Can pulmonary hypertension cause heart failure?

Pulmonary Hypertension and Heart Failure: Pathophysiological Relationship

Yes, pulmonary hypertension can directly cause right-sided heart failure through increased afterload on the right ventricle, leading to progressive right ventricular dysfunction and ultimately right heart failure. 1

Pathophysiology of Pulmonary Hypertension Leading to Heart Failure

Pulmonary hypertension (PH) is defined as a mean pulmonary arterial pressure ≥25 mmHg at rest measured during right heart catheterization 1. The relationship between PH and heart failure follows a clear pathophysiological progression:

1. Initial Impact on Right Ventricle:

   • PH increases afterload on the right ventricle (RV)
   • This forces the RV to generate higher pressures to maintain adequate pulmonary blood flow
   • Progressive RV dysfunction develops as a direct consequence 1

2. Right Ventricular Adaptation and Failure:

   • Initially, the RV responds with hypertrophy to compensate for increased afterload
   • As PH progresses, RV dilation occurs with eventual systolic dysfunction
   • This leads to decreased cardiac output, systemic hypotension, and end-organ damage 1, 2

3. Clinical Syndrome of Right Heart Failure:

   • Chronic right heart failure (RHF) manifests with:
     • Decreased exercise tolerance
     • Poor functional capacity
     • Decreased cardiac output
     • Progressive end-organ damage from venous congestion and underperfusion
     • Cachexia from poor nutrient absorption and proinflammatory state 1

Types of Pulmonary Hypertension and Heart Failure

PH can be classified into several groups, with different relationships to heart failure:

1. Group 1: Pulmonary Arterial Hypertension (PAH)

   • Primary disease of pulmonary vasculature
   • Can lead to isolated right heart failure 1

2. Group 2: PH due to Left Heart Disease

   • Most common form (65-80% of all PH cases) 3
   • Occurs in 60-80% of patients with heart failure 4
   • Can occur with both preserved and reduced ejection fraction 4
   • Creates a bidirectional relationship where left heart failure causes PH, which then causes right heart failure

3. Group 3: PH due to Lung Diseases/Hypoxia

4. Group 4: Chronic Thromboembolic PH

5. Group 5: PH with Unclear/Multifactorial Mechanisms

Pulmonary Hypertensive Crisis and Acute Right Heart Failure

In acute settings, pulmonary hypertensive crises can precipitate acute right heart failure:

• Characterized by sudden increases in pulmonary arterial pressure
• Results in right ventricular failure, systemic hypotension, and myocardial ischemia
• Can be triggered by pain, anxiety, tracheal suctioning, hypoxia, acidosis, or withdrawal of PH-specific therapy 1
• Is a major cause of death in patients with pulmonary arterial hypertension 1

Bidirectional Relationship in Heart Failure with PH

The relationship between heart failure and PH is often bidirectional:

1. Left Heart Failure Leading to PH:

   • Left heart failure causes elevated left atrial pressure
   • This leads to passive backward transmission to pulmonary circulation
   • Initially reversible "passive" PH develops
   • Over time, pulmonary vascular remodeling creates a "reactive" component 4

2. PH Leading to Right Heart Failure:

   • As described above, PH increases RV afterload
   • Progressive RV dysfunction develops
   • Right heart failure ensues

3. Right Heart Failure Worsening Left Heart Function:

   • RV failure can further impair LV function through:
     • Ventricular interdependence (septal shift)
     • Reduced LV preload
     • Pericardial constraint
     • Neurohormonal activation 5

Clinical Implications

1. Prognostic Significance:

   • PH and resulting right heart failure are associated with increased morbidity and mortality 1, 4
   • RV function is a major determinant of functional capacity and prognosis in PAH 1

2. Therapeutic Considerations:

   • Treatment should target the underlying cause of PH
   • In PH due to left heart disease, optimizing left heart function is critical 1
   • Specific PAH therapies may be harmful in some forms of PH, particularly in left heart failure with severe left ventricular systolic dysfunction 6
   • Careful hemodynamic assessment is essential before initiating specific therapies

Important Caveats

• Not all patients with PH will develop right heart failure; the development depends on the severity, duration, and acuity of PH
• The right ventricle's ability to adapt to increased afterload varies among individuals
• Early diagnosis and treatment of PH may prevent or delay the onset of right heart failure
• In patients with congenital heart disease, the risk of developing PH and subsequent right heart failure depends on the size and location of the defect and timing of repair 1

Pulmonary hypertension represents a significant cause of heart failure through its direct effects on right ventricular function, and management should focus on treating both the underlying cause of PH and supporting right ventricular function.