Is Veteran User Status an
Independent Risk Factor for Mortality
After Private Sector CABG?
William B. Weeks, MD, MBA
Dorothy A. Bazos, Ph.D.
David M. Bott, Ph.D.
Stacey L. Campbell, MPH
Edward L. Hannan, Ph.D.
Michael J. Racz, MA
Stephen M. Wright, Ph.D.
Elliott S. Fisher, MD, MPH
This work was funded by the HSR&D Grant ACC 01-117-1
(Utilization, System of Care, and Outcome of CABG in New York Veterans)
Background
• Improving the quality of care for VHA patients
with Coronary Artery Disease is a priority.
• Prior research has reported worse risk-adjusted
outcomes for veterans following AMI and CABG.
• Concerns remain that previous studies may not
have adequately accounted for the increased
burden of illness of veterans who rely on the VHA
health care system for their care.
We know that many veterans who receive care in the VHA
(VHA users) obtain bypass surgery in the private sector...
Study Question One
• Are VHA users who obtain CABG in the
private sector sicker than non-VHA users?
Study Question Two
• Is being a VHA user an independent risk
factor for mortality following CABG in the
private sector?
Data Sources
(Study period: 1997-1999)
• VHA
– Administrative and Enrollment files
• New York State Department of Health
– Cardiac Surgery Reporting System (CSRS)
Methods
• Cohort study
• Study population
–
–
–
–
Males only
Isolated CABG (no other heart or vascular surgery)
Private sector hospitals located in New York State
Discharged January 1, 1997 – December 31, 1999
• Comparison groups
– VHA users
– non-VHA users
• Outcome
– In-hospital mortality after CABG
Methods
• Statistical Methods
– Logistic regression models
• To determine expected mortality risk for each participant
• To determine whether VHA user status is an independent risk
factor for mortality
• Risk Factors – defined by CSRS
–
–
–
–
Demographics
Comorbidity (e.g. diabetes, vascular disease)
Disease Severity
Models included hospital effects
• This allows us to account for possibility that VHA patients
received care in higher or lower quality hospitals
Results – Study Population
Male Population Having Isolated CABG
in NY private sector cardiac facilities 1997-1999
Male VHA and non-VHA users
n = 40,728
VHA user
n = 3,009
non-VHA user
n = 37,719
Deaths = 67
Deaths = 670
Are VHA users sicker?
Male Patients Having Risk Factor
Risk Factor
Demographics
Age <45 years
Age 45-64 years
Age 65 + years
% VHA user % non-VHA user
(n=3,009)
(n=37,719)
p-value
0.3
21.0
78.6
3.2
43.6
53.1
<0.0001
Comorbidity
Stroke
9.8
6.1
<0.0001
Aortoiliac Disease
6.7
5.0
<0.0001
20.2
15.1
<0.0001
7.2
5.5
0.0002
31.0
26.9
<0.0001
2.3
1.7
0.0372
COPD
Calcified Aorta
Diabetes
Renal CR < 2.5
Are VHA users sicker?
Male Patients Having Risk Factor
Risk Factors
% VHA user % non-VHA user
(n=3,009)
(n=37,719)
p-value
Disease Severity
Ejection Fraction (missing)
Ejection Fraction < 20
Ejection Fraction 20-29
Ejection Fraction 30-39
Ejection Fraction 40+
3.7
1.7
8.1
16.0
70.7
2.8
2.0
7.6
14.6
73.0
MI < 6 hrs
MI 6-23 hrs
MI 1- 7days
MI 7 or more days
No previous MI
Left Main Disease
0.8
0.9
13.6
42.8
41.8
26.9
0.9
0.9
14.2
39.2
44.2
24.8
Previous Operations
10.0
6.6
0.0031
0.0352
0.0011
<0.0001
VHA users are sicker than others...
Mortality Rate per 100 population
VHA user
non-VHA User
3
2.5
2
1.5
1
2.33
1.77
0.5
0
Expected Mortality Rates
Veteran user status is not an independent
risk factor for CABG mortality
Multiple Logistic Regression Model
Adjusted
Odds Ratio
95% CI
p-value
VHA user
0.947
(0.726, 1.234) 0.6853
Limitations
• Only looked at CABG Surgery.
• Only looked at male VHA users who had
private sector CABG – male veterans
having CABG in the VHA could still be
sicker.
Conclusions
• Male veterans having CABG in private sector
facilities in NY, who are users of the VHA system
tend to be sicker than male non-VHA users.
• VHA user status is NOT an independent risk factor
for CABG mortality in the private sector.
• VHA users do as well as other male patients in
regard to in-hospital mortality associated with
CABG.
Implications
• Opportunities exist for VHA to improve
CABG outcomes by coordinating where
CABG occurs in the private sector
(hospitals with lower mortality rates).
• Adequate risk adjustment should allow fair
comparisons of VHA to non-VHA care for
veterans.