Chronic thromboembolic pulmonary hypertension

The blockages either result from organised (or hardened) blood clots that usually originate from the deep veins of the lower limbs of the body (thromboembolism) and lodge in the pulmonary arterial tree after passing through the right side of the heart.

When present, the clinical symptoms of CTEPH may resemble those of acute PE, or of idiopathic pulmonary arterial hypertension (iPAH).

[1][2][3][4][5] Current understanding is that CTEPH is a result of “inflammatory thrombosis”:[5] When pro-thrombotic (blood-clot forming) conditions combine with chronic inflammation and infection, non-resolution of thrombus may ensue.

Risk factors for CTEPH include splenectomy, inflammatory bowel disease, chronic thyroid hormone replacement, blood types other than 0, malignancy, infected ventriculo-atrial shunt and permanent intravenous leads.

The recommended diagnostic algorithm stresses the importance of initial investigation using an echocardiogram and V/Q scan and confirmation with right heart catheter and pulmonary angiography (PA).

[11] Specialist imaging using either magnetic resonance or invasive PA is necessary to determine risks and benefits of interventional treatment with PEA or BPA.

Operability of patients with CTEPH is determined by multiple factors among which surgical accessibility of thrombi and the patient-determined risk-benefit ratio are most important.

There is no haemodynamic (e.g., considering pulmonary pressure) or age threshold that should exclude patients from surgery, and concomitant cardiac procedures can be included if necessary.

[15] In contrast to surgical embolectomy for acute PE, treatment of CTEPH necessitates a true bilateral endarterectomy (removal of blockage from the blood vessels) through the medial layer of the pulmonary arteries, which is performed under deep hypothermia (lowering of body temperature) and circulatory arrest (temporary stoppage of blood flow),[16] which is not complicated by cognitive dysfunction.

[12] The definition of post-PEA PH is still not clear, but some data suggest that 500–590 dynes·s·cm−5 may represent a pulmonary vascular resistance (PVR) threshold for poor long-term outcome.

[20] Although BPA technique is still evolving, it may currently be considered for CTEPH patients who are technically non-operable or carry an unfavourable risk-benefit ratio for PEA.