3            Findings

3.1    Trends in revascularisation, 1991–1999

In 1999 a total of 22,551 CABG and 21,489 PTCA admissions were recorded in England. This represents a 66% and 205% increase respectively in the numbers of procedures performed in 1991. In the South West Region, 2,655 CABGs and 1,826 PTCAs were performed in 1999, amounting to 146% and 268% increases in the numbers of procedures carried out in 1991.

Figures 6 and 7 compare the directly standardised CABG and PTCA rates between England and the South West region during the period 1991 to 1999. The rates of the South West region when compared with those of England show similar increases over time, although the rates for these procedures, except for CABGs in males in the latter years, were generally lower in the South West than in England as a whole.

The decline in the revascularisation rates for males in 1997 from the previous year for both CABGs (12% decline) and PTCAs (17% decline) is not easily explained. Since only two centres perform revascularisation in the South West it is possible that operational difficulties (e.g. closure of operating theatres, shortage of ITU beds), failure to record procedures, or an increase in private sector revascularisations contributed to this decline.

Although revascularisation rates are much lower for people aged 75 and over, the proportionate increase in revascularisation in this age group has been much greater, with an approximately four-fold increase in both CABG and PTCA for both men and women.

3.2    Gender variation in revascularisation

Revascularisation rates are consistently higher for men than for women, reflecting lower rates of CHD among women. However, between 1991 and 1999 in England, rates of PTCA for women increased relatively more than rates for men, there being a 2.3 fold increase for women compared to a 1.8 fold increase for men. CABG rates show a similar picture but with smaller increases: a 78% increase for women and 58% increase for men. Trends in the South West show greater increases, reflecting the low baseline in 1991. Women's PTCA rates increased markedly by 350% compared with a 220% increase in men. CABG rates also show much greater increases than the national data: 160% and 124% increases for women and men respectively.

It would appear that the South West has increased use of PTCA more than the rest of England and has differentially increased rates for both CABG and PTCA more among women than men.

Although men were about twice as likely to be admitted to hospital with a diagnosis of acute myocardial infarction and unstable angina in 1999, they were between three and five times more likely than women to have a CABG or PTCA operation ( see Figure 8 ). If admissions due to acute myocardial infarction and unstable angina are taken to be reasonable proxies for need for revascularisation, and assuming that women and men do not differ markedly in their ability to benefit from revascularisation, a two-fold sex difference in CABG and PTCA procedures would be predicted. It seems unlikely that a three to five fold sex difference in revascularisation is due to differences in clinical need or better response to medical treatments. Inequity in use of revascularisation in women is accentuated by older age at presentation (Bowling, 1999; Bowling et al 2001; Dong et al, 1998).

Assuming that women's need is reflected by the female:male ratio of acute myocardial infarction admissions (i.e. need in women is lower than in men) – it is possible to estimate an expected revascularisation rate by applying the female:male acute myocardial infarction ratio to the male revascularisation rate. This expected revascularisation rate is then applied to the female population to obtain the number of procedures required to achieve equity between men and women. Women received 540 CABGs in 1999, but to achieve equity, an extra 587 would have to be done, representing a 22% increase of total CABG procedures. For PTCA, similar calculations yield an extra 208 procedures, amounting to an 11% increase in total NHS PTCA activity.

3.3    Age variation in revascularisation

Figure 9 shows the admission rates for unstable angina from 1995–9 by age group for England and for the South West region. Rates increase from middle age up to 75–79 years before declining.

Admission rates for acute myocardial infarction (figure not shown) show a similar increase with age although they do not decline but reach a plateau at age 85+ years. Both these indicators of need suggest that at least up to the age of 75 to 80 years need continues to rise. However, the mean age of male patients receiving revascularisation has only risen from 59 years in 1991 to 62 years in 1998. Comparable figures for women are 62 years in 1991 and 64 years in 1998. Figures for the South West region show a similar pattern.

As shown in Figures 10 and 11 , revascularisation procedures fall from age 65+ years in both men and women, suggesting that considerable unmet need at older ages exists. As described in section 1.4 , there is evidence to suggest that older people do benefit from revascularisation (TIME Investigators, 2001).

To achieve equitable provision of revascularisation for older people in relation to need it is assumed that the male revascularisation rate at age 60–64 should apply to older ages up to age 79 years in both men and women. Unstable angina admission rates are assumed to provide an index of need (and may be more appropriate than acute myocardial infarction admission rates in this context). Applying the same calculations as those described for gender inequity above, an extra 540 CABG and 450 PTCA procedures would be required in men and an additional 830 CABG and 2080 PTCA procedures would be required in women in the South West, representing 52% and 139% increases in CABG and PTCA procedures respectively.

3.4    Area deprivation in the South West and revascularisation

The association between area deprivation in the South West and revascularisation was non-linear and differed by sex ( see Table 2 ). For men, the lowest rates for both CABG and PTCA were seen for the middle deprivation group with the most and least deprived having higher CABG rates. For women, the most deprived areas had the highest rate of CABG but the least deprived had the highest rate of PTCA.

As specialist units are often based around inner city deprived areas this may explain increased rates in deprived areas. This effect, together with a gender difference, has been noted elsewhere (Ben-Shlomo and Chaturvedi, 1995) and was attenuated after adjustment for geographical proximity.

If provision is closely related to need, it would be expected that revascularisation to unstable angina ratios would be broadly similar. The ratios of revascularisation rates to unstable angina rates (aggregated from 1995–1999 to stabilise year to year variation) compared by ward deprivation quintile group showed that ratios tended to be higher in less deprived areas ( see Table 3 ). These findings suggest that treatment was not equitably provided on the basis of need, but that other factors played a part. A similar picture was seen when revascularisation ratios with acute myocardial infarction admissions were examined.

Assessing the increase in procedures required to achieve equity across deprivation groups, conducted in the same way as for gender and age inequity, shows that an extra 450 CABG and 497 PTCA procedures for men and an additional 1030 CABG and 596 PTCA procedures for women would be required in the South West.

In these analyses, we have not been able to include procedures performed in the private sector. These are likely to further bias findings relating to residents in the least deprived areas and increase differences in the mismatch between need and provision by area deprivation.

3.5 Urban-rural variation in revascularisation

The South West region has a major rural population which raises concern about access to revascularisation for rural residents. This question has been examined by classifying wards as rural or urban (see Methods section 2.3 and Figure 4 ) and comparing the rates of CABG and PTCA ( See Table 4) .

For men, the rates of CABG are substantially lower in rural than in urban areas whereas for women they are only marginally lower in rural compared to urban areas, suggesting that some inequity may exist. However, need for treatment may be lower in rural areas, as in general, rates of coronary heart disease are lower compared with urban areas.

Using admission rates for unstable angina as a proxy for need, there are no significant differences between ratios in urban and rural areas ( see Table 4) ), suggesting that the differences in treatment rates should not be interpreted as demonstrating inequity in relationship to need.

Further work examining the issue of rural deprivation and its influence on need and health care utilisation is planned as it is possible that aggregated analyses of rural-urban revascularisation may hide localised pockets of need.

Distance from a regional revascularisation service may be relevant in understanding access to treatment. Table 5 shows revascularisation ratios for residents of health authorities, listed in order of overall unstable angina rate from lowest to highest, comparing health authority rates to South West region rates. A ratio of 100 implies that the health authority rate is the same as that for the South West region.

Perhaps surprisingly, Avon which hosts the major revascularisation service, provides close to regional averages of revascularisation to its population, although PTCA rates for men are somewhat lower. Somerset is markedly lower in provision of PTCA for both men and women and this is not compensated for by CABG provision which is average for the region. Dorset has a particularly marked level of PTCA procedures at about 50% higher than the regional average. The Plymouth service, located in South and West Devon, appears to be providing an above average level of PTCA to men but about average levels of other revascularisation. No allowance can be made for private sector procedures which may distort these patterns. However, it does not appear that strong proximity effects occur in the South West region.

These rates of revascularisation should be compared with disease burden. Table 5 also shows the admission rates for unstable angina. The health district with the highest apparent need, Cornwall and the Isles of Scilly, has a level of revascularisation very close to the regional average. Dorset, with a level of need close to the bottom of the ranking, has the highest levels of PTCA. These apparent mismatches between need and provision merit further investigation.

3.6    The provision of revascularisation services in the South West

There are two regional centres that provide CABG – Bristol and Plymouth – the latter starting work only in the last 4 years. A third centre is under discussion. PTCA is (or has been) also carried out in Exeter and Taunton. In 1999, a total of 2,655 CABG and 1,826 PTCA procedures were performed on residents of the South West region. However, 30% (787) of CABG and 32% (579) of PTCA procedures were performed outside the South West region (at Southampton, Oxford, Kings, Royal Brompton and Harefield).

In 1999, consultant cardiology provision in the South West was 16% below the national average and was about half that in the London region. Cardio-thoracic surgery provision was also lower – 35% below national levels and two-thirds lower than that of London region. Consultant anaesthetist provision was better with similar rates to national averages ( see Table 6 ).

Data are available on available acute beds, theatres and ITU beds for 1999 or 2000. These show that the South West has an above average provision of acute beds and theatres but has one of the lowest rates of adult intensive care beds in England, at about 78% of the national average, and half of that in London ( see Table 7 ). While these summary statistics demonstrate the differences in overall provision, local circumstances will determine the relative use of theatre sessions for competing priorities in thoracic and oesophageal surgery which may distort the actual availability of this resource.

The Public Health Observatory is part of the South West Observatory, a wider Regional intelligence function, currently supported by the South West Regional Assembly, the Department of Health, the Department for Education and Skills. Government Office South West, the South West of England Regional Development Agency and the Environment Agency.