Circulation. 1995;92:69-72
(Circulation. 1995;92:69-72.)
© 1995 American Heart Association, Inc.
Enrollment in the Health Alliance Plan HMO Is Not an Independent Risk Factor for Coronary Artery Bypass Graft Surgery
Gaetano Paone, MD;
Robert S.D. Higgins, MD;
Trey Spencer, MS;
Norman A. Silverman, MD
From the Division of Cardiac and Thoracic Surgery and Division of
Biostatistics and Research Epidemiology, Henry Ford Hospital, 2799 W. Grand
Blvd, Detroit, Mich.
Correspondence to Gaetano Paone, MD, Division of Cardiac and Thoracic
Surgery, Henry Ford Hospital, 2799 W Grand Blvd, Detroit, MI 48202.
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Abstract
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Background Henry Ford Hospital is the sole
provider of cardiac
surgical services for the Health Alliance Plan, a
health maintenance
organization (HMO) that presently serves
450 000 enrollees.
Methods and Results To determine the effect of managed care
referral patterns on the outcome of coronary artery bypass
graft (CABG) surgery, we retrospectively reviewed two concurrent groups
of patients, 569 HMO patients and 225 patients with
fee-for-service (FFS) insurance, who had undergone isolated
primary CABG surgery between January 1, 1990 and January 31, 1994. The
605 patients with Medicare operated on during the same time frame were
excluded to obviate age bias. Age, sex, use of cardiac medications,
history of prior percutaneous transluminal coronary angioplasty
or thrombolytic therapy, history of recent and remote
myocardial infarction, extent of coronary disease, presence of
preexisting comorbid conditions, and incidence of unstable clinical
syndromes and left ventricular dysfunction (ejection
fraction<40%) were comparable for both groups. Inhospital mortality
(HMO group, 1.9%; FFS group, 2.2%), mean ICU stay (HMO, 2.6±0.3
days; FFS, 2.3±0.3 days), and total hospital length of stay (HMO,
9.8±0.8 days; FFS, 8.6±0.6 days) were likewise similar.
Conclusions These data refute the notion that the
gatekeeper mentality often associated with managed-care health
insurance vehicles results in delayed referral of patients with
coronary artery disease and results in suboptimal outcome.
Key Words: surgery • bypass • coronary disease • managed care
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Introduction
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Henry Ford Hospital is the sole provider
of cardiac surgical
services for the HAP, an HMO that at present
has approximately
450 000 enrollees. In addition, the hospital and
medical group
provide service to members of the community at large who
have
other more traditional health insurance vehicles. This
characteristic,
we believe, affords the opportunity to compare
characteristics
and outcomes in concurrent patient groups who should
theoretically
differ only in the type of health insurance they
have.
The present study was undertaken to determine whether enrollment in
the managed-care program in and of itself had any impact on
clinical characteristics and outcomes in patients with coronary
artery disease referred for CABG surgery at a single institution. To
the best of our knowledge, no such analysis has been previously
reported.
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Methods
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Between January 1, 1990, and January 31, 1994, 1399 patients
underwent
isolated primary CABG surgery. Five hundred sixty-nine
patients
belonged to a managed-care program, HAP; 225 patients were
insured
by a variety of FFS vehicles. These two groups form the basis
of
this report. We excluded from analysis 605 patients who had
Medicare
insurance to obviate any age bias. Data for comparison of
preoperative
demographics, intraoperative parameters, and
postoperative outcomes
for the two study groups were obtained from a
computerized cardiac
surgical database.
The following criteria were applied to all patients: Surgery was
considered emergent if the patient had been taken directly from the
Catheterization Laboratory or Coronary Care
Unit (CCU) after initial consultation. Patients in the CCU who received
intravenous nitrates and/or heparin were classified as
having urgent surgery. All others were categorized as having elective
procedures.
Classification of anginal status was as follows: Patients admitted to
the hospital electively for surgery with angina as their predominant
cardiac symptom were classified as having had chronic stable angina.
Patients who underwent cardiac catheterization for
stable symptoms but who were admitted for other reasons (ie, positive
stress test, threatening anatomy) were likewise classified as
having chronic stable angina. Patients were considered to have had
unstable angina if they had been admitted with new or worsening
symptoms and underwent surgical revascularization
before discharge. The subgroup of patients with postinfarction angina
were those who were admitted either with a documented transmural or
non–Q-wave infarction, who developed postinfarct pain, and who were
subsequently operated on during the same admission. Any patient who was
first discharged from the hospital and then readmitted was classified
as having either chronic stable angina or unstable angina, independent
of the time course relative to the infarct.
Patients were classified as having had renal disease if the
preoperative serum creatinine level was >2.5 mg/dL or if
they had been on dialysis. Chronic obstructive pulmonary
disease (COPD) was recorded as being present if the patient
required pharmacological therapy or carried the diagnosis by history.
Left main coronary artery disease was identified as an
estimated reduction in luminal diameter of 
50%.
All procedures were performed with standard cardiopulmonary
bypass techniques using ascending aortic and single venous cannulation,
with moderate systemic hypothermia (28°C to 32°C). Myocardial
protection was afforded by multidose antegrade cold blood potassium
cardioplegia supplemented with topical iced slush. All proximal and
distal anastomoses were performed during a single period of aortic
cross clamping.
Statistical Analysis
Wilcoxon two-sample rank sum tests were
used to
compare the provider groups (HAP, FFS) with respect to ordinal and
continuous variables. For dichotomous variables,
2 tests were used to compare the proportion
within each provider group with specified traits or conditions. (For
low cell frequencies, a Fisher's exact test was used instead of the
2 test.) An 
-level of 0.05 was used to
interpret the results. All data, where appropriate, are
presented as mean±SEM.
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Results
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Comparisons of preoperative demographics and comorbidity,
preoperative
medical therapy, prior cardiac history, indications for
surgery,
angiographic findings, and operative categories of the two
groups
are shown in Tables 1 through
6
.
One factor was significant
at the
P<.05 level. Preoperative
use of intravenous heparin
was found in 35.7% of HAP
patients versus 26.7% of FFS patients
(
P=.015). One
additional factor approached significance at this
level. In the HAP
population, 65.3% of patients were classified
as having elective
procedures versus 72.4% of those in the FFS
group
(
P=.056).
Intraoperative data for the two groups were as follows: HAP
patients received 2.61±0.04 grafts compared with 2.67±0.06
grafts for
those with FFS insurance (P=.371). Cross-clamp times
(HAP, 44.4±0.8 minutes; FFS, 46.6±1.2 minutes;
P=.138) and
bypass times (HAP, 80.0±1.2 minutes; FFS, 81.4±1.7 minutes;
P=.197) were likewise comparable.
Hospital mortality was 1.9% for HAP patients and 2.2% in the FFS
group (P=.794). Mean length of stay in the ICU was
2.6±0.3
days in the HAP group versus 2.3±0.3 days in the FFS group
(P=.734). Total length of hospital stay was also similar for
the two groups (HAP 9.8±0.8 days versus FFS 8.6±0.6;
P=.911).
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Discussion
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Enrollment in managed-care programs continues to grow, from
2%
in 1970, to 7% in 1984, to 15.9% in 1991.
1 In fact,
recent
estimates suggest that >70% of the insured population in
metropolitan
areas of California now have some form of managed-care
insurance.
2 Data are increasingly available to support the
idea that HMOs
can be effective in controlling costs. A randomized
trial by
the Rand Corporation reported a 25% decrease in expenditures
for
all health care provided to one HMO group compared with the
FFS
system despite the fact that care within the study protocol
was free to
patients in both systems.
3 Savings were largely
due to a
40% decrease in hospital admissions.
The more critical issue is whether limiting expenditures in this manner
comes at the expense of quality care. More specifically, does the
gatekeeper concept central to managed-care programs excessively
limit patient access to tertiary care and ultimately affect patient
outcomes? Lee-Feldstein et al4 reported that for patients
with breast cancer diagnosed between 1984 and 1990, those treated at
HMO hospitals were at significantly greater risk of dying than those
treated at large community hospitals. Ware et al5 reported
worse health outcomes among sick low income patients in the HMO group
when compared with those in the FFS group. Most recently, Mark et
al6 reported that US patients had better functional status
and fewer cardiac symptoms 1 year after acute myocardial infarction
than Canadian patients and noted that patients in Canada underwent
fewer invasive cardiac procedures and had fewer visits to
specialists.They suggested that the more aggressive care in the United
States may have been responsible for the better outcomes.
The intent of this study was to determine whether enrollment in an HMO
had any effect on the outcome of patients with a diagnosis of
coronary artery disease referred for CABG surgery. Our
hypothesis on initiation of this retrospective analysis was
that patients within the HMO group would, because of their presumed
restrictions to subspecialty care, present for surgical therapy at
a later stage of their disease (ie, older age, more extensive anatomic
disease, worse ventricular function). We believed that
these patients would therefore constitute a higher risk cohort and have
suboptimal outcomes when compared with those patients with traditional
FFS insurance vehicles. Given that the treating cardiologists and
surgeons were the same for both groups, we believed we could then
theorize that this difference in outcomes was related to either delayed
recognition or delayed referral by the primary care or gatekeeper
component of the managed-care program.
The results of this analysis, we believe, dispute that
hypothesis. The preoperative characteristics and postoperative outcomes
are quite similar for both groups. This would, we believe, suggest that
there was in fact no delay in diagnosis or referral of patients from
within the HMO group. Furthermore, allowing for exclusion of the
Medicare cohort, the relevant clinical characteristics of the two study
groups are comparable with those of other series for factors such as
sex, presence of preoperative comorbidity, extent of coronary
disease, and previous cardiac event.7 8 9
Despite the great similarity in the patient cohorts, two factors
warrant specific comment. More patients in the HAP group were receiving
intravenous heparin preoperatively than in the FFS group
(35.7% versus 26.7%, P=.015). In addition, 65.3% of
patients in the HMO group underwent elective procedures compared with
72.4% of those with FFS insurance (P=.056). One therefore
achieved significance, and the other closely approached it. These
percentages suggest a proportionate increase in the HMO patients'
level of disease severity on presentation that could
contradict our conclusion relative to the hypothesis. The clinical
indications for surgery were closely comparable for the two groups (ie,
existence of similar percentages in each group of stable and unstable
syndromes). These differences then essentially reflect that a somewhat
greater percentage of patients in the HMO group were receiving heparin
and were in the CCU before surgery. We are concerned that these data
may indicate some increase in overall acuteness for HMO patients; while
not sufficient in our opinion to cause the hypothesis to be rejected,
we believe that continued scrutiny of this issue is certainly
warranted. Ultimately, the clinical significance of these differences
did not affect the early outcomes for patients in the HMO group.
The data presented here are from a retrospective
analysis of patients who had already undergone surgical
revascularization. We therefore cannot account for
patients with known coronary disease or for that matter with
chest pain who have yet to be referred beyond the primary care level.
We likewise have no way of knowing whether patients with more advanced
disease or symptoms are being denied access to specialty care.
Intuitively, it seems likely that if large numbers of HMO patients were
being treated excessively at the primary care level, they would
present with a higher incidence of previous myocardial infarction,
more depressed left ventricular function, and increased
prevalence of congestive heart failure; this was not the case. Unlike
the HMO group, all of whom were treated at this institution, our FFS
group represents some proportion of a population that as a
whole can be, and is being, referred to other institutions in the
community. Again, similarities between the two groups and those of
other series would suggest that our FFS group is not in some way
preselected but rather is quite representative of a
typical cardiac surgical practice.
It should be noted, and in fact emphasized, that the results of this
analysis are specific to a single HMO at a single institution.
The HAP, like other HMOs, employs an internist or a general
practitioner as the "Gatekeeper." The patient cannot
self-refer to tertiary levels of care but must be referred by this
primary care provider. Unlike the general perception of HMO programs,
and indeed the practice at some, there are no direct individual
financial incentives within the program to discourage these primary
care physicians from referring patients to subsequent levels of care
when deemed appropriate. It is therefore neither possible nor
appropriate to further extrapolate these data into a broad-based
endorsement of managed-care health delivery in general. We have no
means of comparing the specifics of the HAP program with those of other
HMOs. We don't know whether the lack of financial incentives at the
primary care level fosters a more timely referral to tertiary care than
would otherwise be expected if such were not the case. Furthermore,
this study involves no cost analyses. Therefore, we wonder
whether it is possible that outcomes were similar because overall cost
expenditures were similar. If so, this would negate the major
theoretical advantage of a managed-care program, which is in fact
presumed to be effective cost savings.
These data document that enrollment in the HAP was not an independent
risk factor for CABG surgery and refute the notion and our hypothesis
that the gatekeeper mentality associated with managed-care programs
would necessarily result in suboptimal outcomes. To go beyond this
conclusion, however, further investigation, including prospective
analyses across large demographic groups and intense and
more-meaningful cost analyses to adjudicate
risk-benefit relations, is needed.
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Selected Abbreviations and Acronyms
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| CABG |
= |
coronary artery bypass graft |
| FFS |
= |
fee-for-service |
| HAP |
= |
Health Alliance Plan |
| HMO |
= |
health maintenance organization |
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Abstract
Introduction