Racial Differences in Long-term Survival among Patients with Coronary Artery Disease

Kevin L. Thomas, MD, FACC; Emily Honeycutt, MBI; Linda K. Shaw, MS; Eric D. Peterson, MD, MPH, FACC

Disclosures

Am Heart J. 2010;160(4):744-751. 

In This Article

Results

Baseline Characteristics

Black patients with significant CAD were younger, were more often female, and had a lower socioeconomic position (Table I). Despite being younger, black patients had higher BMI measurements; a higher prevalence of medical comorbidities including hypertension, diabetes mellitus, cerebrovascular disease, PVD, and HF; and a lower EF relative to white patients. Conversely, whites were more likely than blacks to have a history of angina, cigarette smoking, and hyperlipidemia. Rates of prior MI and the number of diseased vessels did not vary as a function of race.

Use of Revascularization Procedures. Blacks and whites had similar numbers of diseased vessels (Table I). Thirty days following the diagnostic cardiac catheterization, blacks were less likely to have undergone CABG but had similar rates of PCI. Overall, blacks were less likely to receive any coronary revascularization procedure relative to white patients (59.5% vs 68.8%, P < .0001). After adjustment for baseline clinical factors (Table I), race remained an independent predictor of lower odds of coronary revascularization (odds ratio [OR] 0.66, 95% CI 0.60–0.72). In a stratified analysis, black patients with 1-, 2-, or 3-vessel CAD remained less likely to undergo coronary revascularization compared with white patients (P = .0027, P < .0001, and P < .0001, respectively) (Figure 2).

Figure 2.

Bar graph of diseased coronary vessels and revascularization stratified by race.

Crude Long-term Outcomes. The median follow-up among patients in this study was 7.6 years (IQR 3.5–13.0). Black patients had a lower unadjusted survival compared with white patients at 15 years of follow-up (35.3% to 45.1%). Figure 3 provides unadjusted survival curves by race and gender. Black women had the lowest survival (30.7%), and white men had the highest (48.1%).

Figure 3.

Unadjusted survival curves by race and gender.

Clinical Predictors of Mortality. Major clinical factors that predicted long-term mortality included age, EF, diabetes mellitus, COPD, number of diseased vessels, history of peripheral vascular and cerebrovascular disease, cigarette smoking, hypertension, hyperlipidemia, and renal insufficiency.

Adjusted Outcomes. After adjustment for baseline demographics, clinical factors, socioeconomic position, and initial treatment selection, black race was an independent predictor of long-term mortality among patients with CAD in a multivariable model (hazard ratio [HR] 2.54, 95% CI 1.60–4.04, P < .0001). Gender was not an independent predictor of mortality in this analysis (HR 1.00, 95% CI 0.99–1.05, P = .890). After adjustment for clinical and treatment factors that predicted mortality, black women had lower 15-year survival compared with white women (41.5% vs 45.5%, P < .0001); and black men had lower survival compared with white men (43.1% vs 45.8%, P < .0001). However, there were no significant differences in survival between black men and women (P = .900) and between white men and women (P = .575). This observation was consistent over time (Figure 3).

Use of initial coronary revascularization therapy within 30 days of the index cardiac catheterization was associated with lower long-term risk for mortality. In addition, as noted, black patients were less likely to receive coronary revascularization therapy than white patients. Figure 4 provides stratified adjusted survival rates by race and initial therapeutic strategy. After such stratification, black patients had lower survival than similarly treated whites (P value for comparisons < .001).

Figure 4.

Adjusted survival curves by race and revascularization. WM, Whites treated with medical therapy; WR, whites treated with revascularization therapy; BM, blacks treated with medical therapy; BR, blacks treated with revascularization therapy. *Adjusted for all variables in Table I.

Finally, we empirically evaluated through interaction terms whether the impact of specific prognostic factors varied as a function race. The effect of renal insufficiency, smoking, HF severity, COPD, history of cerebrovascular disease, history of PVD, and increasing heart rate on mortality did not differ across race in our population (P > .05 in tests for interaction). Among patients with diabetes mellitus and hypertension, there were no significant racial differences in all-cause mortality. In contrast, the effect of age, EF, and number of diseased vessels on total mortality differed by race. The impact of advancing age on mortality risk was larger in whites (HR 1.81, 95% CI 1.75–1.86) than blacks (HR 1.53, 95% CI 1.44–1.62, P < .001). In addition, lower EF was also associated with higher mortality among whites compared with blacks (HR 1.92, 95% CI 1.81–2.04 and HR 1.65, 95% CI 1.45–1.88, respectively, P = .0092). Extent of CAD (number of diseased vessels) had a slightly worse effect on mortality in white patients (HR 1.32, 95% CI 1.25–1.38) than in black patients (HR 1.20, 95% CI 1.11–1.30, P = .0226) (Figure 5). Interaction terms were included in all adjusted analyses.

Figure 5.

Adjusted HRs and CIs by race with significant interactions. Hazard ratios for the interactions of age, EF, and extent of CAD with race are as follows: per 10-year increase in age, per 5% decrease in EF, and per increase of 1 diseased vessel. .Adjusted for all variables in Table I.

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