Pulmonary Hypertension

PH Fundamentals - Pressure Cooker Lungs

⭐ The 2018 World Symposium on PH updated the hemodynamic definition of PH to a mean pulmonary arterial pressure (mPAP) > 20 mmHg at rest.

• Hemodynamic Criteria:
  • $mPAP > \textbf{20} mmHg$ (defines PH, as per above)
  • For pre-capillary PH: $PAWP \le \textbf{15} mmHg$ & $PVR \ge \textbf{3} \text{ Wood units}$
• Consequence: $\uparrow$ Right Ventricular (RV) afterload $\rightarrow$ RV dysfunction.
• WHO Classification (5 Groups):
  • Gr 1: Pulmonary Arterial Hypertension (PAH) (Idiopathic, heritable, drug/toxin-induced)
  • Gr 2: PH due to Left Heart Disease (LHD) - most common
  • Gr 3: PH due to Lung Diseases/Hypoxia (COPD, ILD, OSA)
  • Gr 4: Chronic Thromboembolic PH (CTEPH) & other pulmonary artery obstructions
  • Gr 5: PH with unclear/multifactorial mechanisms (e.g., sarcoidosis)
• Pathophysiology Triad: Vasoconstriction, vascular proliferation/remodeling, in-situ thrombosis.

Etiology Unmasked - Tiny Troublemakers

• Congenital Heart Disease (CHD)-Associated (APAH-CHD): Most common pediatric cause.
  • Systemic-to-pulmonary shunts (VSD, ASD, PDA) → ↑pulmonary blood flow & pressure.

  ⭐ Eisenmenger syndrome represents the most severe form of pulmonary arterial hypertension associated with congenital heart disease, characterized by a reversed (right-to-left) shunt and cyanosis.

• Persistent Pulmonary Hypertension of Newborn (PPHN):
  • Failure of normal postnatal circulatory transition.
  • Key triggers: Meconium aspiration, RDS, sepsis, diaphragmatic hernia.
• Idiopathic PAH (IPAH): No identifiable cause.
• Other Significant Factors:
  • Genetic predispositions (e.g., BMPR2 mutations).
  • Chronic lung diseases (e.g., BPD, interstitial lung disease).
  • Pulmonary Veno-occlusive Disease (PVOD) / Pulmonary Capillary Hemangiomatosis (PCH) - rare.

Clinical Clues - Huffy Puffy Hearts

• Presenting Features (The "Puffs"):

  • Dyspnea: Exertional, progressing to rest.
  • Fatigue, poor exercise tolerance.
  • Infants: Tachypnea, poor feeding, failure to thrive (FTT).
  • Syncope or dizziness, particularly with exertion.
  • Chest pain (angina-like), palpitations may occur.

• Cardiac Clues (The "Huffy Heart"):

  • Loud, palpable P2 (pulmonic S2).
  • Right ventricular (RV) lift/heave.
  • Murmurs:
    • Tricuspid regurgitation (TR).
    • Pulmonary regurgitation (PR - Graham Steell).
  • RV failure signs (late): Hepatomegaly, edema, ascites.

• Key Diagnostic Pointers:

  • ECG: RVH (e.g., tall R V1), RAD, P pulmonale.
  • CXR: Prominent main PA, RV enlargement, peripheral oligemia.
  • 

  • ⭐ Echocardiography is the primary non-invasive screening tool for PH, estimating pulmonary artery systolic pressure (PASP) via the tricuspid regurgitation jet velocity.

  • RHC: Gold standard. Confirms mPAP ≥ 25 mmHg at rest.

Management Maneuvers - Easing the Squeeze

• General Measures: Oxygen ($SpO_2$ > 92%); Diuretics (RV failure); Anticoagulation (IPAH/HPAH, Warfarin INR 2-3); Avoid triggers (high altitude); Vaccinate.
• Acute Vasoreactivity Testing (AVT): During RHC for IPAH. Uses iNO, IV epoprostenol/adenosine. Positive test predicts CCB response.

  ⭐ Acute vasoreactivity testing during right heart catheterization is crucial in idiopathic PAH to identify patients who may respond to long-term calcium channel blocker therapy.

• Targeted Pharmacotherapy:
  • CCBs (if AVT positive): High-dose Nifedipine, Diltiazem, Amlodipine.
  • If AVT negative or CCB failure (PAH-specific drugs):
    • ERAs: Bosentan, Ambrisentan, Macitentan. ⚠️ Hepatotoxicity, Teratogenic.
    • PDE-5 Inhibitors: Sildenafil, Tadalafil.
    • Prostacyclin Pathway Agonists: Epoprostenol (IV), Treprostinil, Iloprost (inhaled).
    • sGC Stimulators: Riociguat. ⚠️ Teratogenic, Hypotension.
• Combination Therapy: Frequently required for optimal outcomes.
• Interventional/Surgical: Atrial Septostomy (palliative); Lung Transplant (refractory PAH); PTE (for CTEPH).

High‑Yield Points - ⚡ Biggest Takeaways

• Pulmonary Hypertension (PHT): Mean PAP ≥ 25 mmHg at rest.
• Most common cause in children: Congenital Heart Disease (CHD) with L-R shunts.
• Eisenmenger syndrome: Irreversible PHT, shunt reversal, cyanosis.
• Clinical signs: Loud P2, RV heave, exertional dyspnea.
• Gold standard diagnosis: Right heart catheterization for confirmation and severity.
• Management: Treat cause, O2, targeted therapy (e.g., sildenafil, bosentan).
• Idiopathic PHT and Eisenmenger have poor prognosis.