chronic kidney disease, diabetes, and atrial fibrillation.

Patients with in-hospital NSTEMI were less likely to receive acetylsalicylic acid and heparin than persons with out-of-hospital NSTEMI. The proportion of patients receiving invasive intervention was lower in the in-hospital NSTEMI group (61.5% [55.9; 66.9] versus 69.7% [67.6; 71.8]). Crude 30-day mortality was higher for in-hospital NSTEMI than for out-of-hospital NSTEMI (11% [7.9; 15.0] versus 6.5% [5.4; 7.1]) (Table). After adjustment the difference was less pronounced (odds ratio = 1.62 [1.15; 2.49]) (Figure).

Figure

Characteristics associated with 30-day mortality for in-hospital NSTEMI compared to out-ofhospital NSTEMI

Table

Comparison of baseline characteristics, treatment, and outcomes between patients with in-hospital and out-of-hospital NSTEMI

Discussion

The proportion of AMI occurring in the hospital setting was higher for NSTEMI than for STEMI. The established differences between in-hospital and out-of-hospital STEMI were also observed for NSTEMI. Patients with in-hospital NSTEMI were older and had more comorbidities. Mortality was higher for in-hospital NSTEMI and medicinal treatments and invasive interventions were carried out less frequently, in line with the published findings on STEMI.

To better understand why certain comorbidities may be associated with in-hospital NSTEMI, it is necessary to consider the underlying pathophysiological mechanisms. Type 2 AMI arises from a mismatch in cardiac oxygen demand and oxygen supply that, in contrast to type 1 AMI, does not involve plaque rupture and thrombosis. This can happen especially in perioperative stress, sepsis, chronic kidney disease, cardiac arrhythmias, anemia, heart failure, coronary spasm, etc., particularly in the older population (4). Interestingly, we noticed an overlap between the risk factors for in-hospital NSTEMI that we identified (older age, atrial fibrillation, chronic kidney disease, and heart failure) and some of the triggers of type 2 AMI. This indicates that the pathophysiological mechanisms of in-hospital NSTEMI are more related to type 2 AMI.

The literature shows that in-hospital STEMI has higher in-hospital mortality and 1-year mortality than out-of-hospital STEMI (1, 3). Similarly, we found that the 30-day mortality of in-hospital NSTEMI was nearly two times that of out-of-hospital NSTEMI. The potential explanations include the following:

• The presence of concomitant medical conditions in inpatients with atypical symptoms of AMI may lead to delays in diagnosis and treatment (1, 3).
• Patients with in-hospital NSTEMI are probably not initially treated on cardiology wards, which could further delay treatment.
• There are no guideline recommendations for the management of in-hospital NSTEMI.

In our study, we found that patients with in-hospital NSTEMI were treated suboptimally when considering the ESC guidelines for acute coronary syndrome without persisting ST-segment elevation (5), possibly due to contraindications.

Our study has the following limitations: The analysis is confined to two regions of a single federal state of Germany, and only a fraction of AMI cases in these regions were covered by the registry. Additionally, patients with in-hospital NSTEMI may not be referred to cardiology and may thus be less likely to be included in our data, potentially leading to selection bias. Moreover, we had no information on the time of onset of the AMI during the hospital stay. Finally, a Nagelkerke R² of 18% indicates that the considered variables explain only a small part of the variation in 30-day mortality.

Mohamad Assaf, Sara Lückmann, Ljupcho Efremov, Karen Holland, Daniela Costa, Rafael Mikolajczyk

Conflict of interest statement

Different phases of the project were financed from 2013 onwards by various health insurance funds, the Federal Ministry of Health, the German Heart Foundation (Deutsche Herzstiftung), the State Ministry of Labor and Social Affairs, and internal funds of Martin Luther University. The authors declare that no further conflict of interest exists.

Manuscript received on 6 September 2023, revised version accepted on 7 February 2024.

Cite this as:
Assaf M, Lückmann S, Efremov L, Holland K, Costa D, Mikolajczyk R: In-Hospital versus out-of-hospital non-ST-segment-elevation myocardial infarction (NSTEMI)—findings of the RHESA Study. Dtsch Arztebl Int 2024; 121: 409–10. DOI: 10.3238/arztebl.m2024.0032

References

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3. Stehli J, Dagan M, Dinh DT, et al.: Differences in outcomes of patients with in-hospital versus out-of-hospital ST-elevation myocardial infarction: a registry analysis. BMJ Open 2022; 12: e052000

4. Gupta S, Vaidya SR, Arora S, Bahekar A, Devarapally SR: Type 2 versus type 1 myocardial infarction: a comparison of clinical characteristics and outcomes with a meta-analysis of observational studies. Cardiovasc Diagn Ther 2017; 7: 348–58

5. Hamm CW, Bassand JP, Agewall S, et al.: ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation: The Task Force for the management of acute coronary syndromes (ACS) in patients presenting without persistent ST-segment elevation of the European Society of Cardiology (ESC). Eur Heart J 2011; 32: 2999–3054