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CTEPH


CTEPH: an introduction


CTEPH is an increasingly recognised, potentially curable form of PH. Andrew Hirsch introduces this notoriously underdiagnosed condition


Andrew Hirsch MD Associate Professor of Medicine McGill University Division of Pulmonary Disease Jewish General Hospital Montreal, Quebec


Once considered an autopsy curiosity, chronic thromboembolic pulmonary hypertension (CTEPH) is an increasingly recognisable, treatable and potentially curable form of PH. It is defined as mean pulmonary arterial pressure (PAP) greater than 25, with a pulmonary capillary wedge pressure (PCWP) less than 15 in the setting of chronic large vessel vascular obstruction documented on imaging (ventilation perfusion (V/Q), computed tomography angiography (CTA) or angiography) despite an adequate period of anticoagulation.1


CTEPH is notoriously


underdiagnosed, and its true incidence and prevalence remains unknown. Acute pulmonary embolism (PE) is thought to be the initiating factor in the vast majority of cases, although the initial event may be asymptomatic, and remain untreated. Incomplete fibrinolysis results in progressive intraluminal thrombus formation and vascular obstruction. Another component of the disease seems to be the development of progressive small vessel pulmonary arteriopathy in the non-obstructed vascular bed. If untreated, this combination of large- vessel mechanical obstruction and small-vessel vasculopathy results in worsening PH, relentless right ventricular dysfunction and can eventually culminate in death.


Epidemiology


The true incidence of CTEPH remains unknown. In the past, it was felt between 0.1 and 0.5% of patients post-acute PE


developed this disease. In more recent series, the incidence seems to be higher and Pengo et al found an incidence of 3.8% after acute PE developed by two years. There seemed to be a plateau at that time, and no other cases developed if it did not occur by two years.2


Other


Echocardiographic evidence of PH post-PE is also extremely common. Stevinson showed 40% of patients post-acute PE had echocardiograph evidence of PH at six months.4


Only a


small percentage of patients with chronic vascular obstruction on imaging, and echocardiograph evidence of PH develop the clinical syndrome of CTEPH leading one to wonder if it is the end of a


series of non-resolution of acute PE show incomplete clot resolution is extremely common, with V/Q scans remaining abnormal in up to 50% of cases at one year.3


spectrum of incomplete clot resolution after acute PE.


Risk factors


Which patients will develop CTEPH after an acute PE is difficult to determine, but there does appear to be a certain risk profile with an increased risk. Antiphospholipid antibodies are present in 10–20% of patients with CTEPH.5 Large clot burden on initial PE, PH on initial PE, splenectomy, inflammatory states and abnormalities in fibrinolysis may all play a role in determining which patients post PE are at highest risk of developing CTEPH.6


Clinical presentation


Patients with CTEPH have a relatively non-specific presentation, which is why there is often a prolonged period between


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