Previous studies have documented disparities in both access to invasive cardiovascular procedures and outcomes in patients with Medicaid, Medicare, or no insurance. Outcomes by insurance have yet not been examined in a percutaneous coronary intervention (PCI) population. Data from patients undergoing PCI from June 2000 to June 2009 were retrospectively analyzed. Insurance was categorized as private, Medicare, Medicaid, and uninsured, according to the primary insurance at discharge. The outcome variable of interest was major adverse cardiac events (a composite of death, Q-wave myocardial infarction, and target vessel revascularization) at 1 year. Multivariable Cox regression analysis was stratified according to age <65 and ≥65 years. Of the 13,573 patients who had undergone PCI, 6,653 (49.0%) had private insurance, 6,150 (45.3%) had Medicare, 486 (3.6%) had Medicaid, and 284 (2.1%) were uninsured. Of the patients <65 years old, Medicaid (hazard ratio [HR] 1.59, 95% confidence interval [CI] 1.04 to 2.43), Medicare (HR 2.18, 95% CI 1.58 to 2.99), and no insurance (HR 2.41, 95% CI 1.36 to 4.27) were associated with greater rates of adjusted major adverse cardiac events at 1 year compared with private insurance. Of the patients ≥65 years old, only Medicaid (HR 3.07, 95% CI 1.09 to 8.61) was associated with a greater rate of adjusted major adverse cardiac events at 1 year. In conclusion, patients with government-sponsored insurance and no insurance have worse cardiovascular outcomes than patients with private insurance after PCI at 1 year. This implies that the provision of health insurance alone might not have a dramatic effect on cardiovascular outcomes after PCI.
Socioeconomic status has been most commonly approximated by income level; however, it can also be conceptualized by other measures such as an individual’s education, occupation, living environment, and access to medical care. Health insurance (or the lack thereof) is an important measure of one’s access to care, although the effect of insurance type on cardiovascular outcomes has been primarily examined in the setting of acute myocardial infarction (MI). Most of these studies have shown a less utilization of invasive procedures and worse outcomes for patients with Medicaid or no insurance. Because different patterns of reimbursement, practice patterns, and health behaviors might apply to patients with no insurance or government-sponsored insurance, cardiovascular outcomes after percutaneous coronary intervention (PCI) could also vary according to a patient’s primary insurance. We, therefore, sought to examine the effect of insurance type on major adverse cardiac events (MACE) at 1 year in a diverse population undergoing PCI, hypothesizing that patients with Medicaid, Medicare, or no insurance would have greater rates of MACE than patients with private insurance.
Methods
The clinical, procedural, and follow-up data for patients undergoing PCI at a single center were prospectively entered and retrospectively analyzed. Indications for PCI included stable angina pectoris, unstable angina pectoris, and acute MI. This database was then merged with the hospital billing database, which included the primary insurance type (or lack thereof) and zip code for each patient at hospital discharge. The zip code was matched with United States Census Bureau data regarding the median household income by zip code to approximate the patient’s household income. The present study included patients who had undergone PCI from June 2000 to June 2009.
All patients had received aspirin 325 mg and clopidogrel 300 to 600 mg (at the operator’s discretion) before the procedure. Anticoagulation regimens were chosen at the operator’s discretion and included unfractionated heparin targeted to achieve an activated clotting time of 200 to 300 seconds, with or without a glycoprotein IIb/IIIa inhibitor, or bivalirudin 0.75 mg/kg, followed by an infusion of 1.75 mg/kg/hour for the duration of the procedure. After the procedure, aspirin was prescribed indefinitely, and clopidogrel was prescribed for a minimum of 1 month for patients receiving bare metal stents and 6 months for patients receiving drug-eluting stents.
The institutional review board at the Washington Hospital Center and MedStar Health Research Institute (Washington, DC) approved the present study. A dedicated data coordinating center performed all data management and analyses. The prespecified clinical and laboratory data during hospitalization were obtained from the hospital charts and were reviewed by independent research personnel who were unaware of the objectives of the present study. All patients routinely underwent pre- and post-PCI 12-lead electrocardiography to detect procedure-related ischemic changes and/or the presence of new pathologic Q waves. Blood samples were taken at 6 and 24 hours before and after PCI to assess the creatine kinase-MB biomarker level. If the creatine kinase-MB level was elevated to greater than the reference range (4 mg/dl), measurement was repeated every 8 hours until it had returned to less than the reference range. Clinical follow-up evaluations were conducted at 30 days, 6 months, and 1 year by telephone interview or office visits. The occurrence of major late clinical events was recorded and included death (all-cause), Q-wave MI, target vessel revascularization (TVR), and stent thrombosis.
The primary end point was MACE, a composite of death from all causes, Q-wave MI, and TVR. Q-wave MI was defined as the appearance of new pathologic Q waves in the coronary distribution of the treated artery, with an increase in the creatine kinase-MB to ≥2 times the reference value. TVR was defined as revascularization occurring in any area along the previously treated vessel. An acute presentation was defined as presentation with non–ST-segment elevation MI or ST-segment elevation MI. Major bleeding was quantified according to the Thrombolysis In Myocardial Infarction study group definition and consisted of intracranial hemorrhage or clinically overt bleeding, with a decrease in hemoglobin of ≥5 g/dl or hematocrit of ≥15%.
Primary insurance type was categorized as private, Medicare, Medicaid, or uninsured. Race was defined according to the patient’s response at admission. The patients identified themselves as African-American, Caucasian Asian, Hispanic, or Native American, and could only select one category. The patients were then defined as African-American or non-African-American for purposes of comparison.
Two of us (M.A.G., R.W.) were primarily responsible for the data analysis. Continuous variables are presented as mean ± SD and categorical variables as percentages. Differences in continuous variables between groups were compared using Student’s t test. Categorical variables were compared using the chi-square test or Fisher’s exact test, as appropriate. The mean values for the different groups were compared using analysis of variance. Thirty-day and 1-year outcomes were compared using the log-rank test and are presented as Kaplan-Meier percentages. A p value <0.05 was considered statistically significant. To test the independent effects of insurance type and income on the interval to a MACE, we constructed 2 multivariable Cox regression models. Given that a significant interaction was present between patient age and insurance type, we performed separate multivariable regression analyses for patients <65 and ≥65 years old. This was in part because Medicare primarily covers patients with end-stage renal disease in the population <65 years old and covers a much broader range of patients ≥65 years old. Private insurance was used as the reference group for both regression analyses. A very small number of patients ≥65 years old were without insurance, and they were excluded from the regression analysis for patients ≥65 years old.
We selected covariables for both models according to significant univariate p values and overall clinical relevance. The covariables in each model, in addition to insurance type, included black race, age, gender, cardiogenic shock, acute coronary syndrome, current smoking, and a history of PCI, coronary artery bypass grafting, chronic renal insufficiency, congestive heart failure, diabetes mellitus, systemic hypertension, and peripheral vascular disease. Given that certain insurance types (i.e., Medicaid and no insurance) have been tightly linked to median income, we excluded median income by zip code from the models to avoid collinearity. The covariables in the model are expressed as hazard ratios (HRs) with 95% confidence intervals (CIs). Statistical analyses were performed using SAS, version 9.1 (SAS Institute, Cary, North Carolina).
Results
The present study included 13,573 patients who had undergone PCI ( Table 1 ). Overall, 6,653 (49.0%) had private insurance, 6,150 (45.3%) had Medicare, 486 (3.6%) had Medicaid, and 284 (2.1%) were uninsured at hospital discharge after PCI. Patients with Medicaid ($41,087), no insurance ($55,417), and Medicare ($59,459) all had a lower median household income compared to patients with private insurance ($62,463; p <0.001 for trend.) Overall, 8,973 patients (66.1%) were white, 3,482 (25.7%) were black, 473 (3.5%) were Asian, 147 (1.1%) were Hispanic, and 51 (0.4%) were Native American. Patients with Medicare had more co-morbidities, including previous coronary artery bypass grafting or PCI, congestive heart failure, systemic hypertension, hyperlipidemia, chronic renal insufficiency, and peripheral vascular disease. Important exceptions were found, however, with diabetes mellitus more frequent in Medicaid patients, and current smoking much more common in patients with Medicaid or no insurance.
| Variable | Private (n = 6,653) | Medicare (n = 6,150) | Medicaid (n = 486) | Uninsured (n = 284) | p Value |
|---|---|---|---|---|---|
| Age (years) | 57.3 ± 9.4 | 73.3 ± 9.5 | 55.1 ± 10.6 | 53.7 ± 9.0 | <0.001 |
| Men | 4,891 (73.6%) | 3,545 (57.7%) | 262 (54.1%) | 208 (73.2%) | <0.001 |
| Race | |||||
| Caucasian | 4,586 (68.9%) | 4,143 (67.4%) | 95 (19.5%) | 149 (52.5%) | <0.001 |
| African-American | 1,489 (22.4%) | 1,575 (25.6%) | 324 (66.7%) | 94 (33.1%) | <0.001 |
| Asian | 243 (3.7%) | 198 (3.2%) | 17 (3.5%) | 15 (5.3%) | 0.21 |
| Hispanic | 71 (1.1%) | 50 (0.8%) | 17 (3.5%) | 9 (2.2%) | <0.001 |
| Median household income ⁎ | $62463 ± 20,729 | $59459 ± 20,831 | $41087 ± 15,778 | $55417 ± 16,667 | <0.001 |
| ST-segment elevation myocardial infarction | 815 (12.3%) | 567 (9.2%) | 113 (23.3%) | 85 (29.9%) | <0.001 |
| Non–ST-segment elevation myocardial infarction | 578 (8.7%) | 480 (7.8%) | 74 (15.2%) | 55 (19.4%) | <0.001 |
| Shock on presentation | 202 (3.1%) | 250 (4.1%) | 35 (7.3%) | 22 (7.8%) | <0.001 |
| Previous coronary artery bypass surgery | 906 (13.7%) | 1,499 (24.6%) | 64 (13.2%) | 22 (7.8%) | <0.001 |
| Previous percutaneous coronary intervention | 1,562 (24.8%) | 1,551 (27.9%) | 107 (24.0%) | 47 (17.4%) | <0.001 |
| Heart failure | 571 (8.9%) | 1,246 (21.1%) | 86 (18.3%) | 32 (11.7%) | <0.001 |
| Diabetes mellitus | 2,064 (31.3%) | 2,358 (38.7%) | 219 (45.5%) | 77 (27.4%) | <0.001 |
| Hypertension † | 5,492 (82.9%) | 5,523 (90.3%) | 428 (88.2%) | 211 (74.6%) | <0.001 |
| Dyslipidemia ‡ | 5,883 (89.0%) | 5,423 (89.3%) | 406 (84.4%) | 217 (77.2%) | <0.001 |
| Chronic renal insufficiency | 461 (7.0%) | 1,274 (20.9%) | 85 (17.7%) | 11 (3.9%) | <0.001 |
| Peripheral vascular disease | 629 (9.6%) | 1,335 (22.0%) | 61 (12.8%) | 14 (4.9%) | <0.001 |
| Current smoker | 1,842 (27.7%) | 829 (13.5%) | 236 (48.6%) | 164 (57.7%) | <0.001 |
† History of hypertension diagnosed and/or treated with medication or currently treated with diet and/or medication by a physician.
‡ Included patients with previously documented diagnosis of dyslipidemia; patients could be treated with diet or medication; a new diagnosis could be made during present hospitalization by total cholesterol level >160 mg/dl; did not include elevated triglycerides.
Of the 13,573 patients, 51.9% were <65 years old. Of those <65 years old, 81.7% had private insurance, 8.7% had Medicare, 5.8% had Medicaid, and 3.8% were uninsured. Of the patients aged ≥65 years, 85.2% had Medicare, 13.5% had private insurance, 1.1% had Medicaid, and 0.2% were uninsured. The overall prevalence of co-morbidities and MACE rates in the population ≥65 years old was greater than in the population <65 years old; however, the trends for differences by insurance type were similar. Patients with Medicaid (23.3%) or no insurance (29.9%) were more likely to present with ST-segment elevation MI than were patients with Medicare (9.2%) or private insurance (12.3%; p <0.001). A similar trend held for a presentation with non–ST-segment elevation MI, which was more common for patients with Medicaid (15.2%) and no insurance (19.4%) than for those with Medicare (7.8%) or private insurance (8.7%; p <0.001). A presentation with cardiogenic shock was also more common in patients with Medicaid (7.3%) and no insurance (7.8%) than in those with Medicare (4.1%) or private insurance (3.1%; p <0.001).
The overall procedural success rate was 98.0% and did not differ according to insurance type ( Table 2 ). Patients with Medicare were more likely to have undergone PCI of the left main artery or a saphenous vein graft. Patients with private insurance, however, were more likely to have undergone PCI of the left anterior descending artery. Patients with private insurance were also more likely to undergo intravascular ultrasound-guided PCI, although total stented length did not differ by insurance type. Patients with Medicare and private insurance were more likely to have received bivalirudin. In contrast, patients with Medicaid or without insurance were more likely to have received a glycoprotein IIb/IIIa inhibitor. Patients with private insurance were also more likely to have received ≥1 drug-eluting stent (78.2%) than were those with Medicare (72.0%), no insurance (60.1%), or Medicaid (59.9%, p <0.001).
| Variable | Private (n = 10,910) | Medicare (n = 10,457) | Medicaid (n = 764) | Uninsured (n = 480) | p Value |
|---|---|---|---|---|---|
| Coronary vessel of intervention | |||||
| Right | 3,580 (32.8%) | 3,213 (30.7%) | 247 (32.3%) | 168 (35.0%) | 0.005 |
| Left main | 80 (0.7%) | 251 (2.4%) | 1 (0.1%) | 6 (1.3%) | <0.001 |
| Left anterior descending | 4,376 (40.1%) | 3,832 (36.6%) | 280 (36.6%) | 186 (38.8%) | <0.001 |
| Left circumflex | 2,442 (22.4%) | 2,399 (22.9%) | 214 (28.0%) | 113 (23.5%) | 0.004 |
| Saphenous vein graft | 385 (3.5%) | 718 (6.9%) | 19 (2.5%) | 6 (1.3%) | <0.001 |
| Bare metal stent | 6,169 (58.8%) | 5,622 (55.4%) | 379 (51.6%) | 171 (36.5%) | <0.001 |
| Drug-eluting stent | 7,306 (72.9%) | 6,338 (65.9%) | 413 (56.8%) | 252 (55.3%) | <0.001 |
| Procedural success | 10,441 (98.1%) | 10,046 (97.9%) | 739 (98.0%) | 461 (97.3%) | 0.61 |
| Intravascular ultrasound | 6,201 (57.9%) | 5,677 (55.4%) | 378 (50.1%) | 200 (42.3%) | <0.001 |
| Stented length (mm) | 19.9 ± 6.7 | 19.7 ± 6.8 | 20.0 ± 6.2 | 20.6 ± 6.3 | 0.18 |
| Heparin | 1,054 (15.8%) | 840 (13.7%) | 90 (18.5%) | 50 (17.6%) | <0.001 |
| Bivalirudin | 4,807 (72.3%) | 4,727 (76.9%) | 329 (67.7%) | 179 (63.0%) | <0.001 |
| Glycoprotein IIb/IIIa inhibitor | 801 (12.4%) | 447 (7.4%) | 58 (12.1%) | 59 (21.0%) | <0.001 |
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