Pulmonary Vascular Diseases

Pulmonary Embolism - Clot Shot Chaos

• Pathophysiology: Virchow's triad (stasis, hypercoagulability, endothelial injury) → DVT → PE.
• Risk Factors: Immobility, surgery, malignancy, OCPs, pregnancy, thrombophilia.
• Clinical: Sudden dyspnea, pleuritic chest pain. D-dimer: Rules out PE if low pre-test probability (Wells/Geneva).
• Imaging Modalities:
  • CT Pulmonary Angiography (CTPA) - Gold Standard:
    • Direct: Filling defects (central, mural, complete), polo mint, railway track.
    • Indirect: RV strain (RV/LV >1), septal bowing.
  • V/Q Scan:
    • Indications: CTPA contraindicated (contrast allergy, renal failure, pregnancy).
    • Finding: Mismatched perfusion defects (high probability).
  • Chest X-ray (CXR):
    • Often normal. Classic (rare) signs: 📌 WHALES (Westermark, Hampton's, Atelectasis, Low-grade fever, Effusion, Normal).
    • Key signs: Westermark (oligemia), Hampton's hump (wedge opacity).

⭐ A normal chest X-ray is common in patients with pulmonary embolism, but specific signs like Westermark's sign or Hampton's hump, though infrequent, are highly suggestive.

Pulmonary Hypertension - Pressure Cooker Pipes

Defined by mean pulmonary arterial pressure (mPAP) > 20 mmHg at rest. Echocardiography is the initial screening tool.

• WHO Classification of PH (Groups 1-5):

  Group	Type	Key Examples/Etiologies
  1	Pulmonary Arterial Hypertension (PAH)	IPAH, CTD-associated
  2	PH due to Left Heart Disease	LV dysfunction, Valvular disease
  3	PH due to Lung Diseases/Hypoxia	COPD, ILD, OSA
  4	Chronic Thromboembolic PH (CTEPH)	Chronic thromboemboli
  5	PH with Unclear/Multifactorial Mechanisms	Sarcoidosis, Hematologic disorders

• Imaging Findings:

  • CXR: Enlarged central pulmonary arteries, peripheral 'pruning' of vessels, right ventricular enlargement/cardiomegaly, prominent right atrium.

  • CT:

    • Main Pulmonary Artery (MPA) diameter > 29 mm or MPA diameter > ascending aorta diameter.
    • Right Ventricular (RV) hypertrophy (wall thickness > 4mm).
    • RV dilatation (RV/LV diameter ratio > 1).
    • Interventricular septum flattening/bowing into LV.
    • Mosaic attenuation pattern in lung parenchyma.

    ⭐ On CT, a main pulmonary artery diameter greater than 29 mm or exceeding the diameter of the adjacent ascending aorta are key indicators of pulmonary hypertension.

Other Vascular Lesions - Twisted Tubes Terrors

• Pulmonary Artery Aneurysms & Pseudoaneurysms
  • Aneurysm: true (all layers); Pseudo: contained rupture.
  • Causes: Behçet's, infections (Rasmussen’s-TB), iatrogenic, congenital, trauma.
  • Imaging: CTA key.
• Pulmonary Arteriovenous Malformations (PAVMs)
  • Abnormal PA-PV connection (direct shunt).
  • Mostly congenital; strong HHT/Osler-Weber-Rendu link. 📌 HHT: Telangiectasias, AVMs, Epistaxis, Family Hx.
  • Complications: Paradoxical emboli (stroke, brain abscess), hypoxemia.
  • Imaging:
    • CXR: Round/oval opacity, feeding artery & draining vein.
    • CT: Enhancing nidus, feeding artery, draining vein.

  ⭐ The majority of pulmonary arteriovenous malformations (PAVMs) are congenital and are found in approximately 15-30% of patients with Hereditary Hemorrhagic Telangiectasia (HHT).

• Pulmonary Vasculitides (Radiological Focus)
  • Large Vessel (Takayasu): PA stenosis/occlusion, aneurysms.
  • ANCA-assoc. Small Vessel:
    • GPA (Wegener's): Nodules, cavitations, DAH.
    • MPA: DAH, GGOs.

High‑Yield Points - ⚡ Biggest Takeaways

• CTPA is gold standard for Pulmonary Embolism (PE) diagnosis.
• PE X-ray signs: Westermark sign, Hampton's hump, Palla's sign.
• Pulmonary Arterial Hypertension (PAH): Main PA diameter >29 mm, RV hypertrophy.
• Pulmonary Venous Hypertension: Cephalization, Kerley B lines, bat-wing edema.
• Pulmonary AVMs: Congenital nodules with feeding artery & draining vein.
• CTEPH: Mosaic attenuation, webs/bands, post-PE complication_._