Changes in the use of medications after acute myocardial infarction: possible impact on mortality after myocardial infarction and long-term outcome

Revascularization and cardioprotective drug treatment in myocardial infarction patients: how do they impact on patients' survival when delivered as usual care

Background

Randomized clinical trials showed the benefit of pharmacological and revascularization treatments in secondary prevention of myocardial infarction (MI), in selected population with highly controlled interventions. The objective of this study is to measure these treatments' impact on the cardiovascular (CV) mortality rate among patients receiving usual care in the province of Quebec.

Methods

The study population consisted of a "naturalistic" cohort of all patients ≥ 65 years old living in the Quebec province, who survived a MI (ICD-9: 410) in 1998. The studied dependant variable was time to death from a CV disease. Independent variables were revascularization procedure and cardioprotective drugs. Death from a non CV disease was also studied for comparison. Revascularization procedure was defined as percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass graft (CABG). The exposure to cardioprotective drugs was defined as the number of cardioprotective drug classes (Acetylsalicylic Acid (ASA), Beta-Blockers, Angiotensin-Converting Enzyme (ACE) Inhibitors, Statins) claimed within the index period (first 30 days after the index hospitalization). Age, gender and a comorbidity index were used as covariates. Kaplan-Meier survival curves, Cox proportional hazard models, logistic regressions and regression trees were used.

Results

The study population totaled 5596 patients (3206 men; 2390 women). We observed 1128 deaths (20%) within two years following index hospitalization, of them 603 from CV disease. The CV survival rate at two years is much greater for patients with revascularization, regardless of pharmacological treatments. For patients without revascularization, the CV survival rate increases with the number of cardioprotective drug classes claimed. Finally, Cox proportional hazard models, regression tree and logistic regression analyses all revealed that the absence of revascularization and, to a lower extent, absence of cardioprotective drugs were major predictors for CV death, even after adjusting for age, gender and comorbidity.

Conclusion

Considering usual care management of MI in the province of Quebec in 1998, CV survival is positively correlated to the presence of a revascularization procedure and to the intensity of cardioprotective pharmacological treatment. These results are coherent with data from randomized control trials.

Benefits of inpatient initiation of beta-blockers

Clinical trials have demonstrated that beta-blockers effectively reduce mortality in patients after a myocardial infarction (MI) and in patients with chronic heart failure. Treatment guidelines recommend that all patients after MI without a contraindication receive early beta-blocker treatment. Initiation of beta-blockers also should be considered for stable patients who are hospitalized with heart failure. Despite well-documented benefits, however, beta-blockers are still underused. Barriers that cause reluctance by physicians to initiate therapy include the traditional belief that beta-blockers are contraindicated in patients with left ventricular dysfunction, complexity of management, perceived risk of adverse events, and potential for short-term clinical deterioration. Intervention programs promoting beta-blockers for inpatients have increased their use at discharge and after long-term follow-up. Because of pharmacologic differences, agent selection is also critical. Agents must have proven clinical efficacy, an established dose-titration regimen, and desirable pharmacokinetic properties. Increasing the use of these life-saving agents has the potential for substantial clinical impact.

Markedly changed age distribution among patients hospitalized for acute myocardial infarction

OBJECTIVE

To investigate trends in number of hospital admissions due to acute myocardial infarction (AMI) in different age groups during the last decade.

DESIGN

Data on all AMI hospital admissions since 1991 were analysed by gender and by age applying 5-year age groups between ages 60 and 90, and < 60 and > or = 90 as separate groups.

RESULTS

From 1991 to 2000 the number of hospital admissions for AMI was reduced by 18%. In men, AMI rates decreased in all age groups below 80 years and increased in older ages, while in women the corresponding breaking point between decreased and increased rates was 85 years. In the age group < 80 years, men and women included, the number of AMI admissions decreased by 29% (from 11,540 to 8233), while for those > or = 80 there was an increase of 25% (from 2917 to 3659). Over the decade the ratio of the numbers of AMIs in ages above and below 80 years increased from 0.25 to 0.44.

CONCLUSION

Over the last decade a striking change in age distribution among AMI patients took place, with a marked decrease in age groups below 80 years, as opposed to an equally strong increase in the oldest age groups. The development with regard to trends for AMI morbidity in society has been more favourable than what appears from overall numbers of AMIs.