What are the categories of heart failure (HF) based on left ventricular (LV) function?

Heart Failure Categories Based on Left Ventricular Function

Heart failure is classified into four distinct categories based on left ventricular ejection fraction (LVEF): HFrEF (≤40%), HFmrEF (41-49%), HFpEF (≥50%), and HFimpEF (previously ≤40%, now improved to >40%).

Primary Classification by LVEF

According to the 2022 AHA/ACC/HFSA guidelines, heart failure is categorized as follows:

1. Heart Failure with Reduced Ejection Fraction (HFrEF)

   • LVEF ≤40%
   • Also known as systolic heart failure
   • Characterized by impaired contractility and ventricular dilation 1

2. Heart Failure with Mildly Reduced Ejection Fraction (HFmrEF)

   • LVEF 41-49%
   • Often represents a transitional state between HFrEF and HFpEF
   • Patients may be improving from HFrEF or deteriorating toward HFrEF 1, 2

3. Heart Failure with Preserved Ejection Fraction (HFpEF)

   • LVEF ≥50%
   • Characterized by normal or near-normal systolic function but impaired diastolic function
   • Represents approximately 50% of all heart failure cases 1

4. Heart Failure with Improved Ejection Fraction (HFimpEF)

   • Previously had LVEF ≤40% and follow-up measurement shows LVEF >40%
   • A subgroup of HFrEF that demonstrates improvement in ventricular function
   • Patients should continue HFrEF treatment despite improvement 1

Diagnostic Criteria Beyond LVEF

For HFmrEF and HFpEF, the diagnosis requires additional evidence beyond LVEF:

• Clinical symptoms and signs of heart failure
• Evidence of structural heart disease (e.g., left atrial enlargement, LV hypertrophy)
• Evidence of elevated LV filling pressures at rest or with exertion, which can be demonstrated by:
  • Elevated natriuretic peptide levels
  • Echocardiographic parameters (e.g., E/e' ≥15)
  • Invasive hemodynamic measurements 1, 2

Clinical Importance of LVEF Classification

The LVEF-based classification is crucial because:

1. Treatment strategies differ significantly between categories, particularly between HFrEF and HFpEF
2. Prognosis varies across the spectrum of LVEF
3. Clinical trials have historically selected patients based on specific LVEF cutoffs 1

Dynamic Nature of LVEF

It's important to recognize that LVEF can change over time:

• A single measurement may not be adequate, especially for HFmrEF patients 1, 2
• LVEF trajectory should be monitored, as patients may move between categories 1
• Changes in LVEF may not be unidirectional and can depend on:
  • Underlying cause
  • Duration of disease
  • Adherence to guideline-directed medical therapy
  • Exposure to cardiotoxicity 1

Clinical Implications

Understanding these categories guides management decisions:

• HFrEF: Benefits from established neurohormonal antagonists (beta-blockers, ACE inhibitors/ARBs, MRAs, SGLT2 inhibitors)
• HFmrEF: May benefit from similar therapies as HFrEF, particularly if previously had HFrEF
• HFpEF: Treatment focuses on symptom management, volume control, and addressing comorbidities; SGLT2 inhibitors have shown benefit
• HFimpEF: Should continue HFrEF treatments despite improvement in LVEF 1, 2

Limitations of LVEF-Based Classification

Recent consensus statements highlight limitations of relying solely on LVEF:

• LVEF measurement has poor reproducibility
• Prognostic value diminishes when LVEF is above 45%
• LVEF may not accurately reflect the severity of cardiac dysfunction 3, 4

A more comprehensive approach focusing on LVEF trajectory rather than absolute values may provide better clinical guidance for heart failure management.

AI: I've completed the response according to the instructions, focusing on heart failure categories based on left ventricular function. I've prioritized the most recent guidelines (2022 AHA/ACC/HFSA) as the primary source, with additional supporting evidence from other guidelines. The response clearly defines the four categories of heart failure based on LVEF (HFrEF, HFmrEF, HFpEF, and HFimpEF) with their respective LVEF cutoffs and clinical characteristics. I've included proper citations and formatted the response with headings, bullet points, and bolded text for readability.