Little is known about the association between acute prevalent conditions in patients with type 2 Myocardial Infarction (T2MI) and clinical outcomes, particularly between genders. Using the Nationwide Inpatient Sample (2017), we examined outcomes of T2MI in patients stratified by prevalent associated conditions (renal failure, decompensated heart failure, infection, acute respiratory failure, cardiac arrhythmias, bleeding) and gender. Multivariable logistic regression was performed to assess the odds ratios (OR) of in-hospital all-cause mortality in each of the study groups. A total of 38,715 T2MI patients were included in the analysis, of which 47.9% (n = 18,540) were females. Renal failure was the most common prevalent condition in both genders (males: 60%; females: 52.6%). Acute respiratory failure was associated with the greatest odds of mortality (OR 5.46, 95% confidence interval (CI) 5.02 to 5.94) when compared with other conditions: renal failure (OR 2.20 95% CI 2.01 to 2.40), infections (OR 2.96 95% CI 2.72 to 3.21), major bleeding (OR 1.71 95% CI 1.52 to 1.93), arrhythmias (OR 1.30 95% CI 1.19 to 1.43) and decompensated heart failure (OR 0.71, 95% CI 0.65 to 0.77). However, there was no difference in mortality between genders for all acute conditions except renal failure (females OR: 1.02, 95% CI 1.02 to 1.02, p = 0.011). In conclusion, in-hospital mortality after T2MI differs according to the underlying acute condition, with acute respiratory failure being associated with the highest rate of mortality. No significant differences in mortality were observed between genders amongst all prevalent acute conditions, with the exception of renal failure which was marginally higher in females.
Graphical abstract
Acute myocardial infarction (AMI) affects more than 700,000 patients in the United States (US) annually. Myocardial injury in the absence of acute coronary atherosclerotic plaque rupture or thrombosis is usually due to demand-supply mismatch of myocardial oxygenation, and is classed as type 2 myocardial infarction (T2MI). It is believed that up to 58% of all AMI events are classed as T2MI, which is often associated with worse prognosis compared with type 1 myocardial infarction (T1MI). , Several factors have been previously described as physiological stressors that could lead to T2MI, primarily through two mechanisms: decreased myocardial supply and increased myocardial oxygen demand, often in the presence of underlying renal or heart disease. , Although there have been previous reports on the frequency of such conditions amongst patients with T2MI, there are limited data on the association between common acute conditions and in-hospital outcomes in the context of T2MI. Furthermore, while there is data to suggest that females are more likely to present with T2MI compared with males, little is known about sex differences in the distribution of acute conditions and subsequent outcomes after T2MI. The present study was designed to examine the association between prevalent acute conditions and clinical outcomes, stratified by sex, using a nationally representative sample of T2MI hospitalizations in the United States.
Methods
The National Inpatient Sample (NIS) is the largest publicly available all-payer database of hospitalized patients in the US and is sponsored by the Agency for Healthcare Research and Quality as a part of the Healthcare Cost and Utilization Project (HCUP). NIS includes anonymized data on discharge diagnoses and procedures from more than 7 million hospitalizations annually. The NIS dataset constitutes a 20% stratified sample of US community hospitals and provides sampling weights to calculate national estimates that represent more than 95% of the US population.
All adult (≥18 years) hospitalizations for T2MI in 2017 were included, as identified using the International Classification of Diseases, tenth revision (ICD-10 I21.A1). Patient characteristics and procedural data were extracted using the ICD-10 codes provided in Table S1 ( Supplemental Material ) Records with missing data (1.6% of original cohort, n = 630) on the following variables were excluded: elective admission, primary expected payer, death and median household income as illustrated in Figure S1 ( Supplemental Material ). There were no other inclusion or exclusion criteria.
The primary outcome of interest was in-hospital all-cause mortality. The secondary outcome was in-hospital receipt of invasive management, in the form of coronary angiography or PCI.
For exploratory analyses, the prevalence acute conditions associated with T2MI were compared between genders, as were in-hospital mortality and receipt of invasive management. Continuous variables are summarized using medians and interquartile range (IQR) for non-parametric data and were compared using the Kruskal-Wallis test. Categorical variables are summarized as percentages and were analyzed using the chi squared (X 2 ) test.
Several multivariable logistic regression models were constructed to examine the odds ratios (OR) of in-hospital mortality in both genders for each of the most prevalent acute conditions. Covariate selection was a-priori based and included those based on clinical significance and those that may directly influence in-hospital outcomes. All multivariable models also adjusted for the following covariates: age, weekend admission, elective admission, primary expected payer, median household income, hospital bed size, region and teaching status, year of admission, all-cause shock (excluding cardiogenic shock), cardiogenic shock, dyslipidemia, thrombocytopenia, smoking status, previous MI, previous PCI, prior coronary artery bypass grafting (CABG), previous cerebrovascular accident (CVA; stroke or transient ischemic attack), anemia, chronic lung disease, atrial fibrillation (AF), coagulopathies, diabetes, hypertension, liver disease, solid tumors hematological malignancy, metastatic disease, peripheral vascular disease (PVD),valvular heart disease, dementia, . All statistical analyses were performed using SPSS version 26 (IBM Corp, Armonk, New York).
Results
A total of 38,715 patients with an index diagnosis of T2MI were included in the analysis of which 47.9% (n=18,540) were females. Females were more likely to be older (Median age 75 vs 71 years), Medicare-insured (77.9% vs 70.5%), and have a lower median household income (0-25th quartile (32.4% vs 30.5 %). ( Table 1 ) Females also had a higher prevalence of previous CVA (9.1% vs 8.4%), hypertension (24.5% vs 20.2%), chronic pulmonary disease (34% vs 31%), valvular heart disease (12.5% vs 10.4%) and dementia (14.8% vs 10.5%). In contrast, males were more likely to be White (73% vs 70.8%), with a history of previous MI (13.8% vs 9.9%) and previous CABG (22.1% vs 12.2%), and PVD (5.9% vs 4.9%). Males also had a higher prevalence of diabetes (42.8% vs 38.7%), liver disease (6.5% vs 4.5%), thrombocytopenia (10.9% vs 8.8%), coagulopathy (14.7% vs 12.6%) and malignancies (hematological malignancies [2.9% vs 2.1%], metastatic cancer [3.5% vs 3%], and solid tumors 6.9% vs 5.4%]).
| Variable | Male (52.1%) | Female (47.9%) | Total | p-value |
|---|---|---|---|---|
| Number of weighted discharges | 20175 | 18540 | 38715 | |
| Age (years), median (IQR) | 71 (61,82) | 75 (64,85) | 73 (62,83) | <0.001 |
| Ethnicity | <0.001 | |||
| White | 73.0% | 70.8% | 72.0% | |
| Black | 15.5% | 17.3% | 16.3% | |
| Hispanic | 6.7% | 6.9% | 6.8% | |
| Asian/Pacific Islander | 2.2% | 2.1% | 2.2% | |
| Native American | 0.6% | 1.0% | 0.8% | |
| Other | 2.0% | 2.0% | 2.0% | |
| Weekend admission | 25.9% | 26.2% | 26.1% | 0.552 |
| Primary expected payer | <0.001 | |||
| Medicare | 70.5% | 77.9% | 74.1% | |
| Medicaid | 9.6% | 9.0% | 9.3% | |
| Private Insurance | 14.3% | 10.1% | 12.3% | |
| Self-pay | 2.7% | 1.6% | 2.2% | |
| No charge | 0.3% | 0.1% | 0.2% | |
| other | 2.6% | 1.3% | 2.0% | |
| Median Household Income (quartile) | <0.001 | |||
| 0-25 th | 30.5% | 32.4% | 31.4% | |
| 26-50 th | 28.2% | 28.2% | 28.2% | |
| 51-75 th | 23.3% | 22.1% | 22.7% | |
| 76-100 th | 17.9% | 17.3% | 17.6% | |
| All-cause Shock | 6.0% | 5.4% | 5.7% | 0.007 |
| Cardiogenic Shock | 2.9% | 2.8% | 2.8% | 0.914 |
| Co-morbidities | ||||
| Dyslipidaemia | 47.1% | 46.6% | 46.9% | 0.341 |
| Thrombocytopenia | 10.9% | 8.8% | 9.9% | <0.001 |
| Previous MI | 13.8% | 9.9% | 11.9% | <0.001 |
| Previous PCI | 12.5% | 8.1% | 10.4% | <0.001 |
| Previous CABG | 22.1% | 12.2% | 17.3% | <0.001 |
| Previous CVA | 8.4% | 9.1% | 8.7% | 0.008 |
| Anaemia | 31.9% | 32.3% | 32.1% | 0.482 |
| Chronic pulmonary disease | 31.0% | 34.0% | 32.4% | <0.001 |
| Atrial fibrillation | 27.2% | 27.5% | 27.4% | 0.514 |
| Coagulopathy | 14.7% | 12.6% | 13.7% | <0.001 |
| Diabetes | 42.8% | 38.7% | 40.8% | <0.001 |
| Hypertension | 20.2% | 24.5% | 22.2% | <0.001 |
| Liver disease | 6.5% | 4.5% | 5.5% | <0.001 |
| Solid tumours | 6.9% | 5.4% | 6.2% | <0.001 |
| Haematological malignancies | 2.9% | 2.1% | 2.5% | <0.001 |
| Metastatic cancer | 3.5% | 3.0% | 3.3% | 0.004 |
| Peripheral vascular disease | 5.9% | 4.9% | 5.4% | <0.001 |
| Valvular heart disease | 10.4% | 12.5% | 11.4% | <0.001 |
| Dementia | 10.5% | 14.8% | 12.6% | <0.001 |
| Hospital bed size | 0.483 | |||
| Small | 18.6% | 19.1% | 18.8% | |
| Medium | 26.0% | 25.9% | 26.0% | |
| Large | 55.4% | 55.0% | 55.2% | |
| Hospital Region | 0.235 | |||
| Northeast | 24.9% | 24.8% | 24.9% | |
| Midwest | 26.8% | 27.3% | 27.1% | |
| South | 31.6% | 31.9% | 31.8% | |
| West | 16.6% | 15.9% | 16.3% | |
| Location/ Teaching status | 0.014 | |||
| Rural | 8.9% | 9.0% | 9.0% | |
| Urban non-teaching | 17.9% | 19.0% | 18.4% | |
| Urban- teaching | 73.2% | 72.0% | 72.6% |
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