Race, Exercise Training, and Outcomes in Chronic HF
Of patients who self-reported race (n = 2,296), 33% (n = 749) were black. Table I presents baseline characteristics. Blacks were younger, were more often female, and had less ischemic etiology and lower socioeconomic status versus whites. Blacks also tended to have higher body mass index (BMI) and more hypertension and diabetes but less atrial fibrillation. Blacks had shorter 6-minute walk distance and lower peak VO2 at baseline; ( Table II ). Differences in these exercise-testing parameters remained significant after adjustment for sex differences (both P < .01). More than 90% of black and white patients were receiving angiotensin-converting enzyme (ACE) inhibitors/angiotensin receptor blockers, with approximately half as many receiving aldosterone antagonists. Combination hydralazine/nitrate use was greater in blacks than in whites. Blacks were less likely to have an implanted cardioverter/defibrillator (ICD) or cardiac resynchronization therapy (CRT) device; however, there were significant differences in conduction pattern by race. Specifically, more blacks had normal ventricular conduction, and fewer blacks had bundle-branch block morphology (14.7% vs 22.9%).
Adherence to exercise training by exercise minutes per week during the first 3 months and months 10 to 12 was 63 (18–106) in blacks versus 86 (50–125) in nonblacks (P < .001) and 68 (6–167) versus 108 (26–208) (P < .001), respectively. Median exercise volume in the exercise training arm was lower in blacks than in whites (2.9 [1.0–5.0] vs 4.4 [2.4–6.6] MET-h/wk, respectively, during months 1–3).
Overall adverse events were similar in patients of different race (online Appendix Supplementary Table I ), with the exception of more worsening HF in blacks than in whites (36% vs 24%).
Mode-specific event rates for death and hospitalization are presented in the online Appendix Supplementary Table II . Over a median follow-up of 2.5 years, all-cause mortality was 17.9% in blacks and 15.8% in whites. Hospitalization occurred in 67.0% of blacks versus 62.1% of whites. Nearly half of all hospitalizations were for HF in blacks (48.4%) compared with approximately a third in whites (33.9%). Black race was associated with increased mortality/hospitalization and cardiovascular mortality/HF hospitalization ( Table III ). All-cause mortality was similar in black and white patients. Cardiovascular mortality was similar between groups (P = .21), whereas black race was associated with increased hazard for HF hospitalization (HR 1.62, 95% CI 1.37–1.92) (online Appendix Supplementary Table III ).
After multivariable adjustment for the adjustment model covariates, black race remained associated with increased mortality/hospitalization and cardiovascular mortality/HF hospitalization ( Table III ). Figure 1 displays adjusted event curves for the endpoints of mortality/hospitalization, and cardiovascular mortality/HF hospitalization. Exploring the individual components of these end points suggested increased risk, associated with black race for HF hospitalization (adjusted HR 1.58, 95% CI 1.27–1.96), but similar risk for cardiovascular mortality (adjusted P = .18).
After adjustment for additional socioeconomic covariates, black race was no longer associated with a significant increase in mortality/hospitalization (P = .09). The increased risk of cardiovascular mortality/HF hospitalization ( Table III ) and the individual component of HF hospitalization associated with black race remained statistically significant (HR 1.55, 95% CI 1.22–1.97) ( Appendix Supplementary Table III ).
There was no interaction between race and assignment to exercise training on clinical outcomes ( Table IV ). However, there was evidence for an interaction between black race and exercise training for change in 6-minute walk distance (adjusted P = .02). The estimated improvement in 6-minute walk distance with exercise training versus usual care at 3 months was +26 m (95% CI, +18 to +34) in whites versus +11 m (95% CI, 0 to +21) in blacks. No other exercise or health status variable demonstrated a statistically significant interaction with race and exercise training.
Results
Of patients who self-reported race (n = 2,296), 33% (n = 749) were black. Table I presents baseline characteristics. Blacks were younger, were more often female, and had less ischemic etiology and lower socioeconomic status versus whites. Blacks also tended to have higher body mass index (BMI) and more hypertension and diabetes but less atrial fibrillation. Blacks had shorter 6-minute walk distance and lower peak VO2 at baseline; ( Table II ). Differences in these exercise-testing parameters remained significant after adjustment for sex differences (both P < .01). More than 90% of black and white patients were receiving angiotensin-converting enzyme (ACE) inhibitors/angiotensin receptor blockers, with approximately half as many receiving aldosterone antagonists. Combination hydralazine/nitrate use was greater in blacks than in whites. Blacks were less likely to have an implanted cardioverter/defibrillator (ICD) or cardiac resynchronization therapy (CRT) device; however, there were significant differences in conduction pattern by race. Specifically, more blacks had normal ventricular conduction, and fewer blacks had bundle-branch block morphology (14.7% vs 22.9%).
Adherence to exercise training by exercise minutes per week during the first 3 months and months 10 to 12 was 63 (18–106) in blacks versus 86 (50–125) in nonblacks (P < .001) and 68 (6–167) versus 108 (26–208) (P < .001), respectively. Median exercise volume in the exercise training arm was lower in blacks than in whites (2.9 [1.0–5.0] vs 4.4 [2.4–6.6] MET-h/wk, respectively, during months 1–3).
Overall adverse events were similar in patients of different race (online Appendix Supplementary Table I ), with the exception of more worsening HF in blacks than in whites (36% vs 24%).
Mode-specific event rates for death and hospitalization are presented in the online Appendix Supplementary Table II . Over a median follow-up of 2.5 years, all-cause mortality was 17.9% in blacks and 15.8% in whites. Hospitalization occurred in 67.0% of blacks versus 62.1% of whites. Nearly half of all hospitalizations were for HF in blacks (48.4%) compared with approximately a third in whites (33.9%). Black race was associated with increased mortality/hospitalization and cardiovascular mortality/HF hospitalization ( Table III ). All-cause mortality was similar in black and white patients. Cardiovascular mortality was similar between groups (P = .21), whereas black race was associated with increased hazard for HF hospitalization (HR 1.62, 95% CI 1.37–1.92) (online Appendix Supplementary Table III ).
After multivariable adjustment for the adjustment model covariates, black race remained associated with increased mortality/hospitalization and cardiovascular mortality/HF hospitalization ( Table III ). Figure 1 displays adjusted event curves for the endpoints of mortality/hospitalization, and cardiovascular mortality/HF hospitalization. Exploring the individual components of these end points suggested increased risk, associated with black race for HF hospitalization (adjusted HR 1.58, 95% CI 1.27–1.96), but similar risk for cardiovascular mortality (adjusted P = .18).
After adjustment for additional socioeconomic covariates, black race was no longer associated with a significant increase in mortality/hospitalization (P = .09). The increased risk of cardiovascular mortality/HF hospitalization ( Table III ) and the individual component of HF hospitalization associated with black race remained statistically significant (HR 1.55, 95% CI 1.22–1.97) ( Appendix Supplementary Table III ).
There was no interaction between race and assignment to exercise training on clinical outcomes ( Table IV ). However, there was evidence for an interaction between black race and exercise training for change in 6-minute walk distance (adjusted P = .02). The estimated improvement in 6-minute walk distance with exercise training versus usual care at 3 months was +26 m (95% CI, +18 to +34) in whites versus +11 m (95% CI, 0 to +21) in blacks. No other exercise or health status variable demonstrated a statistically significant interaction with race and exercise training.
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