From the Guidelines
Pulmonary vascular markings appear on an X-ray in patients with a significant left-to-right shunt, creating the appearance of left atrial and LV enlargement and increased pulmonary vascular markings. These markings are visible due to the contrast between blood-filled vessels and the air-filled lung tissue surrounding them, representing the pulmonary arteries, veins, and capillaries that carry blood through the lungs 1. The visibility occurs because blood and vessel walls have higher density (greater atomic number) than air, causing them to absorb more X-ray photons. This differential absorption creates the white branching patterns visible against the darker lung fields on the radiograph.
Some key points to consider when interpreting pulmonary vascular markings on an X-ray include:
- Normally, these vascular markings are more prominent in the lower lung zones due to gravity-dependent blood flow and become progressively less visible toward the lung periphery.
- Changes in these markings can indicate various pathologies - increased markings may suggest pulmonary edema or left heart failure, while decreased markings might indicate pulmonary embolism or emphysema.
- In patients with significant PAH, pulmonary vascular markings are diminished at the periphery of the lung, with a prominent pulmonary artery segment 2.
- The ability to properly interpret these vascular patterns is essential for radiologists and clinicians when evaluating lung and cardiac conditions on chest X-rays.
It is crucial to consider the clinical context and other diagnostic criteria when interpreting pulmonary vascular markings, as they can be influenced by various factors, including cardiac output, transpulmonary gradient, and pulmonary vascular disease 2.
From the Research
Pulmonary Vascular Markings on X-ray
Pulmonary vascular markings appear on an X-ray in various conditions, including:
- Pulmonary embolism: Studies have shown that while chest X-ray (CXR) is insensitive for detecting abnormalities of the pulmonary arteries, it can occasionally show findings of pulmonary embolism or infarction 3, 4.
- Chronic thromboembolic pulmonary hypertension (CTEPH): CTEPH is a form of pulmonary hypertension characterized by the persistence of thromboembolic obstructing the pulmonary arteries, and can be detected using ventilation-perfusion scan (V/Q) and computed tomography pulmonary angiogram (CTPA) 5.
- Pulmonary infarction: Pulmonary infarction can occur in patients with pulmonary embolism, and can be detected using multidetector helical CT, which shows a spectrum of findings including peripheral parenchymal opacities and extent of PE 6.
- Saddle pulmonary embolism: Saddle pulmonary embolism represents a large clot and a risk for sudden hemodynamic collapse, and can be detected using computed tomography angiography (CTA) 7.
Conditions Associated with Pulmonary Vascular Markings
Pulmonary vascular markings can be associated with various conditions, including:
- Pulmonary hypertension: Pulmonary hypertension can be caused by various factors, including chronic thromboembolic pulmonary hypertension (CTEPH) 5.
- Malignancy: Malignancy can increase the risk of pulmonary embolism and pulmonary infarction 6.
- Heart failure: Heart failure can increase the risk of pulmonary infarction 6.
- Recent surgery: Recent surgery can increase the risk of pulmonary embolism and pulmonary infarction 7.
Imaging Modalities for Detecting Pulmonary Vascular Markings
Various imaging modalities can be used to detect pulmonary vascular markings, including:
- Chest X-ray (CXR): CXR is insensitive for detecting abnormalities of the pulmonary arteries, but can occasionally show findings of pulmonary embolism or infarction 3, 4.
- Computed tomography pulmonary angiography (CTPA): CTPA is the current standard of care for detecting pulmonary embolism and can provide accurate diagnosis with rapid turnaround time 4.
- Ventilation-perfusion scan (V/Q): V/Q scan is the best test available for establishing the thromboembolic nature of pulmonary hypertension 5.
- Multidetector helical CT: Multidetector helical CT can detect pulmonary infarction and show a spectrum of findings including peripheral parenchymal opacities and extent of PE 6.