Introduction

Chronic thromboembolic pulmonary hypertension (CTEPH) is a disease process that develops in 3% to 4% of patients who sustain an acute pulmonary embolism. The process is principally one of organization of thromboembolic material producing an obstructive vasculopathy in the pulmonary vascular bed. The principles of critical care management are similar to any patient with impaired right ventricular (RV) function and pulmonary hypertension. Pulmonary endarterectomy (PEA) is now established as the definitive treatment.

Pathophysiology and natural history

The mechanisms that underlie this process are incompletely understood but may involve:

1. • in situ propagation of thrombus;

2. • recurrent embolism;

3. • organization of thrombus; or

4. • a secondary obstructive vasculopathy of the pulmonary vascular bed unaffected by embolism itself.

Risk factors for progression to CTEPH include anticardiolipin antibody syndrome, elevated factor VIII levels and splenectomy. Interestingly, other procoagulant states have not been shown to be associated with CTEPH.

The fundamental physiological abnormalities are RV ‘pressure overload’ and disruption of normal ventilation–perfusion matching. The disease may then progress to RV failure and impairment of gas exchange. This is gradual and initially manifests during exercise, but tends to progress to severely limit the patient, even at rest. As with other forms of pulmonary hypertension, CTEPH confers a poor prognosis when severe.