CTEPH (Chronic Thromboembolic Pulmonary Hypertension)

What CTEPH Is

CTEPH, or chronic thromboembolic pulmonary hypertension, is a specific form of pulmonary hypertension caused by blood clots in the lungs that do not fully resolve. Instead of dissolving over time, as most clots eventually do, the clot material organizes into firm, fibrotic tissue that permanently narrows or blocks segments of the pulmonary arteries.

This obstruction forces the right side of the heart to generate higher pressure to push blood through the lungs. Over months to years, that added workload raises pressure in the pulmonary arteries and can progressively strain the right ventricle if the underlying obstruction is not addressed.

How CTEPH Differs From Other Forms of Pulmonary Hypertension

Pulmonary hypertension is not a single disease. It is organized into five World Health Organization groups based on the underlying cause, and CTEPH occupies its own distinct category, WHO group 4.

CTEPH vs. Group 1 Pulmonary Arterial Hypertension

CTEPH vs. Group 1 Pulmonary Arterial Hypertension

Dimension	CTEPH (WHO Group 4)	Pulmonary Arterial Hypertension (WHO Group 1)
Underlying Mechanism	Mechanical obstruction of the pulmonary arteries by unresolved, organized clot material	Abnormal remodeling and narrowing of the small pulmonary arteries themselves
Typical Trigger	Often follows one or more pulmonary embolism events, though not always a recognized one	Connective tissue disease, certain medications or toxins, congenital heart disease, or an idiopathic process with no identified trigger
Key Diagnostic Test	Ventilation-perfusion (V/Q) scan to identify mismatched perfusion defects	Right heart catheterization plus a workup to identify or exclude an underlying associated condition
Potentially Curative Surgery	Yes, pulmonary endarterectomy can be curative for operable disease	No curative surgical option exists
Other Treatment Options	Balloon pulmonary angioplasty and riociguat for inoperable or residual disease, plus lifelong anticoagulation	Pulmonary vasodilator medications targeting specific disease pathways

This is why CTEPH is caused by unresolved blood clots that organize into fibrotic material obstructing the pulmonary arteries, rather than by the type of abnormal small-vessel remodeling seen in group 1 disease. Many patients with CTEPH have had a prior, clearly diagnosed pulmonary embolism, but not everyone does. A meaningful number of patients have no recalled or documented prior clot event, which likely reflects an initial episode that was silent or mild enough that it was never formally identified at the time.

Who Develops CTEPH

The most recognized risk factor for CTEPH is a prior pulmonary embolism. CTEPH develops in a small but clinically important percentage of patients following an acute pulmonary embolism, and a history of multiple or recurrent thromboembolic events appears to further raise that risk compared with a single isolated clot. Underlying conditions that increase clot burden or impair the body’s normal ability to resolve clots, including certain hematologic and autoimmune conditions, can also contribute. Prior splenectomy has been associated with increased risk in some studies, though the reason for this association is not fully established.

Because a meaningful proportion of patients diagnosed with CTEPH have no clear history of a prior clot event, the absence of a known pulmonary embolism does not rule out the diagnosis in someone with otherwise unexplained pulmonary hypertension.

Symptoms

The symptoms of CTEPH are often nonspecific and develop gradually, which is a major reason the condition is frequently diagnosed later than would be ideal. Shortness of breath with exertion is the most common presenting symptom, typically starting subtly and worsening over months. Reduced exercise tolerance and fatigue often accompany it.

As pulmonary pressures rise further, additional symptoms can develop, including lightheadedness or fainting with exertion, chest discomfort, and, as right heart strain progresses, swelling in the legs or abdomen. Persistent breathlessness or reduced exercise capacity that continues for months after an acute pulmonary embolism, sometimes referred to as post-PE syndrome, is a particularly important symptom pattern to recognize, since it can be an early sign of CTEPH.

How CTEPH Is Diagnosed

Because CTEPH is treatable, and potentially curable, in a way that most other forms of pulmonary hypertension are not, confirming or excluding the diagnosis is an important step for anyone found to have unexplained pulmonary hypertension.

The Diagnostic Pathway

1. 01→Ventilation-Perfusion (V/Q) ScanThe key screening test for CTEPH. It compares patterns of airflow and blood flow in the lungs and can reveal mismatched perfusion defects, segments with normal airflow but reduced blood flow, that are characteristic of chronic clot obstruction. A V/Q scan is generally more sensitive for this purpose than a standard chest CT and is recommended in anyone with unexplained pulmonary hypertension.↓
2. 02Right Heart CatheterizationDirectly measures pressures within the pulmonary arteries and the right side of the heart, confirming the presence of pulmonary hypertension and helping grade its severity. It also provides hemodynamic information that is important for treatment planning.↓
3. 03→CT Pulmonary AngiographyDetailed imaging of the pulmonary arteries that helps map the location and extent of obstructing material. This information, along with conventional pulmonary angiography when needed, is used by the surgical team to help determine whether disease is surgically accessible.↓
4. 04Multidisciplinary CTEPH Team AssessmentBecause operability depends on the specific location and extent of disease as well as overall surgical risk, an experienced multidisciplinary team, rather than imaging findings alone, determines whether a patient is a candidate for pulmonary endarterectomy or is better suited to other treatment approaches.

Right heart catheterization. Beyond confirming and grading pulmonary hypertension, this test provides detailed hemodynamic measurements that help guide treatment decisions and monitor response over time.

Pulmonary function testing and DLCO. These tests help evaluate overall respiratory function and can help identify or exclude coexisting lung disease that might contribute to shortness of breath alongside CTEPH.

Treatment

CTEPH is distinct among the pulmonary hypertension groups because it offers the possibility of a curative treatment for eligible patients, alongside effective options for those who are not surgical candidates.

Pulmonary endarterectomy. For patients whose disease is assessed as surgically accessible, pulmonary endarterectomy, a specialized open-heart surgery that removes the obstructing, organized clot material from the pulmonary arteries, can be curative or near-curative. It is performed at a limited number of expert centers given how technically demanding the procedure is, and eligibility is determined by an experienced surgical team rather than by imaging findings alone.

Balloon pulmonary angioplasty. For patients who are not surgical candidates, or who have residual or persistent pulmonary hypertension after pulmonary endarterectomy, balloon pulmonary angioplasty is a catheter-based procedure that opens obstructed pulmonary artery segments. It is typically performed as a series of staged sessions at centers with specific CTEPH expertise.

Riociguat. An FDA-approved oral medication for inoperable CTEPH and for persistent or recurrent pulmonary hypertension after surgery. It works as a soluble guanylate cyclase stimulator and has been shown to improve exercise capacity and reduce pulmonary vascular resistance. Monitoring for side effects, including low blood pressure, is part of ongoing management, and it cannot be combined with certain other medication classes.

Lifelong anticoagulation. Blood thinning medication is continued indefinitely in essentially all patients with CTEPH, including those who undergo surgery, because the underlying tendency toward clot formation or impaired clot resolution persists. This reduces the risk of new or recurrent thromboembolic events that could cause further pulmonary artery obstruction.

When to Seek Evaluation

Evaluation for possible CTEPH is reasonable for anyone with unexplained shortness of breath or reduced exercise tolerance that persists for months after an acute pulmonary embolism, for anyone found to have pulmonary hypertension of unclear cause, and for anyone with symptoms suggestive of right heart strain in the setting of a prior clotting history. Because CTEPH is one of the few causes of pulmonary hypertension that can potentially be cured with surgery, prompt evaluation and, when appropriate, referral to an expert center can meaningfully change the range of treatment options available.

For patients in the North Dallas-Fort Worth area, the pulmonary team at VitalAir Sleep & Lung Center in Frisco, Texas offers evaluation for unexplained shortness of breath and pulmonary hypertension of uncertain cause, which can be an appropriate starting point when CTEPH is a consideration and can help coordinate referral to an expert CTEPH surgical center when indicated.