The aim of the present study was to explore the outcomes of percutaneous coronary intervention (PCI) in patients with rheumatoid arthritis (RA) and coronary heart disease. We identified 25,367 patients from the National Health Insurance Research Database who underwent nonstenting PCI in Taiwan in 2007. Of these patients, 240 had been diagnosed with RA. As a comparison group, we selected 1,200 patients who were matched with the study group by gender and age. We performed conditional logistic regression analysis to compare the outcomes of PCI between the 2 groups. We found no significant differences in the rates of in-hospital mortality (2.5% vs 3.1%, p = 0.628), 90-day readmission for PCI (8.3% vs 7.2%, p = 0.559), or 365-day readmission for PCI (22.5% vs 19.2%, p = 0.236) between the patients with and without RA. Similarly, the conditional logistic regression analyses revealed that patients with RA had no greater adjusted odds of in-hospital mortality (odds ratio 0.94, 95% confidence interval 0.37 to 2.36), 90-day readmission for PCI (odds ratio 1.20, 95% confidence interval 0.37 to 2.36), and 365-day readmission for PCI (odds ratio 1.30, 95% confidence interval 0.92 to 1.83) than the comparison group. In conclusion, our study did not find an increased risk of adverse outcomes among patients with RA after PCI.
Three possible mechanisms have been proposed to explain the excessive mortality observed among patients with rheumatoid arthritis (RA) attributed to cardiovascular disease: (1) the greater prevalence of “traditional” cardiovascular diseases, (2) RA-associated factors such as chronic inflammatory status, and (3) receiving treatment of co-morbidities, in particular, cardiovascular co-morbidities. It has been estimated that those with RA have about a twofold risk of cardiovascular diseases compared to people without RA after taking traditional risk factors into consideration. However, data regarding the outcomes of treatment of coronary heart disease among patients with RA remain limited. One study demonstrated that recurrent cardiac events and deaths occurred more often in patients with RA after acute coronary syndrome, implying worse outcomes among those with RA and coronary heart disease. Our aim was to document the outcomes of percutaneous coronary intervention (PCI) among patients with RA and a control group in a nationwide and longitudinal cohort study.
Methods
The present study used data sourced from the National Health Insurance Research database (NHIRD), published by the Taiwan National Health Research Institute and provided to scientists in Taiwan for research purposes. The NHIRD includes all inpatient and ambulatory care medical benefit claims and registries of contracted medical facilities, medical personnel, and program beneficiaries, constituting approximately 98% of the Taiwanese population of about 23 million. Numerous researchers have used the NHIRD to perform large-scale epidemiologic studies.
Because the NHIRD consists of de-identified secondary data released to the public for research purposes, the present study was exempt from full review by the institutional review board.
We selected patients who had received operational procedure International Classification of Disease, 9th revision, Clinical Modification (ICD-9-CM) codes 36.01, 36.02, or 36.05 (broadly defined as PCI, without stenting) from the NHIRD as the study sample. We then identified 25,367 patients who had undergone PCI from January to December 2007. We excluded patients who had undergone PCI before 2007 (n = 3,254) to increase the likelihood of including only new cases. However, Taiwan began its National Health Insurance program in 1995; thus, we were not able to track the use of medical services before 1996 using the NHIRD and therefore could not exclude patients who had undergone PCI before 1996. Of the 22,113 patients we found who had undergone PCI, 240 had been diagnosed with RA during ambulatory care visits. In the present study, we only considered a patient to have RA if the RA diagnosis had occurred either in an inpatient setting or appeared on ≥2 ambulatory care claims coded from 2006 to 2007. These 240 patients with RA were the study group.
We extracted our comparison group from the remaining 21,873 patients who had undergone PCI in 2007. We first excluded those patients who had received an RA diagnosis in 1996 and 2008. We then randomly selected 1,200 patients (5 for every patient with RA) matched to the study group by gender and age (≤64, 65 to 74, and ≥74 years). Ultimately, 1,440 patients were included in the present study.
The dependent variables were all dichotomous, including in-hospital mortality, 90-day readmission for PCI, and 365-day readmission for PCI.
In addition, to assess the independent effect of RA on the PCI outcomes, we adjusted for a number of potential confounders, including monthly income, number of PCI vessels, a principal diagnosis of myocardial infraction (MI) (ICD-9-CM code 410), a secondary diagnosis of MI, any other non–MI coronary disease diagnosis (ICD-9-CM codes 411 to 414), diabetes (ICD-9-CM code 250), chronic obstructive pulmonary disease (ICD-9-CM codes 490–496), hypertension (ICD-9-CM codes 401 to 405), renal dysfunction (ICD-9-CM codes 580 to 586), congestive heart failure (ICD-9-CM codes 428, 402.01, 402.11, 402.91, 404.01, 404.11, and 404.91), and peripheral vascular disease (ICD-9-CM codes 440 and 443).
The SAS statistical package (SAS System for Windows, version 8.2, SAS Institute, Cary, North Carolina) was used to perform data analysis. Global chi-square analyses were performed to compare the prevalence of medical co-morbidities for patients with and without RA. We also constructed conditional (fixed-effects) logistic regression models in which the observations were conditioned on patient gender and age group to examine the treatment outcome after PCI among patients with and without RA. A 2-sided p value of ≤0.05 was considered statistically significant.
Results
The mean age was 68.8 ± 11.0 years for the sampled patients. The distribution of sociodemographic characteristics and co-morbidities among the sampled patients is listed in Table 1 .
| Variable | RA | p Value | |
|---|---|---|---|
| Yes | No | ||
| Gender | |||
| Male | 132 (55.0%) | 660 (55.0%) | |
| Female | 108 (45.0%) | 540 (45.0%) | |
| Age (years) | 1.000 | ||
| <65 | 68 (28.3%) | 340 (28.3%) | |
| 65–74 | 97 (40.4%) | 485 (40.4%) | |
| >74 | 75 (31.3%) | 375 (31.3%) | |
| No. of PCI arteries | 0.628 | ||
| 1 | 175 (72.9%) | 893 (74.4%) | |
| >1 | 65 (27.1%) | 307 (25.6%) | |
| Diabetes mellitus | 98 (40.8%) | 484 (40.3%) | 0.885 |
| Hypertension | 180 (75.0%) | 773 (64.4%) | 0.002 |
| Chronic obstructive pulmonary disease | 65 (27.1%) | 219 (18.3%) | 0.002 |
| Renal disease | 36 (15.0%) | 127 (10.6%) | 0.049 |
| Congestive heart failure | 37 (15.4%) | 135 (11.3%) | 0.069 |
| Peripheral vascular disease | 14 (5.8%) | 42 (3.5%) | 0.088 |
| Coronary disease | 0.450 | ||
| MI as primary diagnosis | 67 (27.9%) | 364 (30.3%) | |
| MI as secondary diagnosis | 10 (4.2%) | 67 (5.6%) | |
| Other coronary artery disease | 163 (67.9%) | 769 (64.1%) | |
| Hyperlipidemia | 87 (36.3%) | 411 (34.3%) | 0.552 |
| Monthly income | 0.506 | ||
| 0 | 77 (32.1%) | 422 (35.2%) | |
| NT$1–NT$15,840 | 56 (23.3%) | 231 (19.2%) | |
| NT$15,841–NT$25,000 | 83 (34.6%) | 418 (34.8%) | |
| ≥NT$25,001 | 24 (10.0%) | 129 (10.8%) | |
The differences in in-hospital mortality, 90-day readmission for PCI, and 365-day readmission for PCI between patients with and without RA are listed in Table 2 . Consistently, no significant difference was found in the rates of in-hospital mortality, 90-day readmission for PCI, or 365-day readmission for PCI among patients with and without RA.
| Outcome Variable | Total Sample (n = 1,440) | RA | |
|---|---|---|---|
| Yes (n = 240) | No (n = 1,200) | ||
| In-hospital mortality | 43 (3.0%) | 6 (2.5%) | 37 (3.1%) |
| 90-Day readmission for percutaneous coronary intervention | 107 (7.4%) | 20 (8.3%) | 87 (7.2%) |
| 365-Day readmission for percutaneous coronary intervention | 284 (19.7%) | 54 (22.5%) | 230 (19.2%) |
The crude and adjusted odds ratio for in-hospital mortality, 90-day readmission for PCI, and 365-day readmission for PCI among patients with and without RA are listed in Table 3 . Logistic regression analyses conditioned on gender and age group revealed that patients with RA had no greater odds of in-hospital mortality, 90-day readmission for PCI, or 365-day readmission for PCI than patients without RA, after adjusting for monthly income, number of PCI vessels, principal diagnosis of MI, secondary diagnosis of MI, any other non–MI coronary disease, diabetes, chronic obstructive pulmonary disease, hypertension, renal dysfunction, congestive heart failure, and peripheral vascular disease.
| Outcome Variable | RA | |
|---|---|---|
| Yes | No | |
| In-hospital mortality | ||
| Crude odds ratio | 0.81 (0.34–1.93) | 1.00 |
| Adjusted odds ratio | 0.94 (0.37–2.36) | 1.00 |
| 90-Day readmission for percutaneous coronary intervention | ||
| Crude odds ratio | 1.16 (0.70–1.93) | 1.00 |
| Adjusted odds ratio | 1.20 (0.71–2.02) | 1.00 |
| 365-Day readmission for percutaneous coronary intervention | ||
| Crude odds ratio | 1.22 (0.88–1.71) | 1.00 |
| Adjusted odds ratio | 1.30 (0.92–1.83) | 1.00 |
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