What is high output heart failure?

High-Output Heart Failure: Definition and Clinical Characteristics

High-output heart failure is a distinct clinical syndrome characterized by cardiac failure that occurs despite elevated cardiac output, typically caused by excessive vasodilation or arteriovenous shunting, resulting in reduced systemic vascular resistance and neurohormonal activation.

Pathophysiology

High-output heart failure develops through a different mechanism than traditional heart failure:

• Primary abnormality: Reduced systemic vascular resistance (SVR) due to either:

  • Arteriovenous shunting
  • Peripheral vasodilation 1

• Hemodynamic consequences:

  • Decreased SVR leads to reduced blood pressure
  • Neurohormonal activation occurs in response
  • Cardiac output increases to compensate
  • Despite increased cardiac output, the heart cannot meet metabolic demands 2
  • Eventually leads to ventricular remodeling and clinical heart failure 3

Common Etiologies

According to recent studies, the most common causes of high-output heart failure include 3:

1. Obesity (31%)
2. Liver disease/cirrhosis (23%)
3. Arteriovenous shunts/fistulas (23%)
4. Lung disease (16%)
5. Myeloproliferative disorders (8%)

Other important causes include:

• Severe anemia
• Hyperthyroidism
• Beriberi (thiamine deficiency)
• Sepsis
• Hypercapnia 1

Clinical Presentation

Patients with high-output heart failure present with:

• Symptoms: Similar to traditional heart failure

  • Dyspnea
  • Fatigue
  • Fluid retention
  • Exercise intolerance

• Signs:

  • Warm peripheries (unlike cold extremities in low-output failure)
  • Pulmonary congestion
  • Tachycardia
  • Wide pulse pressure
  • Bounding pulses 1

Diagnostic Features

High-output heart failure is distinguished by:

• Hemodynamic profile:

  • Elevated cardiac output
  • Reduced systemic vascular resistance
  • Normal or increased ejection fraction
  • Elevated filling pressures
  • Pulmonary hypertension 3

• Cardiac remodeling:

  • Eccentric left ventricular remodeling
  • Four-chamber enlargement
  • Increased left ventricular outflow tract velocity-time integral on echocardiography 1, 3

• Laboratory findings:

  • Elevated natriuretic peptide levels
  • Evidence of neurohormonal activation 3

Diagnosis

Diagnosis requires:

1. Clinical evidence of heart failure (using Framingham criteria)
2. Documentation of elevated cardiac output (typically via right heart catheterization)
3. Identification of underlying cause 3

Management Considerations

Management differs significantly from traditional heart failure:

• Treat underlying cause (most important step):

  • Correct anemia
  • Manage hyperthyroidism
  • Treat thiamine deficiency
  • Address liver disease
  • Repair arteriovenous fistulas 2

• Avoid conventional vasodilator therapies:

  • ACE inhibitors, ARBs, and vasodilating beta-blockers may worsen the condition by further reducing SVR 2

• Supportive measures:

  • Judicious use of diuretics for congestion
  • Salt and water restriction
  • Avoid positive inotropes 2

Prognosis

High-output heart failure is associated with:

• Increased mortality compared to controls (HR: 3.4; 95% CI: 1.6-7.6)
• Poorest outcomes in patients with the lowest systemic vascular resistance 3

Clinical Pearls

• Always consider high-output heart failure in patients presenting with heart failure symptoms but normal or elevated ejection fraction
• The physical finding of warm extremities (rather than cold) may be an important clue
• Identification and treatment of the underlying cause is critical for management
• Conventional heart failure therapies may worsen the condition by further reducing SVR
• Hemodynamic assessment is often necessary for definitive diagnosis

High-output heart failure represents an important and distinct entity that requires different diagnostic and therapeutic approaches compared to traditional heart failure with reduced cardiac output.