Objective There are large geographical differences in implantable cardioverter defibrillator (ICD) implantation rates for reasons not completely understood. In an increasingly multiethnic population, we sought out to investigate whether ethnicity influenced ICD implantation rates.
Methods This was a retrospective, cohort study of new ICD implantation or upgrade to ICD from January 2006 to February 2019 in recipients of Caucasian or South Asian ethnicity at a single tertiary centre in the UK. Data were obtained from a routinely collected local registry. Crude rates of ICD implantation were calculated for the population of Leicestershire county and were age-standardised to the UK population using the UK National Census of 2011.
Results The Leicestershire population was 980 328 at the time of the Census, of which 761 403 (77.7%) were Caucasian and 155 500 (15.9%) were South Asian. Overall, 2650 ICD implantations were performed in Caucasian (91.9%) and South Asian (8.1%) patients. South Asians were less likely than Caucasians to receive an ICD (risk ratio (RR) 0.43, 95% CI 0.37 to 0.49, p<0.001) even when standardised for age (RR 0.75, 95% CI 0.74 to 0.75, p<0.001). This remained the case for primary prevention indication (age-standardised RR 0.91, 95% CI 0.90 to 0.91, p<0.001), while differences in secondary prevention ICD implants were even greater (age-standardised RR 0.49, 95% CI 0.48 to 0.50, p<0.001).
Conclusion Despite a universal and free healthcare system, ICD implantation rates were significantly lower in the South Asian than the Caucasian population residing in the UK. Whether this is due to cultural acceptance or an unbalanced consideration is unclear.
- implanted cardiac defibrillators
- cardiac arrhythmias and resuscitation science
- health care delivery
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More than four million deaths occur every year due to sudden cardiac death (SCD).1 Implantable cardioverter defibrillators (ICDs) provide prognostic therapy that can abort SCD by terminating ventricular arrhythmias. Landmark trials for primary and secondary preventions of SCD in both ischaemic and non-ischaemic aetiology have established the benefits of ICDs.2 Despite their incorporation into guidelines,3 4 their use remains widely variable.
Due to migration, populations are becoming ever more diverse. There are ethnic differences in cardiovascular disease occurrence, with South Asians (people of Indian, Pakistani, Bangladeshi and Sri Lankan origins) being more likely to suffer from coronary artery and cerebrovascular diseases than those of a Caucasian ethnicity.5–7 Ethnic differences in cardiac pacemaker implantation have been reported in the UK, where those of a South Asian origin have lower rates of implantation compared with the Caucasian population.8 Whether this remains the case for ICD implantation is currently unknown.
Disparity in ICD selection is evident in African–Americans with studies, predominantly of a US population, exhibiting lower rates of implantation that is thought to be multifactorial (patient level such as disease-specific and socioeconomic factors, practices of healthcare professionals and healthcare system delivery factors).9–11 However, very little is known about those of non-Afro-Caribbean ethnicities or ethnic minorities outside of the USA.
Variation in implantation among different ethnicities may be in part be due to genetic differences in susceptibility to cardiovascular disease,12 due to socioeconomic factors such as access to healthcare insurance as seen in the USA13 or due to unconscious bias from physicians.14
According to the UK National Census 2011, South Asians make up the largest ethnic minority (4.9%) in the UK. Many of these are second-generation and third-generation descendants of migrants. In the county of Leicestershire, the South Asian ethnic minority was found to be as high as 15%. The aim of this study was to determine whether there are any disparities in ICD implantation among people of South Asian origin when compared with Caucasian patients in the National Health Service (NHS) with universal health coverage.
Study design and population
This was a retrospective cohort study of ICDs implanted between January 2006 and February 2019 at a single tertiary centre (Glenfield Hospital, University Hospitals of Leicester NHS Trust, Leicester, UK). The study centre is the primary provider of cardiology care and services delivered to the Leicestershire population. It is the only provider of ICD implantation within this county. The study population was obtained from routinely collected local registry data. These registry data are compulsory for every device implantation and are populated by the implanting physician and the cardiac physiologist at the time of the procedure. The registry is up to date and regularly audited and hence provides a complete reflection of ICD implantation activity. Demographic (age, gender and ethnicity), clinical (indication, aetiology, New York Heart Association (NYHA) classification and category of left ventricular systolic function) and procedural (indication, aetiology, procedure date, urgency and type of procedure) data were extracted from this registry. All data were anonymised before analysis. The cumulative ICD implantation rate over the study period was obtained.
The study population comprised individuals of Caucasian and South Asian ethnicities. Other ethnicities (Afro-Caribbean, East Asian, Arab and others) were not considered in this analysis as population size and absolute ICD implantation numbers were small. De novo ICD implants and upgrade from pacemaker/cardiac resynchronisation pacemaker to implantable cardioverter defibrillator were included. Procedures for ICD generator replacement, lead repositioning/replacement, pacemaker implantation and cardiac resynchronisation pacemaker implantation were excluded.
The exposed at-risk population and ethnicity profile of Leicestershire was obtained from the UK National Census (Office for National Statistics). The UK National Census is conducted every 10 years with ethnicity as a compulsory field. The latest census, performed in 2011, provides a sensible assessment of the total and ethnic populations as it falls within the middle interval of the study period. Of note, there has been no mass migration of South Asians or Caucasians into or out of the UK during this period.
The crude cumulative ICD implantation rates per 1000 population were calculated for Caucasians and South Asians. Age-specific rates were calculated for age strata (<25, 25–49, 50–64 and >65 years).
Categorical data were presented as numbers and percentages. Continuous data were presented as means±SD. Differences in categorical and continuous variables were examined using χ2 tests and independent t-tests, respectively.
The cumulative rate was calculated with the numerator as the ICD implantation/upgrades for both ethnicities, in total and for each age strata, while the denominator was the respective population according to the census. In view of differences in age structure between ethnicities, with Caucasians being on average older, ICD implantation/upgrade rates were standardised according to the UK Census 2011 general population. Age-specific ICD implantation/upgrade rates were applied to all age strata for each ethnic group to derive the age-specific expected event rates which allowed summation of the total expected age-standardised events for both ethnic groups. The age-adjusted incidence per 1000 population could then be calculated. Crude and age-standardised risk ratios (RRs) for South Asians compared with Caucasians were calculated. Subgroup analyses for primary and secondary prevention indications were conducted. Ninety-five per cent Wald CIs are provided for all ratios. A p value of <0.05 was considered statistically significant for all tests. All analyses were performed using R Foundation for Statistical Computing (Vienna, Austria).15
The 2011 UK National Census showed the population of Leicestershire to be 980 328, consisting of 761 403 (77.7%) Caucasians, 155 500 (15.9%) South Asians and 63 425 (6.5%) other ethnicities.
Within the study period, there were 2699 procedures recorded, comprising 2601 de novo ICD implantations and 98 upgrades from pacemaker or cardiac resynchronisation therapy to the addition of defibrillator therapy.
After exclusion of non-Caucasian and non-South Asian ethnic groups (n=49), a total of 2650 patients with complete records were retained for study analysis, of which 2436 (91.9%) were Caucasian and 214 (8.1%) were South Asian (figure 1).
The demographic characteristics, clinical information and procedural data as stratified by ethnicity are shown in table 1. Caucasian patients receiving an ICD were older (p<0.001), with less ischaemic heart disease (p=0.009), longer QRS durations (p=0.024), less severe left ventricular systolic impairment (p=0.006) and had fewer implants for a primary prevention indication (p<0.001) than South Asians. The difference in age between the groups was driven by male gender (p<0.001), while the mean ages for female Caucasians and female South Asians were identical (61.5 years). There was no significant difference between gender, urgency of the procedure, NYHA classification and concomitant cardiac resynchronisation therapy between ethnicities.
Cumulative rate by ethnicity, age and indication
The cumulative ICD implantation rate for the general Leicestershire population was 2.75/1000 population. Within the study population of only Caucasian and South Asian ethnicities, the cumulative implantation rate was 2.89/1000 population. The cumulative rate of ICD implantation for primary prevention was 1.82/1000 population and secondary prevention was 1.07/1000 population.
The total cumulative rate was stratified by ethnicity and age for total ICD implantation/upgrade, as well as for primary and secondary preventions (table 2). Primary prevention implantation rates exceeded secondary prevention implantation rates for both ethnicities with greater primary prevention proportion in the South Asian population. The rate increases steeply after the age of 50 years. The unadjusted cumulative total rate was greater for Caucasians (3.20/1000 population) than South Asians(1.38/1000 population), which was the case for both primary and secondary indications.
As the distribution of age in the general population differs between the ethnic groups, with South Asians significantly younger, age-specific rates were calculated for the UK population according to the 2011 Census using the rates observed in the Leicestershire population (table 3). Age-standardised cumulative rates were 2.38/1000 population for Caucasians and 1.78/1000 population for South Asians. Age-standardised cumulative rates for primary prevention indication were 1.47/1000 population for Caucasians and 1.33/1000 population for South Asians, whereas for secondary indication, the rates were 0.91/1000 and 0.45/1000 population, respectively. No adjustment for gender was incorporated, given that there was no significant difference in gender between ethnic groups.
Cumulative rate RR
The crude and age-standardised RRs comparing South Asians with Caucasian are shown in table 4. South Asians are less likely than Caucasians to receive an ICD (RR 0.430, 95% CI 0.374 to 0.495, p<0.001) even when standardised for age (RR 0.747, 95% CI 0.741 to 0.752, p<0.001). This remained the case for primary prevention indications (age-standardised RR 0.906, 95% CI 0.898 to 0.915, p<0.001), while differences in secondary prevention were even greater (age-standardised RR 0.489, 95% CI 0.482 to 0.496, p<0.001).
This study is the first to show differences in ICD implantation rates between South Asian and Caucasian ethnicities. Those of a South Asian ethnicity were significantly less likely to receive an ICD. This difference was observed for both primary and secondary indications. The age-standardised rate difference was most apparent for a secondary prevention indication where Caucasian patients were twice as likely to receive an ICD.
According to the UK National Census 2011, the South Asian ethnicity accounts for the largest ethnic minority in the UK (5%), with Leicestershire demonstrating the largest proportion (15.8%). This allows differences between this ethnic group and those of Caucasian ethnicity to be more readily examined than in other parts of the UK. Furthermore, the study centre is the only ICD provider in the Leicestershire county and hence is well placed to perform such a study and to capture the true rates for the entire population. As there is an equitable healthcare service in the UK as opposed to an insurance-based healthcare system, access to healthcare is less likely to be a confounder that may relate to socioeconomic differences in ethnic groups.
Coronary artery disease is the most common cause of cardiomyopathy, and as such, ICD implantation rates should act as a surrogate marker of disease. It is paradoxical that, despite a greater burden of coronary artery disease, South Asians had lower rates of ICD implantation.5–7 One possible explanation is that South Asians may be underdiagnosed for their suitability for a device due to barriers in access to healthcare as a consequence of low literacy, language barriers and cultural beliefs.16 Our study also seems to suggest that the greatest differences in ICD implantation rates occur in the younger population (≤49 years age), particularly for primary prevention indication. This may reflect barriers to appropriate screening, which may be less available to ethnic minorities, as well as an aversion for probands to inform relatives of inherited disease due to stigma. On the other hand, it may be due to a lower incidence of inherited cardiac conditions among South Asians due to genetic factors. Further work is needed to ascertain this.
Disparities in ICD implantation have been well described in ethnic minorities of an Afro-Caribbean descent. Racial disparities were first noted in the National Hospital Discharge Survey (n=49 517) in the USA, where survivors of cardiac arrest of an African–American ethnicity were less likely to receive an ICD prior to discharge (OR 0.19).17 This finding was echoed soon after for primary prevention device implants in the Medicare database in whom African–Americans were 31% less likely to receive an ICD,11 as well as the American Heart Association’s ‘Get With The Guidelines-Heart Failure’ quality-improvement programme (OR 0.56 and 0.73 for black men and women, respectively).10 Most studies show similar findings for both secondary prevention (OR 0.19–0.24) and primary prevention (0.28–0.73) indications, but much of these data are limited to describing differences in Afro-Caribbean minorities in the USA.9–11 17–20
Hispanics in the USA were similarly less likely to undergo a cardiac resynchronisation defibrillator therapy (OR 0.82).18 In New Zealand, the Asian population had lower rates of ICD implantation (32/million population) than those of European descent (83/million population). Interestingly, the Maori population in New Zealand had the highest implant rates (114/million population) owing to the substantially greater prevalence of coronary artery disease and heart failure hospitalisation, as well as cardiac risk factors, though this may still represent underuse of ICD therapy.21 Much less is known about other ethnicities and those outside of the USA.
Our findings suggest that South Asian subjects undergoing an ICD implant are younger and with more severe left ventricular systolic impairment than Caucasians. This may either reflect biological differences in cardiac pathology occurring at a younger age in South Asians or a perceived lower benefit of ICD therapy in older South Asians compared with Caucasians of a similar age. Similarly in other studies, Afro-Caribbean ICD recipients tended to be younger with more severe left ventricular systolic impairment in comparison with Caucasians.9 18 22 South Asians present to healthcare services with symptoms of heart failure at a younger age, which has been demonstrated in our locality.23 Given the greater prevalence of comorbidities that contribute to the cardiovascular risk profile in South Asians, cardiac disease may present with a more chronic presentation in this cohort. Biological differences in the cardiac substrate that may exist between ethnicities could explain the propensity to ventricular arrhythmia and the considerable difference in secondary prevention ICD implantation rates as seen in our population.
Disparities between ethnicities are seen not only in ICD therapy but also in other cardiovascular therapies. For example, lower rates of percutaneous coronary intervention are seen among African–Americans.24 Ethnic minority groups are less likely to use available diagnostic or therapeutic services, particularly higher technology and newer services, than Caucasians.24 Aversion to certain medical therapies may be due to the invasive nature of the procedure and the perceived risks. For example, African–American patients in the Medicare registry are more likely to refuse coronary reperfusion therapy.25 Alternatively, there may be anxiety towards newer or novel therapies. This hypothesis was examined by Groeneveld et al using an ‘innovativeness’ vignette towards a new drug or device.26 Interestingly, it showed Caucasians were more likely to accept new drug prescriptions than African–Americans, but there was reportedly no difference in acceptance of medical technologies such as implantable devices.
Differences in attitudes among ethnic groups towards medical therapies may be influenced by socioeconomic factors such as literacy, education, social status, greater upward social mobility and wealth. Exposure to larger information sources and a specialist healthcare practitioner may contribute to an improved understanding and greater acceptance of medical procedures. However, counselling for ICD therapy has not been shown to close the disparity in accepting an intervention among African–American patients.20 Broad lessons can be learnt from the efforts addressing disparities in ischaemic heart disease among ethnic minorities in the UK. For example, health policy sets out national standards to deliver services that are accessible and acceptable to all while meeting cultural and linguistic needs.27
Healthcare practitioners are effectively the gatekeepers to ICD therapy. Similarly, they may unknowingly be the barrier to appropriate ICD prescription.28 Schulman et al demonstrated that African–Americans were significantly less likely to be referred for coronary angiography than Caucasians (OR 0.60) in a scenario where physicians viewed a prerecorded and identically scripted interview of hypothetical patients with chest pain of different ethnicities.29 This may be due to the physicians’ perception of risk or due to an unintentional negative perception whereby demographic characteristics influence the physician–patient encounter.14 Physicians may not be aware of racial disparities in healthcare particularly in their own hospital setting and within their own practice.30 As such, this may explain in part why those of ethnic minority groups were also less likely to receive ICD counselling.20
Our results raise a number of key questions: is the difference observed between ethnicities due to patient agreement or physician bias, or is it simply a reflection of a less severe pathological insult resulting in less cardiac injury and/or ventricular arrhythmia owing to biological differences?
Our data are observational and correspond to a single centre providing care to the Leicestershire locality and provides comparison to a single ethnic minority. Hence, it may not be generalisable to the rest of the UK population or other ethnicities. The rates of ICD implantation in other minority ethnic groups were not examined due the low procedure numbers that would preclude reliable statistical comparison. As we used UK Census data, we were not able to correct for any other possible confounders other than age due to the limited heath information provided within this dataset.
Despite the higher prevalence of coronary artery disease in South Asians and equitable healthcare access, the rate of ICD implantation is lower in South Asians residing in the UK compared with Caucasians. Patient and physician factors may contribute to this disparity as seen in other ethnic minority groups outside of the UK. There is considerable unexplained geographical variation in ICD implantation with ethnicity potentially adding to the complexity of possible factors. Further research to determine the causes of this disparity may help provide solutions in order to close this disparity gap.
What is already known on this subject?
There are large geographical differences in implantable cardioverter defibrillator (ICD) implantation rates.
Previous studies have demonstrated differences in ICD implantation rates among African–Americans compared with Caucasians.
Little is known about differences in ICD implantation rates among other ethnic minorities and those ethnic minorities outside the USA.
What might this study add?
This is a single-centre, retrospective cohort study of 2650 ICDs implanted in either the Caucasian population or those of a South Asian ethnicity.
South Asian ICD recipients were younger, with less ischaemic heart disease, shorter QRS duration and less severe left ventricular systolic impairment.
Despite a higher prevalence of ischaemic heart disease in people of South Asian ethnicity, the rate of ICD implantation was lower when compared with the Caucasian population (age-standardised cumulative rate 1.79/1000 vs 2.38/1000 population, respectively).
The difference in ICD implantation rate was more pronounced for ICDs implanted for a secondary prevention indication.
How might this impact on clinical practice?
This study demonstrates the ethnic disparity in ICD provision despite an equitable healthcare service.
Greater efforts to address possible causes of ethnic disparities need to be examined and addressed.
This research was supported by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care East Midlands and the NIHR Leicester Biomedical Research Centre.
Contributors All authors read, approved and contributed significantly to the work. GAN and NJS conceived the study. AM was responsible for planning the study, reviewing the literature, conducting the data collection and writing the manuscript. ZV and BS contributed to the data collection and writing of the manuscript. MFY contributed to the statistical analysis and writing of the manuscript. CB carried out the statistical analysis. VP, MN, XL, JW, KK, NJS and GAN contributed to the writing of the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The study was approved by the institution’s review board and conducted as a local audit. According to the Health Research Authority (HRA) decision algorithm, the study was not classified as research requiring formal HRA or a research ethics committee review.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request.