Who needs an evaluation
Evaluation for CTEPH should be performed in the following cases:
- Patients who have had an acute pulmonary embolism (PE) but continue to complain of dyspnea.
- All patients with diagnosed pulmonary hypertension if they have a history of PE episodes or if the cause of hypertension remains unclear.
It is important to consider that patients with recurrent PE may simultaneously exhibit signs of both acute and chronic pathology.
Imaging Methods
A comprehensive set of methods is used to diagnose and assess the pulmonary vascular bed:
- Ventilation-perfusion (V/Q) scintigraphy: Serves as the screening method of choice. If the perfusion scan is normal, the diagnosis of CTEPH is reliably excluded. Multiple bilateral segmental defects indicate a chronic process, although this is not a strictly specific sign.
- CT angiography (CTA): Plays a leading role. It helps confirm the diagnosis, assess the location and size of chronic thrombi, and rule out other pulmonary parenchymal diseases. For acute PE, this is the first-line method, which also evaluates the right-to-left ventricular diameter ratio (RV/LV $\ge$ 1 is a predictor of poor prognosis).
- Conventional angiography: Remains the "gold standard" for detecting distal forms of chronic CTEPH.
- Dual-energy CT (DECT) and perfusion MRI: Promising techniques for the simultaneous assessment of vessels and pulmonary tissue perfusion.
- MRI: Provides an excellent morphological and functional picture of the heart, but is rarely used in routine practice due to the duration and high cost.
CT signs of CTEPH
CT angiograms reveal direct signs of the thrombotic masses themselves and indirect signs indicating increased pressure in the pulmonary arterial system.
- Direct signs:
- Eccentrically located thrombi forming obtuse angles with the vessel wall.
- Intravascular "webs" or membranes (web).
- Indirect signs:
- Dilatation of the right heart chambers.
- Right ventricular wall thickening due to overload.
Briefly: answers to topical questions
What pulmonary parenchymal changes are detected on CT in chronic thromboembolic pulmonary hypertension?
In chronic thromboembolic pulmonary hypertension, CT reveals the following pulmonary parenchymal changes:
- Mosaic perfusion (mosaic perfusion / mosaic pattern) — reflects hypoperfusion in obstructed vessel beds and normal perfusion or hyperperfusion in patent vessel beds.
- Small subpleural scars or irregular strands.
- Cavities (cavitation).
- Cylindrical bronchiectasis in areas of vascular obstruction.
How do CT signs of an acute thrombus differ from those of a chronic thrombus in PE?
CT signs of acute and chronic thrombosis in PE differ in location, shape, and structure of the filling defect.
| Sign | Acute thrombus | Chronic thrombus |
|---|---|---|
| Location and shape | Fresh filling defect within the vessel lumen | Eccentric location, forms an obtuse angle with the vessel wall |
| Structure and contours | No specific data | Often irregular contours, presence of calcification (density 65–105 HU) |
| Vascular changes | No specific data | Complete obstruction ("cutoff" sign), abrupt narrowing, intravascular webs (webs) and bands (bands), organized mural changes |
What hemodynamic criteria from right heart catheterization are used to diagnose CTEPH?
To diagnose chronic thromboembolic pulmonary hypertension, pulmonary artery pressure parameters are determined.
- Mean pulmonary arterial pressure (mPAP) — must be $\ge$ 25 mmHg.
- Mean pulmonary capillary wedge pressure (mPCWP) — must be $\le$ 15 mmHg.
If anatomical signs are present but mPAP < 25 mmHg, chronic thromboembolic disease is diagnosed rather than hypertension.
What specific scintigraphic patterns (mismatch) are characteristic of CTEPH?
Chronic thromboembolic pulmonary hypertension is characterized by a pattern of mismatched perfusion defects with normal ventilation.
- Mismatched perfusion defects (mismatch) — presence of areas with reduced blood flow with preserved pulmonary ventilation.
- Segmental involvement — detection of at least one segmental or two subsegmental perfusion defects.
- Multiplicity — multiple bilateral segmental perfusion defects strongly indicate the chronic form of the disease.
Class and exam questions
Which method is best suited for ruling out CTEPH?
Ventilation-perfusion (V/Q) scintigraphy. A normal perfusion result reliably rules out this disease.
What direct signs of chronic thrombus are visible on CT?
CT reveals eccentric thrombi with obtuse angles, as well as intravascular connective tissue membranes or "webs".
Why is it important to assess the RV/LV ratio on CT angiography?
A right-to-left ventricular diameter ratio $\ge$ 1 indicates right heart dilatation and is an independent predictor of adverse outcome.
What else to study on this topic
- Evaluation of prognostic scores in suspected PE
- The role of D-dimer in combination with pretest probability
- Indications for compression ultrasonography of deep veins in PE
- Specifics of scintigraphy use in young patients
- Chest X-ray in the evaluation of pulmonary venous hypertension
Master the entire topic in the "Diagnostic Radiology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Chronic Thromboembolic Pulmonary Hypertension" and 2,199 more pages on the subject
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Other topics in the «Chest Radiology» section
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.