Are HFpEF and HFmrEF So Different? The Need to Understand Distinct Phenotypes

Area of Science:

• Cardiology
• Heart Failure Research
• Echocardiography

Background:

• Traditional heart failure (HF) classification relies on ejection fraction (EF) thresholds (<50% or ≥50%).
• The 2016 ESC guidelines introduced heart failure with midrange EF (HFmrEF), encompassing EF between 40% and 49%.
• HFmrEF patients are underrepresented in clinical trials and include those with improved HFrEF or initially preserved EF with impaired systolic function.

Purpose of the Study:

• To analyze the similarities and dissimilarities between HFmrEF and other HF subtypes.
• To question the current EF-based categorization of heart failure.
• To hypothesize that HFmrEF and HFpEF may share more clinical and morphological characteristics than previously thought.

Main Methods:

• Review of existing literature on heart failure classification and EF variability.
• Analysis of clinical and morphological characteristics of different HF subtypes.
• Discussion of the limitations of EF as a sole diagnostic criterion.

Main Results:

• Ejection fraction (EF) is not a fully representative measure of myocardial contractile function and can fluctuate with hemodynamic conditions.
• EF measurements exhibit significant interobserver variability, potentially leading to misclassification of HF subtypes (HFmrEF vs. HFpEF).
• Different HF stages and periods may exhibit distinct pathophysiological mechanisms and adaptations.

Conclusions:

• The current EF-based classification of heart failure may be unreliable due to EF variability and measurement inconsistencies.
• HFmrEF and HFpEF might share underlying pathophysiological mechanisms and clinical features.
• Further research is needed to refine HF classification and understand the distinct characteristics of HFmrEF.