Long-term prognosis after hospital admission for acute myocardial infarction from 1987 to 2006

Abstract

Background

Recent population-based estimates for long-term cardiovascular disease (CVD) mortality after hospitalization for a first acute myocardial infarction (AMI) are not well established.

Methods

Data from the Swedish hospital discharge and death registries were used to record all first-ever hospital admissions in patients (n = 348,772) 35–84 years with AMI from 1987 to 2006 and subsequent all-cause and CVD case fatality during up to 5 years.

Results

During the 20-year period, 28-day case fatality was reduced by almost two thirds in patients aged < 75 years. For cases with a first AMI 1999–2002 long-term case fatality for men surviving the first 28 days and < 55 years was 10.3/1000 person years, with rates of 23.6, 58.0 and 137.0 for men aged 55–64, 65–74 and 75–84 years. Corresponding figures for women were 10.5, 24.3, 51.8, 124.1 deaths/1000 years. In 1999–2002 estimated long-term risk of fatal CVD (based on survival until 2007) for men below 55 years was 6.1/1000 years, and 13.8, 34.6, 92.9 for men aged 55–64, 65–74, and 75–84 years, respectively. Corresponding figures for women were 4.8, 11.9, 30.1, 86.2/1000 years. The total reduction in CVD case fatality was two thirds among patients aged < 55 and approximately one third among those aged 75–84.

Conclusions

Long-term case fatality after hospitalization for AMI decreased markedly from 1987 to 2006, particularly with respect to CVD mortality and in younger patients. However, because of a steep increase in case fatality with age and a large proportion of older patients, long-term prognosis overall still remains poor.

Introduction

Short-term prognosis after an acute myocardial infarction (AMI) has improved markedly over the last decades, after the introduction of modern treatment. Nonetheless, coronary heart disease (CHD) remains a major contributor to morbidity and mortality with more than one in five men and women currently dying from CHD in Europe [1]. To which extent the reduction in in-hospital case fatality translates into improvement of long-term prognosis has not been widely studied in unselected patients. The long-term fate even in young patients with AMI in the pre-thrombolytic era used to be bleak. In a retrospective analysis of 23 published studies where follow-up was completed by 1980 the annual death rate after the first year in patients with a first AMI was 5%, regardless of age or gender [2]. The 10-year death rate after hospital discharge with a first-time MI in these relatively young patients with a mean age of 56 years was 45%, and almost all deaths were due to either AMI or stroke. In a Swedish study of men surviving AMI prior to 1994 and before the age of 60, annual all-cause mortality was 5.5% [3]. The estimated annual mortality from a more recent register based study from Scotland (patients admitted 1990 to 2000) was similar at 5% [4], however, these patients were older (men mean 65, women 72 years).

Patients hospitalized with AMI today differ from AMI patients from prior periods in several respects. Not only is acute treatment today much more active, but there are also significant differences in diagnostics and clinical presentation. With the introduction of troponins as more sensitive markers of myocardial damage, and a new definition of AMI [5], episodes that would either not have been recognized or else received a diagnosis of angina may now be defined as AMI. Additionally, clinical presentation in AMI has changed, with evidence of milder infarctions [6]. Accordingly, it will have to be accepted that strict like-for-like comparisons of prognosis in AMI patients are no longer possible. Even so, from a public health perspective there is still a need to try to establish population-based estimates for long-term mortality in the subsequent years after a first AMI.

One purpose of this study was to examine whether improvement in short-term case fatality in hospitalized patients results in better long-term prognosis. A second purpose was to provide updated age- and gender-specific estimates for annual total and cardiovascular mortality in AMI survivors beyond the first 28 days after hospital admission, while comparing those estimates with those for earlier patients. Therefore, we analysed short- and long-term survival after all first-ever admissions for AMI in a large population of hospitalized patients from 1987 to 2006, with 5-year survival examined in patients hospitalized until 2002.