Abstract
Background: Despite recent advancements in prevention,
treatment, and management options, cardiovascular diseases contribute to
one of the leading causes of morbidity and mortality. Several studies
highlight the compelling evidence for the existence of healthcare
inequities and disparities in the treatment and management control of
cardiovascular diseases.
Aims: To explore the role of racial disparities in the
treatment of various cardiovascular diseases, highlighting the role of
socioeconomic and cultural factors, and ultimately postulate solutions
to eliminate the disparities.
Methods: A comprehensive review of literature was conducted
using appropriate keywords on search engines of SCOPUS, Wiley, PubMed,
and SAGE Journals.
Conclusion: By continued research to eliminate healthcare
inequalities, there exists a potential to improve health-related
outcomes in minority populations.
Introduction
Cardiovascular diseases (CVD) contribute significantly to the rising
cases of morbidity and mortality in Western countries while being a
major health threat in the developing world. CVD encompasses diagnoses
including, but not limited to, Coronary Heart Disease (CHD), strokes,
aortic disease, and peripheral arterial disease
(PAD).1 There exists a positive correlation between
risk factors, such as hypertension, obesity, smoking,
hypercholesteremia, and CVD. According to the World Health Organisation
(WHO), there have been approximately 17.9 million annual deaths from
CVD, which represents 31% of deaths worldwide.2,3
Despite remarkable advancements in risk factor identification, and the
widespread implementation of evidence-based strategies for CVD
management, racial health disparities persist, which play an
indisputable role in predisposing minorities to CVD.1For instance, with data from the United States (US) and the United
Kingdom (UK), CVD accounts for more than one-third of the differences in
mortality rates in ethnic minorities such as Black people compared to
White.4,5 The Institute of Medicine (IOM) report,Unequal treatment: confronting racial and ethnic disparities in
health care , defines health disparities as “racial or ethnic
differences in the quality of healthcare that are not due to
access-related factors or clinical needs, preferences, and
appropriateness of intervention.” This definition recognises the role
of synergistic factors, such as limited health literacy and healthcare
access, inadequate cultural competency and implicit negative biases
amongst physicians as mediators of racial/ethnic
disparities.6
The purpose of this review is to focus on the drawbacks of past CVD
research, explore the role of racial disparities in the treatment of
Hypertension, Coronary Artery Disease, Arrhythmias, Heart Failure, and ,
highlighting the role of socioeconomic and cultural factors in CVD, and
provide future directions to eliminate these disparities in the global
population.
Gaps in Existing Research
Numerous epidemiological studies have documented African-American
disparities in CVD, focusing on the interplay of patient-level,
healthcare, and environmental risk factors. Alongside the study of these
vital factors, there has to be equal emphasis on the primordial factors
(pathophysiological mechanisms) which underlie these racial disparities.
Comprehensive understanding of the in-depth mechanisms can help devise
strategies to improve management and treatment of CVD, promoting
equity.7
The ultimate goal of clinical research is to devise strategies that aim
to prevent and treat disease, where the study population is
representative of the affected population. However, a majority of the
CVD population-based studies (USA) have been largely limited to
White-American and African-American cohorts. Underrepresentation in
medical research has far-reaching implications, that significantly
contribute to healthcare disparities. As the nation’s population begins
to grow, with an increasingly diverse and multicultural patient base,
clinical studies have to incorporate other racial sub-groups, such as
Asian-American cohorts, to better reflect CVD trends in the general
population, which will enable generalisability of results to minority
subgroups.8
A prospective, observational study assessed those at risk for or with
atherothrombotic disease (CAD, PAD, and CVD) from seven racial/ethnic
sub-groups A 2-year follow up highlighted that Blacks had the highest
cardiovascular mortality, and Asians had the lowest cardiovascular
mortality. The study, however, does not define the underlying
aetiologies (social, environmental, cultural factors) amongst the ethnic
sub-groups, and their contribution to the cardiovascular outcomes, which
could be a potential prospect for future research.9
Furthermore, a large number of CVD cohort studies comprised of small
sample sizes and were limited to singular healthcare organisations,
which affected the generalisability of results. There exists wide
variation in components of the intervention, with varying study designs,
contributing to a lack of overall cross-standardisation, impacting the
interpretability of results, and increased the difficulty to draw broad
conclusions across the studies. Considering the retrospective nature of
majority CVD studies, there also arose elements of recall, publication,
and acquiescence biases10
Considering the important shortcomings of past research, a great deal of
work to reduce healthcare disparities to bridge the translation and
fundamental knowledge gaps is essential.
Disparities in treatments:
Hypertension
The term “hypertension” refers to arterial hypertension characterised
by a systolic blood pressure (SBP) exceeding 140mHg, and diastolic blood
pressure (DBP) exceeding 90mmHg. “Treatment” shall refer to generally
adopted prescriptions of antihypertensive drugs such as oral
anticoagulants, diuretics, and digoxin and exclude lifestyle or dietary
measures.11
Several US and UK studies report a higher prevalence and severity of
hypertension in ethnic minorities such as South Asian, Caribbean, and
West African populations compared to White subjects, which is in line
with recent JBS guidelines.12 Studies used for this
review have been summarised in Table 1.
UK and US clinical guidelines indicate that patients of
African/Caribbean origin should be offered calcium channel blockers as
first-line treatment, while patients aged below 55, not of
African-Caribbean origin, should be offered an angiotensin-converting
enzyme inhibitor (ACEI) or an angiotensin receptor antagonist
(ARB).18 European hypertension treatment guidelines
have only recently adopted similar specificity in drug treatments,
however, neglect other ethnic minorities (e.g., South Asians, Chinese),
and conclude that no evidence exists to prove that response to treatment
differs from the general European population.11
The specialised approach to treatment in Black patients has been
attributed to a multitude of physiological attributes such as higher
circulatory levels of endothelin-1 and weaker vasodilation in response
to nitric oxide compared to White patients.19 A
comparative analysis of data from six randomised controlled trials on
the effect of endothelin receptor antagonists (ERAs) on treatment
outcomes measured by the distance patients could walk in six minutes
found that White patients had an increased walk distance compared to
Black patients. This study hypothesised these results to be due to an
insufficient ERA dosage in Black patients20 to
compensate for the increased levels of endothelin-1. Other physiological
attributes affecting response to treatment in other ethnicities include
variations in the phenotypic and genotypic expression of cytochrome P450
enzymes.21
The efficacy of pharmacological treatments has been minimally
investigated in minority ethnicities. Per clinical guidelines, ACEIs
have been proven to be less effective in Black patients due to increased
risk of morbidities such as stroke and heart failure, while those
prescribed thiazide-like diuretics achieved better falls in blood
pressure.22 Brewster et al. analysed pooled data on
the ability of antihypertensive drug therapy in lowering blood pressure
and did not find any evidence to suggest a differing efficacy of
hypertension drugs in South Asians.23 A lack of
resources in that area renders the data inconclusive. More research
needs to be conducted on not only drug efficacy in the South Asian
population but also rates of morbidity and mortality following drug
therapy.
Most studies recognise that ethnic minorities do not meet treatment
goals or receive treatment despite eligibility for hypertension
medication. A major challenge in achieving control is thought to be
medical compliance.24 Various sources have uncovered
lower rates of adherence in Black patients in comparison to White
patients25, 26, a trend synonymous with several other
ethnic minorities such as Chinese and South Asians.27
Coronary Artery Disease
Coronary Artery Disease (CAD/CHD) is characterised by the narrowing of
the coronary arteries, reducing blood flow and leading to angina, while
complete blockage may induce a heart attack. Treatment for CAD currently
comprises medication, surgical procedures, or both depending on the
severity and extent of the disease.28 Studies used for
the review have been summarised in Table 2.
A higher incidence of CAD has been reported in South Asian patients than
other ethnic minorities in the UK, which remains in line with Joint
British Societies (JBS) guidelines of date.12 These
guidelines also detail the lower risk of the African-Caribbean
population of CAD by comparison.
Although treatment guidelines are universal across all ethnicities, the
age whereby the patient would require treatment and efficacy of the
treatment is variable. Iantorno et al., in his retrospective analysis,
compared Black women who had undergone percutaneous coronary
intervention (PCI) in response to conditions caused by CAD (e.g., stable
angina and acute coronary syndrome) with White women of the same
circumstance. Results indicated that Black women were younger and had
more risk factors than Whites and were more likely to present with acute
coronary syndrome.34 These results reiterated the
findings of a different study comparing Black and White patients
undergoing isolated CABG, which indicated that black patients were
younger, with more comorbidities, and presented more severely than their
White counterparts.35 Population studies have also
proven that Hispanic patients undergoing CABG are generally younger than
their White counterparts.36
Some studies also report disparities experienced by ethnic minorities in
terms of quality and accessibility to treatment. One study pointed out
the lower likelihood of Black patients with acute MI being admitted to a
facility capable of revascularisation37, while another
found Black patients at the receiving end of longer revascularisation
times, notably more so if they were also male38. In
addition to poor accessibility, minority ethnic groups have had similar
access to healthcare but remained less likely to undergo
revascularisation or cardiac procedures.39
A US study comparing postoperative complications 30 days following the
procedure in Black, White and Asian patients who had undergone CABG
found that Black and Asian patients had higher rates of postoperative
pulmonary morbidity and mortality. The same ethnic minorities also had
longer hospital stays post-op.40
A deficiency in the literature on other ethnic minorities has proven to
be limiting in terms of fully evaluating treatment responses and where
literature has been published, it has been overwhelmingly focused on
Asian migrant populations in the Western world as opposed to native
Asian populations.40,41 It has been noted in various
papers that additional research on racial disparities in treatment is
detrimental in tailoring healthcare better suited to each patient and
improving treatment outcomes in populations that only continue to become
increasingly diverse.42 This is a theme Gijsberts et
al. have aimed to cater to in their multivariable Cox regression
analysis comparing mortality in patients undergoing coronary
angiography, revascularisation or CAD in the Netherlands and patients in
Singapore, consisting of three large Southeast Asian ethnic subgroups,
Malays (highest mortality rate), Chinese and
Indians.43
Arrhythmias
Arrhythmias are abnormalities of the electrical properties of the heart
which causes a change in the rhythm and/or heartbeat rate. Arrhythmias
can be categorised on the basis of site and cardiac frequency.Treatment
for arrhythmias include anti-arrhythmic medication, catheter ablation,
cardioversion, implantable pacemakers and cardioverter-defibrillators
(ICD).44 This section will discuss treatments for
atrial fibrillation (AF) given its overall prevalence in developed
countries and published literature. Table 3 summarises the studies used
for the purpose of this review.
The incidence of AF does not appear to differ between ethnicities, some
studies even noting a higher incidence of AF in White patients over
patients from ethnic minorities.50,51 Conversely
however, Black patients have a higher prevalence of risk factors
associated with AF compared to their White counterparts, a phenomenon
referred to as the ‘racial paradox’.52, 53 The
mechanism is poorly understood and requires further research to
ascertain causes and effects.
The main barriers to treatment for minority ethnics exist in the racial
disparities surrounding patient awareness and treatment efficacy.
Awareness of having AF and its clinical implications is significantly
lower in Black patients compared to Whites. Furthermore, studies have
noted that Black patients were about one fourth as likely to be
prescribed warfarin than Whites.46 This likely due to
the lower efficacy of warfarin treatment on AF in Black patients, with
studies noting the increased dosage requirement and shorter time in
therapeutic range (TTR) of internalised normal ratio
(INR).49,54
Inconsistent results have been yielded from the various studies that
have been performed evaluating the reduced prescription of non-vitamin K
oral anticoagulants (NOACs) in minority ethnics.50,53A 2018 study comparing the rates of prescription of OACs among Black,
White, and Hispanic AF patients calculated a 27% decrease in the
likelihood of receiving NOACs in Black patients but deemed that figure
insignificant after accounting for socioeconomic
factors.55 A recent 2020 study, however, found that
Black, Asian, and other minority ethnics were in fact, significantly
less likely to receive any OACs, the difference continuing to be
significant even after accounting for socioeconomic
factors.56 The efficacy and required doses of OACs
have not been performed in populations with adequate representation of
ethnic minorities, and therefore cannot be commented on at this
time.53,56
Several studies have also noted that non-White populations are less
likely to be treated with rhythm control modalities and are instead
treated with a rate control modality. Following rhythm control
modalities, White patients were more likely to undergo cardioversion, be
prescribed antiarrhythmic medication, and undergo interventional AF
procedures, such as catheter ablation and surgery than Black and
Hispanic patients. They also had higher implantation rates of
cardioverter defibrillators and permanent
pacemakers.48,49
Some studies attribute these disparities to the poorer access to
healthcare experienced by minority ethnics, which have been theorised to
be a consequence of lower literacy, cultural norms, and language
barriers. This is thought to lead to a lack of recruitment of ethnic
minorities in clinical trials.57 Further research
seems necessary in discerning the causation of these differences.
Heart Failure
Heart failure (HF) is a circulatory condition caused by structural and
functional changes that adversely affect the pumping (systole) and
filling (diastole) of the heart leading to elevated intracardiac
pressures or reduced resting cardiac output resulting in a myriad of
symptoms. HF can be acute (reduced left ventricular ejection filling) or
chronic (preserved left ventricular ejection fraction). Treatment for
heart failure currently range from medications to device
implantations(pacemakers, ICDs) and surgical
procedures.58
Various sources comment on the high prevalence and susceptibility of HF
in patients of African descent.58 Black and Hispanic
patients in the US and South Asians in the UKhave also been found to
develop HF at a younger age. Black patients generally have more adverse
treatment outcomes. More recent studies examining HF prevalence in UK
ethnic minorities have not been performed. Overall, more research needs
to be done to identify the determinants of outcome differences across
ethnicities. A summary of studies used for the purpose of this review
have been detailed in Table 4.
The efficacy of pharmacological treatment across ethnicities have yet to
be explored adequately especially non-Black ethnic minorities. HF drugs
commonly used unless contraindicated include ACEIs, ARBs and diuretics.
Many sources have reported reduced efficacy of ACEIs and spironolactone
in Blacks, while conflicting results have been obtained from studies
involving beta blockers.67,68 Shekelle et al.’s
meta-analysis of four randomised controlled trials (RCTs) of beta
blockers would estimate the relative risk (RR) of mortality to be 0.97
in Blacks and 0.69 in Whites. However, upon removal of data from one of
the four RCTs, the RR of black patients reduced to 0.67. This was
hypothesised to be due to the small sample size of black patients in the
analysis, a weakness experienced by many other
studies.69
Of note, the addition of combinedhydralazine and isosorbide dinitrate is
recommended for use in Black patientsby the European Society of
Cardiology (ESC) following evidence of reduced morbidity and mortality
rates in black HF patients.70 Given the hypothesis
that reduced efficacy of ACEIs in Black patients is due to reduced
bioactivity of nitric oxide (NO), these results are thought to emphasise
using NO enhancing therapies in Black patients.19,71The increase in efficacy has only been clearly examined and proven in
Black patients, due to scarcity of literature on other ethnic
minorities.70
Medical compliance to HF drugs is also a factor in predicting outcomes
in ethnic minorities. In the US, an observational study comparing
medical adherence across ethnicities found that Native Americans, Black,
Hispanic and Asian patients had lower rates of adherence than their
White counterparts despite drug coverage by Medicare which is suggestive
of other factors such as health beliefs surrounding adherence and
eventual outcomes of treatment.72
Role of socioeconomic & cultural factors
Various studies have utilised a variety of approaches to conceptualise
and measure the inverse relationship between SES and the risk of CVD, in
terms of education, employment status, occupation, annual income and
social class.
Intensive studies concerning pathophysiology of atherosclerosis have
shed light on the environmental contribution to atherosclerotic disease
and CVD alongside non-modifiable risk factors, such as age and genetics.
Variation in the geographical location, and diversity of cultural and
social practices alter CVD risk. Cumulative data from the Nurse’s Health
Study73 and the Health Professionals follow-up study
suggested that 82% and 62% of coronary events, respectively could have
been avoided if the study participants adhered to a healthy, low-risk
lifestyle. However, obscurity of the cumulative impact of various
environmental factors and mechanisms influencing CVD limits the validity
of these studies.74
A systematic review conducted to study disparities in CVD care
highlighted gaps in well-established markers, such as SES which is an
important social determinant of health.5 Recent
studies have established good evidence regarding modifiable factors,
such as SES and cultural factors which act as stronger determinants of
health-related outcomes when compared to race. Likewise, the studies
emphasised on the diminishing effect of disparate care when factors,
such as SES are controlled for, which eventually leads to the influence
of race being zeroed down.75 The reviews have
identified an inverse relationship between education and CVD, with lower
educational attainment being associated with higher incidence of
hypertension, physical inactivity, sedentary lifestyle which contribute
as risk factors to CVD.
A large-scale cohort study, the Prospective Urban Rural Epidemiologic
(PURE) study recruited adults aged between 35 and 70 years from
low-income, middle-income and high-income countries to explore the
influence of economic levels on the CVD mortality. The results suggested
the presence of an inverse relationship between SES and CVD mortality,
with the gradient being steepest for the low-income countries. The study
also concluded the greater influence of the educational factor than the
household income on CVD incidence and death rate, with associations of
poorer access to healthcare systems in low-income and middle-income
countries.76
Clinical patient data from the Hypertension Detection and Follow-up
program (HDFP) examined the association between SES, measured in terms
of education and the prevalence of hypertension in Black and White
racial groups. As anticipated, education was inversely associated with
incidence on hypertension in both the racial groups, irrespective of
sex. The relationship was more pronounced, however, in the younger Black
patient sub-group compared to the Whites. Nevertheless, SES reflected in
terms of education alone couldn’t completely explain the association
with CVD, as despite equal educational attainment between both patient
sub-groups, greater cases of hypertension were reported in the Blacks.
These fluctuations could be explained in terms of other contributing
environmental factors and genetic factors, such as Vitamin D
levels.74
A community-based cross-sectional study of 347 adults aged 18 to 17
years old in Nepal concluded an increased risk of CVD in individuals
without any educational background.77 Moreover, a
prospective UK SABRE analysis of a cohort of 1090 Europeans and 1006
South Asians studied the association of four healthy behaviours (high
fibre diet, non-smoker, moderate alcohol consumption, and physically
active) and CVD outcomes. Over a 21-year follow-up, lower adherence to
the four healthy behaviours led to a 2 to 3-fold increased incidence CHD
risk in both ethnic groups .78
A conclusive overview of the studies emphasizes on the significant
contribution of SES to the aetiology, development of CVD and subsequent
mortality and morbidity.
Future Perspectives