• A normal V/Q scan (ventilation/perfusion scintigraphy) can rule out CTEPH.

• Typical signs of CTEPH are partially or completely occluded pulmonary arteries, wall thickening, and intravascular bands

Pulmonary hypertension is characterized by elevated pressure in the pulmonary arteries. The non-specific cardiovascular and respiratory symptoms include dyspnea on exertion, fatigue, chest pain, and syncope.

The clinical classification of pulmonary hypertension is based on its etiology. When it is induced by persisting pulmonary artery obstructions after a pulmonary embolus, it is classified as group 4 = chronic thromboembolic pulmonary hypertension (CTEPH).

CTEPH is a rare and progressive form of pulmonary hypertension. It results from chronic thromboembolic material in the lung arteries, intimal fibrosis, and fibromuscular proliferation. If untreated, CTEPH can be fatal.

Registry data from the US and Europe show: 12-25 percent of diagnosed CTEPH patients do not report a history of acute thromboembolic disease (Pepke-Zaba et al.; Kerr et al.)

First Choice: V/Q Scan for Ventilation and Perfusion

Who should be screened for CTEPH?

• Acute pulmonary embolism patients with persistent cardio-pulmonary symptoms after 3 months of anticoagulation (Simoneau et al. 2017)
• All patients with pulmonary hypertension (Galiè et al. 2015)
• Patients with unexplained exertional dyspnea without evident cardiopulmonary pathology (Auger et al. 2012)

If echocardiography shows high or intermediate probability of pulmonary hypertension, a V/Q scan (ventilation/perfusion scintigraphy) should be considered. A normal V/Q scan can rule out CTEPH. If the V/Q scan is abnormal, the patient should be referred to an expert center for pulmonary hypertension.

Typical CTEPH appearance in V/Q scans: normal ventilation with perfusion defects.

Diagnostic Tools – Non-Imaging

Blood and immunological tests are not useful for diagnosing pulmonary hypertension, but they can reveal underlying conditions.

In pulmonary function tests, most patients with pulmonary arterial hypertension have a mild restrictive component.

Cardiopulmonary exercise testing can quantify the degree of relative hypoperfusion of the lung and the systemic circulation during exercise. Thereby, it may help grading the severity of exercise limitation and document treatment response.

CT in CTEPH

Computed tomography reliably demonstrates cardiac and vascular changes related to pulmonary hypertension. It can identify parenchymal lung diseases.

Typical signs of CTEPH are

• partially or completely occluded arteries
• vessel wall thickening
• lucent intravascular lines (bands)

Mosaic perfusion of the lungs is also more often seen in CTEPH than in other types of pulmonary hypertension.

Parenchymal densities and transpleural collaterals can occur in CTEPH.

Single energy CT versus DECT

Compared to single energy CT, dual energy CT (DECT) has advantages, says Digumarthy:

• monochromatic images possible
• material decomposition (iodine / H2O)
• better contrast resolution by reconstructing images of lower energy
• additional information on perfusion in the lobes by using iodine concentration and distribution
• lower contrast medium volume needed
• virtual non-contrast images can be calculated by artificial iodine subtraction

Pulmonary Thromboendarterectomy

Pulmonary thromboendarterectomy is the preferred and potentially curative option for CTEPH patients, says Digumarthy. It involves the careful removal of chronic thrombotic material, thickened intima, and associated fibrous material.

References

1. Auger WR et al. Evaluation of patients with chronic thromboembolic pulmonary hypertension for pulmonary endarterectomy. Pulm Circ 2012:2:155-62.
https://dx.doi.org/10.4103%2F2045-8932.97594

2. Galiè N et al. 2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Heart J 2016;37:67-119.
https://doi.org/10.1093/eurheartj/ehv317

3. Kerr KM et al. Results From the United States Chronic Thromboembolic Pulmonary Hypertension Registry. Chest 2021:S0012-3692(21)01083-7.
https://doi.org/10.1016/j.chest.2021.05.052

4. Pepke-Zaba J et al. Chronic thromboembolic pulmonary hypertension (CTEPH): results from an international prospective registry. Circulation 2011;124:1973-81.
https://doi.org/10.1161/circulationaha.110.015008

5. Simonneau G et al. The pathophysiology of chronic thromboembolic pulmonary hypertension. Eur Respir Rev 2017:26:160112.
https://doi.org/10.1183/16000617.0112-2016