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Geographic, Ethnic and Socioeconomic Factors Influencing Access to Implantable Cardioverter Defibrillators (ICDs) in New Zealand
ORIGINAL ARTICLE
Original Article
Geographic, Ethnic and Socioeconomic Factors Influencing Access to Implantable Cardioverter Defibrillators (ICDs) in New Zealand David Wilson, MRCP a , Scott A. Harding, FRACP a , Iain Melton, FRACP b , Nigel A. Lever, FRACP c , Martin K. Stiles, FRACP d , Dean Boddington, FRACP e , Spencer Heald, FRACP d and Peter D. Larsen, PhD a,∗ a
Wellington Cardiovascular Research Group, Wellington Hospital, New Zealand b Cardiology Department, Christchurch Hospital, New Zealand c Green Lane Cardiovascular Service, Auckland City Hospital, New Zealand d Cardiology Department, Waikato Hospital, New Zealand e Cardiology Department, Tauranga Hospital, New Zealand
Background: We examined equity of access to implanted cardioverter defibrillators (ICDs) in New Zealand in 2010 by district health board (DHB), ethnicity and socioeconomic status. Methods: All new ICD recipients in 2010 were examined according to home district health board, ethnicity according to the national health database, and socioeconomic status using the NZDep index. Results: During 2010, 352 new ICDs were implanted nationwide, giving an overall implantation rate of 80.6/million. However, implant rates varied significantly across the 20 DHBs with the highest implant rate observed in Tairawhiti at 192.3/million, and the lowest at 22/million in the Nelson region. There was also significant variation in implant rate by ethnicity, with Maori ethnicity at an implant rate of 114/million, European patients at 83/million, Pacific Island patients at 47/million and Asian patients an implant rate of 32/million. There was no significant difference in number of implants by socioeconomic decile. Conclusions: The variance in implantation rate by district health board and by ethnicity suggests that access to ICD therapy is not equitable in New Zealand. Investigation into causes of inequity of access is required. (Heart, Lung and Circulation 2012;21:576–581) © 2012 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier Inc. All rights reserved. Keywords. Implantable cardioverter-defibrillators; Health equity; Cardiovascular disease
Background
I
mplantation rates of cardioverter defibrillators (ICDs) in New Zealand have increased over the last 10 years from 23/million in 2001 [1] to 77/million in 2009 [2]. Most of the patients receiving these devices have either survived a previous potentially lethal ventricular tachyarrythmia (secondary prevention) or have been classified at high risk of sudden cardiac death from arrhythmias most commonly due to left ventricular dysfunction (primary prevention). Despite this increase, we have previously argued that the rate of implantation of ICDs in NZ is low [3,4]. The rate of implantation is lower than other countries with Received 28 February 2012; received in revised form 5 April 2012; accepted 22 April 2012; available online 16 May 2012 ∗
Corresponding author at: University of Otago, Wellington, PO Box 7343, Wellington South, New Zealand. Tel.: +64 4 918 5103; fax: +64 4 389 5318. E-mail address: [email protected] (P.D. Larsen).
similar or lower burdens of cardiovascular disease, such as Australia where the 2009 implant rate was 160/million [2]. In addition, we have shown that a significant proportion of patients suffering community cardiac arrest have preexisting indications for an ICD but have not been referred for this life-saving therapy [4]. In exploring barriers to referral to ICD, we have reported regional variation in access to investigations, and variations in attitudes to ICDs as potential contributors to the low implant rate [5]. One of the Ministry of Health’s objectives for the treatment of cardiovascular disease in New Zealand is to reduce geographical, ethnic and socioeconomic inequality in access to therapy [6]. How geographic, ethnic and socioeconomic factors contribute to the low overall ICD implant rate in NZ has not been previously examined. In order to investigate equity of access to ICDs in New Zealand we examined all 2010 new ICD implants by district health board (DHB), ethnicity and socioeconomic status.
© 2012 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier Inc. All rights reserved.
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Table 1. Implant Rates by DHB. Rank 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
DHB Tairawhiti West Coast South Canterbury Bay of Plenty Lakes Hutt Taranaki Hawke’s Bay Waitemata Waikato Northland Auckland Wairarapa Canterbury Manukau Capital & Coast Midcentral Southern Wanganui Nelson Marlborough
Implants
Population
Implant Rate (95% CI)
% Primary
9 6 9 32 15 18 12 17 48 32 13 34 3 35 31 15 8 10 2 3
46,805 33,040 56,075 210,980 103,290 144,570 109,530 155,270 537,550 364,790 157,800 451,100 40,210 507,010 490,350 292,260 168,160 302,530 63,670 138,540
192 (67–318) 182 (36–327) 161 (57–271) 152 (99–204) 145 (72–220) 125 (67–182) 110 (48–172) 110 (57–162) 89 (64–115) 88 (57–118) 82 (38–127) 75 (46–159) 75 (46–96) 69 (46–92) 63 (41–85) 51 (25–77) 48 (15–81) 33 (13–55) 31 (12–75) 22 (3–46)
56 17 33 56 57 61 50 47 42 45 46 41 50 40 33 66 62 40 50 100
The table gives total number of implants, total population, implant rates/million population and percentage implants that were for primary prevention. Rank order is based upon implant rate.
Methods
Statistics
Retrospective implant data for all new ICDs (including CRT-D devices) was requested from all the ICD implant centres in New Zealand from 1 January 2010 to 31 December 2010. The following fields per case were collected: National Health Index (NHI) number, date of birth, gender, ethnicity and indication (primary or secondary). Implant indication was defined as secondary prevention if the patient has survived a cardiac arrest or experienced ventricular tachyarrhythmia needing external intervention or lasting for more than 30 s. Primary prevention was defined as the absence of cardiac arrest or ventricular tachyarrhythmia requiring intervention. We did not include patients who were receiving replacement ICDs or undergoing a procedure for revision of an existing ICD system. Each case was assigned to a District Health Board (DHB) according to home address on the National Health Database. ICD device implantation rates/million for regions and DHBs were calculated using projected 2010 DHB populations based on the national census in 2006 (New Zealand All DHBs Estimated Resident Population 2006–2026. 2010 Stats NZ population projections). Ethnicity was taken from the National Health Index database. NZDep2006 is an updated version of the NZDep91, NZDep96, and NZDep2001 indexes of socioeconomic deprivation [7]. NZDep2006 combines nine variables from the 2006 census which reflect eight dimensions of deprivation. Each patient was linked to a mesh block on the basis of their home address using Statistics New Zealand interactive boundary map (http://apps.nowwhere.com.au/StatsNZ/Maps) and from the meshblock was linked to a decile ranking from the NZDep2006 atlas.
We compared the observed implant rate and proportion of devices for primary prevention between geographic locations, ethnic groups and socioeconomic deciles to an expected uniform distribution using Chi-squared test. We calculated 95% confidence intervals for implant rate by DHB and by ethnicity assuming a Poisson distribution.
Results Overall Implant Rate During 2010 352 new ICD systems were implanted, giving a national implantation rate of 80.6/million. The mean patient age was 57 years (range 10–83 years) and 78% of patients were male. In 46% of cases the ICD indication was for primary prevention.
Regional Variability Implantation rates across DHBs are shown in Table 1 and Fig. 1. There was significant variation across DHBs, with the highest implant rate observed in Tairawhiti at 192.3/million, and the lowest at 21.7/million in Nelson (p > 0.001, Chi-squared test). The median DHB implant rate was 85/million. A single implant has an effect on the calculated implant rate that is inversely proportional to the size of the DHB. For this reason it is not surprising that the variance in implant rates is greatest in DHBs with smaller populations (Fig. 2), and this is also reflected in wider 95% confidence limits in the implant rates (Table 1). Despite this, there is still large variation in the implant rate in DHBs with a population over 200,000 people. There was no statistical correlation between DHB size and implant rate (rho-0.40, p = 0.08, Spearman rank correlation).
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Figure 1. Implant rates/million population are given for each of the 20 district health boards in New Zealand.
The proportion of ICDs implanted for primary prevention also differed considerably, ranging from 100% in Nelson to 17% in West Coast, with a median of 50% observed in 4 DHBs (p ≥ 0.001, Chi-squared test).
Ethnicity Of the devices implanted, 70% were implanted in patients with European ethnicity, at an implant rate of 83/million (95% confidence interval 72–93/million), 22% in patients with Maori ethnicity at an implant rate of 114/million (88–140/million), 4% in Pacific Island patients at an implant
rate of 47/million (21–71/million) and 4% in Asian patients at an implant rate of 32/million (16–48/million). This difference in implant rate was statistically significant (p < 0.0001, Chi squared test). The proportion of devices that were for primary prevention was 46% for European, 45% for Maori, 50% for Pacific Islanders, and 66% for Asian patients (not statistically significant).
Socioeconomic Status of ICD Recipients Socioeconomic status was calculated for 345 of the 352 new implants. The NZDep system was unable to rate status
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Figure 2. Plot of implant rate/million population against DHB population.
Figure 3. Number of implants by socioeconomic decile. Decile 1 represents the highest socioeconomic status and Decile 10 the lowest.
Discussion
for seven patients. There was no significant difference in number of implants by decile (see Fig. 3). The proportion of devices implanted for primary prevention did not differ significantly across deciles.
New ICD implants in 2010 in New Zealand show marked differences by geography and ethnicity, but not by socioeconomic status. The proportion of devices implanted for primary prevention also differs geographically, but not by ethnicity or socioeconomic status. Across the five centres implanting ICDs in New Zealand there are differences in both implant rate and the number of specialists implanting devices. The national implantation rate for ICDs in New Zealand in 2010 was 80.6/million, with 46% for primary prevention
Implant Centres There are five centres in New Zealand implanting ICDs. Four of these are tertiary referral centres while the fifth (Tauranga) is a secondary centre. The number of operators varies between one and three, and the implants/operator/year between an average of 30–49 (Table 2). Table 2. Implant rates by implant centres. Implanting Centre
Population Served
Operators
Implants/operator
Implants/million
Operators/million 1.7 3.2 4.7 1.4 1.9
Auckland Waikato Tauranga Wellington Christchurch
1,792,070 624,415 210,980 708,870 1,037,195
3 2 1 1 2
49 35 30 44 30
76 112 142 62 58
Total
4,373,530
9
–
–
–
The table gives total population, number of operators implanting devices, implant rates/operator, implant rates/million population and operators/million population.
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reasons. While there is no current data estimating the number of New Zealand patients who meet standard indications for ICDs, we have previously demonstrated that an unmet need exists by showing that patients presenting with sudden cardiac death frequently have an underlying indication for an ICD [4]. The New Zealand implant rate is also significantly lower than the implant rate in Australia, which in 2009 was 160/million [2], and the average implant rate in Europe, which was 159/million in 2007 [8]. UK estimates of the number of patients meeting ICD indications have ranged from 450/million [9] to upwards of 750/million [8]. On this basis, we continue to argue that there is a current under-usage of this life saving technology in New Zealand. The geographical variation in implantation rates observed in this study is statistically significant, with rates between 22/million and 193/million. However, it is important to note that with implantation being an infrequent event and given the small population in each DHB, the 95% confidence intervals (if a Poisson distribution is assumed) are wide. Further to this, the implant rates have not been adjusted for any variation in age of the population within each DHB, or for underlying disease state both of which would be important in determining the extent to which need for ICDs is being met equally throughout the country. In order to qualify for ICD implantation, patients must first be identified as at risk, referred to the appropriate service for consideration of device implantation and finally, if the patient meets the accepted criteria be listed for and subsequently undergo device implantation. Deficiencies in any of these steps is likely to result in a lower than ideal device implantation rate. We have previously demonstrated that a significant proportion of the cardiologists and physicians caring with patients likely to have ICD indications were not aware of current ICD guidelines, or the effectiveness of ICD therapy [5]. In addition, limited access to investigations such as echocardiography may contribute to a difficulty in identifying patients with indications [5,10]. While access to expertise may also be a factor limiting the extent to which patients with indications are actively looked for, the implant rates in tertiary referral centres own DHBs patients remained relatively low (range 51/million to 88/million), suggesting that access to expertise cannot be the only factor limiting identification of patients for implantation. In a country with a population of just over 4.3 million people, there are currently only five centres implanting ICDs, and nine clinicians doing this work. This gives a rate of 1.1 implant centres/million population and 2 implanters/million. While data on the number of implanters/million in other countries is not accessible, Italy has 4.4 implant centres/million and Germany 6.8/million [8]. The lack of capacity to implant devices given the limited number of centres and clinicians currently involved is likely to be a significant limiting factor in current implantation. Currently in New Zealand, ICDs are funded by individual District Health Boards (DHBs). There is no defined National budget for ICD services and the true costs
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involved with implantation and follow up are yet to be well established for the New Zealand environment. Clarity regarding funding for ICDs and for expanded capacity to implant and follow-up ICD patients would be required before a significant change in implant rate could be achieved. Maori continue to have significantly higher rates of ischaemic heart disease and heart failure than non-Maori [11,12], and so it is probable that a greater need for ICDs exists in Maori patients. Consistent with this, the implant rate in Maori patients was greater than in European patients. In contrast, Pacific peoples had a substantially lower ICD implant rate compared to those of European descent despite a higher prevalence of cardiovascular disease [13]. Further work is required to determine the need for ICDs in different ethnic groups and to explore potential barriers to access. Our analysis of access to ICDs by socioeconomic status shows that there was not a significant link between socioeconomic status and implant rate. Given that lower socioeconomic status is associated with a higher ageadjusted rate of cardiovascular disease [13], this may not represent true equity of access by socioeconomic status. We observed that the proportion of ICDs implanted for primary prevention was just under 50%. While this has increased from a proportion of 25% in the 2000–2005 period [14], the greatest proportion of unmet need is in the primary prevention population [4,8]. In the United States 82% of devices implanted are for primary prevention [8], although questions about the suitability of all of these implants have been raised [15]. While the data is retrospective, it is recent and has been obtained from implanting centres and we believe it to be accurate. The data collected only represents one year worth of data, and may not reflect longer term trends in implantation. Socioeconomic status is based upon the 2005 census data, and ethnicity is derived from the National Health Admissions database and both of these sources of data may contain some inaccuracies. Despite these limitations, this is the first study to examine potential geographic, ethnic and socioeconomic inequalities in access to ICD implantation in New Zealand.
Conclusion We have identified significant regional and ethnic variation in implantation rates of ICD devices in New Zealand. Improving screening, investigation and referral processes will lead to an increase in total implant rates, predominantly for primary prevention reasons. Addressing these pre-implantation factors may reduce the current inequity to some degree but greater understanding of the reasons for these differences is also required. Establishing a prospective national database of these devices and continually monitoring access as part of a quality improvement process is required in order to achieve equity of access to ICDs in New Zealand.
Acknowledgements Thanks to the cardiac physiologists and implanting physicians at Auckland, Waikato, Tauranga, Wellington and Christchurch hospitals for assistance in identification of all new implants in 2010. Thanks to Bijia Shi for assistance with data entry.
References [1] Mond HG, Whitlock RML. The Australian and New Zealand cardiac pacing and implantable cardioverter-defibrillator survey: calendar year 2001. Heart Lung Circ 2004;13(June (2)):145–9. [2] Mond HG, Whitlock RML. The Australian and New Zealand cardiac pacing and implantable cardioverter-defibrillator survey: calendar year 2009. Heart Lung Circ 2011;20(February (2)):99–104. [3] Larsen PD, De Silva P, Harding SA, Woodcock E, Lever NA. Use of implantable cardioverter defibrillators in the New Zealand context from 2000 to 2007. N Z Med J 2010;123(1309):76–85. [4] Burgess SN, Harding SA, Melton IC, Lever NA, Swain AH, Shi B, et al. An unmet need for implantable cardioverterdefibrillators in New Zealand. Europace 2011;13(September (9)):1299–303. [5] McHale B, Harding SA, Lever NA, Larsen PD. A national survey of clinician’s knowledge of and attitudes towards implantable cardioverter defibrillators. Europace 2009;11(October (10)):1313–6. [6] Ministry of Health. Diabetes and cardiovascular disease quality improvement plan. Wellington: Ministry of Health; 2008 [February].
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[7] Salmond C, Crampton P. NZDep2006 index of deprivation. Wellington: Department of Public Health; 2007. [8] Camm AJ, Nisam S. European utilization of the implantable defibrillator: has 10 years changed the ‘enigma’? Europace 2010;12(August (8)):1063–9. [9] Plummer CJ, John Irving R, McComb JM. The incidence of implantable cardioverter defibrillator indications in patients admitted to all coronary care units in a single district. Europace 2005;7(May (3)):266–72. [10] Bridgman PG, Ashrafi AN, Mann S, Whalley GA, SCANZ collaborators. Survey of clinical echocardiography in New Zealand (SCANZ). N Z Med J 2008;121(February (1269)):34–44. [11] Riddell T. Heart failure hospitalisations and deaths in New Zealand: patterns by deprivation and ethnicity. N Z Med J 2005;118(January (1208)):U1254. [12] Tobias M, Yeh L-C, Wright C, Riddell T, Chan WC, Jack¯ son R, et al. The burden of coronary heart disease in Maori: population-based estimates for 2000–02. Aust N Z J Public Health 2009;33(August (4)):384–7. [13] Chan WC, Wright C, Riddell T, Wells S, Kerr AJ, Gala G, et al. Ethnic and socioeconomic disparities in the prevalence of cardiovascular disease in New Zealand. N Z Med J 2008;121(November (1285)):11–20. [14] Wilson D, Shi B, Harding S, Lever N, Larsen P. Implantable cardioverter defibrillators (ICDs): a longterm view. Intern Med J 2011 [Epub ahead of print; December 29]. [15] Al-Khatib SM, Hellkamp A, Curtis J, Mark D, Peterson E, Sanders GD, et al. Non-evidence-based ICD implantations in the United States. JAMA 2011;305(January (1)): 43–9.
ORIGINAL ARTICLE
Heart, Lung and Circulation 2012;21:576–581
Original Article
Geographic, Ethnic and Socioeconomic Factors Influencing Access to Implantable Cardioverter Defibrillators (ICDs) in New Zealand David Wilson, MRCP a , Scott A. Harding, FRACP a , Iain Melton, FRACP b , Nigel A. Lever, FRACP c , Martin K. Stiles, FRACP d , Dean Boddington, FRACP e , Spencer Heald, FRACP d and Peter D. Larsen, PhD a,∗ a
Wellington Cardiovascular Research Group, Wellington Hospital, New Zealand b Cardiology Department, Christchurch Hospital, New Zealand c Green Lane Cardiovascular Service, Auckland City Hospital, New Zealand d Cardiology Department, Waikato Hospital, New Zealand e Cardiology Department, Tauranga Hospital, New Zealand
Background: We examined equity of access to implanted cardioverter defibrillators (ICDs) in New Zealand in 2010 by district health board (DHB), ethnicity and socioeconomic status. Methods: All new ICD recipients in 2010 were examined according to home district health board, ethnicity according to the national health database, and socioeconomic status using the NZDep index. Results: During 2010, 352 new ICDs were implanted nationwide, giving an overall implantation rate of 80.6/million. However, implant rates varied significantly across the 20 DHBs with the highest implant rate observed in Tairawhiti at 192.3/million, and the lowest at 22/million in the Nelson region. There was also significant variation in implant rate by ethnicity, with Maori ethnicity at an implant rate of 114/million, European patients at 83/million, Pacific Island patients at 47/million and Asian patients an implant rate of 32/million. There was no significant difference in number of implants by socioeconomic decile. Conclusions: The variance in implantation rate by district health board and by ethnicity suggests that access to ICD therapy is not equitable in New Zealand. Investigation into causes of inequity of access is required. (Heart, Lung and Circulation 2012;21:576–581) © 2012 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier Inc. All rights reserved. Keywords. Implantable cardioverter-defibrillators; Health equity; Cardiovascular disease
Background
I
mplantation rates of cardioverter defibrillators (ICDs) in New Zealand have increased over the last 10 years from 23/million in 2001 [1] to 77/million in 2009 [2]. Most of the patients receiving these devices have either survived a previous potentially lethal ventricular tachyarrythmia (secondary prevention) or have been classified at high risk of sudden cardiac death from arrhythmias most commonly due to left ventricular dysfunction (primary prevention). Despite this increase, we have previously argued that the rate of implantation of ICDs in NZ is low [3,4]. The rate of implantation is lower than other countries with Received 28 February 2012; received in revised form 5 April 2012; accepted 22 April 2012; available online 16 May 2012 ∗
Corresponding author at: University of Otago, Wellington, PO Box 7343, Wellington South, New Zealand. Tel.: +64 4 918 5103; fax: +64 4 389 5318. E-mail address: [email protected] (P.D. Larsen).
similar or lower burdens of cardiovascular disease, such as Australia where the 2009 implant rate was 160/million [2]. In addition, we have shown that a significant proportion of patients suffering community cardiac arrest have preexisting indications for an ICD but have not been referred for this life-saving therapy [4]. In exploring barriers to referral to ICD, we have reported regional variation in access to investigations, and variations in attitudes to ICDs as potential contributors to the low implant rate [5]. One of the Ministry of Health’s objectives for the treatment of cardiovascular disease in New Zealand is to reduce geographical, ethnic and socioeconomic inequality in access to therapy [6]. How geographic, ethnic and socioeconomic factors contribute to the low overall ICD implant rate in NZ has not been previously examined. In order to investigate equity of access to ICDs in New Zealand we examined all 2010 new ICD implants by district health board (DHB), ethnicity and socioeconomic status.
© 2012 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier Inc. All rights reserved.
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Table 1. Implant Rates by DHB. Rank 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
DHB Tairawhiti West Coast South Canterbury Bay of Plenty Lakes Hutt Taranaki Hawke’s Bay Waitemata Waikato Northland Auckland Wairarapa Canterbury Manukau Capital & Coast Midcentral Southern Wanganui Nelson Marlborough
Implants
Population
Implant Rate (95% CI)
% Primary
9 6 9 32 15 18 12 17 48 32 13 34 3 35 31 15 8 10 2 3
46,805 33,040 56,075 210,980 103,290 144,570 109,530 155,270 537,550 364,790 157,800 451,100 40,210 507,010 490,350 292,260 168,160 302,530 63,670 138,540
192 (67–318) 182 (36–327) 161 (57–271) 152 (99–204) 145 (72–220) 125 (67–182) 110 (48–172) 110 (57–162) 89 (64–115) 88 (57–118) 82 (38–127) 75 (46–159) 75 (46–96) 69 (46–92) 63 (41–85) 51 (25–77) 48 (15–81) 33 (13–55) 31 (12–75) 22 (3–46)
56 17 33 56 57 61 50 47 42 45 46 41 50 40 33 66 62 40 50 100
The table gives total number of implants, total population, implant rates/million population and percentage implants that were for primary prevention. Rank order is based upon implant rate.
Methods
Statistics
Retrospective implant data for all new ICDs (including CRT-D devices) was requested from all the ICD implant centres in New Zealand from 1 January 2010 to 31 December 2010. The following fields per case were collected: National Health Index (NHI) number, date of birth, gender, ethnicity and indication (primary or secondary). Implant indication was defined as secondary prevention if the patient has survived a cardiac arrest or experienced ventricular tachyarrhythmia needing external intervention or lasting for more than 30 s. Primary prevention was defined as the absence of cardiac arrest or ventricular tachyarrhythmia requiring intervention. We did not include patients who were receiving replacement ICDs or undergoing a procedure for revision of an existing ICD system. Each case was assigned to a District Health Board (DHB) according to home address on the National Health Database. ICD device implantation rates/million for regions and DHBs were calculated using projected 2010 DHB populations based on the national census in 2006 (New Zealand All DHBs Estimated Resident Population 2006–2026. 2010 Stats NZ population projections). Ethnicity was taken from the National Health Index database. NZDep2006 is an updated version of the NZDep91, NZDep96, and NZDep2001 indexes of socioeconomic deprivation [7]. NZDep2006 combines nine variables from the 2006 census which reflect eight dimensions of deprivation. Each patient was linked to a mesh block on the basis of their home address using Statistics New Zealand interactive boundary map (http://apps.nowwhere.com.au/StatsNZ/Maps) and from the meshblock was linked to a decile ranking from the NZDep2006 atlas.
We compared the observed implant rate and proportion of devices for primary prevention between geographic locations, ethnic groups and socioeconomic deciles to an expected uniform distribution using Chi-squared test. We calculated 95% confidence intervals for implant rate by DHB and by ethnicity assuming a Poisson distribution.
Results Overall Implant Rate During 2010 352 new ICD systems were implanted, giving a national implantation rate of 80.6/million. The mean patient age was 57 years (range 10–83 years) and 78% of patients were male. In 46% of cases the ICD indication was for primary prevention.
Regional Variability Implantation rates across DHBs are shown in Table 1 and Fig. 1. There was significant variation across DHBs, with the highest implant rate observed in Tairawhiti at 192.3/million, and the lowest at 21.7/million in Nelson (p > 0.001, Chi-squared test). The median DHB implant rate was 85/million. A single implant has an effect on the calculated implant rate that is inversely proportional to the size of the DHB. For this reason it is not surprising that the variance in implant rates is greatest in DHBs with smaller populations (Fig. 2), and this is also reflected in wider 95% confidence limits in the implant rates (Table 1). Despite this, there is still large variation in the implant rate in DHBs with a population over 200,000 people. There was no statistical correlation between DHB size and implant rate (rho-0.40, p = 0.08, Spearman rank correlation).
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Figure 1. Implant rates/million population are given for each of the 20 district health boards in New Zealand.
The proportion of ICDs implanted for primary prevention also differed considerably, ranging from 100% in Nelson to 17% in West Coast, with a median of 50% observed in 4 DHBs (p ≥ 0.001, Chi-squared test).
Ethnicity Of the devices implanted, 70% were implanted in patients with European ethnicity, at an implant rate of 83/million (95% confidence interval 72–93/million), 22% in patients with Maori ethnicity at an implant rate of 114/million (88–140/million), 4% in Pacific Island patients at an implant
rate of 47/million (21–71/million) and 4% in Asian patients at an implant rate of 32/million (16–48/million). This difference in implant rate was statistically significant (p < 0.0001, Chi squared test). The proportion of devices that were for primary prevention was 46% for European, 45% for Maori, 50% for Pacific Islanders, and 66% for Asian patients (not statistically significant).
Socioeconomic Status of ICD Recipients Socioeconomic status was calculated for 345 of the 352 new implants. The NZDep system was unable to rate status
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Figure 2. Plot of implant rate/million population against DHB population.
Figure 3. Number of implants by socioeconomic decile. Decile 1 represents the highest socioeconomic status and Decile 10 the lowest.
Discussion
for seven patients. There was no significant difference in number of implants by decile (see Fig. 3). The proportion of devices implanted for primary prevention did not differ significantly across deciles.
New ICD implants in 2010 in New Zealand show marked differences by geography and ethnicity, but not by socioeconomic status. The proportion of devices implanted for primary prevention also differs geographically, but not by ethnicity or socioeconomic status. Across the five centres implanting ICDs in New Zealand there are differences in both implant rate and the number of specialists implanting devices. The national implantation rate for ICDs in New Zealand in 2010 was 80.6/million, with 46% for primary prevention
Implant Centres There are five centres in New Zealand implanting ICDs. Four of these are tertiary referral centres while the fifth (Tauranga) is a secondary centre. The number of operators varies between one and three, and the implants/operator/year between an average of 30–49 (Table 2). Table 2. Implant rates by implant centres. Implanting Centre
Population Served
Operators
Implants/operator
Implants/million
Operators/million 1.7 3.2 4.7 1.4 1.9
Auckland Waikato Tauranga Wellington Christchurch
1,792,070 624,415 210,980 708,870 1,037,195
3 2 1 1 2
49 35 30 44 30
76 112 142 62 58
Total
4,373,530
9
–
–
–
The table gives total population, number of operators implanting devices, implant rates/operator, implant rates/million population and operators/million population.
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reasons. While there is no current data estimating the number of New Zealand patients who meet standard indications for ICDs, we have previously demonstrated that an unmet need exists by showing that patients presenting with sudden cardiac death frequently have an underlying indication for an ICD [4]. The New Zealand implant rate is also significantly lower than the implant rate in Australia, which in 2009 was 160/million [2], and the average implant rate in Europe, which was 159/million in 2007 [8]. UK estimates of the number of patients meeting ICD indications have ranged from 450/million [9] to upwards of 750/million [8]. On this basis, we continue to argue that there is a current under-usage of this life saving technology in New Zealand. The geographical variation in implantation rates observed in this study is statistically significant, with rates between 22/million and 193/million. However, it is important to note that with implantation being an infrequent event and given the small population in each DHB, the 95% confidence intervals (if a Poisson distribution is assumed) are wide. Further to this, the implant rates have not been adjusted for any variation in age of the population within each DHB, or for underlying disease state both of which would be important in determining the extent to which need for ICDs is being met equally throughout the country. In order to qualify for ICD implantation, patients must first be identified as at risk, referred to the appropriate service for consideration of device implantation and finally, if the patient meets the accepted criteria be listed for and subsequently undergo device implantation. Deficiencies in any of these steps is likely to result in a lower than ideal device implantation rate. We have previously demonstrated that a significant proportion of the cardiologists and physicians caring with patients likely to have ICD indications were not aware of current ICD guidelines, or the effectiveness of ICD therapy [5]. In addition, limited access to investigations such as echocardiography may contribute to a difficulty in identifying patients with indications [5,10]. While access to expertise may also be a factor limiting the extent to which patients with indications are actively looked for, the implant rates in tertiary referral centres own DHBs patients remained relatively low (range 51/million to 88/million), suggesting that access to expertise cannot be the only factor limiting identification of patients for implantation. In a country with a population of just over 4.3 million people, there are currently only five centres implanting ICDs, and nine clinicians doing this work. This gives a rate of 1.1 implant centres/million population and 2 implanters/million. While data on the number of implanters/million in other countries is not accessible, Italy has 4.4 implant centres/million and Germany 6.8/million [8]. The lack of capacity to implant devices given the limited number of centres and clinicians currently involved is likely to be a significant limiting factor in current implantation. Currently in New Zealand, ICDs are funded by individual District Health Boards (DHBs). There is no defined National budget for ICD services and the true costs
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involved with implantation and follow up are yet to be well established for the New Zealand environment. Clarity regarding funding for ICDs and for expanded capacity to implant and follow-up ICD patients would be required before a significant change in implant rate could be achieved. Maori continue to have significantly higher rates of ischaemic heart disease and heart failure than non-Maori [11,12], and so it is probable that a greater need for ICDs exists in Maori patients. Consistent with this, the implant rate in Maori patients was greater than in European patients. In contrast, Pacific peoples had a substantially lower ICD implant rate compared to those of European descent despite a higher prevalence of cardiovascular disease [13]. Further work is required to determine the need for ICDs in different ethnic groups and to explore potential barriers to access. Our analysis of access to ICDs by socioeconomic status shows that there was not a significant link between socioeconomic status and implant rate. Given that lower socioeconomic status is associated with a higher ageadjusted rate of cardiovascular disease [13], this may not represent true equity of access by socioeconomic status. We observed that the proportion of ICDs implanted for primary prevention was just under 50%. While this has increased from a proportion of 25% in the 2000–2005 period [14], the greatest proportion of unmet need is in the primary prevention population [4,8]. In the United States 82% of devices implanted are for primary prevention [8], although questions about the suitability of all of these implants have been raised [15]. While the data is retrospective, it is recent and has been obtained from implanting centres and we believe it to be accurate. The data collected only represents one year worth of data, and may not reflect longer term trends in implantation. Socioeconomic status is based upon the 2005 census data, and ethnicity is derived from the National Health Admissions database and both of these sources of data may contain some inaccuracies. Despite these limitations, this is the first study to examine potential geographic, ethnic and socioeconomic inequalities in access to ICD implantation in New Zealand.
Conclusion We have identified significant regional and ethnic variation in implantation rates of ICD devices in New Zealand. Improving screening, investigation and referral processes will lead to an increase in total implant rates, predominantly for primary prevention reasons. Addressing these pre-implantation factors may reduce the current inequity to some degree but greater understanding of the reasons for these differences is also required. Establishing a prospective national database of these devices and continually monitoring access as part of a quality improvement process is required in order to achieve equity of access to ICDs in New Zealand.
Acknowledgements Thanks to the cardiac physiologists and implanting physicians at Auckland, Waikato, Tauranga, Wellington and Christchurch hospitals for assistance in identification of all new implants in 2010. Thanks to Bijia Shi for assistance with data entry.
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ORIGINAL ARTICLE
Heart, Lung and Circulation 2012;21:576–581