87. Pulmonary embolism - classification, etiology, pathogenesis, clinical manifestations.

Pulmonary embolism - classification, etiology, pathogenesis, and clinical manifestations.

Pulmonary embolism is a sudden blockage of a pulmonary artery or its branches, most commonly by a thrombus originating from the deep veins of the legs (deep vein thrombosis —DVT).

Classification

By size and location

By hemodynamic effect

Etiology

Source (most common)

• Deep vein thrombosis (DVT) of lower limbs (femoral, iliac, popliteal veins).

Predisposing factors (Virchow's triad)

Pathogenesis

1. Thrombus forms in systemic veins → dislodges → travels via venous system and right heart → lodges in pulmonary artery.
2. Mechanical obstruction → increased pulmonary vascular resistance → acute pulmonary hypertension → right ventricular strain/failure.
3. Ventilation-perfusion (V/Q) mismatch → areas ventilated but not perfused → hypoxemia.
4. Release of mediators (serotonin, thromboxane) → vasoconstriction → further worsening of V/Q mismatch.

Clinical manifestations

Classic triad

• Sudden dyspnea (most common symptom).
• Pleuritic chest pain (sharp, worse with breathing).
• Hemoptysis (due to pulmonary infarction).

Other symptoms

• Tachypnea (most common sign).
• Tachycardia.
• Syncope (massive PE).
• Hypotension, shock (massive PE).

Signs of DVT

• Swollen, painful leg.
• Calf tenderness (Homan’s sign).

Severe cases

• Cyanosis.
• Distended neck veins.
• Signs of acute right heart failure.