What causes increased pressures in heart failure?

Increased Pressures in Heart Failure: Pathophysiological Mechanisms

Increased pressures in heart failure result primarily from structural and functional cardiac abnormalities that impair the heart's ability to fill with or eject blood, leading to elevated ventricular filling pressures, pulmonary congestion, and systemic fluid retention. 1, 2

Mechanisms of Increased Pressures

Left Ventricular Dysfunction

1. Systolic Dysfunction:

   • Reduced contractility leads to decreased ejection fraction
   • Increased end-systolic and end-diastolic volumes
   • Elevated left ventricular end-diastolic pressure (LVEDP) due to incomplete emptying 1

2. Diastolic Dysfunction:

   • Impaired active relaxation (dependent on myocyte calcium resequestration)
   • Increased passive stiffness due to:
     • Myocardial fibrosis
     • Ventricular hypertrophy
     • Altered extracellular matrix composition 1, 2
   • Results in elevated filling pressures even with normal ejection fraction 1

Neurohormonal Activation

• Activation of renin-angiotensin-aldosterone system (RAAS) causes:
  • Vasoconstriction (increased afterload)
  • Sodium retention
  • Fluid retention 2
• Sympathetic nervous system activation increases:
  • Heart rate
  • Contractility
  • Peripheral vascular resistance 3
• Initially compensatory but eventually contributes to disease progression

Ventricular Remodeling

• Cardiac remodeling includes:
  • Chamber dilatation
  • Hypertrophy
  • Increased sphericity
  • Myocyte hypertrophy (adding sarcomeres in parallel) 1, 2
• Enhanced synthesis and deposition of extracellular matrix proteins
• Progressive accumulation of myocardial fibrosis 1

Hemodynamic Consequences

Elevated Left-Sided Pressures

• Increased left ventricular end-diastolic pressure
• Elevated left atrial pressure
• Pulmonary venous hypertension
• Pulmonary congestion and edema 1
• Symptoms: dyspnea, orthopnea, paroxysmal nocturnal dyspnea 2

Elevated Right-Sided Pressures

• Right ventricular dysfunction (often secondary to left-sided failure)
• Elevated right atrial pressure
• Increased jugular venous pressure
• Systemic venous congestion leading to:
  • Peripheral edema
  • Hepatomegaly
  • Ascites 1

Specific Pathophysiological Patterns

Heart Failure with Reduced Ejection Fraction (HFrEF)

• Primary defect in systolic function (EF ≤40%)
• Reduced cardiac output
• Compensatory mechanisms lead to increased filling pressures 1
• Neurohormonal activation contributes to fluid retention and increased pressures

Heart Failure with Preserved Ejection Fraction (HFpEF)

• Normal or near-normal ejection fraction (EF ≥50%)
• Primary defect in diastolic function
• Impaired ventricular relaxation and increased stiffness
• Elevated filling pressures despite preserved systolic function 1
• Often associated with hypertension, aging, and myocardial fibrosis 4

Common Precipitating Factors for Increased Pressures

• Medication non-adherence
• Dietary indiscretion (excessive sodium intake)
• Acute myocardial ischemia
• Uncontrolled hypertension
• Arrhythmias (especially atrial fibrillation)
• Infections
• Renal dysfunction 1

Clinical Implications

• Elevated filling pressures correlate with symptom severity
• Persistent elevation of filling pressures predicts poor outcomes
• Monitoring and managing filling pressures is a key treatment goal
• Therapies targeting neurohormonal activation (ACE inhibitors, beta-blockers, mineralocorticoid receptor antagonists) help reduce pressures and improve outcomes 5, 6

Pitfalls and Caveats

1. Elevated pressures may persist despite apparent clinical improvement
2. Normal ejection fraction does not exclude elevated filling pressures
3. Aggressive diuresis can cause preload depletion and decreased cardiac output 1
4. Multiple comorbidities (especially in elderly) can complicate pressure management 7
5. Optimal blood pressure target in heart failure remains debated, but values near 130/80 mmHg appear appropriate 4

Understanding these pathophysiological mechanisms is crucial for appropriate diagnosis, monitoring, and treatment of heart failure to reduce morbidity and mortality.