Influence of Racial Disparities in Procedure Use on Functional Status Outcomes Among Patients With Coronary Artery Disease
http://www.100md.com
循环学杂志 2005年第3期
the University of Alberta, Edmonton, Alberta, Canada (P.K.)
Duke Clinical Research Institute, Duke University, Durham, NC (P.K., B.L.L., E.R.D., E.D.P.)
Mid America Heart Institute, Kansas City, Mo (J.A.S.).
Abstract
Background— Although black cardiac patients receive fewer revascularization procedures than whites, it is unclear whether this has a detrimental impact on outcomes. The objective of our study was to compare 6-month functional status and angina outcomes among blacks and whites with documented coronary disease and to assess whether differential use of revascularization procedures affects these outcomes.
Methods and Results— We identified a prospective cohort of 1534 white and 337 black patients undergoing cardiac catheterization between August 1998 and April 2001. Health status was assessed at baseline and 6 months with the Short-Form 36 (SF-36) Health Survey and the Seattle Angina Questionnaire (SAQ) Angina Frequency Scale. Compared with whites, blacks received fewer coronary revascularization procedures (52.5% versus 66.0%; P<0.01). By 6 months, blacks had similar mortality (odds ratio, 1.03; 95% CI, 0.57 to 1.9) but worse scores in 5 SF-36 domains (physical, social, role physical, role emotional, and mental health function). Blacks also reported higher rates of angina at 6 months than whites (34.2% versus 24.6%; P<0.01). After adjustment for baseline functional status and clinical and demographic variables, blacks had significantly worse summary physical component scores, summary mental component scores, and SAQ Angina Frequency Scale scores. However, differences in physical component summary scores and SAQ scores between blacks and whites were no longer significant after adjustment for revascularization status.
Conclusions— Our study is among the first to document greater symptoms and functional impairment among black cardiac patients relative to whites. Differential use of coronary revascularization may contribute to the poorer functional outcomes observed among black patients with documented coronary disease.
Key Words: ethnic groups ; coronary disease ; health status ; quality of life
Introduction
Studies have consistently found that black cardiac patients receive fewer coronary revascularization procedures relative to their white counterparts.1–14 The consequences of these racial disparities in cardiac procedure use remain unclear, however. Although certain studies3,15 have associated lower procedure use among blacks with lower long-term survival rates, others have not.16–18 Beyond potential impacts on survival, differential use of coronary revascularization also may affect patient symptoms, functional status, and overall quality of life.19,20 To date, however, there has been no information on the association of racial differences in revascularization and subsequent patient symptoms or functional outcomes.
We therefore undertook a longitudinal assessment of clinical outcomes, angina symptoms, and functional status among black and white patients with coronary disease at cardiac catheterization. We also examined the use of cardiovascular procedures in the 2 racial groups and determined the extent to which revascularization affected health status outcomes.
Methods
Study Sample
Between August 1998 and April 2001, patients aged 45 years treated at Duke University Medical Center and diagnosed with significant coronary artery disease (CAD) (1 vessel with 75% stenosis) by elective diagnostic cardiac catheterization were enrolled in a prospective longitudinal assessment of functional outcomes. Patients with congenital heart disease, primary valvular disease, prior coronary artery bypass grafting (CABG), or percutaneous intervention (PCI) within the previous 6 months were excluded from the study. Patient race was based on patients’ self-reported primary classification. Those whose race was classified as other than black or white were excluded. The Duke University Medical Center institutional review board approved the study protocol. Eligible patients were approached to participate in the study, and informed consent was obtained. The rate of agreement to participate in the study was high among both white and black patients (85% and 81%, respectively). There was no difference in 6-month mortality rate among patients who agreed to participate and those who refused to participate in the study. The final study sample consisted of 1871 patients, of whom 1534 were white and 337 were black (Figure 1).
Data Collection and Follow-Up
The following detailed demographic and clinical data were abstracted from the patients’ medical records at the time of cardiac catheterization.
Demographic Variables
These variables included age, sex, marital status, years of education, and insurance status.
Clinical Variables
Clinical variables included body mass index, history of myocardial infarction (MI), acute MI, congestive heart failure, valve disease, cerebrovascular disease, peripheral vascular disease, hypertension, chronic pulmonary disease, diabetes mellitus, arthritis/degenerative joint disease, cancer, hyperlipidemia, current smoking, substance abuse, depression, anxiety, end-stage renal disease, creatinine levels, and ejection fraction. In addition to these comorbidities, the extent of coronary disease was summarized by both the number of diseased vessels and the Duke CAD index (a detailed characterization of disease severity incorporating the location and severity of stenoses).21
Treatment
Revascularization status, ie, whether the patient had undergone PCI or CABG, was assessed during both the index hospital stay (when the diagnostic cardiac catheterization was performed) and during the 6-month follow-up period. At Duke University Medical Center, decisions about revascularization are made by the cardiology service. Within this service, there is no distinction between private and public service, and there is no difference in care by patients’ ability to pay or their socioeconomic status. In addition to revascularization, rates of use of evidence-based medications, namely, aspirin, ;-blockers, ACE inhibitors, and lipid-lowering agents, were assessed.
Functional Status Measures
Baseline health-related quality of life surveys were conducted by trained interviewers within 24 hours of diagnostic catheterization using validated instruments: the Seattle Angina Questionnaire (SAQ) Angina Frequency Scale22 and the RAND Short-Form 36 (SF-36) Health Survey.23 The SAQ Angina Frequency Scale22 is an assessment of the presence of angina, its frequency, and the number of times the patient had to take nitroglycerin for angina. The scale ranges from 0 to 100, with higher scores indicating better functional status and quality of life. The RAND SF-36 provides information on 8 domains: physical functioning; role limitations due to physical problems; bodily pain; general health perception; vitality; social functioning; role limitations due to emotional problems; and mental health. The SF-36 scores range from 0 to 100, with higher scores indicating better health. These domain scores are further aggregated to calculate the physical and mental component summary (PCS and MCS, respectively) scores.24,25
Trained personnel conducted 6-month assessments via structured telephone interviews. Interview content included subsequent cardiac hospitalizations or revascularization procedures, medication use, and the health status measurements collected at baseline. Reported cardiac events and revascularization procedures were confirmed via hospital medical records. Complete baseline and 6-month functional assessment was available for 89% of white patients and 88% of black patients (Figure 1).
Clinical Outcomes
In addition to functional status outcomes, data on mortality status and on whether the patient was rehospitalized within 6 months were collected. A composite end point of 6-month death/MI was defined as death or rehospitalization for MI.
Statistical Analysis
Demographic and clinical characteristics of black and white patients were compared with the use of 2 tests for categorical data and t tests and nonparametric Mann-Whitney tests for continuous variables. Logistic regression analysis was used to examine the association of race and revascularization status, 6-month mortality, and a composite outcome of 6-month death and hospitalization for (repeated) MI, after adjustment for the aforementioned baseline demographic and clinical characteristics.
Baseline and 6-month functional status between the 2 racial groups was compared by t tests. Linear regression was used to examine whether race was a predictor of 6-month SF-36 domain scores and SAQ Angina Frequency Scale scores after adjustment for demographic and clinical variables, as well as baseline scores for each domain.
We conducted sequential multivariable regression analyses to determine the impact of race on functional outcomes (SF-36 PCS and MCS scores and the SAQ Angina Frequency Scale). Three sequential linear regression models were developed for each outcome: the first examined the unadjusted relationship between race and each outcome; the second examined this relationship after adjustment for baseline functional status, baseline demographic, and clinical factors; and the third examined this relationship after adjustment for both baseline factors and revascularization status. All analyses were performed with the use of SPSS (version 11.5).
Results
Baseline Characteristics and Functional Status
At the time of cardiac catheterization, baseline physical, social, and emotional role functioning was worse among blacks than whites (Table 2). In contrast, black patients reported better vitality scores (46.4 versus 40.8; P<0.01). There were no significant differences in either PCS or MCS scores between the 2 groups. There were no significant differences between the 2 groups in angina symptoms or in the SAQ Angina Frequency Scale scores.
Patterns of Evidence-Based Medication Use and Treatment
There were no significant differences in the use of aspirin (72% in black and 70% in white; P=0.60), ;-blockers (65% in black and 60% in white; P=0.16), and lipid-lowering agents (42% in black and 44% in white; P=0.63) between the 2 groups. However, black patients had higher rates of ACE inhibitor use (51%) than white patients (38%; P<0.01.)
In contrast, rates of PCI (26.8% versus 33.4%; P=0.03) and CABG (26.1% versus 33.7%; P<0.01) during index hospitalization were lower in blacks than whites, respectively. Differences in revascularization rates between whites and blacks were also more marked among those with multivessel disease (Figure 2). By 6 months, the difference in combined revascularization rates remained significant: 54.8% among blacks versus 68.7% among whites (P<0.01). These racial differences in revascularization use at 6 months were significant after adjustment for baseline demographics and clinical characteristics (odds ratio [OR], 0.53; 95% CI, 0.40 to 0.71).
Clinical Outcomes
Clinical status data at 6 months were available for all patients. During the 6-month follow-up period, 38.6% of blacks and 38.7% of whites had been rehospitalized (P>0.99). Six-month mortality rates were 6.5% among black patients and 4.6% among white patients (P=0.17). Similarly, 6-month death/MI composite rates were 10.4% among black patients and 7.3% among white patients (P=0.07). After adjustment for other demographic and clinical characteristics, race was not significantly associated with death (black/white OR, 1.03; 95% CI, 0.57 to 1.9) or with the composite death/MI outcome (OR, 1.10; 95% CI, 0.69 to 1.8).
Six-Month Functional Status Outcomes
Functional status data were available on 1662 patients (89%) who survived to 6 months after diagnostic cardiac catheterization. Compared with patients who responded (n=1662), nonrespondents (n=116, excluding patients who died) were older and had higher rates of congestive heart failure, valve disease, and cerebrovascular disease. In contrast, respondents had higher rates of hyperlipidemia and 3-vessel disease. There was no difference in race among respondents and nonrespondents.
Impact of Treatment on Functional Status and Angina Symptoms
Discussion
The recent report of the Institute of Medicine, titled "Unequal Treatment: Confronting Racial and Ethnic Disparities in Health Care," notes that the strongest and most consistent evidence of racial and ethnic disparities in healthcare is to be found in cardiovascular care.26 However, although studies to date have documented racial differences in the use of diagnostic and therapeutic procedures, whether these care differences result in negative heath outcomes among blacks remains unclear. Our study is among the first to document that black patients diagnosed with coronary disease undergo fewer revascularization procedures and have worse angina symptoms and functional status than their white counterparts.
In our examination, after baseline adjustment, black race was associated with worse 6-month outcomes in 5 of the 8 functional status domains (physical function, social function, role physical, role emotional, and mental health). Black patients also reported significantly higher rates of angina at 6 months (34.2%) than whites (24.6%; P<0.01) and scored worse on the SAQ Angina Frequency Scale.
There are multiple potential explanations for the observed differences in functional outcomes between black and white cardiac patients. First, there were racial differences in demographics, comorbid illness, and disease severity that could have affected downstream functional recovery (Table 1). However, race remained a significant predictor of angina and functional status domains after adjustment for these demographic and clinical differences.
Black patients also reported a greater degree of functional impairment at the time of baseline cardiac catheterization than whites. These differences are consistent with other studies and may reflect delayed presentation or slower clinical evaluation of blacks relative to whites.27–29 After we accounted for self-reported baseline functioning, black race remained a significant predictor of poorer 6-month outcomes, however. With regard to angina symptoms, blacks and whites had similar baseline angina scores, yet blacks had more symptoms at follow-up.
Variation in pharmacological treatment is another potential contributor to our observed differences in functional outcomes. However, our study found reported use of cardiac medications to be similar between blacks and whites.
Finally, differences in the use of revascularization procedures may have contributed to the observed results. Randomized clinical trials such as Randomized Intervention Treatment of Angina (RITA-2) and Angioplasty Compared with Medical Therapy (ACME) have demonstrated that patients undergoing revascularization procedures have significantly better quality of life outcomes than those treated medically.30,31 In our study revascularization appeared to "explain" the racial differences in 6-month functional outcomes. Although the impact is modest, inclusion of revascularization in the multivariable models had an attenuating effect on the impact of race, and it was no longer significantly associated with either the SF-36 PCS scores or the SAQ Angina Frequency Scale scores. There may be several potential explanations for the persistence of racial differences in MCS even after adjustment for revascularization: It may imply that blacks report lower MCS despite care, and there may be other factors intrinsic to race that have not yet been identified that may explain these differences.
The reader should be aware of potential limitations of this study. First, our study documents a single center’s experience, and the extent to which these results are generalizable to the rest of the country remains to be examined. However, other studies have demonstrated similar racial differences in revascularization.32 Second, race may be a marker for other differences in socioeconomic and social support factors or comorbidities that are not currently captured in the study.33 Third, although we assessed other potential treatment differences, such as the reported use of medications, we did not have full details on dosing, rates of compliance, or other care aspects such as the frequency with which patients visited their healthcare providers. Finally, we examined outcomes at only 6 months. Several studies have suggested that the impact of differential use of revascularization may be observed in longer-term outcomes.3,34 Therefore, the full impact of racial differences in revascularization may only be available by longer-term assessment.
Conclusion
This study demonstrates significant racial differences in functional outcomes in black patients with documented CAD relative to their white counterparts. Differential use of revascularization procedures appears to contribute to these observed differences in health states. These findings support ongoing efforts designed to reduce racial disparities in cardiac care as a means of improving long-term patient outcome.
Acknowledgments
This study was supported in part by a grant from the Paul Beeson Physician Faculty Scholars in Aging Research, American Federation for Aging Research, and Alliance for Aging Research. Dr Kaul was supported by a fellowship award from the Canadian Institute of Health Research, Heart and Stroke Foundation of Canada, and Alberta Heritage Foundation for Medical Research.
References
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Taylor HA Jr, Canto JG, Sanderson B, Rogers WJ, Hilbe J. Management and outcomes for black patients with acute myocardial infarction in the reperfusion era. Am J Cardiol. 1998; 82: 1019–1023.
Chen J, Rathore SS, Radford MJ, Wang Y, Krumholz HM. Racial differences in the use of cardiac catheterization after acute myocardial infarction. N Engl J Med. 2001; 344: 1443–1449.
Gray RJ, Nessim S, Khan SS, Denton T, Matloff JM. Adverse 5-year outcome after coronary artery bypass surgery in blacks. Arch Intern Med. 1996; 156: 769–773.
Maynard C, Every NF, Martin JS, Weaver WD. Long-term implications of racial differences in the use of revascularization procedures (the Myocardial Infarction Triage and Intervention registry). Am Heart J. 1997; 133: 656–662.
Petersen LA, Wright SM, Peterson ED, Daley J. Impact of race on cardiac care and outcomes in veterans with acute myocardial infarction. Med Care. 2002; 40: I-86–I-96.
Smith SC, Dove JT, Jacobs AK, Kennedy JW, Kereiakes D, Kern MJ, Kuntz RE, Popma JJ, Schaff HV, Williams DO, Gibbons RJ, Alpert JP, Eagle KA, Faxon DP, Fuster V, Gardner TJ, Gregoratos G, Russell RO, Smith SC Jr. ACC/AHA Guidelines for Percutaneous Coronary Intervention (revision of the 1993 PTCA guidelines): a report of the American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1993 Guidelines for Percutaneous Transluminal Coronary Angioplasty). J Am Coll Cardiol. 2001; 37: 2239i–lxvi.
Eagle KA, Guyton RA, Davidoff R, Ewy GA, Fonger J, Gardner TJ, Gott JP, Herrmann JC, Marlow RA, Nugent W, O’Connor GT, Orszulak TA, Rieselbach RE, Winters WL, Yusef S, Gibbons RJ, Alpert JS, Garson A Jr, Gregoratos G, Russell RO, Ryan TJ, Smith SC Jr. ACC/AHA Guidelines for Coronary Artery Bypass Graft Surgery: Executive Summary and Recommendations: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1991 Guidelines for Coronary Artery Bypass Graft Surgery). Circulation. 1999; 100: 1464–1480.
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Smedley BD, Stith AY, Nelson AR, eds, for the Committee on Understanding and Eliminating Racial and Ethnic Disparities in Health Care. Unequal Treatment: Confronting Racial and Ethnic Disparities in Health Care. Washington, DC: National Academy Press; 2002.
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Johnson PA, Goldman L, Orave EJ, Garcia T, Pearson SD, Lee TH. Comparison of the Medical Outcomes Study Short-Form 36-Item Health Survey in black patients and white patients with acute chest pain. Med Care. 1995; 33: 145–160.
Pocock SJ, Henderson RA, Clayton T, Lyman GH, Chamberlain DA. Quality of life after coronary angioplasty or continued medical treatment for angina: three-year follow-up in the RITA-2 trial. J Am Coll Cardiol. 2000; 35: 907–914.
Strauss WE, Fortin T, Hartigan P, Folland ED, Parisi AF. A comparison of quality of life scores in patients with angina pectoris after angioplasty compared with after medical therapy: outcomes of a randomized clinical trial. Circulation. 1995; 92: 1710–1719.
Kressin NR, Petersen LA. Racial differences in the use of invasive cardiovascular procedures: review of the literature and prescription for future research. Ann Intern Med. 2001; 135: 352–366.
Kaplan JB, Bennett T. Use of race and ethnicity in biomedical publication. JAMA. 2003; 289: 2709–2716.
Kaul P, Armstrong PW, Chang WC, Naylor CD, Granger CB, Lee KL, Peterson ED, Califf RM, Topol EJ, Mark DB. Long-term mortality of patients with acute myocardial infarction in the United States and Canada: comparison of patients enrolled in Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO)-I. Circulation. 2004; 110: 1754–1760.(Padma Kaul, PhD; Barbara )
Duke Clinical Research Institute, Duke University, Durham, NC (P.K., B.L.L., E.R.D., E.D.P.)
Mid America Heart Institute, Kansas City, Mo (J.A.S.).
Abstract
Background— Although black cardiac patients receive fewer revascularization procedures than whites, it is unclear whether this has a detrimental impact on outcomes. The objective of our study was to compare 6-month functional status and angina outcomes among blacks and whites with documented coronary disease and to assess whether differential use of revascularization procedures affects these outcomes.
Methods and Results— We identified a prospective cohort of 1534 white and 337 black patients undergoing cardiac catheterization between August 1998 and April 2001. Health status was assessed at baseline and 6 months with the Short-Form 36 (SF-36) Health Survey and the Seattle Angina Questionnaire (SAQ) Angina Frequency Scale. Compared with whites, blacks received fewer coronary revascularization procedures (52.5% versus 66.0%; P<0.01). By 6 months, blacks had similar mortality (odds ratio, 1.03; 95% CI, 0.57 to 1.9) but worse scores in 5 SF-36 domains (physical, social, role physical, role emotional, and mental health function). Blacks also reported higher rates of angina at 6 months than whites (34.2% versus 24.6%; P<0.01). After adjustment for baseline functional status and clinical and demographic variables, blacks had significantly worse summary physical component scores, summary mental component scores, and SAQ Angina Frequency Scale scores. However, differences in physical component summary scores and SAQ scores between blacks and whites were no longer significant after adjustment for revascularization status.
Conclusions— Our study is among the first to document greater symptoms and functional impairment among black cardiac patients relative to whites. Differential use of coronary revascularization may contribute to the poorer functional outcomes observed among black patients with documented coronary disease.
Key Words: ethnic groups ; coronary disease ; health status ; quality of life
Introduction
Studies have consistently found that black cardiac patients receive fewer coronary revascularization procedures relative to their white counterparts.1–14 The consequences of these racial disparities in cardiac procedure use remain unclear, however. Although certain studies3,15 have associated lower procedure use among blacks with lower long-term survival rates, others have not.16–18 Beyond potential impacts on survival, differential use of coronary revascularization also may affect patient symptoms, functional status, and overall quality of life.19,20 To date, however, there has been no information on the association of racial differences in revascularization and subsequent patient symptoms or functional outcomes.
We therefore undertook a longitudinal assessment of clinical outcomes, angina symptoms, and functional status among black and white patients with coronary disease at cardiac catheterization. We also examined the use of cardiovascular procedures in the 2 racial groups and determined the extent to which revascularization affected health status outcomes.
Methods
Study Sample
Between August 1998 and April 2001, patients aged 45 years treated at Duke University Medical Center and diagnosed with significant coronary artery disease (CAD) (1 vessel with 75% stenosis) by elective diagnostic cardiac catheterization were enrolled in a prospective longitudinal assessment of functional outcomes. Patients with congenital heart disease, primary valvular disease, prior coronary artery bypass grafting (CABG), or percutaneous intervention (PCI) within the previous 6 months were excluded from the study. Patient race was based on patients’ self-reported primary classification. Those whose race was classified as other than black or white were excluded. The Duke University Medical Center institutional review board approved the study protocol. Eligible patients were approached to participate in the study, and informed consent was obtained. The rate of agreement to participate in the study was high among both white and black patients (85% and 81%, respectively). There was no difference in 6-month mortality rate among patients who agreed to participate and those who refused to participate in the study. The final study sample consisted of 1871 patients, of whom 1534 were white and 337 were black (Figure 1).
Data Collection and Follow-Up
The following detailed demographic and clinical data were abstracted from the patients’ medical records at the time of cardiac catheterization.
Demographic Variables
These variables included age, sex, marital status, years of education, and insurance status.
Clinical Variables
Clinical variables included body mass index, history of myocardial infarction (MI), acute MI, congestive heart failure, valve disease, cerebrovascular disease, peripheral vascular disease, hypertension, chronic pulmonary disease, diabetes mellitus, arthritis/degenerative joint disease, cancer, hyperlipidemia, current smoking, substance abuse, depression, anxiety, end-stage renal disease, creatinine levels, and ejection fraction. In addition to these comorbidities, the extent of coronary disease was summarized by both the number of diseased vessels and the Duke CAD index (a detailed characterization of disease severity incorporating the location and severity of stenoses).21
Treatment
Revascularization status, ie, whether the patient had undergone PCI or CABG, was assessed during both the index hospital stay (when the diagnostic cardiac catheterization was performed) and during the 6-month follow-up period. At Duke University Medical Center, decisions about revascularization are made by the cardiology service. Within this service, there is no distinction between private and public service, and there is no difference in care by patients’ ability to pay or their socioeconomic status. In addition to revascularization, rates of use of evidence-based medications, namely, aspirin, ;-blockers, ACE inhibitors, and lipid-lowering agents, were assessed.
Functional Status Measures
Baseline health-related quality of life surveys were conducted by trained interviewers within 24 hours of diagnostic catheterization using validated instruments: the Seattle Angina Questionnaire (SAQ) Angina Frequency Scale22 and the RAND Short-Form 36 (SF-36) Health Survey.23 The SAQ Angina Frequency Scale22 is an assessment of the presence of angina, its frequency, and the number of times the patient had to take nitroglycerin for angina. The scale ranges from 0 to 100, with higher scores indicating better functional status and quality of life. The RAND SF-36 provides information on 8 domains: physical functioning; role limitations due to physical problems; bodily pain; general health perception; vitality; social functioning; role limitations due to emotional problems; and mental health. The SF-36 scores range from 0 to 100, with higher scores indicating better health. These domain scores are further aggregated to calculate the physical and mental component summary (PCS and MCS, respectively) scores.24,25
Trained personnel conducted 6-month assessments via structured telephone interviews. Interview content included subsequent cardiac hospitalizations or revascularization procedures, medication use, and the health status measurements collected at baseline. Reported cardiac events and revascularization procedures were confirmed via hospital medical records. Complete baseline and 6-month functional assessment was available for 89% of white patients and 88% of black patients (Figure 1).
Clinical Outcomes
In addition to functional status outcomes, data on mortality status and on whether the patient was rehospitalized within 6 months were collected. A composite end point of 6-month death/MI was defined as death or rehospitalization for MI.
Statistical Analysis
Demographic and clinical characteristics of black and white patients were compared with the use of 2 tests for categorical data and t tests and nonparametric Mann-Whitney tests for continuous variables. Logistic regression analysis was used to examine the association of race and revascularization status, 6-month mortality, and a composite outcome of 6-month death and hospitalization for (repeated) MI, after adjustment for the aforementioned baseline demographic and clinical characteristics.
Baseline and 6-month functional status between the 2 racial groups was compared by t tests. Linear regression was used to examine whether race was a predictor of 6-month SF-36 domain scores and SAQ Angina Frequency Scale scores after adjustment for demographic and clinical variables, as well as baseline scores for each domain.
We conducted sequential multivariable regression analyses to determine the impact of race on functional outcomes (SF-36 PCS and MCS scores and the SAQ Angina Frequency Scale). Three sequential linear regression models were developed for each outcome: the first examined the unadjusted relationship between race and each outcome; the second examined this relationship after adjustment for baseline functional status, baseline demographic, and clinical factors; and the third examined this relationship after adjustment for both baseline factors and revascularization status. All analyses were performed with the use of SPSS (version 11.5).
Results
Baseline Characteristics and Functional Status
At the time of cardiac catheterization, baseline physical, social, and emotional role functioning was worse among blacks than whites (Table 2). In contrast, black patients reported better vitality scores (46.4 versus 40.8; P<0.01). There were no significant differences in either PCS or MCS scores between the 2 groups. There were no significant differences between the 2 groups in angina symptoms or in the SAQ Angina Frequency Scale scores.
Patterns of Evidence-Based Medication Use and Treatment
There were no significant differences in the use of aspirin (72% in black and 70% in white; P=0.60), ;-blockers (65% in black and 60% in white; P=0.16), and lipid-lowering agents (42% in black and 44% in white; P=0.63) between the 2 groups. However, black patients had higher rates of ACE inhibitor use (51%) than white patients (38%; P<0.01.)
In contrast, rates of PCI (26.8% versus 33.4%; P=0.03) and CABG (26.1% versus 33.7%; P<0.01) during index hospitalization were lower in blacks than whites, respectively. Differences in revascularization rates between whites and blacks were also more marked among those with multivessel disease (Figure 2). By 6 months, the difference in combined revascularization rates remained significant: 54.8% among blacks versus 68.7% among whites (P<0.01). These racial differences in revascularization use at 6 months were significant after adjustment for baseline demographics and clinical characteristics (odds ratio [OR], 0.53; 95% CI, 0.40 to 0.71).
Clinical Outcomes
Clinical status data at 6 months were available for all patients. During the 6-month follow-up period, 38.6% of blacks and 38.7% of whites had been rehospitalized (P>0.99). Six-month mortality rates were 6.5% among black patients and 4.6% among white patients (P=0.17). Similarly, 6-month death/MI composite rates were 10.4% among black patients and 7.3% among white patients (P=0.07). After adjustment for other demographic and clinical characteristics, race was not significantly associated with death (black/white OR, 1.03; 95% CI, 0.57 to 1.9) or with the composite death/MI outcome (OR, 1.10; 95% CI, 0.69 to 1.8).
Six-Month Functional Status Outcomes
Functional status data were available on 1662 patients (89%) who survived to 6 months after diagnostic cardiac catheterization. Compared with patients who responded (n=1662), nonrespondents (n=116, excluding patients who died) were older and had higher rates of congestive heart failure, valve disease, and cerebrovascular disease. In contrast, respondents had higher rates of hyperlipidemia and 3-vessel disease. There was no difference in race among respondents and nonrespondents.
Impact of Treatment on Functional Status and Angina Symptoms
Discussion
The recent report of the Institute of Medicine, titled "Unequal Treatment: Confronting Racial and Ethnic Disparities in Health Care," notes that the strongest and most consistent evidence of racial and ethnic disparities in healthcare is to be found in cardiovascular care.26 However, although studies to date have documented racial differences in the use of diagnostic and therapeutic procedures, whether these care differences result in negative heath outcomes among blacks remains unclear. Our study is among the first to document that black patients diagnosed with coronary disease undergo fewer revascularization procedures and have worse angina symptoms and functional status than their white counterparts.
In our examination, after baseline adjustment, black race was associated with worse 6-month outcomes in 5 of the 8 functional status domains (physical function, social function, role physical, role emotional, and mental health). Black patients also reported significantly higher rates of angina at 6 months (34.2%) than whites (24.6%; P<0.01) and scored worse on the SAQ Angina Frequency Scale.
There are multiple potential explanations for the observed differences in functional outcomes between black and white cardiac patients. First, there were racial differences in demographics, comorbid illness, and disease severity that could have affected downstream functional recovery (Table 1). However, race remained a significant predictor of angina and functional status domains after adjustment for these demographic and clinical differences.
Black patients also reported a greater degree of functional impairment at the time of baseline cardiac catheterization than whites. These differences are consistent with other studies and may reflect delayed presentation or slower clinical evaluation of blacks relative to whites.27–29 After we accounted for self-reported baseline functioning, black race remained a significant predictor of poorer 6-month outcomes, however. With regard to angina symptoms, blacks and whites had similar baseline angina scores, yet blacks had more symptoms at follow-up.
Variation in pharmacological treatment is another potential contributor to our observed differences in functional outcomes. However, our study found reported use of cardiac medications to be similar between blacks and whites.
Finally, differences in the use of revascularization procedures may have contributed to the observed results. Randomized clinical trials such as Randomized Intervention Treatment of Angina (RITA-2) and Angioplasty Compared with Medical Therapy (ACME) have demonstrated that patients undergoing revascularization procedures have significantly better quality of life outcomes than those treated medically.30,31 In our study revascularization appeared to "explain" the racial differences in 6-month functional outcomes. Although the impact is modest, inclusion of revascularization in the multivariable models had an attenuating effect on the impact of race, and it was no longer significantly associated with either the SF-36 PCS scores or the SAQ Angina Frequency Scale scores. There may be several potential explanations for the persistence of racial differences in MCS even after adjustment for revascularization: It may imply that blacks report lower MCS despite care, and there may be other factors intrinsic to race that have not yet been identified that may explain these differences.
The reader should be aware of potential limitations of this study. First, our study documents a single center’s experience, and the extent to which these results are generalizable to the rest of the country remains to be examined. However, other studies have demonstrated similar racial differences in revascularization.32 Second, race may be a marker for other differences in socioeconomic and social support factors or comorbidities that are not currently captured in the study.33 Third, although we assessed other potential treatment differences, such as the reported use of medications, we did not have full details on dosing, rates of compliance, or other care aspects such as the frequency with which patients visited their healthcare providers. Finally, we examined outcomes at only 6 months. Several studies have suggested that the impact of differential use of revascularization may be observed in longer-term outcomes.3,34 Therefore, the full impact of racial differences in revascularization may only be available by longer-term assessment.
Conclusion
This study demonstrates significant racial differences in functional outcomes in black patients with documented CAD relative to their white counterparts. Differential use of revascularization procedures appears to contribute to these observed differences in health states. These findings support ongoing efforts designed to reduce racial disparities in cardiac care as a means of improving long-term patient outcome.
Acknowledgments
This study was supported in part by a grant from the Paul Beeson Physician Faculty Scholars in Aging Research, American Federation for Aging Research, and Alliance for Aging Research. Dr Kaul was supported by a fellowship award from the Canadian Institute of Health Research, Heart and Stroke Foundation of Canada, and Alberta Heritage Foundation for Medical Research.
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