Definition

Thrombotic occlusion of the pulmonary arterial system.

Epidemiology

Common cause of acute chest pain with respiratory distress In 80% of cases however, acute pulmonary embolism remains asymptomatic.

Etiology, pathophysiology, pathogenesis

Usually originating in the pelvic or leg veins, the thrombi restrict the blood supply to the lung This leads to capillary damage, transudation, hemorrhage, and occasionally necrosis.

Imaging Signs

Modality of choice

CTA and, to a lesser extent, ventilation/perfusion scanning (lung scan).

Radiographic findings

Nonspecific inconclusive findings: Platelike atelectasis High-riding diaphragm Pleural effusion Local oligemia (Westermark sign) Rarely pulmonary infarction, appearing as a wedge-shaped opacity with a pleural base.

CT findings

Directly demonstrates embolisms in the pulmonary arterial system (filling defects).

Nuclear medicine

Wedge-shaped perfusion defect.

Pathognomonic findings

Intraluminal contrast filling defects Signs of right heart strain.

Clinical Aspects

Typical presentation

Asymptomatic in about 80% of cases, rendering clinical diagnosis difficult Typical triad of chest pain, respiratory distress, and hemoptysis occurs in only about 5% Deep venous thrombosis in the pelvis or lower extremity is present in less than 50%.

Therapeutic options

Anticoagulation and fibrinolysis A venal caval filter may be indicated in deep venous thrombosis in the pelvis or lower extremity where medical treatment is ineffective or contraindicated.

Course and prognosis

Good with therapy Fatal in about 20% of cases if left untreated.

What does the clinician want to know?

Confirm or exclude diagnosis Extent (unilateral or bilateral, central or peripheral).

Fig. 9.1 Massive bilateral pulmonary embolism in a 79-year-old man with acute coronary syndrome. CTA shows thrombi incompletely blocking the blood flow in both main pulmonary trunks, the superior and inferior lobe arteries, and the segmental branches: findings are consistent with acute pulmonary embolism. The plain chest radiographs were normal.

Fig. 9.2 Pulmonary infarct in a 47-year-old woman with protein S deficiency. The plain chest radiograph shows a faint wedge-shaped area of opacification with a pleural base in the right upper lung field and a second smaller area in the middle lung field consistent with infarct pneumonia. The patient had a known history of thromboembolic disease, which had led to occlusion of the inferior vena cava. Collateralization via the expanded azygos vein (*, arrows).

Tips and Pitfalls

Insufficient filling of the pulmonary arteries Breathing artifacts.

Selected Reference

Guilabert JP et al. Can multislice CT alone rule out reliably pulmonary embolism? A prospective study. Eur J Radiol 2007; 62: 220–226

Definition

Abnormally elevated blood pressure in the pulmonary artery (mean pulmonary arterial pressure at rest > 25 mmHg, with exercise > 30 mmHg).

Epidemiology

Idiopathic form is rare Secondary forms are far more common.

Etiology, pathophysiology, pathogenesis

Increase in pulmonary arterial pressure due to cardiac pathology (left-to-right shunt, mitral stenosis, anomalous pulmonary venous connection, etc.) or pulmonary pathology (thromboembolic disease [CTEPH], emphysema, pulmonary fibrosis, etc.) This leads to dilatation of the central pulmonary arteries Findings in idiopathic pulmonary arterial hypertension include fibrosis and proliferative muscularization of arterioles Pulmonary arterial hypertension is classified as idiopathic, familial, or associated; the latter occurs in disorders such as venous occlusive disease or capillary hemangiomatosis.

Imaging Signs

Modality of choice

Radiographs, CTA, pulmonary angiography.

Radiographic findings

Dilated central pulmonary arteries (diameter of the middle part of the right pulmonary artery > 16 mm in men, > 14 mm in women) with abrupt changes in caliber toward the periphery Signs of right heart strain—enlarged area of contact between the anterior wall of the heart and the sternum, prominent pulmonary trunk, prominent main pulmonary artery segment.

CTA findings

The pulmonary trunk is wider than the ascending aorta Abrupt changes in caliber In CTEPH there are mural irregularities, intraluminal webs and bands, ste-noses, and/or thromboembolic vascular occlusion Mosaic perfusion Signs of right heart strain—right ventricular dilatation and hypertrophy with protrusion of the interventricular septum against the left ventricle.

Pulmonary angiographic findings

Vascular picture is identical to CTA.

Pathognomonic findings

Dilated central pulmonary arteries with abrupt changes in caliber toward the periphery.

Clinical Aspects

Typical presentation

Symptoms are nonspecific—dyspnea during exercise Limited exercise tolerance Fatigue Advanced-stage disease shows signs of right heart failure.

Therapeutic options