Author + information
- Judith E. Mitchell, MD∗ ()
- ↵∗Reprint requests and correspondence:
Dr. Judith E. Mitchell, Department of Cardiology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Box 1199, Brooklyn, New York 11203-2098.
- cardiac resynchronization therapy
- changing demographics
- heart failure in blacks
- implantable cardioverter defibrillator
- ventricular tachyarrhythmias
The composition of the population according to race/ethnicity is changing. In 2014 the proportions of non-Hispanic white and minority populations were 62% and 38%, respectively. Projected change of the racial and ethnic diversity for 2060 is: non-Hispanic whites 44%, minorities 56% (1). A transformation in the landscape of heart failure (HF) is also projected. There are 5.7 million people with HF, and by 2030 it is expected to increase to >8 million people, or 1 in every 33. This anticipated growth is in part due to the shifting racial and ethnic diversity (2).
Blacks are disproportionately affected by HF with onset and death at younger ages compared with non-Hispanic whites. (3,4) The longitudinal study, CARDIA (Coronary Artery Risk Development in Young Adults), which followed 5115 participants (52% African American [AA]; 18 to 30 years of age at baseline) over a 20-year period showed the incident HF rate for AA to be 20 times that found in whites, and blacks had a 1 in 100 chance of developing HF while still in their 30s or 40s (3).
Determinants of the observed differences in HF between blacks and whites have been attributed to higher rates and/or severity of comorbidities such as hypertension (HTN), obesity, diabetes, and renal insufficiency. Differences in the natural history of ventricular dysfunction, reduced access to medical care, lower medical literacy, and cultural and socioeconomic factors have also been proposed (3–5).
The cumulative result creates a profile of HF in blacks personified by higher New York Heart Association functional class, more frequent hospitalizations, and a higher risk of sudden cardiac death (5–7). With differences so compelling and consequences so fatal, it is crucial to focus on prevention and effective HF management in this racial group. However, with few exceptions, young, racial, and ethnically diverse subjects do not comprise a significant cohort of prior or current HF trials.
In this issue of JACC: Clinical Electrophysiology, in a new study using data from MADIT-CRT (Multicenter Automatic Defibrillator Implantation With Cardiac Resynchronization Therapy), Sabbag et al. (8) sought to analyze the risk of ventricular tachyarrhythmias (VTA) or death in black and white subjects with mild (New York Heart Association functional class 1 or 2) systolic dysfunction (ejection fraction of ≤30%), left bundle branch block, and QRS duration of ≥130 ms, implanted with an implantable cardioverter-defibrillator (ICD) or defibrillator and combined cardiac resynchronization therapy (CRT-D). This retrospective analysis reaffirmed prior study results showing that blacks with HF are younger, more likely to have nonischemic HF, and sicker, with a greater proportion of diabetes and HTN. Less atrial fibrillation was recorded in blacks, and women accounted for a larger percentage of those with HF compared with whites.
After 4 years of follow-up, the investigators found the cumulative probability for a first VTA or death significantly higher among black patients compared with whites. Telling is the figure in the publication showing that treatment with CRT-D is associated with a lower rate of VTA or death compared with ICD-only therapy among both black and white patients. However, the curves representing the probability of VTA or death with or without CRT-D remained higher for blacks compared with whites. Although blacks derived benefit from the CRT-D, excess risk remained. In fact, the mortality curve for blacks with CRT-D appeared similar to that of whites with ICD only. Notably, the race-to-treatment interaction was not significant, suggesting that the clinical benefit of the therapy was not determined by race.
An unexpected finding in the current study was the inversed VTA risk with systolic blood pressure values among black patients. An increase of 18% in the risk of VTA or death was noted for every 5-mm Hg reduction in blood pressure.
HTN is a major public health problem affecting 80 million U.S. adults or about 33% of the overall adult population. Among the highest prevalence in the world is found in blacks, with HTN present in at least 45% of the black population. Although HTN is an antecedent in 74% of all people with HF, it is the most common etiology of HF in blacks (9). One of the hallmarks of HF prevention is effective blood pressure control. With aggressive blood pressure control, the risk of new HF can be decreased by about 50%, even in patients with diabetes. For patients at higher risk, that is, with a history of prior MI, the risk reduction may be even greater (10). In CARDIA, the number of black patients with HTN who needed to be treated to avoid a case of HF was only about 21 (3).
Further, the association of HTN with premature ventricular contractions (PVCs) was found to be consistent for all forms of PVCs in the ARIC (Atherosclerosis Risk In Communities) study, a population-based cohort study. The odds ratio for HTN increased from 1.31 for a single PVC to 1.41 for frequent PVCs and to 2.20 for complex PVCs (7). ARIC also found that the prevalence of PVCs on a 2-min electrocardiograph had a strong, direct relationship to AA race.
On the basis of all we know about HTN in blacks, the observations of the seemingly incongruent finding of increased VTA risk with lower systolic blood pressure in blacks require an explanation. The investigators speculate that this finding may be a marker of decompensated HF and hemodynamic instability, both potential precursors to VTA. Although plausible, and certainly hypothesis generating, the small sample size necessitates caution with any proposed interpretation of this finding.
Another independent risk factor for VTA or death among blacks was larger cardiac volumes. Similar impact of left ventricular size on survival has been shown in advanced HF (11).
Last, with 2 notable exceptions, drug therapy was comparable in backs and whites. Significantly greater use of digoxin in blacks was reported. However, multivariate analysis of the risk of VTA or death by race showed similar results across the spectrum with or without digoxin in the model. Statin use was recorded significantly less in blacks. Despite fewer prior myocardial infarctions, the higher prevalence of diabetes suggests greater usage may have been warranted. The importance of this difference is that the pleiotropic actions of statins may include antiarrhythmic properties (12).
The major limitation of the study is the small sample size of blacks, only 8%. Furthermore, this was a post hoc analysis with all the inherent limitations.
Eliminating disparate outcomes for racial and ethnic groups is one of the goals of our health care system. There has been a closing of the gap in the implantation of guideline-directed ICD and CRT-D that existed between blacks and whites (5). This study supports the guideline-directed implantation of ICD or CRT-D therapy in HF patients without consideration of race/ethnicity.
Remarkably, in ARIC, greater than the association of PVCs with AA race was the higher prevalence of PVCs seen with low educational attainment. Eliminating the obstacles to inclusion to HF medical and device trials, abolishing inequity in medical therapy, and providing equal access to preventive and specialty care are imperative. In addition, addressing the socioeconomic and educational disparities affecting blacks is a continuing challenge demanding urgent innovative and multipronged approaches.
↵∗ Editorials published in JACC: Clinical Electrophysiology reflect the views of the authors and do not necessarily represent the views of JACC: Clinical Electrophysiology or the American College of Cardiology.
Dr. Mitchell has reported that she has no relationships relevant to the contents of this paper to disclose.
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