Discrepancy between results of randomized control studies and retrospective analysis: the case of statin therapy effect on one-year mortality in patients with decompensated heart failure

Association is not causation: treatment effects cannot be estimated from observational data in heart failure

Aims

Treatment 'effects' are often inferred from non-randomized and observational studies. These studies have inherent biases and limitations, which may make therapeutic inferences based on their results unreliable. We compared the conflicting findings of these studies to those of prospective randomized controlled trials (RCTs) in relation to pharmacological treatments for heart failure (HF).

Methods and results

We searched Medline and Embase to identify studies of the association between non-randomized drug therapy and all-cause mortality in patients with HF until 31 December 2017. The treatments of interest were: angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, mineralocorticoid receptor antagonists (MRAs), statins, and digoxin. We compared the findings of these observational studies with those of relevant RCTs. We identified 92 publications, reporting 94 non-randomized studies, describing 158 estimates of the 'effect' of the six treatments of interest on all-cause mortality, i.e. some studies examined more than one treatment and/or HF phenotype. These six treatments had been tested in 25 RCTs. For example, two pivotal RCTs showed that MRAs reduced mortality in patients with HF with reduced ejection fraction. However, only one of 12 non-randomized studies found that MRAs were of benefit, with 10 finding a neutral effect, and one a harmful effect.

Conclusion

This comprehensive comparison of studies of non-randomized data with the findings of RCTs in HF shows that it is not possible to make reliable therapeutic inferences from observational associations. While trials undoubtedly leave gaps in evidence and enrol selected participants, they clearly remain the best guide to the treatment of patients.

Acute heart failure registry from high-volume university hospital ED: comparing European and US data

BACKGROUND

Acute heart failure (AHF) is associated with a poor prognosis.

OBJECTIVES

The objectives of this study are to describe mechanisms of AHF and to identify the predictors for all-cause mortality by patients admitted for hospitalization by emergency departments (EDs) as well as to compare European and American data.

METHODS

We designed a prospective registry of consecutively admitted patients for AHF to a high-volume university hospital ED during a 1-year period (n=202; age, 75±11 years; 51% men; ejection fraction, 38%±15%).

RESULTS

The major causes of AHF were coronary artery disease, often with concomitant mitral regurgitation, hypertension, or atrial fibrillation (>90% of cases). At admission, 24.9% of patients had preserved ejection fractions (>50%); and only 7.7% fulfilled the definition of diastolic AHF. The 30-day and long-term mortality (median follow-up, 793 days) were 20.3% and 31.0%, respectively. A low systolic blood pressure (P=.006), reduced ejection fraction (P=.044), and low serum hemoglobin level (P<.01) emerged as the strongest predictors of all-cause mortality. In patients with AHF without acute myocardial infarction (MI) (63.9%), prescription, at discharge, of statins (P<.05) was independently associated with all-cause mortality.

CONCLUSIONS

The patient's blood pressure, ejection fraction, and hemoglobin values, at admission, were identified as the strongest predictors of all-cause mortality. In AHF not triggered by acute MI, long-term use of statins may be associated with reduced survival. The prevalence of diastolic AHF is low. The American AHF population had similar baseline characteristics; needed fewer intensive care unit admissions; had a better 30 days of prognosis, lower incidence of MI, and de novo AHF diagnoses. In a similar subgroup, we observed similar incidences of inotropic support and mechanical ventilation. Our results could not be generalized to all patients with AHF admitted to US EDs.