This study demonstrates that differences in payer/insurance status affect patient outcomes following cardiac valve procedures. These results reveal that Uninsured, Medicaid, and Medicare patients incur worse unadjusted and risk-adjusted outcomes compared to those with Private Insurance. More importantly, Uninsured and Medicaid payer status independently increases the risk of adjusted in-hospital mortality and the likelihood of postoperative complications above that of Medicare status even after directly accounting for socioeconomic status as well as hospital related factors and several measures of co-morbid disease that are frequently encountered in low-income patient groups. In addition, significant differences in resource utilization were detected among payer groups, as Medicaid patients accrued the longest average hospital length of stay and highest total costs.
The relationship between insurance status and cardiac surgical outcomes remains ill-defined. Few studies have attempted to demonstrate disproportionate outcomes in cardiac surgery patients based on insurance status but are relatively small, single institution analyses.21, 22
To our knowledge, prospective evaluation of this trend within cardiac operations has not been previously performed. One of the largest series, conducted by Zacharias and colleagues (2005) at the Medical University of Ohio, retrospectively analyzed 6,377 patients, documenting worse long-term survival for Medicaid patients undergoing CABG operations at an urban, community hospital.22
Alternatively, Higgins et al. (1998) concluded that payer status and race was not associated with early mortality following CABG among a specific cohort of 2,776 black patients.21
These conflicting reports may be explained by a relatively small patient population relative to the present study.
The effect of insurance status has been performed in other types of subspecialty surgery. In a study of over 225,000 vascular surgery patients, Giacovelli et al (2008) demonstrated that insurance status predicted disease severity,5
and Kelz et al. (2004) reported that Medicaid and uninsured patients encountered worse postoperative outcomes following colorectal cancer resections.23
In the later series of 13,415 patient records, Medicaid patients were found to incur a 22% increased risk of complications during hospital admission and a 57% increased risk of in-hospital death compared to those with private insurance. Recently, a comprehensive review of major surgical outcomes reported a 97% and 74% increase in the risk-adjusted odds of surgical mortality for Medicaid and Uninsured surgical patients, which included patients undergoing CABG operations.12
The findings of this study are likely multifactorial in origin and represent the interaction of several factors. First, elective operations were more commonly performed in patients with Medicare or Private Insurance, while Medicaid and Uninsured patients more commonly underwent non-elective (urgent and/or emergent) operations. The higher incidence of emergent operations among Medicaid and Uninsured populations and the presumed negative effect on outcomes is well documented.5, 24, 25
In our analyses, operative urgency status was accounted for in each predictive model, and the differences in payer groups remain significant. In addition, the confounding influence of inadequate preoperative resuscitation in the emergent setting may contribute to compromised outcomes for these patients. Secondly, the immeasurable influence of physician and healthcare system bias may negatively impact Medicaid and Uninsured patients. For many surgical patients, private insurance status often allows for referral to expert surgeons for their disease while referral patterns for Medicaid and Uninsured patients may have differed. For these complex operations, the impact of surgeon volume on outcomes has been well established, and expert surgeons have been shown to significantly impact outcomes.26
Third, differences in comorbid disease may serve as a proxy for larger social and lifestyle influences between payer groups as Medicaid and Uninsured patients had the highest incidence of drug and alcohol abuse as well as depression and psychoses. Finally, deficits in access to care, poor health maintenance, and delayed diagnosis may have resulted in the presentation of more advanced valve disease among the Medicaid and Uninsured patient populations.
Other explanations for inherent differences between payer populations have been previously described. Studies have identified factors such as language barriers and low as well as poor nutrition and health maintenance.2, 27
However, payer status impacts several different areas of health care delivery. Differences exist in not only access, but also in the type of primary care that patients receive. Prior studies have suggested that Medicaid and Uninsured patients receive the majority of primary care within Emergency Departments.28, 29
In fact, fewer diagnostic studies during emergency department visits and decreased in-patient hospitalizations following specialty consultations have been documented for these populations compared to private insurance patients.30
Furthermore, Medicaid and Uninsured populations often present with more advanced disease compared to privately insured patients, and patient insurance type has been shown to affect access to cancer screening, treatment, and outcomes.31, 32
Payer status may also effect hospital discharge processes as discharge from the hospital may be delayed for Medicaid and Uninsured populations due to lack of support and resources to be cared for properly at home.
This study has several noteworthy limitations. First, the retrospective study design introduces inherent selection bias; however, the strict methodology and randomization of the NIS database reduces the influence of this bias. Second, NIS is a large, administrative database, and there exists a potential for unrecognized miscoding among diagnostic and procedure code. The performed data analyses allow us to comment upon statistical measures of association and do not establish a cause and effect relationship between payer status and risk adjusted outcomes. This study reports short-term outcomes as NIS records reflect inpatient admissions. Consequently, the results reported herein may underestimate the true incidence of perioperative mortality and morbidity following patient discharge. Certain assumptions regarding individual status may also impact data analyses as the potential for dual insurance eligibility and cross over between payer groups exists. However, NIS records reflect the primary payer status at the time of discharge, mitigating the effect of such scenarios. In addition, it is possible that a small percentage of Privately Insured patients may have “inadequate” coverage and may more closely resemble those without insurance with respect to poor health maintenance and advanced disease. In addition, we are unable to comment on the nature, etiology or degree of cardiac valve disease, which may impact perioperative morbidity and mortality rates. Finally, in our data analyses we are unable to include adjustments for other well-established cardiac surgical risk factors such as low preoperative albumin levels, poor nutritional status, preoperative cardiac functional status (NYHA Class), ventricular function, or cardiopulmonary bypass use and/or exposure times. However, as our sensitivity analyses proved resilient to the presence of a potentially unmeasured confounder, it is unlikely that inclusion of such factors in our analyses would change our primary results.