Pulmonary Hypertension Primer

OVERVIEW

  • Pulmonary hypertension is present when mean pulmonary artery pressure exceeds 25 mm Hg at rest or 30 mm Hg with exercise.

CAUSES

  • Mediator induced or hypoxic vasoconstriction
    • Post-transplant
    • ARDS
    • OSA
    • Sepsis
    • Post cardiac surgery
    • Kyphoscoliosis
    • Loss of vascular architecture in chronic lung disease (emphysema, COPD, CF)
  • Obstruction of vessels
    • PA: thromboembolism, vasculitis, mediastinal tumour or fibrosis
    • PV: pulmonary venocclusive disease
  • Acute cardiac conditions
    • Mitral Stenosis or regurgitation
    • VSD
    • LV infarct

PATHOPHYSIOLOGY

  • Cardiac causes
    • LV disease -> ↑ LA pressure -> ↑ pulmonary venous pressure -> ↑ PAP -> ↑PVR
    • L to right shunt will also cause high PVP
  • Respiratory causes
    • Hypoxic vasoconstriction -> PHT
  • Which leads to:
    • Vasoconstriction
    • Altered vascular endothelium and smooth muscle function
    • Cellular remodelling
    • Increased vascular contractility
    • Lack of relaxation in response to various endogenous vasodilators
    • Fibrosis of vascular tissue

HISTORY

  • Progressive SOB
  • Fatigue
  • Chest pain (like angina)
  • Syncope
  • Interrogate for conditions that can produce pulmonary hypertension (murmurs, collagen disease, valve pathology, VTE, OSA, alcohol consumption, chronic respiratory disease)

EXAMINATION

  • Prominent ‘a’ wave
  • Palpable P2
  • Right heart failure – increased JVP, (large V waves), parasternal heave, TR murmur, hepatomegaly, peripherial edema
  • Other signs of CHF
  • Hypoxaemia

DIAGNOSIS

  • Right-heart cath: mean pulmonary artery pressure > 25mmHg @ rest and > 30mmHg with exercise
    • Mild = 25-40mmHg
    • Moderate = 41-55mmHg
    • Severe = > 55mmHg
  • Functional assessment
    • I – no limitation on physical activity (no SOB, fatigue, chest pain or syncope)
    • II – minimal limitation of physical activity (comfortable @ rest, but develop symptoms on normal physical activity)
    • III – marked limitation of physical activity (comfortable @ rest but symptoms on less than normal activity)
    • IV – unable to perform any physical activity, RHF, symptoms @ rest

ADDITIONAL INVESTIGATIONS

  • ECG: RVH, RAD, p-pulmonale, tall R waves in V1, right ventricular strain
  • CXR: RVH on lateral (loss of retrosternal space), prominent pulmonary vascular
  • ECHO: RVH, estimation of PAP
  • Pulmonary function tests
  • DLCO: low
  • ABG
  • V/Q scan
  • High resolution CT: parenchymal disease suspected
  • Serology testing
  • LFT’s – hepatic congestion, end-stage disease
  • iNO provocation test: if lowers PA pressure -> Ca2+ antagonists may be helpful

MANAGEMENT

  • Goals
  1. Optimize PAP
  2. Optimize RV preload
  3. Avoid RV ischemia and failure
  • Chronic Pulmonary Hypertension
    • General:
      • Warfarin: in CTEPH, improved survival, INR 1.5-2.5
      • O2, diuretics, digoxin
      • vaccination to prevent respiratory infections (influenza, pneumococcal)
    • Specific
      • Calcium channel blockers: small proportion of patients respond well
      • Prostanoids: prostacyclin, epoprostenol, treprostinil, inhaled iloprost, beraprost
      • Endothelin receptor antagonists: bosentan
      • Phosphodiesterase inhibitors: ino-dilators, dipyridamole, sildenafil
    • Definitive: lung transplant