Fact-sheet: Acute pulmonary thromboembolism


Updated on 11/15/2024 at 5:45 PM

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Definition

Obstruction of one or more pulmonary arteries, most often by a fibrin-cruoric thrombus.
Serious complication of deep vein thrombosis of the lower limbs.

Clinical features

Three highly suggestive presentations:

  • acute dyspnea, of sudden onset +/- signs of right heart failure,
  • pulmonary infarctus: basithoracic pain of pleuritic character +/- hemoptysis,
  • shock state with acute right heart failure

Signs of severity = essentially signs of acute cor pulmonale: tachycardia, hepatojugular reflux, jugular venous distension, arterial hypotension, signs of peripheral shock, repolarization abnormalities, presence of a right bundle branch block, a P wave, a right axis deviation (S1Q3), right ventricular hypertrophy, +/- signs of low cardiac output (drowsiness, lipothymia, or syncope).

Laboratory findings

D-dimers: a low level makes thromboembolic disease highly unlikely, but an elevated level is not conclusive.
Coagulation workup (aPTT, PT-INR): check for the absence of a coagulation disorder, and before starting anticoagulant therapy.
Arterial blood gas: hypoxia and hypocapnia.

Radiography

  • Performed emergently at the patient's bedside.
  • Objectives:
    - Rule out other causes of tachypnea: infectious pneumonia, pneumothorax, or pulmonary sub-edema.
    - Assess the likely diagnostic yield of a ventilation/perfusion scintigraphy.
    - Serves as a baseline for follow-up.
  • Normal in 20% of cases.
  • Signs of right heart involvement: right atrial and right ventricular hypertrophy
  • Dilatation of the pulmonary artery proximal to the arterial obstruction (Fleischner sign).
  • Hypoperfusion (relative hyperlucency) on the side of a massive PE (Westermark sign).
  • Moderate pleural effusion.
  • Pulmonary infarctus image (Hampton's hump).
  • Band atelectasis.

Ultrasound

Transthoracic ultrasound: Assess the hemodynamic impact of the pulmonary embolism.

Signs of acute cor pulmonale:

  • right ventricular dilatation,
  • displacement of the interventricular septum toward the left ventricle,
  • dilatation of the main pulmonary artery.

Rapidly establish the differential diagnosis with: tamponade, aortic dissection, cardiogenic shock.

In 10% of cases it allows visualization of the thrombus in the right heart chambers.

CT

Direct visualization of the intravascular thrombus: central or marginal intravascular hypodensity, surrounded by contrast material, with regular or irregular margins.

Complete obstruction of the artery: intravascular hypodensity occupying the entire arterial lumen.
Parenchymal signs:

  • peripheral areas of consolidation abutting the pleura,
  • subsegmental areas of atelectasis,
  • pleural effusion,
  • triangular peripheral consolidation with a broad pleural base and truncated apex pointing toward the hilum, a typical appearance of pulmonary infarctus,
  • peripheral parenchymal consolidation with a rim-like pattern and central reticulations (early-stage pulmonary infarctus)
  • perfusion defect on the iodine map (dual-energy CT)

Assessment for right ventricular dysfunction, acute cor pulmonale:

  • interventricular septal shift - paradoxical septum,
  • contrast reflux into the IVC,
  • right ventricular dilatation (larger than the left)

MRI

MRI is not routinely used for the diagnosis of pulmonary embolism.
However, T1-weighted morphologic imaging can detect pulmonary infarctus: subpleural parenchymal consolidations with high signal intensity.

This allows differentiation from tumor masses, nonhemorrhagic pneumonia, or ventilatory disorders.

Vascular intervention

X-Ray Angiography of the pulmonary arteries remains the reference standard but is now largely replaced by thoracic CT angiography.

Nuclear medicine

Ventilation-perfusion scintigraphy: Typically, decreased uptake on perfusion scintigraphy with normal ventilation scintigraphy in the same area.

Management

Hospitalization
Oxygen therapy
Intravenous or subcutaneous anticoagulation with heparin or LMWH at a therapeutic dose, with transition to a VKA within 7 days.
If the pulmonary embolism is severe with a life-threatening risk, intravenous thrombolysis should be considered.

In case of contraindication to or failure of thrombolysis, as a last resort, surgical rescue thrombectomy may be considered via sternotomy under cardiopulmonary bypass.
Preventive treatment: early mobilization after surgery or childbirth to prevent deep vein thrombosis; compression of the lower limbs with compression stockings.

Differential diagnosis

  • Pulmonary artery sarcoma
  • Myocardial infarction
  • Emotional hyperventilation
  • Asthma
  • Atelectasis
  • Pneumothorax
  • Aortic dissecting aneurysm
  • Pleural effusion
  • Pulmonary carcinomatosis