While the death rate from cardiovascular disease (CVD) continues to decline in Australia, CVD remains the main cause of death (about a third of all deaths) in the community.1,2 In the context of Australia’s ageing population, the total CVD burden is expected to increase in the coming decades.2 With major improvements in acute care, including the implantation of stents and cardiac surgery, many of those who suffer an acute cardiovascular event will survive. Counterbalancing this is the fact that sudden death still accounts for about a quarter of all CVD presentations.2,3 It is estimated that 1.4 million Australians are CVD survivors (about 7% of the population) and the direct health care costs of managing these conditions accounts for 11% of total health expenditure in Australia.2,4 It is well known that those who have overt CVD are at the highest risk of future events.5 This group is a key target for secondary prevention strategies aimed at reducing the risk of future events.6 It has also been well documented through many large-scale clinical trials that therapeutic management of CVD risk factors in this population yields convincing benefits in terms of reduction in CVD risk.7-9 In primary prevention (for people who have not experienced a cardiovascular event), the clustering of three or more CVD risk factors has also been shown to increase the risk of future events. Thus, primary prevention strategies focus on identifying and controlling CVD risk factors in this group.10
One of the major health challenges facing contemporary Australian society is controlling the rapid rise in obesity and diabetes in the population. The impact of obesity on CVD risk factors like high blood pressure, dyslipidaemia and diabetes has been well documented.11 However, the impact of obesity on major cardiovascular outcomes, in secondary prevention, such as cardiovascular death, non-fatal stroke, non-fatal myocardial infarction, and vascular interventions is more controversial.12
While a number of Australian studies have shown that CVD risk factor management in those with existing disease and those at highest risk is suboptimal, there are no data available in Australia to inform on the outcomes for patients being managed for both primary and secondary CVD prevention in general practice.13,14 In addition, there is little information to determine the impact of diabetes and obesity on clinical outcomes in patients at risk of and being managed for CVD.
The international REACH Registry was an observational longitudinal study of the management of people with, or at high risk of, atherothrombosis.15,16 The REACH Registry methods have been published previously.13-15 In brief, it recruited 67 888 patients in 44 countries across the world.15,17 In Australia, 2873 patients were recruited through 273 general practices across the country. Information was collected by medical record review performed by study nurses. To increase the generalisability, each participating general practitioner recruited up to a maximum of 15 consecutive patients.
The study population comprised participants aged 45 years or older who had established coronary artery disease (CAD), cerebrovascular disease (CerVD), peripheral arterial disease (PAD) or at least three CVD risk factors. Only patients with established CAD, CerVD or symptomatic PAD were included in any classification of diseases in any vascular beds. In Australia, all participants had ankle brachial index (ABI) measurements taken at baseline, with PAD defined as an ABI of less than 0.9. The measurement of ABI was only used to determine whether a participant had a low ABI as one of the risk factors rather than as established PAD. Therefore, no one was upgraded to being considered to have disease in two or three vascular beds on the basis of an ABI measurement alone. Eligible risk factors were: systolic blood pressure ≥ 150 mmHg despite therapy for at least 3 months; dyslipidaemia treated with medication; current smoking of at least five cigarettes per day; age 65 years or older for men and 70 years or older for women; being treated for diabetes mellitus; diabetic nephropathy; ABI < 0.9; asymptomatic carotid stenosis of ≥ 70%; and carotid intima media thickness of two times or more that of adjacent sites. Participants who were involved in clinical trials or were hospitalised at the time of enrolment were excluded from the registry.13 Obesity was defined as a body mass index of ≥ 30 kg/m2.
Baseline examinations were conducted from 1 March to 30 June 2004, and all participants were followed up through the GP via case note review and interview.
Events were not independently adjudicated. However, death records and hospital admission records for all reported cardiovascular events were sourced and verified to report clinical outcomes. REACH clinical event definitions have been described in detail elsewhere.16 In brief, cardiovascular death included fatal myocardial infarction, fatal stroke and other cardiovascular death, including heart failure. Non-fatal events included non-fatal myocardial infarction, non-fatal stroke, and hospitalisation for cardiac procedures including percutaneous coronary interventions and cardiac surgery.
All statistical analyses were performed using SPSS for Windows, version 15.0 (SPSS Inc, Chicago, Ill, USA). Data were reported as crude rates, and P values of less than 0.05 were considered statistically significant. Logistic regression analyses were applied to determine the impact of cardiovascular drugs on clinical outcomes at 1 year. The results were reported as adjusted odds ratios (OR).
Of the 2873 participants enrolled in the Australian REACH Registry, 1-year follow-up data were available for 2847. Australia had one of the highest retention rates of all 44 countries participating in the global REACH Registry: 98% at year 1.16 Box 1 shows baseline characteristics for Australian participants included in the 1-year follow-up analysis as well as for those who did not attend for follow-up. No significant systematic differences were observed between those who were and were not followed up at 1 year, with the exception that those who were followed up were slightly older and had a higher prevalence of hypertension. Furthermore, except for the age of investigators, there was no difference in the characteristics of participating GPs. Cardiovascular drug use remained high at 1 year, with 78.6% taking statins and 63.1% taking aspirin. However, only 38.6% were taking β-blockers. These figures were almost identical to baseline drug use of 78.9%, 64.5% and 37.2% for the three drugs, respectively.
Overall, the annual death rate was 2.3% (65 deaths), with cardiovascular deaths accounting for 60% (39 deaths; 1.4% overall). The impact of CVD in this group was high, with the annual combined rate for the hard clinical events of cardiovascular death, non-fatal myocardial infarction or stroke ranging from 2.0% for those with multiple risk factors (Box 2A), 6.6% for those with PAD (Box 2B) to 14.3% in those with disease in two to three vascular beds (Box 2A). When hospitalisation for atherothrombotic events was included in a combined end point, these rates increased two- to threefold, being 4.2% for those with multiple risk factors (Box 2A), 21.0% for those with PAD (Box 2B) and 39.3% for those with vascular disease in two to three beds (Box 2A).
Box 3 shows event rates with 95% CIs for patients classified according to their risk factors and overt disease. Obese patients had an event rate of 9.3% for the combined end points of cardiovascular death, non-fatal myocardial infarction, non-fatal stroke and hospitalisation for atherothrombotic events, versus 10.9% and 11.6% in the overweight and normal weight groups, respectively. The highest combined end points and hospitalisation for atherothrombotic events among those without established disease were among patients with hypertension and diabetes (13.0% and 11.6% respectively).
Box 4 shows the event outcomes on the basis of cardiovascular drug use at baseline in this secondary prevention population. Cardiovascular deaths were more likely to occur among patients who did not use statins compared with those who did (OR, 2.1; 95% CI, 1.1–4.3). Patients who did not use statins were also more likely to experience combined cardiovascular death, non-fatal myocardial infarction and stroke (OR, 2.1; 95% CI 1.3–3.5).
To our knowledge, this is the first report on “hard” clinical outcomes in patients being managed for CVD risk factors in Australian general practice. For this group of high-risk patients, fatal and non-fatal event rates increased with increasing evidence of diffuse CVD. Patients with PAD constitute one of the highest risk groups and, while the baseline level of cardiovascular drug treatment is high and on par with specialist medical practice,13 those not receiving statin therapy seem to be at substantially increased risk over 1 year for cardiovascular death, non-fatal myocardial infarction and non-fatal stroke.
Previously published Australian REACH data on the use of drugs among groups with different atherothrombotic diseases showed that patients with PAD used fewer antiplatelet, antihypertensive and lipid-lowering agents.18,19 The same observation was made in international REACH Registry data.16,17 This may explain the higher risk borne by patients with PAD.
Furthermore, it has been previously reported that in primary care, although the prevalence of PAD is high, awareness of this disease is low.20 Asymptomatic PAD can be detected through a relatively simple ABI measurement, and our findings highlight the importance of identifying PAD and managing risk factors in this high-risk group.
The impact of obesity on hard clinical events, in particular cardiovascular death, observed in our prospective analysis is consistent with the “obesity paradox” that has been identified in other populations and cardiovascular studies.21-23 For example, in a cohort of outpatients with established heart failure, a higher body mass index was associated with a lower mortality risk; and overweight and obese patients had a lower risk of death than those at a healthy weight.21 While these observations have also been reported in patients with hypertension and heart disease,22 little is known of the underlying mechanisms, and a better understanding of the obesity paradox24,25 is required.
The impact of diabetes and its consequences in relation to cardiovascular death and illness has been widely promoted in Australia over the past decade.24-26 Most guidelines have recommended that diabetes be considered as a coronary risk equivalent, but this has recently been the focus of considerable debate. Our findings are consistent with the observation that, compared with patients with overt CVD, diabetes alone does not have as large an impact on major clinical events.3
While the Australian REACH Registry cohort is a subset of the international REACH Registry3,27,28 our findings reflect what Australian GPs confront in terms of the clinical outcomes for patients managed for CVD. Clearly, our study has limitations in terms of sample size, and it could be argued that the 273 GPs may not be representative of all GPs in Australia. Selection biases in terms of a potentially more compliant group who are willing to be followed over the 12 months should also be considered in the interpretation of our findings.
2 Rates of atherothrombotic events* according to number of locations† and type of vascular disease at baseline
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3 One-year event rates* for atherothrombotic events according to their risk factors and overt disease
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Received 9 June 2011, accepted 22 December 2011
Abstract
Objective: To report on 1-year cardiovascular (CV) event rates in patients with established cardiovascular disease (CVD) or with multiple cardiovascular risk factors.
Design, patients and setting: Prospective cohort study of 2873 patients at high risk of atherothrombosis based on the presence of multiple risk factors and overt coronary artery disease (CAD), cerebrovascular disease (CerVD) or peripheral arterial disease (PAD) presenting to 273 Australian general practitioners; this study was conducted as part of the international REACH Registry.
Main outcome measures: One-year rates of cardiovascular death, myocardial infarction, stroke, and hospitalisation for cardiovascular procedures.
Results: The cardiovascular death rate at 1 year was 1.4%. The combined cardiovascular death, non-fatal MI, stroke and hospitalisation rate for vascular disease affecting one location at 1 year was 11%. Even for patients with no overt disease, but with multiple risk factors, the 1-year combined event rate was 4.2%. The highest combined event rate was in patients with PAD (21.0%), and in patients with atherothrombotic disease identified in all three locations (coronary arteries, cerebrovascular system and peripheral arteries) at 39%.
Conclusion: The rate of clinical events in community-based patients with stable atherothrombotic disease increases dramatically with the severity of disease and the number of vascular beds involved. Where disease was evident in all three locations, and for patients with PAD alone, the 1-year risk of cardiovascular events was substantially increased. Poor adherence to statin therapy in the secondary preventive setting is a major treatment gap that needs to be closed; the influences of obesity and diabetes warrant further investigation.