Coronary heart disease trends in France and elsewhere

In this issue the MONICA (monitoring trends and determinants in
cardiovascular disease) team from Toulouse reports on myocardial infarction
trends in south west France between 1985*and 1993. 1There were 3263*events
in men and there appeared to be an annual decrease of around 2% in both
event rate and mortality rates. Twenty eight day case fatality fell by about
3% per year for first events and by 6% for recurrent events. The confidence
intervals, however, are very wide around these estimates. The authors have
concluded that the decrease in myocardial infarction mortality was
predominantly attributable to reduction in case fatality and, by inference,
improvements in acute management. It should be noted that there were few
events in women. 1

The Toulouse report updates an earlier description of the same population
for the period 1985-90, 2and provides local detail as part of the much
larger MONICA project recently reported elsewhere. 3Curiously, the attack
rates and case fatality rates in the present report are quite different from
those in the earlier one. 2In the overall MONICA analysis, 10*year trends in
37*populations highlighted mortality declines in the majority and
substantial declines in 12*populations. 3In men, the annual mean change in
coronary event rates averaged 4.3% compared with only 2.1% reduction in case
fatality, an overall pattern very different from the Toulouse experience.
Another curiosity, however, is that the main MONICA report seems to show the
pattern of change in Toulouse in keeping with the overall findings and,
therefore, not as in the present report. 1*3Having noted the substantial
contributions from changes in survival, the MONICA investigators emphasised
that "the major determinants of decline in CHD [coronary heart disease]
mortality is whatever drives changing coronary event rates". 3

The Toulouse paper highlights five key issues: trends in event rates, trends
in mortality, trends in case fatality, inferences about treatment effects
(secondary prevention), and inferences about cardiovascular risk factors
(primary prevention). 1Coronary heart disease mortality statistics are the
epidemiological rock to which all other phenomena can be most safely tied 4.
One of the great achievements of the MONICA programme has been the general
validation of routine mortality statistics across the majority of the
21*countries. It is perhaps not surprising that two of the lowest coronary
heart disease mortality rates are reported in Japan and in France where
substantial numbers of coronary deaths are coded as something else.
5However, the general trends are clear. In the majority of industrialised
countries coronary heart disease mortality has fallen by a third or a half
in the last two decades. Falls have been steeper in younger age groups and
more affluent social classes. 3*6Trends in myocardial infarction and
coronary heart disease event rates have generally mirrored trends in
mortality. Various reports of increases in non-fatal acute myocardial
infarction rates have a complex explanation which includes a reduction in
hospital admission thresholds, an increase in the sensitivity of enzyme
diagnostic tests, and financial pressures to recode non-specific coronary
disease as frank acute myocardial infarction. 7

Trends in case fatality are easier to describe than to explain. The majority
of reports from the USA, UK, Europe, and Australasia show substantial
reductions in case fatality. 3*7-10 The Nottingham series represents a major
exception. 11 Because case fatality is the ratio between death and total
events, it remains vulnerable to denominator expansion. Meticulous and
consistent definitions therefore become crucial. 7*8However, both short term
and long term case fatality after acute myocardial infarction remain
substantial and individual treatments achieve relative mortality reductions
of only 20% or 30%. 6Thus in every 100*patients admitted with an acute
myocardial infarction, no more than five deaths might be expected to be
prevented or postponed by the combination of thrombolysis and aspirin, for
instance. 12

Most other epidemiological studies also suggest that a decline in event
rates and, by implication, primary and secondary prevention, contributes at
least as much, if not more, to the reduction in coronary mortality in
developed countries. Indeed, this is the conclusion of the overall MONICA
study 3and appears to have been true of Toulouse during the period covered
in the principal MONICA report. 2Furthermore, when the combined effects of
cardiological treatments are modelled in Australasia, USA, or Europe, they
generally can explain no more than half of the mortality reduction. 6*13 *14
These same models suggest that a larger mortality reduction is attributable
to falls in the major cardiovascular risk factors smoking, cholesterol, and
blood pressure. 6*13 *14

In conclusion, the totality of the epidemiological data supports strong
policy initiatives on both primary and secondary prevention. 3*6*13
Cardiovascular risk factors can be reduced in entire populations through
comprehensive and integrated prevention programmes. 15 Furthermore, in
patients with established coronary heart disease, there is extensive
evidence on the effectiveness and cost effectiveness of secondary preventive
cardiological treatments, and correspondingly strong arguments for
increasing treatment levels from 40% to at least 80% of eligible patients 16
and, in Britain at least, unequivocal government support. 17 Undoubtedly,
optimum treatment of acute myocardial infarction is also of the upmost
importance. The scourge of coronary heart disease continues to require a
multifaceted attack.

SIMON CAPEWELL ,JOHN MCMURRAY
MRC Clinical Research Initiative in Heart Failure, Wolfson Building (Level
3), University of Glasgow., Glasgow G12 8QQ, UK, email:
[email protected]