Diagnosis and Understanding Your Tests for CTEPH

Navigating the diagnosis of CTEPH requires specific tests that go beyond the standard workup for heart or lung issues. To confirm CTEPH, doctors must prove two things: that there are physical blockages in the lung’s arteries, and that these blockages are causing high blood pressure in the lungs—all while the patient has been on blood thinners for at least 3 months ^[1].

The Gold Standard Screening: The V/Q Scan

While a CT scan is often the first test used when someone has trouble breathing, it is not the best tool for spotting CTEPH. The Ventilation/Perfusion (V/Q) Scan is the preferred initial screening test ^[2][3].

A V/Q scan compares how air moves in your lungs (ventilation) to how blood flows through them (perfusion). In a patient with CTEPH, the report will often show “mismatched perfusion defects.” This means that while air is reaching certain parts of the lung, the blood flow is blocked by old scar tissue ^[4][3]. Because V/Q scans are more sensitive than standard CT scans for this specific condition, a “normal” V/Q scan is often enough to rule out CTEPH entirely ^[5][6].

Confirming the Pressures: Right Heart Catheterization

If your screening tests suggest CTEPH, you will need a Right Heart Catheterization (RHC). This is a procedure where a thin tube (catheter) is guided into a vein, through the right side of your heart, and into the pulmonary arteries to measure pressures and blood flow directly ^[4].

According to the 2022 ESC/ERS guidelines, a diagnosis of CTEPH is confirmed when the RHC shows these three specific values ^[1][7]:

• mPAP (Mean Pulmonary Artery Pressure): Greater than 20 mmHg. (Note: This threshold was lowered from 25 mmHg in 2022 to catch the disease earlier) ^[7].
• PAWP (Pulmonary Arterial Wedge Pressure): Less than or equal to 15 mmHg. This ensures the high pressure is coming from the lung’s arteries, not from a problem with the left side of the heart ^[1].
• PVR (Pulmonary Vascular Resistance): Greater than 2 Wood units (WU). This measures how much “push back” the heart feels from the lung’s vessels ^[7].

Seeing the Damage: CTPA and Angiography

Once the high pressure is confirmed, doctors use CT Pulmonary Angiography (CTPA) or Digital Subtraction Angiography (DSA) to map out exactly where the scars are located. These tests look for specific signs of chronic disease, such as “webs” (thin strings of tissue), “bands,” or “eccentric thickening” (narrowing of the vessel walls) ^[4][8]. These maps are essential for the surgical team to decide if the blockages can be removed.

Your Diagnostic Checklist

To ensure a complete and accurate diagnosis, you should confirm that these steps have been completed:

1. 3 Months of Anticoagulation: You have been on blood thinners for at least 3 months to see if the clots dissolve naturally ^[1].
2. V/Q Scan: To screen for mismatched blood flow defects ^[2].
3. Right Heart Catheterization: To get precise pressure measurements (mPAP, PAWP, and PVR) ^[4].
4. Advanced Imaging (CTPA/DSA): To visualize the “webs and bands” for treatment planning ^[4].
5. Expert Review: Your results should be reviewed by a multidisciplinary team at a specialized CTEPH center ^[9].