Chronic thromboembolic pulmonary hypertension: do we need a new definition?

Chronic thromboembolic pulmonary hypertension (CTEPH) is the end result of persistent obstruction of the pulmonary arteries following episodes of acute and/or recurrent pulmonary emboli [1]. Pulmonary hypertension probably stems from a smaller pulmonary arterial cross sectional area due to thrombus organisation and a redistribution of blood flow through the patent pulmonary arterial bed producing an additional microvasculopathy [2]. Consequently many patients develop pulmonary hypertension despite adequate anticoagulation [3]. Once pulmonary hypertension occurs, the prognosis is poor due to right heart failure with a survival similar to other forms of pre-capillary pulmonary hypertension [4]. Patients suffering from CTEPH typically present with progressive dyspnoea that worsens over a period of months to years [5]. Dyspnoea is related to hypoxaemia, dead space ventilation and right heart dysfunction, severely affecting the quality of life [6, 7].