Pulmonary Vascular Diseases

Pulmonary Hypertension - Pressure Cooker Lungs

• Definition: Mean Pulmonary Arterial Pressure (mPAP) > 20 mmHg at rest, confirmed by Right Heart Catheterization (RHC). Pulmonary Vascular Resistance (PVR) > 3 Wood units is also significant. $PVR = (mPAP - PAWP) / CO$.

• Pathophysiology: Vasoconstriction, vascular remodeling (medial hypertrophy, intimal proliferation, fibrosis), in-situ thrombosis, inflammation.

• Symptoms: Progressive dyspnea (most common), fatigue, exertional chest pain, lightheadedness, syncope.

• Signs: Loud P2 (often palpable), RV heave/lift, tricuspid regurgitation murmur, ↑JVP (prominent 'a' or 'v' waves), hepatomegaly, peripheral edema, ascites.

• WHO Classification (Simplified):

  Group	Category	Key Examples
  1	Pulmonary Arterial Hypertension (PAH)	Idiopathic (IPAH), Heritable, CTD-PAH, Drug-induced
  2	PH due to Left Heart Disease (LHD)	HFrEF, HFpEF, Valvular heart disease
  3	PH due to Lung Diseases &/or Hypoxia	COPD, ILD, Sleep-disordered breathing, Alveolar hypoventilation
  4	PH due to PA Obstructions (CTEPH)	Chronic Thromboembolic Pulmonary Hypertension
  5	PH with Unclear/Multifactorial Mechanisms	Hematologic, Systemic, Metabolic disorders, Misc.

• Simplified Diagnostic Algorithm:

• Key Investigations: ECG (RV hypertrophy/strain, RAE), CXR (enlarged PAs, RVH), Echocardiogram (initial non-invasive screening & PAP estimation), RHC (gold standard for diagnosis, severity & vasoreactivity), V/Q scan (essential to rule out CTEPH), PFTs, HRCT chest.

• Management Goals:

  • Treat underlying cause (e.g., LHD, lung disease).
  • Supportive therapy: Oxygen (if hypoxic), diuretics (for RV failure), anticoagulation (esp. IPAH, HPAH, CTEPH).
  • Targeted therapies (primarily for PAH Group 1): Prostanoids (e.g., epoprostenol), Endothelin Receptor Antagonists (ERAs, e.g., bosentan, ambrisentan), PDE5 inhibitors (e.g., sildenafil, tadalafil), soluble Guanylate Cyclase (sGC) stimulators (e.g., riociguat).

⭐ Right Heart Catheterization (RHC) is mandatory for the diagnosis of pulmonary hypertension and to guide therapy, especially in PAH (Group 1).

Pulmonary Embolism - Clot on the Block

Thrombus obstructs pulmonary artery. Pathophys: Virchow's Triad (endothelial injury, stasis, hypercoagulability).

• Risk Factors: Prior VTE, surgery (ortho), cancer, immobility, OCPs/HRT, pregnancy, thrombophilias (Factor V Leiden).
• Features: Sudden dyspnea, pleuritic pain, cough, hemoptysis. Signs: tachypnea, tachycardia, DVT signs; hypotension (massive PE).
• Diagnosis:
  • Wells' Score (PE likely >4):

    Criteria	Pts
    DVT signs	3
    PE #1 Dx	3
    HR >100	1.5
    Immob/Surg <4wk	1.5
    Prev DVT/PE	1.5
    Hemoptysis	1
    Malignancy	1

  • D-dimer (rules out in low prob.), CTPA (gold standard), V/Q scan (if CTPA C/I).
  • ECG: S1Q3T3 (📌), RBBB, sinus tachy. CXR: Often normal; Westermark sign, Hampton's hump.

• Management:
  • Supportive: O2, fluids/pressors.
  • Anticoagulation: LMWH/UFH then DOACs/VKA (≥3 months).
  • Thrombolysis (alteplase): For massive PE.
  • Catheter-directed therapy/embolectomy: Severe cases. IVC filter if anticoagulation C/I.

⭐ The S1Q3T3 pattern on ECG, though classic, is neither sensitive nor specific for pulmonary embolism.

Cor Pulmonale & CTEPH - Right Heart's Burden

• Cor Pulmonale: RV hypertrophy/dilation from lung structure/function diseases or pulmonary vasculature (excludes LHD).
  • Causes: COPD (most common), ILD, cystic fibrosis, severe kyphoscoliosis, chronic PE, primary PH.
  • Pathophysiology: Pulmonary hypertension → ↑RV afterload → RV dysfunction.
  • Clinical Features: Underlying lung disease symptoms + dyspnea, fatigue, exertional syncope, peripheral edema, ascites, JVD, loud P2, RV heave, tricuspid regurgitation.
• CTEPH (Chronic Thromboembolic Pulmonary Hypertension): PH Group 4; unresolved PE leads to obstruction.
  • Diagnosis: V/Q scan (key screening: mismatched perfusion defects); confirm: RHC, CTPA, pulmonary angiography.
  • Management:
    • Lifelong anticoagulation.
    • Pulmonary Endarterectomy (PEA) - potentially curative if eligible.
    • Balloon Pulmonary Angioplasty (BPA) - for non-operable distal disease.
    • Medical: Riociguat.

  ⭐ Pulmonary endarterectomy (PEA) is the treatment of choice and offers a potential cure for eligible patients with CTEPH.

High‑Yield Points - ⚡ Biggest Takeaways

• Pulmonary Embolism (PE): CTPA for diagnosis; anticoagulation for treatment. Wells score stratifies risk.
• Pulmonary Arterial Hypertension (PAH): Mean PAP ≥25 mmHg; right heart catheterization for diagnosis.
• Cor Pulmonale: RV failure from chronic lung disease, typically COPD.
• Fat Embolism Syndrome: Triad: respiratory distress, neurological deficits, petechial rash post-trauma.
• Massive PE: Presents with hypotension; requires thrombolysis or embolectomy.
• D-dimer: High negative predictive value helps exclude PE in low-risk individuals.