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Difficulty: HardInterpreting Imaging Results

A 62-year-old man presents to the outpatient clinic reporting an eight-month history of progressive shortness of breath during physical exertion. He also describes new-onset swelling in both lower legs and intermittent, poorly localized chest discomfort. Three years ago, the patient suffered an unprovoked deep vein thrombosis in his right popliteal vein, which was successfully managed with three months of oral anticoagulant therapy.

Vital signs show a temperature of 37.0°C (98.6°F), blood pressure of 132/82 mmHg, heart rate of 84/min, and respiratory rate of 16/min. Physical examination is notable for distended jugular veins. Cardiac auscultation reveals a loud pulmonary component of the second heart sound (P2) and a right-sided third heart sound (S3). Lung fields are clear to auscultation.

A computed tomography pulmonary angiography (CTPA) is obtained. The radiologist notes significant right ventricular enlargement with bowing of the interventricular septum toward the left ventricle. Within the main and lobar pulmonary arteries bilaterally, there are eccentric, partially calcified filling defects that form obtuse angles with the vessel walls. Intravascular webs and bands are visible in several segmental branches. Lung windows demonstrate a mosaic attenuation pattern.

Based on the clinical presentation and imaging findings, which of the following is the most likely diagnosis?

  1. Chronic thromboembolic pulmonary hypertensionAnswer
  2. B
    Acute massive pulmonary embolism
  3. C
    Idiopathic pulmonary arterial hypertension
  4. D
    Primary pulmonary artery sarcoma
  5. E
    Fibrosing mediastinitis

Answer

Chronic thromboembolic pulmonary hypertension
The correct answer is chronic thromboembolic pulmonary hypertension (CTEPH). The patient's presentation of progressive dyspnea, right-sided heart failure, and a history of deep vein thrombosis is highly suspicious for CTEPH. On CT pulmonary angiography, CTEPH is uniquely characterized by eccentric, partially calcified filling defects that form obtuse angles with the vessel wall, representing organized, fibrotic thrombus that has incorporated into the vascular intima. Intravascular webs, bands, and abrupt vessel narrowing are also pathognomonic. Mosaic attenuation on lung windows reflects regional variations in pulmonary perfusion. These specific imaging findings clearly distinguish chronic organized thrombi from acute emboli.

Step-by-Step Solution

1
Analyze the patient's clinical presentation.
The patient has a chronic (eight-month) history of progressive dyspnea, signs of right-sided heart failure (elevated JVP, right-sided S3), and a prior history of unprovoked deep vein thrombosis.
Establishing the temporal course and risk factors points toward a chronic progressive process rather than an acute cardiopulmonary event.
2
Interpret the right heart findings on the computed tomography pulmonary angiography (CTPA).
Right ventricular enlargement and septal bowing indicate elevated pulmonary vascular resistance and significant right heart strain.
These findings confirm the presence of clinically significant pulmonary hypertension.
3
Analyze the specific vascular filling defects described in the imaging report.
The defects are eccentric, partially calcified, form obtuse angles with the vessel wall, and are accompanied by intravascular webs and bands.
Detailed imaging interpretation differentiates between acute and chronic disease; eccentric defects and webs are pathognomonic for chronic organized thrombus incorporated into the vessel wall.
4
Synthesize the clinical and imaging data to determine the diagnosis.
The combination of chronic right heart failure, a history of DVT, and diagnostic CTPA findings confirms chronic thromboembolic pulmonary hypertension (CTEPH).
Integrating the patient's history with highly specific radiologic signs is required to reach the correct diagnostic conclusion.

Key Concept

Differentiating acute versus chronic pulmonary embolism on CT pulmonary angiography by identifying specific vascular signs (e.g., eccentric defects, obtuse angles, and webs for chronic; central defects and acute angles for acute).
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Topics

Interpreting Imaging Results

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