Chronic kidney disease (CKD) in patients with ST-elevation myocardial infarction (STEMI) is associated with worse outcomes. We assessed the impact of CKD on guideline directed coronary revascularization and outcomes among STEMI patients. The Nationwide Inpatient Sample dataset from 2012-2014 was used to identify patients with STEMI using International Classification of Diseases, Ninth Revision, Clinical Modification codes. Patients were categorized as non-CKD, CKD without dialysis, and CKD with dialysis (CKD-HD). Outcomes were revascularization, death and acute renal failure requiring dialysis (ARFD). A total of 534,845 were included (88.9% non-CKD; 9.6% CKD without dialysis, and 1.5% CKD-HD). PCI was performed in 77.4% non-CKD, 56.2% CKD without dialysis, and 48% CKD-HD patients (p < 0.0001). In-hospital mortality and ARFD were significantly higher in CKD patients (16.5% and 40.6%) compared with non-CKD patients (7.12% and 7.17%) (p < 0.0001). In-hospital mortality was significantly lower in patients treated revascularization compared with patients treated medically (non-CKD: adjusted odds ratio (aOR) 0.280, p < 0.0001; CKD without dialysis: aOR 0.39, p < 0.0001; CKD-HD: aOR 0.48, p < 0.0001). CKD was associated with higher length of hospital stay and cost (5.86 ± 13.97, 7.57 ± 26.06 and 3.99 ± 11.09 days; p < 0.0001; $25,696 ± $63,024, $35,666 ± $104,940 and $23,264 ± $49,712; p < 0.0001 in non-CKD, CKD without dialysis and CKD-HD patients respectively). In conclusion, CKD patients with STEMI receive significantly less PCI compared with patients without CKD. Coronary revascularization for STEMI in CKD patients was associated with lower mortality compared to medical management. The presence of CKD in patients with STEMI is associated with higher mortality and ARFD, prolonged hospital stay and higher hospital cost.
Chronic kidney disease (CKD) is a common comorbidity among patients presenting with ST elevation myocardial infarction (STEMI) and primary percutaneous coronary intervention (PCI) is the standard of care for STEMI patients. Several studies have shown that patients with CKD who present with STEMI do not receive guideline-directed interventions compared to patients with normal renal function. – A project that linked the US Renal Data System database with the National Registry of Myocardial Infarction 3 showed that the patients on dialysis more often experienced prehospital delays in the management of acute myocardial infarction due to less suspicion of acute coronary syndrome and lower percentage of dialysis patients having chest pain as compared to non-dialysis patients. Moreover, patients with renal dysfunction who presented with STEMI or left bundle branch block received less reperfusion therapy compared to those with normal renal function. Studies have shown that patients with moderate to severe CKD who presented with STEMI have significantly higher in-hospital mortality compared to patients with normal renal function. Higher mortality in CKD patients presenting with STEMI could be secondary to suboptimal care in addition to comorbidities. The primary objective of this study was to assess the impact of CKD on guideline-directed PCI among patients with STEMI. The secondary objective was to assess in-hospital clinical outcomes, length of hospital stay (LOS) and cost of care for patients with CKD admitted to hospital with a primary diagnosis of STEMI.
Methods
A cross-sectional study was conducted utilizing data obtained from the Agency for Healthcare Research and Quality, Nationwide Inpatient Sample (NIS) database from 2012 to 2014. The NIS is the largest publicly available all-payer inpatient healthcare database in the United States, providing nationally representative data for inpatient hospitalization. This is a publicly available database with deidentified patient information and therefore does not require institutional review board approval. Unweighted data contain records for more than 7 million hospital stays each year, sampled from nearly 20% of US community hospitals (nonfederal, short term, general and specialty). , Sample weighting was applied to achieve national representation as suggested by the Agency for Healthcare Research and Quality. The NIS database is internally validated, and results are shown to correlate well with other US hospitalization discharge databases. The data were analyzed in accordance to the methodology previously published.
We queried the NIS database using the International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) codes. Included were patients admitted to hospital with a primary diagnosis of STEMI with and without CKD. Patients with CKD were identified using ICD-9-CM codes 5851 (stage1), 5852 (stage 2), 5853 (stage 3), 5854 (stage 4), 5855 (stage 5), and 5859 (unspecified). Patients with ESRD were identified using the diagnosis code for CKD requiring dialysis (5856), Patients with CKD were sub-grouped into CKD requiring dialysis (CKD-HD) and CKD not requiring dialysis.
The baseline patient characteristics included age, gender, race, comorbidities, hospital region, hospital type, hospital bed size, household income, and payer status. The severity of comorbid conditions was assessed using the Deyo modification of the Charlson Co-morbidity Index (CCI). Teaching hospitals were defined as those with an American Medical Association approved residency/fellowship program, a faculty member of the Council of Teaching Hospitals, or those having a ratio of full time equivalent hours for interns and residents to patients of 0.25 or greater.
The guideline directed interventional or revascularization outcomes were coronary angiography, PCI, use of thrombolytic agents, coronary artery bypass grafting (CABG), use of intra-aortic balloon pump (IABP) and percutaneous mechanical circulatory assist devices as appropriate. The primary clinical outcomes were in-hospital mortality, acute renal failure requiring dialysis and secondary clinical outcomes were other post-procedural complications. Average LOS and hospital cost of care were also compared between groups. The NIS database contains data on total hospital charges, representing the amount that hospitals billed for services. NIS data was merged with cost-to-charge ratios to obtain the cost of hospitalization. , Using the merged data elements from the cost-to-charge ratio files and the total charges reported in the NIS database, the hospital’s total charge data was converted to standardized cost estimates by multiplying total charges with the appropriate cost-to-charge ratio. , Costs were then adjusted for inflation according to the US consumer price index. The predictors of mortality, prolonged LOS (days) (>75th percentile or not) or higher hospital cost (adjusted for inflation, >75th percentile or not) were assessed.
The Pearson Chi-Square test was used to evaluate differences between CKD groups for categorical outcomes. Logistic regression analyses were conducted to evaluate bivariate and multivariable associations between comorbidities and mortality. The variable analyzed were CKD status (CKD vs non-CKD; CKD without dialysis vs non-CKD; CKD-HD vs non-CKD), controlling for demographic characteristics, anemia due to blood loss, congestive heart failure (CHF), chronic lung disease, anemia due to deficiency, diabetes, liver disease, hypertension, peripheral vascular disease (PVD), peptic ulcer disease excluding bleeding, dyslipidemia, tobacco use, atrial fibrillation or flutter, prior PCI, prior CABG, prior cerebrovascular accidents (CVA), PCI, thrombolysis, and CABG. Same logistic regression model adjusting for the same comorbidities was used to assess the effect of revascularization versus medical management. Based on condition index and variance inflation factor (VIF), no collinearity was detected since all condition indexes were less than 20 and VIF less 1.30.
Results
The baseline patient characteristics are presented in Table 1 . The p-value for all the baseline characteristics comparison is <0.0001. The clinical outcomes are presented in Tables 2 and 3 and Figure 1 . In-hospital mortality was significantly lower in patients treated with coronary revascularization (PCI or CABG) compared to patients treated medically across all groups of patients (non-CKD: adjusted odds ratio (aOR) 0.280, confidence interval (CI) 0.28 to 0.29, p < 0.0001; CKD without dialysis: aOR 0.39, CI 0.37 to 0.24, p < 0.0001; CKD-HD: aOR 0.48, CI 0.43 to 0.53, p < 0.0001) . Acute renal failure requiring dialysis was also significantly lower in patients who had revascularization compared to patients treated medically across all groups (non-CKD: aOR 0.58, CI 0.56 to 0.59, p < 0.0001; CKD without dialysis: aOR 0.90, CI: 0.86 to 0.93, p < 0.0001).
| Variable | Total | Chronic kidney disease status | ||
|---|---|---|---|---|
| None | Not on dialysis | On dialysis | ||
| Sample size a | ||||
| Unweighted | 106,969 | 95,092 (88.9%) | 10,257 (9.6%) | 1,620 (1.5%) |
| Weighted | 534,845 | 475,460 (88.9%) | 51,285 (9.6%) | 8,100 (1.5%) |
| Age (Years) b | 63.6 ± 30.6 | 62.5 ± 30.0 | 73.3 ± 28.5 | 66.8 ± 30.0 |
| 18–34 | 6,360 (1.2%) | 6,145 (1.3%) | 155 (0.3%) | 60 (0.7%) |
| 35–49 | 74,245 (13.9%) | 71,475 (15.0%) | 2,115 (4.1%) | 655 (8.1%) |
| 50–64 | 212,395 (39.7%) | 199,050 (41.9%) | 10,665 (20.8%) | 2,680 (33.1%) |
| 65–79 | 159,975 (29.9%) | 137,645 (29.0%) | 18,945 (36.9%) | 3,385 (41.8%) |
| ≥80 | 81,870 (15.3%) | 61,145 (12.9%) | 19,405 (37.8%) | 1,320 (16.3%) |
| Racial category | ||||
| NH white | 388,325 (77.7%) | 348,010 (78.4%) | 36,315 (75.5%) | 4,000 (51.9%) |
| Other (not white) | 111,220 (22.3%) | 95,740 (21.6%) | 11,770 (24.5%) | 3,710 (48.1%) |
| Sex | ||||
| Male | 363,035 (67.9%) | 325,900 (68.6%) | 32,370 (63.1%) | 4,765 (58.8%) |
| Female | 171,775 (32.1%) | 149,530 (31.5%) | 18,910 (36.9%) | 3,335 (41.2%) |
| Insurance | ||||
| Public c | 284,135 (53.2%) | 237,125 (50.0%) | 40,130 (78.4%) | 6,880 (85.1%) |
| Private d | 179,310 (33.6%) | 170,315 (35.9%) | 8,080 (15.8%) | 915 (11.3%) |
| Self-pay/other | 70,220 (13.2%) | 66,940 (14.1%) | 2,990 (5.8%) | 290 (3.6%) |
| Hospital size | ||||
| Small | 61,105 (11.4%) | 53,555 (11.3%) | 6,735 (13.1%) | 815 (10.1%) |
| Medium | 141,135 (26.4%) | 125,130 (26.3%) | 13,715 (26.7%) | 2,290 (28.3%) |
| Large | 332,605 (62.2%) | 296,775 (62.4%) | 30,835 (60.1%) | 4,995 (61.7%) |
| Urbanity | ||||
| Urban | 488,860 (91.4%) | 435,480 (91.6%) | 45,785 (89.3%) | 7,595 (93.8%) |
| Rural | 45,985 (8.6%) | 39,980 (8.4%) | 5,500 (10.7%) | 505 (6.2%) |
| Region | ||||
| Northeast | 91,485 (17.1%) | 81,490 (17.1%) | 8,450 (16.5%) | 1,545 (19.1%) |
| Midwest | 126,245 (23.6%) | 111,990 (23.6%) | 12,860 (25.1%) | 1,395 (17.2%) |
| South | 213,760 (40.0%) | 191,110 (40.2%) | 19,445 (37.9%) | 3,205 (39.6%) |
| West | 103,355 (19.3%) | 90,870 (19.1%) | 10,530 (20.5%) | 1,955 (24.1%) |
| CCI | ||||
| 1 | 212,765 (39.8%) | 212,765 (44.8%) | 0 (0.0%) | 0 (0.0%) |
| 2 | 169,600 (31.7%) | 160,865 (33.8%) | 7,905 (15.4%) | 830 (10.3%) |
| >2 | 152,480 (28.5%) | 101,830 (21.4%) | 43,380 (84.6%) | 7,270 (89.8%) |
b – Mean and standard deviation reported on variable label line with frequencies and percentages reported below.
c – Includes Medicaid & Medicare.
| Total (n = 534,845) | Chronic kidney disease status | |||||
|---|---|---|---|---|---|---|
| None (n = 475,460) | Not on dialysis (n = 51,285) | p-Value | On dialysis (n = 8,100) | p-value | ||
| Procedure ‡ | ||||||
| Coronary Angiography | 448,930 (83.9%) | 408,455 (85.9%) | 35,235 (68.7%) | <0.0001 | 5,240 (64.7%) | <0.0001 |
| PCI | 400,600 (74.9%) | 367,900 (77.4%) | 28,810 (56.2%) | <0.0001 | 3,890 (48.0%) | <0.0001 |
| Drug-eluting stents | 271,265 (50.7%) | 251,705 (52.9%) | 17,385 (33.9%) | <0.0001 | 2,175 (26.9%) | <0.0001 |
| Single-vessel PCI | 325,525 (86.9%) | 299,600 (87.1%) | 23,080 (84.8%) | <0.0001 | 2,845 (81.3%) | <0.0001 |
| Multi-vessel PCI | 49,075 (13.1%) | 44,290 (12.9%) | 4,130 (15.2%) | <0.0001 | 655 (18.7%) | <0.0001 |
| Thrombolysis | 5,955 (1.1%) | 5,465 (1.2%) | 455 (0.9%) | <0.0001 | 35 (0.4%) | <0.0001 |
| CABG | 32,860 (6.1%) | 28,670 (6.0%) | 3,615 (7.1%) | <0.0001 | 575 (7.1%) | <0.0001 |
| IABP | 47,750 (8.9%) | 41,370 (8.7%) | 5,525 (10.8%) | <0.0001 | 855 (10.6%) | <0.0001 |
| PVAD | 3,575 (0.7%) | 2,955 (0.6%) | 495 (1.0%) | <0.0001 | 125 (1.5%) | <0.0001 |
| Clinical outcome ‡ | ||||||
| Cardiogenic shock | 61,475 (11.4%) | 50,675 (10.7%) | 9,150 (17.8%) | <0.0001 | 1,650 (20.4%) | <0.0001 |
| Acute renal failure * | 56,120 (10.5%) | 34,095 (7.2%) | 20,830 (40.6%) | <0.0001 | 1,195 (14.8%) | <0.0001 |
| In-hospital mortality | 43,665 (8.2%) | 33,855 (7.1%) | 7,825 (15.3%) | <0.0001 | 1,985 (24.5%) | < 0.0001 |
| Anemia/hemorrhage † | 16,100 (4.3%) | 16,100 (3.4%) | 5,190 (10.1%) | <0.0001 | 1,430 (17.7%) | <0.0001 |
| Temporary pacemaker | 11,570 (2.5%) | 11,570 (2.4%) | 1,720 (3.4%) | <0.0001 | 315 (3.9%) | <0.0001 |
| Any cardiac complication | 12,850 (2.4%) | 11,640 (2.5%) | 1,020 (2.0%) | <0.0001 | 190 (2.4%) | 0.55 |
| Hemorrhage or hematoma | 11,600 (2.2%) | 10,120 (2.1%) | 1,275 (2.5%) | <0.0001 | 205 (2.5%) | 0.01 |
| PP respiratory failure | 6,120 (1.1%) | 5,070 (1.1%) | 835 (1.6%) | <0.0001 | 215 (2.7%) | <0.0001 |
| Permanent pacemaker | 3,000 (0.6%) | 2,200 (0.5%) | 705 (1.4%) | <0.0001 | 95 (1.2%) | <0.0001 |
| Pericardial complications | 1,730 (0.3%) | 1,475 (0.3%) | 195 (9.7%) | 0.007 | 60 (0.7%) | < 0.0001 |
| Vascular complications | 160 (0.0%) | 145 (0.0%) | 10 (0.0%) | 0.17 | 5 (0.1%) | 0.11 |
| Length of hospital Stay § | 4.23 ± 11.9 | 3.99 days ± 11.1 | 5.86 days ± 14.0 | <0.0001 | 7.57 days ± 26.0 | <0.0001 |
| Cost of care § | $23,638 ± $52,454 | $23,266 ± $49,722 | $25,697 ± $62,996 | <0.0001 | $32,630 ± $104,858 | <0.0001 |
‡ Frequency & percent, chi-square p-value
| CKD vs No CKD | ||||||
|---|---|---|---|---|---|---|
| Unadjusted | p-value | Adjusted | p-value | |||
| OR | 95% CI | AOR | 95% CI | |||
| Clinical outcome | ||||||
| Cardiogenic shock | 1.86 | (1.82–1.91) | <0.0001 | 1.50 | (1.46–1.54) | <0.0001 |
| Acute renal failure * | 7.63 | (7.48–7.79) | <0.0001 | 5.29 | (5.17–5.41) | <0.0001 |
| In-hospital mortality | 2.58 | (2.52–2.65) | <0.0001 | 1.67 | (1.62–1.72) | <0.0001 |
| Anemia/hemorrhage † | 3.58 | (3.48–3.69) | <0.0001 | 1.74 | (1.68–1.80) | <0.0001 |
| Temporary pacemaker | 1.42 | (1.36–1.49) | <0.0001 | 1.16 | (1.10–1.23) | < 0.0001 |
| Any cardiac complication | 0.83 | (0.78 – 0.88) | <0.0001 | 0.78 | (0.73–0.84) | <0.0001 |
| Hemorrhage or hematoma | 1.18 | (1.11–1.24) | <0.0001 | 1.03 | (0.97–1.10) | 0.29 |
| PP respiratory failure | 1.67 | (1.56–1.79) | <0.0001 | 1.23 | (1.14–1.32) | <0.0001 |
| Permanent pacemaker | 2.94 | (2.71–3.19) | <0.0001 | 1.67 | (1.52–1.83) | <0.0001 |
| Pericardial complications | 1.39 | (1.21–1.58) | <0.0001 | 1.19 | (1.03–1.39) | 0.02 |
| Vascular complications | 0.83 | (0.49–1.41) | <0.0001 | 1.00 | (0.58–1.74) | <0.0001 |
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