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LONG-TERM PROGNOSTIC FACTORS AFTER MYOCARDIAL INFARCTION: 17-YEAR FOLLOW-UP OF THE TRACE REGISTRY

Thomas Kümler

Summary

LONG-TERM PROGNOSTIC FACTORS AFTER MYOCARDIAL INFARCTION: 17-YEAR FOLLOW-UP OF THE TRACE REGISTRY  

 

BACKGROUND AND OBJECTIVES 
Cardiovascular diseases are the leading cause of morbidity and mortality in the industrialized world, with myocardial infarction (MI) and heart failure being among the most frequent conditions.  

The randomised controlled trials of long-term medical therapy have evaluated treatments administered over a limited number of years, yet guidelines recommend treatment indefinitely.  Increasing prevalence of heart failure has been reported using administrative registers, which could be a result of changing recording habits. In addition the availability of administrative registers is increasing.  

This thesis focused on analysis of the long-term persistence of prognostic factors after MI. The prognostic factors examined were left ventricular systolic function and heart failure, diabetes and renal function. Moreover, I analyzed the validity of a heart failure diagnosis in administrative registries to examine whether discharge coding of heart failure could be used for the study of the incidence and prevalence of heart failure.  

 METHODS 
 For the study of the validity of a heart failure diagnosis, I used the Copenhagen Hospital Heart Failure Study (CHHF) registry. This trial included all consecutive patients above the age of 40 years admitted to one Copenhagen City hospital over a 12-month period. By comparing the diagnosis of heart failure made by the regular staff clinicians with the heart failure diagnosis according to the European Society of Cardiology criteria, I evaluated sensitivity, specificity, and predictive values.  

I studied the long-term persistence of prognostic factors after MI using data from the The Trandolapril Cardiac Evaluation (TRACE) Registry, which consist of 6676 consecutive patients with MI. The study was conducted in 27 centres in Denmark from 1992 to 1994. Mortality was analysed with Kaplan-Meier survival curves and landmark analyses were illustrate the prognostic significance of risk factors in 2-year intervals. Relative risk estimates were derived from a Cox proportional-hazards regression model.  

RESULTS 
 A registered diagnosis of heart failure (n=126) carried a specificity of 99% and a sensitivity of 29% for all patients. The positive predictive value was 81% and the negative predictive value was 90%. 
 All the studied risk factors carried long-term prognostic significance. Left ventricular systolic function estimated as wall motion index (WMI) was a significant prognostic factor until 10 years of follow-up. The prognostic significance of HF persisted for 8 years.  Diabetes retained prognostic significance throughout the length of the follow-up period while renal function was a prognostic factor for 10-12 years depending on whether renal function was evaluated with se-creatinine or estimated GFR. 

CONCLUSIONS  
HF is severely underreported in the Danish National Hospital Register. Administrative registers can be used to identify large groups of patients with HF for epidemiological studies but is not suitable for use in studies of prevalence and incidence of HF in a population. All the studied risk factors for all-cause mortality following MI showed long-term persistence. This underlines the importance of an evaluation of these risk factors in the risk stratification of patients with MI and indirectly supports the guideline recommended lifelong pharmacological therapy.