Acute myocardial infarction in patients with end-stage renal disease (ESRD) is associated with increased risk of morbidity and mortality. Limited data are available on the contemporary trends in management and outcomes of ST-elevation myocardial infarction (STEMI) in patients with ESRD. We analyzed the 2003 to 2011 Nationwide Inpatient Sample databases to examine the temporal trends in STEMI, use of mechanical revascularization for STEMI, and in-hospital outcomes in patients with ESRD aged ≥18 years in the United States. From 2003 to 2011, whereas the number of patients with ESRD admitted with the primary diagnosis of acute myocardial infarction increased from 13,322 to 20,552, there was a decrease in the number of STEMI hospitalizations from 3,169 to 2,558 (p trend <0.001). The overall incidence rate of cardiogenic shock in patients with ESRD and STEMI increased from 6.6% to 18.3% (p trend <0.001). The use of percutaneous coronary intervention for STEMI increased from 18.6% to 37.8% (p trend <0.001), whereas there was no significant change in the use of coronary artery bypass grafting (p trend = 0.32). During the study period, in-hospital mortality increased from 22.3% to 25.3% (adjusted odds ratio [per year] 1.09; 95% confidence interval 1.08 to 1.11; p trend <0.001). The average hospital charges increased from $60,410 to $97,794 (p trend <0.001), whereas the average length of stay decreased from 8.2 to 6.5 days (p trend <0.001). In conclusion, although there have been favorable trends in the utilization of percutaneous coronary intervention and length of stay in patients with ESRD and STEMI, the incidence of cardiogenic shock has increased threefold, with an increase in risk-adjusted in-hospital mortality, likely because of the presence of greater co-morbidities.
Cardiovascular disease is the leading cause of death in patients with end-stage renal disease (ESRD), accounting for about 45% of overall mortality. Approximately 20% of these deaths from cardiac causes can be attributed to acute myocardial infarction (AMI). Several hypotheses have been put forward to explain the increased ischemic burden in patients with ESRD, including the high prevalence of diabetes mellitus and hypertension in these patients, along with other less well-established factors, such as low concentrations of high-density lipoprotein cholesterol, hyperhomocysteinemia, hyperparathyroidism, increased calcium-phosphate product, increased oxidative stress, and decreased nitric oxide activity. Previous studies have shown that AMI in patients with ESRD is associated with worse short- and long-term survival compared with the general population. Multiple clinical trials have demonstrated improved outcomes with reperfusion in patients presenting with ST-elevation myocardial infarction (STEMI); however, patients with ESRD have traditionally been excluded from these studies. Given the lack of both prospective data and evidence-based recommendations on the treatment of STEMI in the presence of renal dysfunction, patients with ESRD and STEMI are less likely to undergo coronary revascularization or receive proved medical therapies, such as aspirin, β blockers, statin drugs, and angiotensin-converting enzyme inhibitors. Recent data on the trends in management and outcomes of STEMI in patients with ESRD are limited. The primary objective of this study was to examine the temporal trends in revascularization and in-hospital outcomes in patients with ESRD hospitalized with STEMI using the Nationwide Inpatient Sample (NIS) databases from 2003 to 2011.
Methods
Data were obtained from the 2003 to 2011 NIS databases. The NIS, sponsored by the Agency for Healthcare Research and Quality as a part of the Healthcare Cost and Utilization Project, is the largest publicly available all-payer inpatient care database in the United States. It contains discharge-level data provided by states (n = 46 in 2011) that participate in the Healthcare Cost and Utilization Project. The NIS includes data from ∼8 million hospital stays each year from about 1,000 hospitals designed to approximate a 20% stratified sample of all community hospitals (defined as “all nonfederal, short-term, general, and other specialty hospitals, excluding hospital units of institutions”) in the United States. Criteria used for stratified sampling of hospitals include hospital ownership, patient volume, teaching status, urban or rural location, and geographic region. Discharge weights are provided for each patient discharge record and were used to obtain national estimates.
We used the International Classification of Diseases, Ninth Edition, Clinical Modification ( ICD-9-CM ), codes 410.xx, to identify all patients ≥18 years with the principal diagnosis of AMI (n = 5,901,826). Patients with the principal diagnosis of STEMI were then identified using ICD-9-CM codes 410.01, 410.11, 410.21, 410.31, 410.41, 410.51, 410.61, 410.81, and 410.91 (n = 2,213,831). We chose the principal diagnosis because it is considered the primary reason for hospital admission. We considered the patients to have ESRD if they had either the diagnosis code for chronic kidney disease requiring long-term dialysis (585.6) or the procedure code for hemodialysis (39.95) or peritoneal dialysis (54.98). We excluded patients who underwent hemodialysis who concomitantly had an ICD-9-CM code indicating acute renal failure (584.5 to 584.9). This approach has been used in previous studies using administrative databases to accurately identify patients with AMI, STEMI, and ESRD. We used ICD-9-CM procedure codes to identify patients who underwent percutaneous coronary intervention (PCI) (00.66, 36.01, 36.02, 36.05, 36.06, and 36.07) or coronary artery bypass grafting (CABG) (36.1x). Patients with a concomitant diagnosis of cardiogenic shock were identified using ICD-9-CM code 785.51.
We initially studied the trend in proportion of STEMI in adult patients with ESRD and AMI. We then examined the trends in utilization of PCI and CABG in patients with ESRD and STEMI and the incidence of cardiogenic shock in these patients. Our primary outcome of interest was all-cause in-hospital mortality, defined as “died” during the hospitalization encounter in the NIS database. We used the average length of stay and total hospital charges as secondary outcomes. We analyzed the trends in in-hospital mortality, average length of stay, and average total hospital charges in patients with ESRD and STEMI.
Baseline patient characteristics used included demographics (age, gender, race, primary expected payer, weekday vs weekend admission, median household income for patient’s zip code), all Elixhauser co-morbidities (except chronic renal failure) as defined by the Agency for Healthcare Research and Quality, other clinically relevant co-morbidities (smoking, dyslipidemia, known coronary artery disease, family history of coronary artery disease, previous myocardial infarction, previous PCI, previous CABG, carotid artery disease, dementia, and atrial fibrillation), presentation (anterior wall, inferior wall, or other STEMI), in-hospital procedures (Swan-Ganz catheterization, PCI, CABG, intra-aortic balloon pump, and blood transfusion), and in-hospital complications (gastrointestinal bleeding and acute cerebrovascular accident). A list of ICD-9-CM codes and Clinical Classifications Software codes used to identify co-morbidities, in-hospital procedures, and complications is provided in the Supplementary Table 1 . Hospital characteristics such as hospital region (Northeast, Midwest, South, and West), bed size (small, medium, and large), location (rural, urban), and teaching status were also included.
Weighted data were used for all analyses. For trend analysis, we used the Mantel-Haenszel chi-square test of linear association for categorical variables and linear regression for continuous variables. To assess whether the utilization of PCI, CABG, other in-hospital procedures, in-hospital mortality, and in-hospital complications have changed over time, unadjusted and multivariable adjusted logistic regression models were constructed for the overall cohort. Our independent variable, calendar year, was entered as a continuous variable in the regression models to obtain unadjusted and adjusted odds ratios (ORs, per year) for the overall temporal trend. To determine if there was a temporal variability from year-to-year in in-hospital mortality, we also evaluated calendar year as a categorical variable, with 2003 as the reference year. The regression models adjusted for demographics, hospital characteristics, all Elixhauser and other clinically relevant co-morbidities, and presentation as listed in Table 1 . Race was missing in 18.7% of the study population and, therefore, was not included in the regression models. Temporal trends in average length of stay and total hospital charges were examined using linear regression models with log-transformed length of stay and total hospital charges, respectively.
| Variable | 2003 (%) | 2004 (%) | 2005 (%) | 2006 (%) | 2007 (%) | 2008 (%) | 2009 (%) | 2010 (%) | 2011 (%) | Overall (%) | p Value ∗ |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Number of cases (weighted) | 3,169 | 2,833 | 2,627 | 3,525 | 3,302 | 3,124 | 2,759 | 2,723 | 2,558 | 26,620 | <0.001 |
| Age, mean ± standard deviation (years) | 67.5 ± 12.1 | 67.0 ± 12.4 | 68.0 ± 12.4 | 67.0 ± 13.0 | 67.1 ± 12.4 | 67.2 ± 13.2 | 66.6 ± 12.7 | 66.2 ± 12.5 | 66.5 ± 12.5 | 67.0 ± 12.6 | <0.001 |
| Women | 47.3 | 41.8 | 49.7 | 46.2 | 46.7 | 46.1 | 45.4 | 43.7 | 41.0 | 45.4 | <0.001 |
| Race | 0.141 | ||||||||||
| Caucasian | 45.1 | 55.2 | 55.8 | 59.2 | 56.2 | 53.7 | 51.7 | 52.3 | 51.0 | 53.3 | |
| African-American | 29.9 | 22.3 | 23.1 | 21.7 | 24.8 | 26.1 | 23.4 | 24.3 | 28.1 | 24.9 | |
| Hispanic | 12.8 | 12.6 | 11.9 | 13.4 | 9.9 | 12.3 | 15.6 | 12.9 | 13.1 | 12.7 | |
| Asian or Pacific Islander | 8.0 | 6.2 | 4.7 | 3.0 | 4.9 | 4.5 | 5.7 | 5.3 | 4.0 | 5.1 | |
| Native American | 0.4 | 0.2 | 0.4 | 0.9 | 0.7 | 0.9 | 1.0 | 2.4 | 1.1 | 0.9 | |
| Other | 3.9 | 3.5 | 4.0 | 1.8 | 3.5 | 2.5 | 2.6 | 2.9 | 2.8 | 3.0 | |
| Primary expected payer | <0.001 | ||||||||||
| Medicare | 82.3 | 79.8 | 84.2 | 82.2 | 79.0 | 80.6 | 82.3 | 78.2 | 82.7 | 81.2 | |
| Medicaid | 7.5 | 7.7 | 4.6 | 6.4 | 5.6 | 5.8 | 6.2 | 6.4 | 4.2 | 6.1 | |
| Private insurance | 8.8 | 10.9 | 9.4 | 10.5 | 13.7 | 11.5 | 9.7 | 12.6 | 10.9 | 10.9 | |
| Self-pay | 0.4 | 0.8 | 0.9 | 0.3 | 0.8 | 1.2 | 0.8 | 1.4 | 1.4 | 0.9 | |
| No charge | 0.3 | 0.2 | 0.2 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.1 | |
| Other | 0.6 | 0.5 | 0.7 | 0.7 | 0.8 | 0.9 | 1.1 | 1.4 | 0.9 | 0.8 | |
| Median household income | 0.087 | ||||||||||
| 0 to 25 th percentile | 31.9 | 34.2 | 31.7 | 31.6 | 34.9 | 33.4 | 31.4 | 37.0 | 36.8 | 33.6 | |
| 26 th to 50 th percentile | 30.5 | 26.3 | 27.0 | 27.5 | 23.1 | 28.8 | 26.3 | 23.7 | 21.9 | 26.2 | |
| 51 st to 75 th percentile | 19.7 | 21.1 | 19.5 | 21.8 | 22.8 | 20.4 | 24.9 | 22.6 | 22.5 | 21.7 | |
| 76 th to 100 th percentile | 18.0 | 18.5 | 21.8 | 19.1 | 19.2 | 17.4 | 17.4 | 16.7 | 18.9 | 18.5 | |
| Weekend admission | 22.7 | 24.2 | 21.3 | 24.5 | 23.5 | 25.9 | 22.6 | 25.6 | 26.8 | 24.1 | <0.001 |
| Hospital characteristics | |||||||||||
| Region | <0.001 | ||||||||||
| Northeast | 24.5 | 19.9 | 18.8 | 20.7 | 16.1 | 16.2 | 15.9 | 17.9 | 15.1 | 18.5 | |
| Midwest | 18.4 | 20.2 | 18.3 | 22.5 | 22.8 | 18.4 | 21.1 | 20.6 | 21.1 | 20.4 | |
| South | 32.3 | 35.8 | 40.7 | 34.9 | 40.3 | 44.2 | 40.5 | 40.2 | 38.2 | 38.4 | |
| West | 24.8 | 24.2 | 22.2 | 22.0 | 20.8 | 21.2 | 22.5 | 21.2 | 25.6 | 22.7 | |
| Bed size † | <0.001 | ||||||||||
| Small | 10.1 | 8.6 | 5.4 | 11.3 | 9.1 | 9.8 | 8.9 | 9.4 | 7.6 | 9.0 | |
| Medium | 22.4 | 22.5 | 20.7 | 24.2 | 24.2 | 21.0 | 19.9 | 16.4 | 21.2 | 21.6 | |
| Large | 67.5 | 68.8 | 73.9 | 64.5 | 66.7 | 69.2 | 71.2 | 74.2 | 71.2 | 69.4 | |
| Urban location | 87.8 | 94.1 | 91.5 | 90.6 | 88.0 | 91.0 | 90.7 | 88.5 | 89.5 | 90.1 | 0.026 |
| Teaching hospital | 49.5 | 48.6 | 42.1 | 49.0 | 44.5 | 43.1 | 47.3 | 47.7 | 47.7 | 46.7 | 0.190 |
| Comorbidities ‡ | |||||||||||
| Smoker | 9.2 | 9.7 | 10.7 | 10.2 | 11.0 | 12.6 | 18.3 | 19.4 | 21.9 | 13.4 | <0.001 |
| Dyslipidemia | 17.9 | 22.3 | 25.9 | 23.4 | 29.4 | 34.9 | 40.6 | 43.4 | 50.1 | 31.4 | <0.001 |
| Coronary artery disease | 61.4 | 60.7 | 62.0 | 58.6 | 62.1 | 68.2 | 72.6 | 72.8 | 75.2 | 65.5 | <0.001 |
| Family history of coronary artery disease | 0.8 | 0.6 | 1.7 | 0.1 | 1.2 | 1.1 | 2.4 | 2.1 | 2.2 | 1.3 | <0.001 |
| Prior myocardial infarction | 7.7 | 8.4 | 7.8 | 7.1 | 6.9 | 9.3 | 9.5 | 13.5 | 14.8 | 9.3 | <0.001 |
| Carotid artery disease | 1.3 | 0.7 | 1.0 | 0.5 | 1.5 | 1.1 | 1.9 | 0.7 | 3.0 | 1.2 | <0.001 |
| Dementia | 2.2 | 1.4 | 0.5 | 1.2 | 1.2 | 1.3 | 1.7 | 1.7 | 2.9 | 1.5 | 0.004 |
| Atrial fibrillation | 19.0 | 22.7 | 19.1 | 24.5 | 19.5 | 14.8 | 16.3 | 15.7 | 22.3 | 19.4 | <0.001 |
| Congestive heart failure | 53.2 | 56.7 | 53.2 | 47.8 | 51.9 | 40.6 | 44.1 | 44.5 | 46.1 | 48.7 | <0.001 |
| Prior percutaneous coronary intervention | 5.5 | 5.9 | 7.2 | 7.7 | 8.0 | 8.2 | 11.7 | 14.4 | 13.0 | 8.9 | <0.001 |
| Prior coronary artery bypass grafting | 9.2 | 9.9 | 8.6 | 4.9 | 7.5 | 9.3 | 11.4 | 9.1 | 12.2 | 9.0 | <0.001 |
| Acquired immune deficiency syndrome | 0.6 | 0.4 | 0.0 | 0.7 | 0.2 | 0.0 | 0.1 | 0.8 | 0.2 | 0.3 | 0.239 |
| Alcohol abuse | 0.3 | 1.2 | 0.4 | 0.5 | 1.4 | 0.6 | 0.3 | 0.5 | 1.2 | 0.7 | 0.411 |
| Deficiency anemia | 31.7 | 33.6 | 28.1 | 27.5 | 30.0 | 36.0 | 46.2 | 48.2 | 55.3 | 36.8 | <0.001 |
| Rheumatoid arthritis/collagen vascular diseases | 1.2 | 1.6 | 0.6 | 2.1 | 2.3 | 1.7 | 2.5 | 2.0 | 1.9 | 1.8 | <0.001 |
| Chronic blood loss anemia | 1.9 | 0.9 | 1.9 | 2.1 | 1.5 | 1.0 | 1.1 | 0.7 | 0.4 | 1.3 | <0.001 |
| Chronic pulmonary disease | 16.9 | 17.5 | 20.4 | 17.5 | 21.3 | 14.8 | 17.4 | 16.5 | 16.7 | 17.7 | 0.034 |
| Coagulopathy | 5.3 | 3.2 | 6.3 | 7.0 | 7.6 | 7.0 | 7.9 | 8.8 | 8.6 | 6.9 | <0.001 |
| Depression | 3.8 | 4.1 | 3.3 | 3.3 | 2.8 | 6.0 | 4.4 | 5.6 | 4.4 | 4.2 | <0.001 |
| Diabetes mellitus (uncomplicated) | 23.7 | 25.1 | 25.5 | 27.5 | 28.4 | 31.2 | 32.9 | 31.2 | 31.4 | 28.5 | <0.001 |
| Diabetes mellitus (complicated) | 32.8 | 31.7 | 29.1 | 24.0 | 25.3 | 23.0 | 27.8 | 28.5 | 28.1 | 27.6 | <0.001 |
| Drug abuse | 1.2 | 1.0 | 1.4 | 1.5 | 1.7 | 2.0 | 1.3 | 0.7 | 2.3 | 1.5 | 0.05 |
| Hypertension | 79.1 | 81.2 | 82.6 | 82.1 | 83.5 | 84.9 | 85.1 | 86.4 | 89.1 | 83.7 | <0.001 |
| Hypothyroidism | 5.9 | 5.7 | 9.1 | 8.2 | 6.0 | 9.8 | 11.5 | 9.1 | 11.7 | 8.5 | <0.001 |
| Liver disease | 1.3 | 1.5 | 0.8 | 2.2 | 1.8 | 2.5 | 2.1 | 2.1 | 3.1 | 1.9 | <0.001 |
| Lymphoma | 1.0 | 0.5 | 0.3 | 1.0 | 0.8 | 1.6 | 1.1 | 0.5 | 0.4 | 0.8 | 0.773 |
| Fluid and electrolyte disorder | 26.0 | 27.1 | 26.4 | 30.7 | 28.0 | 29.8 | 29.3 | 35.0 | 39.1 | 30.0 | <0.001 |
| Metastatic cancer | 0.5 | 0.3 | 0.8 | 0.4 | 0.7 | 0.5 | 0.2 | 0.6 | 0.7 | 0.5 | 0.609 |
| Other neurologic disorders | 5.4 | 7.0 | 6.2 | 7.2 | 7.1 | 7.9 | 9.1 | 7.7 | 7.2 | 7.2 | <0.001 |
| Obesity | 5.3 | 3.6 | 4.3 | 3.6 | 5.4 | 7.7 | 11.3 | 9.1 | 12.1 | 6.8 | <0.001 |
| Paralysis | 2.9 | 2.5 | 3.0 | 3.0 | 1.9 | 1.9 | 3.4 | 2.7 | 2.6 | 2.6 | 0.808 |
| Peripheral vascular disease | 20.1 | 15.5 | 17.2 | 16.9 | 18.5 | 20.0 | 24.9 | 25.7 | 29.0 | 20.6 | <0.001 |
| Psychoses | 1.3 | 1.4 | 0.9 | 1.9 | 1.2 | 2.0 | 1.7 | 2.0 | 3.0 | 1.7 | <0.001 |
| Pulmonary circulation disorders | 0.3 | 0.3 | 0.4 | 0.0 | 0.0 | 0.1 | 0.2 | 0.0 | 0.2 | 0.2 | 0.003 |
| Solid tumor without metastasis | 1.1 | 1.8 | 1.1 | 0.9 | 0.7 | 0.8 | 1.5 | 1.3 | 1.5 | 1.2 | 0856 |
| Peptic ulcer (nonbleeding) | 0.0 | 0.0 | 0.2 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.087 |
| Valvular disease | 1.5 | 0.8 | 0.8 | 0.4 | 0.1 | 0.0 | 0.4 | 0.3 | 0.4 | 0.5 | <0.001 |
| Weight loss | 3.7 | 4.7 | 4.8 | 4.9 | 4.9 | 4.4 | 6.2 | 4.3 | 7.0 | 5.0 | <0.001 |
| Presentation | <0.001 | ||||||||||
| Anterior wall STEMI | 27.0 | 22.3 | 23.0 | 23.8 | 27.0 | 27.1 | 24.4 | 22.0 | 21.4 | 21.4 | |
| Inferior wall STEMI | 25.6 | 22.4 | 27.8 | 31.5 | 33.4 | 30.4 | 29.1 | 35.6 | 32.6 | 29.8 | |
| Other STEMI | 47.4 | 55.3 | 49.2 | 44.7 | 39.6 | 42.6 | 46.5 | 42.4 | 46.0 | 45.8 |
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