Process of Care in Peripheral Arterial Disease
Tracie C. Collins MD MPH
Houston VA Medical Center
Houston, TX
Funding Period: October 2002 - September 2005

BACKGROUND/RATIONALE:
PAD, blockage of the leg arteries due to atherosclerosis, can lead to leg amputation or bypass revascularization. Although the functional status and quality of life implications of leg amputation are self-evident, many fail to realize the limitations of bypass surgery [30-day mortality of 2-8%; 5-year graft failure rates of 20 to 90%; 5-year risk of amputation of 20%]. Because of the risk for adverse outcomes in patients with PAD, research is needed to better understand how to optimize the care provided to patients with this disease.

OBJECTIVE(S):
The management of PAD includes atherosclerotic risk factor control to reduce the risk of poor outcomes. Poor outcomes in PAD are either systemic or localized to the legs. While much research has focused on adverse systemic outcomes in patients with PAD, less has been done to determine those factors that are related to adverse limb events. The purpose of this study is to examine the association of process of care and the level of risk factor control with adverse outcomes (primary – surgical limb outcomes; secondary – mortality) in patients with PAD.

METHODS:
We performed a retrospective cohort study of patients who have undergone diagnostic testing within the Houston VA Medical Center vascular laboratory from 1995 to 1998. We reviewed the vascular laboratory results for the ankle-brachial index (ABI; the ratio of the systolic blood pressure in the ankle to the systolic blood pressure in the arm) for each patient. For those patients who screened positive for PAD based on an ABI result of < 0.9, we performed a chart review. We defined time zero as three years prior to the vascular laboratory visit and we followed patients from this point forward until the first adverse limb event (i.e., lower extremity bypass surgery or amputation), death, or the end of the study (i.e., December 31, 2001). We reviewed each chart for information on the process of care for patients with PAD, including physicians’ efforts to manage atherosclerotic risk factors, and actual level of risk factor control. Through chi-square analyses and multivariate Cox regression modeling, we have determined the association of the level of risk factor control with each adverse event.

FINDINGS/RESULTS:
We identified 816 patients with PAD as diagnosed during 1995 to 1998. Of these patients, 796 had available chart information. The mean age was 65± 9.9 years) and 230 (28.9 percent experienced an adverse limb event (136, lower-extremity bypass; 94, lower-extremity amputation), and 354 (44.5 percent) died. Patients with two or more risk factors other than hypertension had a hazard ratio of 3.1 for lower-extremity bypass surgery. For lower-extremity amputation, modifiable risk factors associated with increased risk included use of lipid-lowering agents < 50 percent of prescribed time and control of diabetes mellitus for fewer than 75 percent of visits. Following the index date, each 10 percent increase in days of antiplatelet therapy reduced risk of death by 10 percent.

Poor lipid and glucose control were associated with increased risk for major limb event. Antiplatelet therapy protected against mortality. These data suggest that risk-factor management (specifically low-density lipoprotein and glucose control) and antiplatelet therapy are critical for a system-based process-of-care approach in PAD patients.

IMPACT:
The results of this study will identify the potential role of diabetes and lipid control to reduce adverse limb outcomes in PAD. This information will be disseminated to clinicians, researchers, and policy-makers. We will also translate the results for patients and family members so that our veterans can be informed about PAD.

PUBLICATIONS:

Journal Articles

1. Collins TC, Kroll TL, Krueger PN, Willson P, Ashton CM, Sharf BF. A qualitative approach to developing a patient-derived intervention to increase exercise in peripheral arterial disease. Journal of Cardiopulmonary Rehabilitation. 2006; 26(2): 92-100.
2. Collins TC, Suarez-Almazor M, Bush RL, Petersen NJ. Gender and peripheral arterial disease. Journal of the American Board of Family Medicine. 2006; 19(2): 132-40.
3. Collins TC, Suarez-Almazor M, Peterson NJ. An absent pulse is not sensitive for the early detection of peripheral arterial disease. Family Medicine. 2006; 38(1): 38-42.
4. Eason SL, Petersen NJ, Suarez-Almazor M, Davis B, Collins TC. Diabetes mellitus, smoking, and the risk for asymptomatic peripheral arterial disease: whom should we screen? Journal of The American Board of Family Practice. 2005; 18(5): 355-61.
5. Collins TC, Petersen NJ, Suarez-Almazor M. Peripheral arterial disease symptom subtype and walking impairment. Vascular Medicine (London, England). 2005; 10(3): 177-83.
6. Collins TC, O'Malley K, Petersen NJ, Suarez-Almazor ME. The lifestyle and clinical survey: a pilot study to validate a medical history questionnaire. Federal Practitioner. 2005; 22: 25-46.
7. Collins TC, Petersen NJ, Suarez-Almazor M, Ashton CM. Ethnicity and peripheral arterial disease. Mayo Clinic Proceedings. 2005; 80(1): 48-54.
8. Collins TC, Suarez-Almazor M, Petersen NJ, O'Malley KJ. A Spanish translation of the Walking Impairment Questionnaire was validated for patients with peripheral arterial disease. Journal of Clinical Epidemiology. 2004; 57(12): 1305-15.
9. Kressin NR, Chang BH, Whittle J, Peterson ED, Clark JA, Rosen AK, Orner M, Collins TC, Alley LG, Petersen LA. Racial differences in cardiac catheterization as a function of patients' beliefs. American Journal of Public Health. 2004; 94(12): 2091-7.
10. Collins TC, Beyth RJ. Process of care and outcomes in peripheral arterial disease. American Journal of The Medical Sciences. 2003; 325(3): 125-34.
11. Collins TC, Petersen NJ, Menke TJ, Souchek J, Foster W, Ashton CM. Short-term, intermediate-term, and long-term mortality in patients hospitalized for stroke. Journal of Clinical Epidemiology. 2003; 56(1): 81-7.

DRA: Chronic Diseases
DRE: Etiology, Prevention, Communication and Decision Making
Keywords: Cardiovasc’r disease, Education (patient), Risk factors
MeSH Terms: none