The pulmonary circulation: the radiology of adaptation

Proximal Interruption of Pulmonary Artery: Spectrum of Radiological Findings With Emphasis on Chest Radiograph and Contrast-Enhanced Computed Tomography (CECT)

Introduction Proximal interruption of pulmonary artery (PIPA) is a congenital anomaly presenting with aberrant termination of the pulmonary artery at the hilum. It results in a variety of radiological and clinical manifestations. Clinically, isolated PIPA can be asymptomatic till late adulthood or can present with dyspnoea, chest discomfort, hemoptysis and recurrent infections. PIPA can be associated with multiple cardiovascular anomalies such as tetralogy of Fallot (TOF), ventricular septal defects (VSD), and scimitar syndrome. We present a spectrum of cases with both isolated proximal interruption of the pulmonary artery and cases associated with other cardiovascular abnormalities. Typical chest radiographs and chest contrast-enhanced computed tomography (CECT) findings are discussed and demonstrated in detail. Proper and early diagnosis is a crucial step as it can significantly modify the treatment choice, thereby reducing morbidity. Objective To document the different presentations of the proximal arrest of pulmonary arteries, to document associations with cardiovascular and pulmonary manifestations, and to elaborate on and demonstrate the various radiological imaging findings. Material and methods All the cases that were reported with proximal interruption of pulmonary artery on the CECT studies conducted between 2019 and 2022 at a tertiary care hospital in Telangana, India. The demographic data, clinical presentation, chest radiographs, and chest CECT were collected retrospectively. Data analysis was done using Microsoft Excel 2019 to calculate descriptive statistics. A total of 22 cases were identified of which three cases were excluded of as they were previously operated and 19 cases were taken as the study population. Results Nineteen patients were included in the study. Demographic details, clinical history, CECT, and chest radiographs were collected wherever available. The majority of the cases belonged to the ≤ 10 yrs age group with the most common clinical presentation being a previous diagnosis of tuberculosis or recurrent upper respiratory tract infections. The predominant findings on chest radiographs were deviation of the trachea to the affected side, volume loss in the ipsilateral lung field, and compensatory hyperinflation of the contralateral lung field. On the CECT chest, the main findings were interrupted pulmonary artery, hypoplastic lung fields with bronchiectasis, or ground glassing. Associated cardiovascular and pulmonary malformations were identified with notable cases: TOF, right-sided aortic arch and scimitar syndrome. Their typical imaging findings have been elucidated and discussed in detail. Conclusions Patients with recurrent respiratory infections or hemoptysis having hypoplastic lung field with hyperinflation of the contralateral lung on chest radiographs should be evaluated for pulmonary artery interruptions. Chest CECT allows evaluation of the bronchial tree and lung parenchyma at the same time which helps distinguish pulmonary interruption from conditions such as Swyer-James-Macleod syndrome, pulmonary hypoplasia, thromboembolism and arteritis. Cases with PIPA can also be associated with cardiovascular and pulmonary anomalies such as TOF, partial anomalous pulmonary venous connection (PAPVC), and VSD. The knowledge of these associations is essential as they can influence the mode of treatment and can help reduce the long-term morbidity and mortality associated with the condition.

Proximal interruption of the pulmonary artery: A review of radiological findings

OBJECTIVES

Proximal interruption of the pulmonary artery (PIPA) has various clinical manifestations. This review focused on and summarized the clinical and radiological features of PIPA, based on relevant literature studies.

METHODS

The study included a total of 25 PIPA cases in the Guangzhou Women and Children's Medical Center between January 2015 and December 2021. Conventional chest photographs and chest computed tomography angiography (CCTA) of patients with PIPA were analyzed and summarized.

RESULTS

The radiological results showed that 17 cases were right-sided and 8 cases were left-sided PIPA. Additionally, the percentage of pulmonary hypoplasia on the affected side was 44%, 36% for pulmonary hypertension, 28% for the mosaic sign, 20% for subpleural cystic lucency shadow, 20% for subpleural serrated shadow, 20% for collateral vessel thickening, 16% for subpleural band-like parenchyma, 12% for pneumonia, and 56% for patent ductus arteriosus.

CONCLUSION

The clinical manifestations of PIPA are non-specific. Awareness of this anomaly, based on radiological manifestations, particularly those observed on CCTA images, is important for ruling out alternative diagnoses and implementing appropriate management.

Proximal Interruption of the Pulmonary Artery: A Case Series

We present a few cases of Proximal Interruption of the Pulmonary Artery, an uncommon developmental anomaly associated with congenital heart disease. The cases had varied clinical presentations. Chest radiograph showed a hypoplastic lung with an ipsilateral small hilum on the side of the interruption and hyperinflation of the contralateral lung. Contrast CT confirmed the diagnosis, demonstrating non-visualization of the left or right pulmonary artery, and other related findings.

Imaging diagnosis of isolated proximal interruption of the right pulmonary artery in a patient presenting with respiratory complications following travel to a high-altitude region

Proximal interruption of the pulmonary artery (PA) is a rare congenital vascular anomaly with an estimated prevalence of 1 in 200,000 young adults. Patients with isolated proximal interruption of the right PA are usually asymptomatic but can present with breathlessness, haemoptysis, recurrent chest infections, pulmonary hypertension or respiratory failure. Such symptoms may be unmasked by pregnancy or at high altitude. We present a case of an isolated interruption of the right PA in a 29-year-old male with a history of cough and breathlessness, requiring hospitalization and ventilator support after travel to a hilly region. Laboratory reports showed normal haemogram and normal renal and liver function tests. Screening test for deep vein thrombosis/pulmonary embolism were negative. Echocardiogram was normal and did not show any evidence of elevated PA pressures. All serial X-rays were reviewed and showed one consistent finding: right lung volume loss with transmediastinal herniation of the left lung to the right side. We discuss the radiological and clinical features along with treatment options for the condition.

Congenital absence of the right interlobar pulmonary artery: HRCT findings

We report a case of unilateral idiopathic pulmonary fibrosis-like changes in the right middle and lower lobe without lung volume changes and with normal upper lobe owing to congenital absence of the right interlobar pulmonary artery on chest computed tomography.

HRCT Findings of Proximal Interruption of the Right Pulmonary Artery

The purpose of this study is to present the characteristic HRCT findings of the lung parenchyma in patients with proximal interruption of the right main pulmonary artery. HRCT findings of proximal interruption of the right pulmonary artery demonstrated reticular opacities, septal thickening, subpleural consolidation, cystic lung changes, and pleural thickening in all 5 patients; bronchial dilation and bronchial wall thickening in 4 patients; and subpleural ground glass opacity (GGO) in 3 patients. The changes may be caused by absent pulmonary artery perfusion and development of systemic vessel collateralization.

Mechanism of mosaic attenuation of the lungs on computed tomography in induced bronchospasm

The purpose of this study was to investigate whether hypoxic pulmonary vasoconstriction is the major determinant of the computed tomography (CT) pattern of mosaic attenuation in asthmatic patients with induced bronchoconstriction. Thin-section CT was performed at suspended full inspiration immediately and 30 min after methacholine bronchoprovocation in 22 asthmatic subjects, who were randomly assigned to breathe room air (group A, n = 8), oxygen via nasal prongs at 5 l/min (group B, n = 8), and oxygen via face mask at 12 l/min (group C, n = 6). CT changes were quantified in terms of global lung density and density in hypodense and hyperdense areas. Lung parenchymal density increases were greatest in group C and greater in group B than in group A, globally (P = 0.03) and in hypodense regions (P = 0.01). On bivariate analysis, the only change in cross-sectional area was related to change in global density. In hypodense regions, density change was related both to reduction in cross-sectional area (P < 0.0005) and to oxygen administration (P = 0.01). After correction for changes in global lung density, only oxygen was independently related to density increase in hypodense areas (P = 0.02). In induced bronchoconstriction, the CT appearance of mosaic attenuation can be largely ascribed to hypoxic vasoconstriction rather than to changes in lung inflation.

Swyer-James syndrome documented by spiral CT angiography and high resolution inspiratory and expiratory CT: an accurate single modality exploration

Spiral CT angiography was performed in a patient suspected of having pulmonary embolism. The right pulmonary system was normal. The left arterial system was small but patent. The left upper lobe was small and hyperlucent. The left lower lobe was collapsed and contained bronchiectasis. The bronchi were patent. High resolution CT in inspiration and expiration confirmed air trapping in the left upper lobe. A diagnosis of Swyer-James syndrome of the left upper lobe was made.

Comparison of computed tomographic lung density with haemodynamic data of the pulmonary circulation

Computed tomographic (CT) lung density measurements were prospectively correlated with pulmonary haemodynamic data in 33 patients with chronic heart disease. Cardiac catheterisation and five specific computed tomographic scans (three at nearly total lung capacity, one at functional residual capacity, and one at residual volume) were performed. There was a significant correlation between anterior lung density and mean pulmonary artery pressure (r = 0.86), pulmonary vascular resistance (r = 0.80), and pulmonary artery wedge pressure (r = 0.65). Lung density, as measured by CT, thus provides a valuable estimate of pulmonary arterial pressure and pulmonary vascular resistance, but is affected by other pathological conditions, such as emphysema and congestional or post-inflammatory fibrosis.