Key Points

• Chronic thromboembolic pulmonary hypertension is underdiagnosed and undertreated.
• Pulmonary endarterectomy remains the gold standard treatment in operable patients
• Candidates for pulmonary endarterectomy must have pulmonary vascular obstructive disease with significant hemodynamic and cardiopulmonary impairment.
• Pulmonary endarterectomy must be bilateral, conducted in the plane of the media, and performed under cardiopulmonary bypass with intermittent circulatory arrest.
• Postoperative intensive care is focused on minimizing pulmonary vascular resistance and limiting pulmonary reperfusion edema.

The incidence of pulmonary embolism is unknown, however it is estimated that 600,000 episodes occur annually in the United States, and of these only 150,000 are diagnosed.[1],[2],[3]Clot resolution after anticoagulation therapy is the typical outcome, with minimal residual irregularities or obstructions left within the pulmonary arteries (PAs). However, a small subset of patients will ultimately manifest chronic thromboembolic pulmonary hypertension (CTEPH).[2] The World Health Organization (WHO) classifies pulmonary hypertension (PH) secondary to CTEPH as group IV pulmonary hypertension which is due to the organization of unresolved thromboemboli in the medial layer of the pulmonary arteries, resulting in decreased cross-sectional area and resultant macrovascular obstruction. This results in distal vascular remodeling leading to vasoconstriction and ultimately the elevated PA pressures (mPAP>25mmHg) and right heart strain that characterize CTEPH.[4]

Group IV pulmonary hypertention due to CTEPH is the only type of PH that can potentially be cured with pulmonary thromboendarterectomy surgery (PTE).[5] Studies suggest that anywhere from 0.1% - 4.8% of patients go on to develop CTEPH after acute pulmonary embolism (PE) and up to 10% with recurrent PEs.[6],[7],[8],[9],[10] This means that between 500 and 2500 new cases of CTEPH are generated annually in the United States. Because only 150 to 175 operations are done each year for CTEPH in the United States, this disease appears to be underdiagnosed and undertreated. Risk factors for the development of CTEPH have not been identified, but risk does appear to be increased in patients with prothrombotic states and chronic medical conditions.[11] About 90% of the patients have no detectable coagulation abnormalities; 10% have a lupus anticoagulant, and fewer than 1% have deficiencies of AT3, protein C, or protein S or deficiencies or other abnormalities of factor V Leiden.[12]