Reassess Hospital Costs and Mortality Between Myocardial Infarction With and Without ST‐Segment Elevation in a Modern Context

ABSTRACT

Background

Patients with ST‐segment elevation myocardial infarction (STEMI) may have higher hospitalization costs and poorer prognosis than non‐ST‐segment elevation myocardial infarction (NSTEMI).

Methods

A single‐center retrospective study was conducted on 758 STEMI patients and 386 NSTEMI patients from January 1, 2020 to May 30, 2023 aimed to investigate the differences in cost and mortality.

Results

STEMI patients had higher maximal troponin I (15,222.5 (27.18, 40,000.00) vs. 2731.5 (10.73, 27,857.25), p < 0.001) and lower left ventricular ejection fraction (LVEF) (56% (53%, 59%) vs. 57% (55%, 59%), p < 0.001) compared to NSTEMI patients. The clinical symptoms were mainly persistent or interrupted chest pain/distress in either STEMI or NSTEMI patients. STEMI patients had a significantly higher risk of combined hypotension than NSTEMI patients (8.97% vs. 3.89%, p = 0.002), and IABP was much more frequently used in the STEMI group with a statistical difference (2.90% vs. 0.52%, p = 0.015). STEMI patients have statistically higher hospitalization costs (RMB, ¥) (31,667 (25,337.79, 39,790) vs. 30,506.91 (21,405.96, 40,233.75), p = 0.006) and longer hospitalization days (10 (8, 11) vs. 9 (8, 11), p = 0.001) compared to NSTEMI patients. Although in‐hospital mortality was higher in STEMI patients, the difference was not statistically significant (3.56% vs. 2.07%, p = 0.167). Multivariable logistic regression was performed and found that systolic blood pressure and NT‐proBNP were risk factors for patient death (OR ≥ 1).

Conclusion

STEMI patients are more likely comorbid cardiogenic shock, heart failure complications with higher hospitalization costs and longer hospitalization days. And relatively more use of acute mechanical circulatory support devices such as IABP.

Trial Registration

ChiCTR2300077885

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1. Introduction

Acute coronary syndromes (ACS), the most prevalent cardiovascular disease, is one of the leading causes of high morbidity and mortality worldwide, especially acute myocardial infarction (AMI) (O'Gara et al. ²⁰¹³), AMI is employed when there is evidence of ischemic damage resulting in necrosis of the cardiac muscle. AMI can be divided into ST‐elevation myocardial infarction (STEMI) and non‐ST‐elevation myocardial infarction (NSTEMI) based on whether the ST segment is elevated on the electrocardiogram (ECG), and they share a common pathophysiological basis (O'Gara et al. ²⁰¹³; Grines and Mehta ²⁰²¹), both STEMI and NSTEMI require percutaneous coronary intervention (PCI) to open the culprit vessel to restore myocardial blood supply and reduce mortality (Davis and Blankenship 2023). Studies have confirmed that the lesion morphology of culprit vessel in STEMI is relatively simple compared to NSTEMI (Murakami et al. 2022; Mayr et al. ²⁰²²), and some conventional equipment can accomplish PCI to open the culprit vessel, whereas the culprit vessel in NSTEMI may be more complex than that of STEMI, and the total cost in‐hospital may be higher than that of STEMI (Murakami et al. 2022; Ghani et al. ²⁰²²), while STEMI is more likely to be combined with complications than NSTEMI, which may lead to increased hospitalization costs and poorer prognosis.

Over the past decades, there have been countless studies comparing NSTEMI and STEMI in terms of clinical symptoms, prognosis, etc. (Xu et al. 2020; Byun et al. ²⁰¹⁸; Zhao et al. ²⁰²²; Fu et al. ²⁰¹⁹; Ängerud et al. ²⁰¹⁷), but whether there is a difference in hospitalization costs and culprit vessel still requires further evidence, especially in the current medical model. Therefore, our study aimed to compare STEMI with NSTEMI by describing and statistically comparing the differences in hospitalization costs and clinical characteristics such as mortality.

2. Methods and Materials

A single‐center retrospective study was performed by analyzing patients with STEMI and NSTEMI admitted to our hospital from January 1, 2019 to May 30, 2023. The study population was divided into NSTEMI and STEMI groups with a primary endpoint on hospitalization costs and mortality at discharge. We also analyzed the variability in the type of culprit vessel and in‐hospital medication, other clinical characteristics between the two groups.

Our hospital has two catheter rooms for PCI and several cardiovascular specialists to perform PCI, also an intra‐aortic balloon pump (IABP), temporary pacemakers, and extracorporeal membrane oxygenation (ECMO) to protect the patients undergoing PCI. Whether to activate IABP, temporary pacemaker, ECMO, etc. should be judged according to the patient's hemodynamics, heart rate, lung rales, etc. STEMI patients were mostly treated with emergent PCI and efforts were made to shorten the door‐to‐wire time in each procedure. The timing of the PCI was selected based on the GRACE score in NSTEMI patients, but most NSTEMI patients were performed as emergent PCI for early opening of narrowed vessel. After patients were discharged due to improvement or death, the total cost of hospitalization and the cause of death were collected. The medication regimen during hospitalization and the type of culprit blood vessels were also statistically analyzed.

Our study was approved by the Institutional Review Board of the First Affiliated Hospital of Xi'an Medical University (No. XYXFY2022LSK‐055). The study was in accordance with the Declaration of Helsinki 1975, revised in 2013 (World Medical Association ²⁰¹³), and the written informed consent was waived due to the retrospective study design.

2.1. Statistical Analysis

Data for categorical variables are expressed as percentages, as mean ± standard deviation for normally distributed continuous variables, or as median and interquartile range for non‐normally distributed continuous variables. Categorical variables were compared by chi‐square test or rank tests. The Wilk–Shapiro test was used to determine whether continuous variables were normally distributed, and normally distributed continuous variables were compared using an unpaired Student's t‐test. In addition, continuous variables were compared using the Mann–Whitney U test. Univariate and multivariate logistic regression models were used to explore independent predictors of death. p value less than 0.05 was of statistical significance unless otherwise indicated. All analysis was performed with SPSS.

3. Results

Retrospective analysis of patients admitted to our department for acute myocardial infarction (AMI) from January 1, 2020 to May 30, 2023. A total of 9 patients were excluded due to incomplete data, and a total of 1144 patients were included, including 758 in the STEMI group and 386 in the NSTEMI group.

Baseline demographics and clinical characteristics are shown in Table 1. The proportion of males, as well as the maximal troponin I were higher in the STEMI group than in the NSTEMI group, and there was a statistically significant difference between the two groups (p < 0.05). In the NSTEMI group, an underlying history of previous diseases such as hypertension and ischemic cerebrovascular disease was higher than that of the STEMI group with statistical differences (p < 0.05), and also LVEF of the patients in the NSTEMI group was higher than that of the STEMI group with statistical difference. Comparisons of clinical symptoms, vascular lesions as well as intraoperative conditions are shown in Table 2. Regardless of the STEMI group or the STEMI group, the clinical symptoms were mainly persistent or interrupted chest pain and chest distress, but the percentage of persistent chest pain/chest distress was higher in the STEMI (79.68% in STEMI vs. 54.92% in NSTEMI), whereas the interrupted chest pain/chest distress was lower (15.70% in STEMI vs. 38.08% in NSTEMI) when compared to NSTEMI group. In terms of pacemaker implantation, IABP and ECMO use, the rate of IABP use in the STEMI group was higher than that in the NSTEMI group and with a statistical difference (2.90% in STEMI vs. 0.52% in NSTEMI, p = 0.015). Although ECMO was used in seven patients in the STEMI group, there was no significant difference between the two groups (p = 0.135).

TABLE 1.

Baseline demographics and clinical characteristics for all patients.

	NSTEMI (n = 386)	STEMI (n = 758)	p
Demographics
Male, n (%)	299 (77.46%)	633 (83.51%)	0.013
Mean age (years)	60.82 ± 12.78	59.46 ± 14.38	0.053
Vital signs
Breathing rate (bpm)	18.5 (18, 20)	18 (18, 20)	0.756
Pause (bpm)	78 (66, 90)	75 (63, 86)	0.005
Heart rate (bpm)	77 (66, 90)	74 (63, 86)	0.007
Systolic BP (mm Hg)	139 (120, 160)	130 (115, 150)	< 0.001
Diastolic BP (mm Hg)	82 (70, 93)	80 (70, 93)	0.024
Risk factors and medical history, n (%)
Hypertension	179 (46.37%)	289 (38.13%)	0.007
Diabetes history	108 (27.98%)	184 (24.27%)	0.463
Smoke	142 (36.79%)	294 (38.79%)	0.510
Early CVD family history	4 (1.04%)	6 (0.79%)	0.933
Previous revascularization	47 (12.18%)	66 (8.71%)	0.063
Known dyslipidemia	88 (22.80%)	171 (22.56%)	0.808
History of cerebrovascular disease	31 (8.03%)	40 (5.28%)	0.068
Ischemic	30 (7.77%)	36 (4.75%)	0.039
Hemorrhagic	1 (0.26%)	4 (0.53%)	0.857
Peripheral artery disease	0 (0.00%)	0 (0.00%)	—
History of COPD	5 (1.30%)	10 (1.32%)	0.973
Chronic renal insufficiency	5 (1.30%)	8 (1.06%)	0.947
History of gastrointestinal ulcer	4 (1.04%)	5 (0.66%)	0.743
Laboratory examination
TG (mg/mL)	1.49 (1.04, 2.18)	1.42 (1.02, 2.06)	0.396
TC (mg/mL)	3.97 (3.37, 4.68)	4.02 (3.46, 4.70)	0.591
HDL‐C (mg/mL)	1.01 (0.90, 1.17)	1.02 (0.90, 1.19)	0.782
LDL‐C (mg/mL)	2.83 (2.35, 3.34)	2.82 (2.36, 3.38)	0.555
Maximal hs‐Troponin I (ng/mL)	2731.5 (10.73, 27,857.25)	15,222.5 (27.18, 40,000.00)	< 0.001
NT‐proBNP (pg/mL)	811.5 (317.25, 1994.5)	966.5 (318.75, 2578)	0.126
LV ejection fraction (%)	57 (55, 59)	56 (53, 59)	< 0.001

Abbreviations: BP, blood pressure; COPD, chronic obstructive pulmonary disease; HDL‐C, high‐density lipoprotein cholesterol; LDL‐C, low‐density lipoprotein cholesterol; TC, cholesterol; TG, triglyceride.

TABLE 2.

Comparison of clinical symptoms and intraoperative conditions.

	NSTEMI (n = 386)	STEMI(n = 758)	p
Clinical symptoms of patients, n (%)
Persistent precordial chest pain/distress	212 (54.92%)	604 (79.68%)	< 0.001
Interrupted chest pain/distress	147 (38.08%)	119 (15.70%)
Back pain	3 (0.78%)	1 (0.13%)
Mandibular/tooth pain	0 (0.00%)	4 (0.53%)
Palpitation	1 (0.26%)	1 (0.13%)
Persistent upper abdomen pain	12 (3.11%)	12 (1.58%)
Dizziness	1 (0.26%)	4 (0.53%)
Syncope	0 (0.00%)	6 (0.79%)
Absence of symptoms	10 (2.59%)	7 (0.92%)
Killip classification, n(%)
I	352 (91.19%)	689 (90.90%)	0.097
II	23 (5.96%)	36 (4.75%)
III	4 (1.04%)	3 (0.40%)
IV	7 (1.81%)	30 (3.96%)
Invasive strategy (angiography and subsequent revascularization), n (%)	370 (95.85%)	756 (99.74%)	< 0.001
LAD	131 (33.94%)	377 (49.74%)
RCA	85 (22.02%)	262 (34.56%)
LCX	119 (30.83%)	67 (8.84%)
LM	6 (1.55%)	7 (0.92%)
D	7 (1.81%)	14 (1.85%)
AM	1 (0.26%)	0 (0.00%)
OM	7 (1.81%)	3 (0.40%)
Intermediate branch	2 (0.52%)	3 (0.40%)
IABP use, n (%)	2 (0.52%)	22 (2.90%)	0.015
Temporary pacemaker use, n (%)	2 (0.52%)	6 (0.79%)	0.881
ECMO use, n (%)	0 (0.00%)	7 (0.92%)	0.135

Abbreviations: AM, acute marginal artery; D, diagonal branches; ECMO, extracorporeal membrane oxygenation; IABP, intra‐aortic balloon pump; LAD, left anterior descending artery; LCX, left circumflex artery; LM, left main artery; OM, obtuse marginal branch; RCA, right coronary artery; RI, ramus intermedius artery.

Patients in the STEMI group had a significantly higher risk of combined hypotension than the NSTEMI group (8.97% in STEMI vs. 3.89% in NSTEMI, p = 0.002). Others such as heart failure, mechanical complications, and ventricular aneurysm were different between the two groups but without statistical difference (p > 0.05) (Table 3). There were 27 deaths during hospitalization in the STEMI group and eight deaths in the NSTEMI group (Figure 1B), which shared no statistically significant difference in MACE events between the two groups. Both hospitalization fees and inpatient days were higher in the STEMI group and showed a statistical difference (Table 3). STEMI patients have higher hospitalization costs (RMB, ¥) (31,667 (25,337.79, 39,790) vs. 30,506.91 (21,405.96, 40,233.75), p = 0.006) and longer hospitalization days (10 (8, 11) vs. 9 (8, 11), p = 0.001) compared to NSTEMI patients.

TABLE 3.

Clinical outcomes and costs for NSTEMI and STEMI patients.

	NSTEMI (n = 386)	STEMI (n = 758)	p
Postoperative complications, n (%)
Heart failure	55 (14.25%)	136 (17.94%)	0.113
Hypotension	15 (3.89%)	68 (8.97%)	0.002
Mechanical complications	0 (0.00%)	6 (0.79%)	0.187
Acute kidney injury	8 (2.07%)	23 (3.03%)	0.343
Bleeding	4 (1.04%)	12 (1.58%)	0.456
Ventricular aneurysm	5 (1.30%)	5 (0.66%)	0.449
Respiratory failure	4 (1.04%)	20 (2.64%)	0.075
Medication during hospitalization, n (%)
Clopidogrel	380 (98.45%)	750 (98.94%)	0.468
Aspirin	386 (100.00%)	758 (100.00%)	1.000
β‐Blocker	210 (54.40%)	424 (55.94%)	0.622
Statins	264 (68.39%)	516 (68.07%)	0.913
ACEI/ARB/ARNI	302 (78.24%)	684 (90.24%)	< 0.001
In‐patient days (day)	9 (8, 11)	10 (8, 11)	0.001
Hospitality costs (RMB, ¥)	30,506.905 (21,405.96, 40,233.75)	31,667 (25,337.79, 39,790)	0.006
MACE in hospital (n (%))	8 (2.07%)	27 (3.56%)	0.167
Cardiovascular death, n (%)	7 (1.81%)	27 (3.56%)	0.146
Non cardiovascular death, n (%)	1 (0.26%)	0 (0.00%)	0.733

Abbreviations: ACEI/ARB, angiotensin‐converting enzyme inhibitors/angiotensin receptor blocker; MACE, major adverse cardiovascular events.

FIGURE 1.

(A) Incidence of in‐hospital MACEs in MI patients. The error bars indicate the 95% confidence interval of the sampling errors. (B) Incidence of in‐hospital MACEs in male patients compared to female patients.

In our study, although there was no statistically significant difference in MACE events between the two groups, patients with STEMI had higher mortality in the hospital compared to patients with NSTEMI (3.56% in STEMI vs. 2.07% in NSTEMI). Univariate and multivariable logistic regressions were performed to assess independent risk factors for MACEs, and systolic blood pressure and NT‐proBNP were risk factors for patient death (OR ≥ 1) (Figure 1A), and there was a statistical difference in systolic blood pressure between the two groups in this experiment (p < 0.001), while there was no statistical difference in NT‐proBNP (p = 0.126).

4. Discussion

Based on our study, STEMI patients have higher hospitalization costs and longer hospitalization days compared to NSTEMI patients, which is also as same as other studies (Murakami et al. 2022). The following factors should be considered to explain the differences. First, STEMI patients typically have higher disease severity and more extensive coronary artery blockage than NSTEMI patients with severe myocardial damage and complications, resulting in longer hospital stays and higher hospitalization costs (Mayr et al. 2022; Andreou ²⁰²²; Han et al. ²⁰²²). Second, patients with STEMI usually have more urgent conditions and may require more rapid and complex medical interventions to obtain TIMI‐3 flow as soon as possible (Fu et al. 2019; Ängerud et al. ²⁰¹⁷; Blondheim et al. ²⁰¹⁸). While TIMI flow grade is often 3 at the time of coronary angiography in NSTEMI patients. STEMI patients often need to use advanced medical techniques and equipment, and intensive care treatments that require more medical resources. These factors may lead to increased length and cost of hospitalization. What's more, patients with STEMI may be at higher risk for complications such as heart failure, arrhythmias, hypotension, cardiac rupture, or mechanical complications (Andreou 2022; Grines and Marshall ²⁰²¹; Mitsis and Gragnano ²⁰²¹). These complications may require additional medical interventions and longer hospital stays, thus increasing hospitalization costs. However, as medical technology improves, hospitalization days for STEMI patients will supposedly be shorter, and the cost of hospitalization will be reduced (Grines and Marshall 2021).

In our study, there was a higher proportion of men with myocardial infarction and a higher proportion of men than women in the death population. This is also consistent with the results of some other studies (Bachelet et al. 2021; Alabas et al. ²⁰¹⁷). However, it is important to emphasize that despite the higher proportion of men among STEMI patients, this is not direct evidence that gender is an independent factor affecting patient outcomes. In this study, men in‐hospital mortality was higher than female, but whether this difference is dependent on differences in baseline characteristics and comorbidities remains controversial, which needs further research to investigate the specific reasons behind this difference and its impact on the disease course and outcome. Also, we found that the incidence of MACE events in hospitals was higher in STEMI than in NSTEMI with no statistical difference in our study, which was different from other studies (Murakami et al. 2022; Han et al. ²⁰²¹). Thus, well‐designed investigations with other variables should be conducted to corroborate the findings of this study. But in terms of prognosis, many studies have found that there was no difference in long‐term mortality (Xu et al. 2020; Mitsis and Gragnano ²⁰²¹; Malmberg et al. ²⁰²⁰).

Multiple multicenter randomized, controlled trials (RCTs) studies have confirmed that there is no statistical difference between men and women in all‐cause mortality from acute myocardial infarction (Bachelet et al. 2021; Alabas et al. ²⁰¹⁷; Shah et al. ²⁰²²). But in our study, the mortality rate either STEMI or NSTEMI was higher in men than in women with statistically different (p < 0.001). This may be related to the larger proportion of males in our baseline information in the STEMI group, which also coincides with the fact that a higher proportion of our men smoke than women in our country. Obesity rates may also be slightly higher in men than in women. As we all know that smoking and obesity themselves are the risks for MACE events in myocardial infarction (O'Gara et al. ²⁰¹³; Ibanez et al. ²⁰¹⁷).

Systolic blood pressure and NT‐proBNP were risk factors for patient death, which suggests a higher risk of death in MI patients combined with hypotension and heart failure. Previous studies have also confirmed that patients with myocardial infarction combined with heart failure and cardiogenic shock have less chance of undergoing PCI, and their in‐hospital and 30‐day mortality are higher (Kapur, Thayer, and Zweck ²⁰²⁰; Bahit et al. ²⁰¹³). We doctors should assess the patient's vital signs and cardiac function and the initiation of appropriate acute mechanical circulatory support devices (e.g., IABP, ECMO) early, and urgent revascularization to restore coronary TIMI grade 3 blood flow, only then do we may have a chance to improve the patient's prognosis and reduce the risk of death. Close monitoring of blood pressure, NT‐proBNP, and LVEF is also required after revascularization to detect any combination of hypotension and heart failure.

4.1. Limitations

Some of the limitations of this study are as follows. First, as a single‐center retrospective study, it only reveals important correlations and does not prove causality. Second, this study only provides real data on hospitalization costs, length of stay, and prognosis of patients with NSTEMI and STEMI. Further studies combining propensity‐matched or risk‐adjusted and randomized prospective controlled studies are needed to assess the prognostic variability and the variability associated with the duration of hospitalization for NSTEMI and STEMI. Third, although we performed multivariate logistic regression analysis to overcome the limitations of this retrospective study, the results were still affected by unobserved confounding factors.

5. Conclusion

This real‐world retrospective cohort study of STEMI versus NSTEMI patients supports that mortality in‐hospital shares no differences. While STEMI patients have higher hospitalization costs and longer hospitalization days compared to NSTEMI patients.

6. New Knowledge Gained

IABP was much more frequently used in STEMI patients compared with NSTEMI. What's more, STEMI patients have higher hospitalization costs and longer hospitalization days. Even though STEMI patients had higher mortality in hospital compared to NSTEMI patients, there was no statistical difference.

Author Contributions

Honglan Ma: conceptualization, writing – original draft preparation, writing – review and editing. Sen Wu: data analysis. Jinlong Cao and Tianzhi Cai: supervision. The authors revised the manuscript for intellectual content. All authors have read and approved the final manuscript.

Ethics Statement

The study was reviewed and approved by the Ethics Committee of The First Affiliated Hospital of Xi'an Medical University (NO. XYYFY2022LSK‐055). The written informed consent was waived due to the retrospective study design.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.