Updated: 9/15/2020

Pulmonary Hypertension

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Snapshot
  • A 37-year-old woman is referred to the pulmonologist’s office from her PCP for worsening shortness of breath. She reports that she has had increasing dyspnea on exertion and fatigue for the past 3 years, but it has gotten much worse in the last 2 months. She used to walk around the neighborhood with her friends but now gets short of breath with occasional chest pain just walking around the house. Her past medical history is otherwise completely negative. On physical exam, she has a JVP of 13 cm H
    2
    O, a loud P2, an S3, a right-sided heave, a liver palpable 3 cm below the costal margin, and bilateral leg edema. She is sent for a trans-thoracic echocardiogram which estimates a high pulmonary artery systolic pressure and shows right ventricular hypertrophy and right heart failure. The diagnosis is confirmed with a right heart catheterization and she is started on epoprostenol.
Introduction
  •  Clinical definition
    • mean pulmonary artery pressure ≥ 20 mmHg
      • normal = 8-20 mmHg
      • gold standard for measurement is right heart catheterization
  • Epidemiology
    • incidence
      • varies by etiology; affects all ages, races, and genders
      • can be very rare (~4 cases per million for idiopathic pulmonary hypertension (IPAH))
      • or relatively common 10-40% of patients with at-risk associated diseases (below)
    • demographics
      • females > males
        • up to 9:1 (for IPAH)
  • Etiologies

    Etiologies of Pulmonary Hypertension
    Primary Etiologies
    Etiology Key Points
    Idiopathic pulmonary arterial hypertension (IPAH)
    • By definition, the cause is unknown
    Hereditary pulmonary arterial hypertension (HPAH)
    • Mutation in the BMPR-2 gene
      • acts normally to inhibit smooth muscle growth
    • Mnemonic: Blocker of Muscle PRoliferation
    • More common in women (9:1)
    • Poor prognosis
    Secondary Etiologies 
    Etiology (secondary to)
    Key Points
    Autoimmune disease
    • Systemic sclerosis > SLE >> RA
    • Inflammation of vessel wall leads to scarring and stiff vessels
    Drugs
    • Direct pulmonary vasoconstriction
      • e.g., cocaine or methamphetamine
    Infection
    • Schistosomiasis
      • leading cause of pulmonary hypertension in endemic areas
    • HIV
    Left-to-right shunt
    • Increased flow to pulmonary system
      • e.g., from congenital heart defects
    Left heart disease
    • Decreased cardiac output backs blood into pulmonary circuit
      • e.g., left heart failure or mitral valvular disease
    Lung disease/hypoxia
    • Decreased oxygen delivery leads to hypoxemic pulmonary vasoconstriction
      • e.g., COPD, obstructive sleep apnea, obesity hypoventilation syndrome, or high altitudes
    Thromboembolic disease
    • Chronic, recurrent micro-emboli decrease the cross-sectional area of pulmonary vessels
    Unclear/miscellaneous
    • e.g., carcinoid syndrome, sarcoidosis, vasculitis, or metabolic disorders 
  • Pathogenesis
    • common final pathway for all etiologies
      • luminal injury from increased pulmonary pressure
      • smooth muscle proliferation of the media and intima
      • fibrosis resulting in plexiform lesions on pathology  
    • fibrosis leads to stiff vessels
    • increased pulmonary vascular resistance (PVR)
    • right ventricle has to pump harder to overcome resistance
    • right ventricular hypertrophy 
    • right heart failure
  • Associated conditions
    • schistosomiasis
    • systemic sclerosis
    • SLE
    • HIV 
    • persistent pulmonary hypertension of the newborn
  • Prognosis
    • progressive and fatal if untreated
    • incurable
      • treatment focuses on slowing the disease progression
    • rate of progression is variable
    • for IPAH and HPAH, 5-year survival is approximately 50%
Presentation
  • Symptoms
    • dyspnea on exertion
    • fatigue
    • if subsequent right heart failure
      • exertional chest pain (angina)
      • exertional syncope
      • swelling
      • RUQ pain (from hepatic congestion)
      • anorexia (from hepatic congestion)
  • Physical examination
    • loud P2 on auscultation
    • right-sided heave
      • from right ventricular hypertrophy
    • if subsequent right heart failure
      • elevated JVP
      • hepatomegaly
      • S3 heart sound

Imaging
  • Echocardiogram  
    • usually first step in the workup
    • right ventricular hypertrophy
    • enlarged pulmonary arteries
    • estimated pulmonary arterial systolic pressure
      • estimated from flow rate across the tricuspid valve
  • Chest radiograph
    • enlarged pulmonary arteries
    • pruning of peripheral vessels
  • CT angiography  
    • enlarged pulmonary trunk and pulmonary arteries
Studies
  • Labs
    • BNP
      • non-specific
  • Diagnostic procedures
    • right heart catheterization
      • allows measurement of pulmonary arterial pressures
      • gold standard for diagnosis
  • Diagnosis
    • clinical diagnosis by appropriate history, physical exam, and imaging/lab findings
    • very likely if echocardiogram estimates high pressures
    • if few or ambiguous clinical findings, may need to confirm with right heart cath (early IPAH and HPAH)
Differential
  • Congestive heart failure (without PH)
    • clinically very similar
    • distinguishing factors
      • typically, a long history of heart attacks, coronary artery disease, hypertension, and/or other risk factors for heart failure
      • can be distinguished by echo and/or cath
  • Coronary artery disease
    • can also present with exertional chest pain, shortness of breath, and fatigue
    • distinguishing factors
      • positive stress testing
      • coronary vessel occlusion and normal pulmonary pressures upon catheterization
  • Liver disease
    • can present with lower extremity swelling and RUQ pain
    • distinguishing factors
      • lack of respiratory symptoms
      • normal JVP
Treatment
  • Management approach
    • as PH is incurable, management is focused on slowing disease progression and alleviating symptoms
    • for PH secondary to other disease (heart, lung, etc…), treat the underlying cause
  • Medical
    • for symptoms
      • oxygen
      • diuretics
      • exercise therapy
    • PH-specific therapies
      • prostacyclin (PGI2)
        • epoprostenol (IV) and iloprost (inhaled)
        • mechanism
          • vasodilation
        • side effects
          • jaw pain and flushing
      • endothelin receptor antagonists (bosentan) 
        • endothelin-1 (ET-1) is a potent vasoconstrictor in the lungs
        • mechanism
          • blocks the ET-1 receptor to decrease vasoconstriction
        • side effects
          • hepatotoxic
      • PDE-5 inhibitors (sildenafil)
        • nitric oxide is a vasodilator
          • PDE-5 helps to break down nitric oxide
        • mechanism
          • blocks PDE-5, increasing NO, and thus vasodilation
        • side effects
          • headache
Complications
  • Cor pulmonale 
    • right-sided congestive heart failure secondary to pulmonary disease
  • Chronic hypoxemic respiratory failure
 

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