Previous studies, such as the World Health Organisation MONICA (monitoring trends and determinants in cardiovascular disease) project, have demonstrated the rapid and progressive uptake of medical care that has been shown in randomised clinical trials to reduce cardiovascular mortality [Lancet 2000;355:688-700]. However, there are relatively few population based studies available that describe how this apparent uptake of evidence-based therapy translates to actual long-term survival following myocardial infarction (MI) or death rates from coronary heart disease in the real world.
In order to address this question Briffa and co-workers examined the impact of evidence based medical treatment and coronary revascularisation on the long term survival of 4,451 patients registered by the MONICA project who were admitted to hospital with acute MI between 1984 to 1993 in Perth, Western Australia. Patients who died in the first 28 days were excluded. The cohort was divided into 3 subgroups according to date of admission (1984-7, 1988-90, and 1991-3), which allowed for temporal changes in the use medical therapy to be identified (table 1).
|
Treatment |
Cohort 1 1984-7 (n = 1745) |
Cohort 2 1988-90 (n = 1395) |
Cohort 3 1991-3 (n = 1311) |
P value |
|
Thrombolytic therapy |
12% |
37% |
49% |
<0.001 |
|
Antiplatelet |
45% |
91% |
97% |
<0.001 |
|
Β blocker |
66% |
82% |
88% |
<0.001 |
|
ACE inhibitor |
9% |
15% |
29% |
<0.001 |
|
Lipid lowering drugs |
2% |
3% |
5% |
<0.001 |
|
Coronary revascularisation (<12 months since AMI) |
2% |
31% |
38% |
0.001 |
|
All cause 12-year mortality |
29.9% (27.7-32.1) |
26.4% (24.1-28.8) |
22.3% (20.0-24.6) |
28% relative risk reduction (cohort 1 vs. cohort 3) |
|
Proportion of total deaths caused by cardiovascular disease |
70% |
66% |
61% |
N/A |
Over 12 year follow up, patients from the most recent subgroup (1991-3) had a 7.6% (95% CI, 4% to 11%) reduction in absolute events or a 28% lower relative risk reduction (RRR) (16 to 38%) when compared with the cohorts who presented earlier, either 1984-7 or 1988-90.
This improved survival persisted after adjustment for demographic factors, coronary risk factors, severity of disease, and event complications; adjusted RRR, 26% (14% to 37%), but was absent after further adjustment for medical treatments in hospital and coronary revascularisation procedures within 1 year of index presentation, which may provide support for their favourable influence on mortality.
Although observational data must always be interpreted with caution the observations made in the present study suggest improved survival rates which appear to correspond with the initiation evidence based treatment. Consequently, this data describes how improved cardiovascular survival observed in the setting of clinical trials may translate into a ‘real world’ population based setting.
· Briffa T, Hickling S, Knuiman M et al. Long term survival after evidence based treatment of acute myocardial infarction and revascularisation: follow-up of population based Perth MONICA cohort, 1984-2005. BMJ 2009;338:b36