Intravascular Ultrasound Imaging of Pulmonary Arteries: Pulmonary Thromboembolic Disease
Chronic Pulmonary Thromboembolic Disease: Recent clinical studies have also showed the ability of pulmonary IVUS to diagnose chronic pulmonary thromboemboli. Ricou et al used an 8F 20 MHz IVUS catheter to detect abnormalities in the left and right pulmonary arteries of patients with chronic thromboemboli. These abnormalities were described as either marked thickening of the vessel wall or a crescentic layer of thickening. Using these criteria, chronic organized thrombi or tumor were identified at surgery in all of the abnormal segments of the pulmonary artery seen by IVUS. About 90% of the segments that were considered normal by IVUS were free of chronic thromboemboli at surgery. buy birth control
Diagnosis of Other Vessel Wall Abnormalities: IVUS of the pulmonary artery can also be used to evaluate vessel wall abnormalities in primary and secondary forms of pulmonary hypertension. Although in vivo measurements of pulmonary artery wall thickness are not possible since the outer adventitial layer of the vessel is embedded in air-filled lung parenchyma, it is possible to assess qualitatively abnormalities in the pulmonary vascular walls that are not detected by other imaging modalities. In primary pulmonary hypertension, IVUS has shown thickened walls with a granular appearance and reduced lumen area. An intravascular ultrasound of the proximal pulmonary artery of a patient with primary pulmonary hypertension is shown in Figure 3. This was subsequently shown to be severe intimal hyperplasia at autopsy (Fig 3).lfi Responses to vasodilators and prognosis in primary pulmonary hypertension are related to the amount of intimal hyperplasia vs medial hypertrophy. It remains to be determined, however, whether IVUS can distinguish between these two pathologic responses in primary pulmonary hypertension.
Figure 3. IVUS image of a pulmonary artery in vivo in a patient with primary pulmonary hypertension (left) and cross section of about the same region obtained at subsequent necropsy (right). The patient died during a single-lung transplant surgery within 3 weeks of the IVUS study. Reproduced with permission, from reference 41.