Heart failure after myocardial infarction : contemporary trends, determinants and prognostic implications : nationwide observational studies

Abstract

Coronary artery disease (CAD) is one of the leading causes of heart failure (HF). The overall aim of this thesis is to describe contemporary epidemiology of post myocardial infarction HF including temporal trends, changes in patient characteristics, its determinants and prognostic implications, as well as the long-term risk of HF admission. We also examined adherence patterns to beta-blocker treatment after acute myocardial infarction (AMI) and subsequent implications on outcome using a nationwide myocardial infarction registry.

The thesis includes four papers. The first paper described the incidence, temporal trends, and prognostic impact of HF complicating acute AMI. The second paper investigated the incidence, determinants and prognostic implications of HF with normal ejection fraction (HFNEF) that occurs in the setting of AMI. The third paper investigated the risk and predictors of HF admission among survivors of AMI. Finally, the fourth paper investigated the pattern of adherence to beta-blocker treatment in one-year AMI survivors, and assessed predictors of better adherence and subsequent implications on long-term all-cause mortality and/or HF admissions.

The incidence of in-hospital HF during an index hospitalization for AMI decreased by 39% with an absolute risk reduction (ARR) of 18% over 13 years with more pronounced reduction among STEMI (ARR 22%) than NSTEMI (ARR 14%) patients, p<0.001. The use of rapid revascularization treatment and evidence-based pharmacologic treatment increased over the years (1996-1997 vs. 2008). Patients with clinical HF after AMI had a higher risk for death (adjusted HR: 2.09; 95% CI: 2.06 to 2.13). However, mortality was decreasing over time, showing the potential for a further decrease with even better treatment strategies.

HF with normal EF was a relatively less common form of HF in the setting of AMI but its occurrence was associated with at least a 3-fold increase in mortality compared to patients with NEF and no HF. Interestingly, patients who had evidence of left ventricular systolic dysfunction (LVEF <50%) without clinical HF had better long-term prognosis than patients with HFNEF, underscoring the importance of clinical findings such as pulmonary rales to predict higher risk of mortality complementary to EF.

Long-term survivors of MI without a previous history of HF remain at risk of late-onset HF (LOHF) with in-hospital HF being a strong predictor. Out of 150,566 AMI survivors without prior HF, 19.4% (n=29,194) were readmitted due to HF during the study period (2004-2013). However, the incidence of LOHF after AMI showed a declining trend over the years which largely seems to be related to a decreasing burden of comorbidities and an improved evidence-based revascularization strategy and pharmacologic treatment.

Out of 38,597 one-year AMI survivors, 31.1% were non-adherent to beta-blocker treatment one year after the index event. Patients with LVSD (REF) without signs of HF and patients with HFREF were more likely to receive beta-blockers at discharge and adhere to treatment one year after the index AMI. Better adherence was associated with improved long-term outcomes in all patients except in patients with HFNEF. Of note, the long-term prognostic advantage seen also in low-risk patients highlights the need for future studies.

In conclusion, though gains have been made in AMI treatment, the lingering problem of HF underscores the importance of interventions at all levels that mitigate its occurrence starting from primordial preventive measures, early identification and treatment of risk factors, prompt and effective treatment of AMI and implementation of evidence-based secondary prevention therapies while ensuring the continuous monitoring of epidemiological trends.