McDermott MM, Mandapat AL, Moates A, Albay M, Chiou E, Celic L, Greenland P. Knowledge and Attitudes Regarding Cardiovascular Disease Risk and Prevention in Patients With Coronary or Peripheral Arterial Disease. Arch Intern Med. 2003;163(18):2157-2162. doi:10.1001/archinte.163.18.2157
We compared perceptions regarding risk of cardiovascular events and benefits of cardiovascular disease (CVD) risk factor reduction between patients with peripheral arterial disease (PAD), patients with coronary artery disease (CAD), and patients without atherosclerosis (no disease).
Participants with no disease (n = 142) had a normal ankle-brachial index and no clinically evident atherosclerosis (group 1). The PAD participants (n = 136) had an ankle-brachial index less than 0.90 and no other clinically evident atherosclerosis (group 2). Participants with CAD (n = 70) had a normal ankle-brachial index and a history of heart disease (group 3). Participants were interviewed regarding risk of mortality, CVD, and the importance of CVD risk factor reduction for hypothetical patients with PAD and CAD.
All groups reported that risks of myocardial infarction, stroke, and death were higher for a patient with CAD than for a patient with PAD. Group 2 was less likely than group 3 to believe that PAD is associated with an extremely high risk of stroke (13.3% vs 28.7%; P = .005) or mortality (10.9% vs 26.6%; P = .003). Group 2 was less likely than group 1 to believe that a patient with PAD has a very high risk of myocardial infarction (13.1% vs 23.8%; P = .02), stroke (13.3% vs 27.5%; P = .003), or mortality (10.9% vs 24.3%; P = .004). Compared with group 3, a smaller percentage of patients in group 2 reported that cholesterol lowering was very important in PAD (57.5% vs 75.8%; P = .005).
Compared with other patients, those with PAD underestimated the high risk of cardiovascular events associated with PAD and the benefits of cholesterol-lowering therapy. These findings may help explain the low rates of CVD risk factor control previously reported in patients with PAD.
PATIENTS' GROWING demand for medical information and the exponential increase in patient-accessible health care information have contributed to a changing physician-patient relationship, in which patients increasingly influence their medical care.1- 8 Patients' requests for treatment and attitudes about the importance of treatment are major determinants of physician behavior regarding prescription of preventive interventions.7,8 In addition, patients' perceptions of their personal risk of an adverse event and the effectiveness of preventive therapy influence the degree to which preventive health and risk-reduction behaviors are adopted by patients.9,10
Men and women with lower extremity peripheral arterial disease (PAD) have a 3- to 6-fold increased rate of mortality from cardiovascular disease (CVD) compared with age-matched men and women without PAD.11- 13 The risks of future cardiovascular events in patients with PAD are comparable with those in patients with coronary artery disease (CAD).14 Cardiovascular disease risk factor reduction is recommended for patients with PAD to reduce their high incidence of heart disease and stroke.15,16 However, recent data document that patients with PAD are undertreated for CVD risk factors compared with patients with CAD.17- 19 Reasons for undertreatment of CVD risk factors are not well understood. Because of the growing body of literature suggesting that patients' knowledge and attitudes influence preventive therapy, we sought to determine whether patients with PAD are aware of the increased risk of CVD associated with PAD and whether they are aware of the importance of CVD risk factor treatment for patients with PAD. The purpose of this study was to compare knowledge and attitudes regarding future risk of heart disease and stroke between patients with PAD and patients with CAD and between patients with PAD and patients with no clinically evident atherosclerosis. The results may help determine reasons for undertreatment of CVD risk factors in patients with PAD and ultimately influence patient education accordingly.
The study protocol was approved by the institutional review board at the Feinberg School of Medicine at Northwestern University, Chicago, Ill. Participants were part of a large prospective observational study of PAD and lower extremity functioning (the Walking and Leg Circulation Study [WALCS]).20 The WALCS participants were 55 years and older and were identified from vascular laboratories and a large general medicine practice in Chicago, Ill.20
The WALCS participants with PAD were identified consecutively from men and women diagnosed with PAD in noninvasive vascular laboratories from 3 study institutions. Although we did not systematically collect data on reasons for referral to the noninvasive vascular laboratory, patients with PAD are typically referred for testing because of leg symptoms, nonhealing lower extremity ulcers, or follow-up from prior lower extremity revascularization. A small number of participants with PAD were identified from among consecutively identified men and women in a large general internal medicine practice at Northwestern University. All participants with PAD had an ankle-brachial index (ABI) less than 0.90 at their baseline study visit.
Approximately half of the WALCS participants without PAD were identified consecutively from patients with appointments in Northwestern University's general internal medicine practice. The remaining half of the participants without PAD were identified from consecutive patients who had undergone testing in 3 Chicago-area noninvasive vascular laboratories and had normal findings on lower extremity arterial examination. These latter participants were typically referred to the noninvasive vascular laboratories because of leg symptoms or nonhealing lower extremity ulcers. Participants without PAD had an ABI between 0.90 and 1.49 at their baseline study visit.
Exclusion criteria for the WALCS have been reported previously20 and are summarized briefly as follows: nursing home residents, wheelchair-bound patients, patients with dementia, and patients with foot or leg amputations were excluded. Non–English-speaking patients were excluded because study investigators were not fluent in non-English languages. Patients with cerebrovascular disease were also excluded so that we could focus on lower extremity PAD.
The ABI was measured using previously established methods.21,22 After participants rested supine for 5 minutes, a hand-held Doppler probe (Nicolet Vascular Doppler Pocket Dop II, Golden, Colo) was used to measure systolic blood pressure in the right brachial artery, right dorsalis pedis and posterior tibial arteries, left dorsalis pedis and posterior tibial arteries, and left brachial artery. Each pressure was measured twice (in the order listed and then in reverse order). The ABI was calculated in each leg by dividing average pressures in each leg by the average of the 4 brachial pressures.20,21 The lowest leg ABI measurement was used to classify participants with vs those without PAD.
Participants were classified into 1 of 3 mutually exclusive groups according to their atherosclerotic disease status: group 1, patients with no clinically evident atherosclerosis; group 2, patients with PAD (ABI <0.90) and no other clinically evident atherosclerosis; and group 3, patients with CAD and a normal ABI (ABI, 0.90-1.49). Group 1 was included to determine whether the beliefs of patients with PAD were substantially different from patients with no atherosclerosis. Coronary artery disease was defined as a history of angina, myocardial infarction, heart failure, or coronary revascularization.
The questionnaire asked about current health behavior regarding CVD prevention. Participants were questioned about their personal exercise habits, cholesterol-lowering interventions, and antiplatelet therapy (ie, "Do you exercise regularly?" "Do you regularly take aspirin as a way to treat or prevent heart disease?"). A second section described a hypothetical patient with PAD or CAD and asked participants to estimate the risk of heart disease, stroke, and death for each patient. Answers were chosen from a 5-point Likert scale ranging from extremely likely to extremely unlikely. In a third section of the questionnaire, participants were asked about the importance of specific CVD risk factor interventions (ie, smoking cessation, regular exercise, cholesterol lowering, and antiplatelet therapy) for the hypothetical patients with PAD and CAD. Participants responded on a 5-point Likert scale ranging from very important to very unimportant.
We documented the presence of comorbid CVD using methods from the Women's Health and Aging Study and the Cardiovascular Health Study.23 Disease-specific algorithms that combine data from patient report, medical record review, medications, laboratory values, physical examination, and a primary care physician questionnaire were used to verify and document history of angina, myocardial infarction, heart failure, and stroke.23 History of coronary revascularization was considered present if it was reported by the patient or found during medical record review.
Cholesterol levels were obtained from nonfasting participants. Total cholesterol levels were measured enzymatically using enzymatic reaction with peroxidase/phenol-4-aminophenazone indicator reaction.24 The concentration of high-density lipoprotein cholesterol was determined using a direct enzymatic colorimetric assay.25
We used χ2 tests to compare differences in categorical variables between the 3 groups. For risk of adverse outcomes, participants were categorized according to whether they indicated that the risk of each cardiovascular event was extremely high (score of 5 on a 5-point Likert scale) for the hypothetical PAD and CAD patients. For CVD risk factor reduction, participants were categorized according to whether they indicated that each risk factor intervention was very important (score of 5 on a 5-point Likert scale) for the hypothetical PAD and CAD patients. Analyses of variance were used to compute statistical significance for comparisons in continuous variables between patients in group 1, group 2, and group 3. To understand better the origin of statistically significant differences between all 3 groups, additional χ2 analyses and analyses of variance were performed to determine whether differences in categorical and continuous variables between group 1 vs group 2 and between group 2 vs group 3 were statistically significant. The Bonferroni method was used to adjust for multiple comparisons for the χ2 and analysis of variance tests. Analyses of covariance were performed to determine whether differences in patients' beliefs were significantly different between group 1, group 2, and group 3, adjusting for age, sex, and education level. To better understand the origin of statistically significant differences between all 3 groups, additional analyses of covariance were performed to determine whether differences were statistically significant between group 1 vs group 2 and between group 2 vs group 3. Again, the Bonferroni method was used to adjust for multiple comparisons for the analyses of covariance.
Among 740 participants in the WALCS, 440 met criteria for group 1, group 2, or group 3. Of these 440, 17 had dropped out of the WALCS and 21 had died before they could be interviewed. Of the remaining 402, 9 refused and 45 could not be reached for interview. Thus, 348 (86.6%) of those eligible participated.
Among group 2 participants, 33.1% had classic symptoms of intermittent claudication, 19.1% had no exertional leg symptoms, and 47.8% had exertional leg symptoms other than intermittent claudication. Table 1 gives the characteristics of study participants according to disease status. Total cholesterol levels were lowest in group 3, while high-density lipoprotein cholesterol levels were highest in group 1. Group 1 had the highest prevalence of current exercise and the lowest prevalence of current antiplatelet therapy. Group 2 had the highest prevalence of current cigarette smoking.
Table 2 gives the percentages in each group who believe that the risks of myocardial infarction, stroke, and death are extremely high in a patient with PAD and patient with CAD. Within each of the 3 groups, more participants reported that the risks of myocardial infarction, stroke, and mortality were extremely high for the patient with CAD compared with the patient with PAD. In pairwise comparisons, group 3 was significantly more likely than group 2 to report that a patient with PAD has an extremely high risk of stroke (28.7% vs 13.3%; P = .005) and an extremely high risk of death (26.6% vs 10.9%; P = .003). Group 1 was significantly more likely than group 2 to report that the risk of myocardial infarction (23.8% vs 13.1%; P = .02), stroke (27.5% vs 13.3%; P = .003), and mortality (24.3% vs 10.9%; P = .004) were extremely high for a patient with PAD.
Table 3 gives the proportions of participants who believe that various CVD risk factor interventions are extremely important for the hypothetical patient with PAD and the hypothetical patient with CAD. Participants in all groups were more likely to indicate that cholesterol-lowering therapy and antiplatelet therapy were very important for the hypothetical patient with CAD compared with the hypothetical patient with PAD. Group 3 was significantly more likely than group 2 to believe that cholesterol lowering is very important for a patient with PAD (75.8% vs 57.5%; P = .005). There were no other significant differences in beliefs regarding the importance of risk factor reduction between the 3 groups.
Results in Table 2 and Table 3 did not substantially change when we repeated analyses, excluding group 2 participants with exertional leg symptoms. Thus, the presence vs absence of exertional leg symptoms did not influence the attitudes and knowledge of group 2 participants regarding the risk of cardiovascular events and the importance of atherosclerotic risk factor therapy in PAD.
We found that patients with PAD, CAD, and no clinically evident atherosclerosis substantially underrecognized the high risk of cardiovascular events and mortality associated with PAD. Although CAD and PAD patients have comparable risks of cardiovascular events and mortality,14 participants in each group ranked these risks as lower for patients with PAD than for patients with CAD. Participants in each of the 3 groups were also more likely to indicate that cholesterol-lowering therapy is very important for a patient with CAD compared with a patient with PAD.
Furthermore, we found that patients with PAD were significantly less likely than the other patient groups to believe that the risks of myocardial infarction, stroke, and death were extremely high in a patient with PAD. However, we did not observe that patients with CAD underestimated the risks of these events for a CAD patient compared with the other patient groups. Our findings suggest that patients with PAD are more likely to underestimate the cardiovascular risks associated with PAD compared with patients with CAD and patients with no disease. Potential explanations for PAD patients' underrecognition of their increased risk of cardiovascular events and death include denial of the seriousness of PAD, inadequate education about the risks associated with PAD, or both.
Several previous studies have documented undertreatment of CVD risk factors in patients with PAD.17- 19,22 In the PAD Awareness, Risk, and Treatment: New Resources for Survival (PARTNERS) study of the prevalence and treatment of PAD in general medicine practices across the United States, participants with PAD were treated less intensively than CAD participants with antihypertensives, antiplatelet therapy, and cholesterol-lowering therapy. The PARTNERS study included 6979 participants 50 years and older, of whom 29% had PAD based on screening with the ABI. In addition to the PARTNERS study, we have previously reported that patients with established PAD are undertreated for CVD risk factors compared with patients with established CAD.17
Reasons for undertreatment of CVD risk factors in patients with PAD are not well understood. A recent national survey study documented deficiencies in physician knowledge and attitudes regarding the importance of atherosclerotic risk factor treatment for patients with PAD.26 Based on our findings reported herein, poor awareness by PAD patients of their risks of cardiovascular events and the importance of CVD risk factor treatment may also be factors influencing low rates of risk factor treatment and control in PAD. Previous studies show that patients' perceptions regarding their personal risk of adverse events and the ability of preventive therapy to forestall these adverse events influence the degree to which patients adopt preventive health behaviors.9,10 In addition, the explosion of patient-targeted health care information and increasing desire among patients to participate in health care decisions have led to a large and growing body of work indicating that patients increasingly influence their prescription of preventive practices.1- 8 Thus, patient factors may influence the intensity of risk factor reduction in PAD.
We are aware of only 1 other study assessing PAD patients' knowledge about their risk of future heart disease.27 In this study, 883 patients in 2 primary care rural practices in western Maryland completed a questionnaire about their risk for CVD. The mean ± SD age of study participants was 61 ± 15 years, 60% were female, and 99% were white. Among 23 participants with PAD, 9% considered themselves at very high risk and 17% considered themselves at very low risk for CVD. In comparison, 21% of the 56 participants with a history of myocardial infarction considered themselves at very high risk and 4% considered themselves at very low risk for CVD. In the present study, PAD participants' assessment of their risk of cardiovascular events was comparable with that of patients with no heart disease. In contrast to our study, this prior study included only 23 patients with PAD and did not compare perceptions of risk between different patient groups. In addition, the earlier study was conducted during a time of lower expectations by physicians and patients concerning the likely benefits of risk factor interventions and preventive treatments.
Our study has some limitations, including the fact that we excluded patients who had PAD in conjunction with clinically evident CAD. In addition, all participants were 55 years or older at the start of the study, individuals with severe functional limitations at baseline were excluded, and most participants with PAD were identified from noninvasive vascular laboratories. While identifying participants with PAD from noninvasive vascular laboratories meant that these participants had previously documented, recognized PAD, our findings may not be generalizable to patients with PAD who are identified from other settings or who do not have previously established PAD. Similarly, our findings regarding participants with no atherosclerosis may not be generalizable to individuals who have not attended general medical clinics or been referred to a noninvasive vascular laboratory. Based on our inclusion criteria, all participants had had encounters with clinicians in the past. Thus, their knowledge about the significance of PAD and importance of risk factor treatment in PAD is likely to be better than individuals without these encounters.
While previously reported data demonstrate that CVD risk factors are undertreated in patients with PAD compared with patients with CAD,17- 19 data reported herein show that several risk factor treatments were comparable between participants in the 3 groups. Potential reasons for the comparable levels of risk factor treatment between PAD and CAD patients in our study include (1) temporal improvement in the intensity of CVD risk factor treatment in patients with PAD since the earlier studies were published and (2) potential selection bias if PAD participants in the present study are more health conscious than PAD patients in previous studies. The PAD participants in the present study may be more health conscious than PAD patients in previous studies because all were participating voluntarily in a prospective observational study of lower extremity functioning in PAD. If PAD participants in our study are more health conscious than the typical patient with PAD, then our findings reported herein could be an underestimate of the extent to which patients with PAD misjudge their cardiovascular risk and the importance of CVD risk factor treatment.
In conclusion, these data show that patients with PAD need to be educated about their high risk of future cardiovascular events and the importance of CVD risk factor reduction for them. Future study is needed to determine whether PAD patients' knowledge about their disease can be improved and, if so, whether it will reduce their high risk of cardiovascular events and mortality.
Corresponding author and reprints: Mary McGrae McDermott, MD, 675 N St Clair, Suite 18-200, Chicago, IL 60611 (e-mail: firstname.lastname@example.org).
Accepted for publication November 28, 2002.
This study was supported by grants R01 HL-58099 and R01-HL63226 from the National Heart, Lung, and Blood Institute, Bethesda, Md, and grant RR-00048 from the National Center for Research Resources, National Institutes of Health, Bethesda. Dr McDermott is supported in part by an Established Investigator Award from the American Heart Association, Dallas, Tex.