Abstract
Unilateral pulmonary artery agenesis (UPAA) is the complete absence of either the right or left pulmonary artery. It is a rare congenital malformation, usually associated with other cardiac defects; however, in some cases, it may occur as an isolated lesion, typically affecting the right side. Patients with isolated right pulmonary artery agenesis are often diagnosed incidentally on chest radiographs in adulthood. Rare cases are associated with multiple systemic collaterals that supply the affected lung. We report the case of a 69-year-old man with the absence of a right pulmonary artery, arterial supply to the right lung from the celiac trunk, and communication of the collaterals with a marginal branch arising from the right coronary artery. UPAA is a rare congenital anomaly that may present with nonspecific symptoms, such as dyspnea and recurrent chest infections. Clinicians should consider UPAA in the differential diagnosis of respiratory symptoms, particularly in adult patients with unexplained symptoms.
Keywords
Introduction
Unilateral pulmonary artery agenesis (UPAA) is an uncommon congenital anomaly, with a prevalence of approximately 1 in 200,000. 1 It results from the failure of migration and rotation of the sixth aortic arch during embryogenesis. 2
UPAA may be associated with other congenital cardiovascular anomalies or may occur as an isolated anomaly, without any additional abnormalities.
Isolated right-sided UPAA is twice as frequent as left-sided UPAA.
The diagnosis of isolated UPAA in infancy is nearly impossible, as patients are typically asymptomatic. In adulthood, however, UPAA may progress, leading to clinical manifestations such as recurrent lung infections, dyspnea, chest pain, exercise intolerance, and/or hemoptysis. 3
In isolated UPAA, the affected lung is characterized by developed collateral arteries originating from systemic circulations, including the subdiaphragmatic, phrenic, subclavian, internal mammary, bronchial, and/or intercostal arteries. 4
Monitoring asymptomatic patients with echocardiography is recommended to detect early signs of pulmonary hypertension. Treatment options for UPAA may include revascularization, closure of the collateral arteries, or pneumonectomy. However, there are currently no established guidelines for the treatment approach in these patients. 5
In this article, we report the case of a 69-year-old man with isolated right-sided UPAA and decreased lung volume on the affected side, supplied by extensive collateral arteries arising from the celiac trunk, as well as branches from the internal thoracic and dorsal scapular arteries on the right side. Another large, tortuous branch was found arising directly from the anterior aspect of the thoracic aorta, just beyond the arch.
Additionally, the collaterals communicate with a marginal branch arising from the proximal-mid course of the right coronary artery. All these branches supply the right lung in place of the pulmonary artery. This case is reported in accordance with the CARE guidelines, which aim to enhance the transparency and robustness of reporting surgical cases. 6
Case presentation
A 69-year-old man with a known medical history of hypertension, diabetes, and nonobstructive coronary artery disease was admitted to the hospital. The patient, a former smoker, presented with a progressive history of chronic shortness of breath, worsening with exertion and improving with rest, associated with a history of productive cough and recurrent chest infections, warranting hospitalization and intensive care unit (ICU) admission at the Al-Ahli hospital, Hebron on May 2023.
On admission, the patient looked dyspneic, with an oxygen saturation of 85% (SpO2). Blood pressure was normal with a regular heart rate of 70 beats per minute.
Lung examination revealed decreased air entry on the right side associated with right basilar crepitations. Cardiac examination revealed negative findings. There was no evidence of peripheral edema, cyanosis, or clubbing, and the jugular venous pressure was not raised.
His laboratory tests results on admission, including a complete blood cell count, were within the normal range; his C-reactive protein, blood urea nitrogen, creatinine, cholesterol, high-density lipoprotein, low-density lipoprotein, and triglyceride levels were 11 mg/L, 12 mg/dL, 0.8 mg/dL, 167 mg/dL (low risk: <200 mg/dL), 44 mg/dL (moderate risk: 35–45 mg/dL), 114 mg/dL (low risk: <129 mg/dL), and 103 mg/dL (low risk: <150 mg/dL), respectively.
Serum electrolytes revealed the following findings: Na = 140 mEq/L, K = 5.3 mEq/L, and chloride = 108 mmol/L.
Tropinin levels were 2.2 ng/L (health patient <30 ng/L). Electrocardiography revealed regular sinus rhythm.
Chest radiography revealed right lung collapse and shifting of the mediastinum to the right side, with left lung hyperinflation (Figure 1).
Chest radiograph showing a small right lung with diminished vascular markings and an ipsilateral mediastinal shift. Compensatory hyperinflation of the left lung, with prominent left pulmonary artery and vascular markings.
Chest computed tomography (CT) scan revealed ipsilateral unilateral absence of the right pulmonary artery with consequent small ipsilateral lung volume, mediastinal shift of both lungs, and a right peri-lymphaticreticulonodular pattern (Figure 2).
Chest computed tomography scan revealing ipsilateral unilateral absence of the right pulmonary artery (red arrow).
Echocardiography revealed mild diastolic dysfunction and mildly dilated right ventricle and right atrium, mild tricuspid regurgitation, and an estimated systolic pulmonary arterial pressure (sPAP) of 51 mmHg at rest; otherwise, the findings were normal.
CT angiography (Figure 3) revealed agenesis of the right main pulmonary artery, with massive collateral branches arising from the celiac trunk in addition to the common hepatic, splenic, and left gastric arteries arising from the thoracic cavity and fusing with the collateral vessels in the subphrenic level; these branches were approximately 6 mm in diameter. Moreover, the branches arising from the internal thoracic and dorsal scapular arteries on the right side measured approximately 6.5 mm and 5.4 mm near their origin. Another large and tortuous branch appeared to arise directly from the anterior aspect of the thoracic aorta just beyond the arch (measured approximately 5.5 mm near its origin). A communication of the collaterals with a marginal branch arising from the proximal-mid course of the right coronary artery was observed. The CT angiogram also revealed an enlarged left atrium and an enlarged left pulmonary artery arising from the right ventricle (psudotrunk), measuring up to 27 mm in diameter. No other remarkable cardiac findings were noted.
A coronary angiography demonstrating a coronary artery fistula between the proximal portion of the right coronary artery and the pulmonary artery.
The patient was referred for cardiac catheterization, which revealed normal left main coronary artery, left anterior descending artery (mid-to-very mild atheroma), and right coronary artery (normal, with a fistula to the right pulmonary artery).
The patient was admitted in the in the coronary care unit and treated with beta-blockers, bronchodilators, antibiotics, and anticoagulants, after obtaining informed consent from the patient for treatment. He responded well with improved oxygen saturation.
Discussion
UPAA is an uncommon congenital anomaly, with an estimated occurrence rate of 1 in every 200,000 to 1 in every 300,000 individuals. Although its precise prevalence is difficult to identify,2,7 the first report on this congenital anomaly was described and published by Ten Harkel in 2002. 8
UPAA occurs due to the involution of the proximal portion of the sixth aortic arch, leading to the absence of the proximal pulmonary artery. Meanwhile, the distal portion is frequently observed as either a small vessel or a fibrous cord. 2 This could be attributed to a sequence of events taking place either prior to or during the 5th or 6th week of gestation. 7
Agenesis of the right pulmonary artery is more common than agenesis of the left pulmonary artery and is often associated with congenital cardiac anomalies when detected in infancy (tetralogy of Fallot or truncus arteriosus). In contrast, isolated UPAA is much less common and usually affects the right pulmonary artery.2,7,9 The average age for diagnosing isolated pulmonary artery agenesis (PAA) was reported as 14 years. 7
In cases of PAA, the affected lung receives blood supply from systemic collaterals. These collaterals, such as bronchial, intercostal, internal thoracic, or subdiaphragmatic arteries, can enlarge over time and may rupture, potentially causing severe complications such as massive hemoptysis. The presence of coronary or celiac trunk collaterals is rare, and its implications vary among different patients. 2
PAA is usually diagnosed in childhood and is rare in adults. 7 The clinical manifestation of individuals with an absent right pulmonary artery varies. According to several authors, approximately 15% of patients may exhibit no symptoms throughout their lifetime 10 or have no specific symptoms, such as recurrent pulmonary infections (37%), decreased exercise tolerance, and mild dyspnea during exertion (40%),7,8 Less frequently reported symptoms include hemoptysis (20%) and signs of pulmonary hypertension.
Our patient presented with a productive cough and recurrent chest infections warranting hospitalization and ICU admissions. He also complained of chronic shortness of breath, which increased with exertion. His diagnosis was delayed until it was incidentally detected on imaging.
Imaging studies that are usually helpful in establishing the diagnosis of UPAA include CT angiography, contrast-enhanced CT, chest radiography, ventilation-perfusion scans, and digital subtraction angiography (DSA). 7
Chest radiography is usually performed as the initial diagnostic step, revealing a collapsed affected lung, with mediastinal and cardiac structures shifted towards the affected side. In addition, ipsilateral grossly diminished pulmonary vascular markings of the affected lung, a small hemithorax and intercostal bone space, ipsilateral hemidiaphragm elevation, and hyperinflation of the contralateral. 8
Chest radiography revealed right lung collapse and mediastinum shift to the right side, with left lung hyperinflation in this case.
Chest CT and magnetic resonance imaging can help with the diagnosis and evaluation of congenital heart defects. 8
Chest CT performed in our patient revealed ipsilateral absence of the right pulmonary artery with consequent small ipsilateral lung volume, mediastinal shift of both lungs, and a right peri-lymphatic reticulonodular pattern. High-resolution CT scanning can also assess the presence of bronchiectasis in cases of recurrent pulmonary infections. 8
Although DSA is considered the gold standard for imaging and can aid in establishing a therapeutic plan for PAA, 10 CT angiography provides visualisation of extensively developed systemic collateral circulation. CT angiography in the present case revealed collaterals arising from the celiac trunk in addition to the common hepatic, splenic, and left gastric arteries. Moreover, branches arising from the internal thoracic and dorsal scapular arteries were also evident on the right side. Another large and tortious branch arising directly from the anterior aspect of the thoracic aorta just beyond the arch was also seen. A communication was present between the collaterals and a marginal branch arising from the proximal-mid course of the right coronary artery.
The presence of associated coronary collaterals can have varying effects. They may either reduce myocardial perfusion, leading to ischemia or infarction via steal phenomena, or have no impact on the coronary circulation, as blood flow through collaterals typically occurs during systole, not diastole. 2
Echocardiography can also be performed to exclude other cardiac abnormalities and confirm the presence of pulmonary hypertension. 11 Echocardiography in the present case revealed mild diastolic dysfunction, mildly dilated right atrium and right ventricle, mild tricuspid regurgitation, and pulmonary arterial hypertension (sPAP was 51 mmHg at rest).
Owing to the rarity of PAA, treatment modalities lack consensus and are tailored based on the clinical signs and symptoms and collateral circulation status of the patient. Options include transcatheter arterial embolization (TAE) and surgery. Selective TAE is preferred for uncomplicated collaterals, while caution is advised for cases with more complex collateral patterns arising in multiple directions, particularly in elderly patients, due to procedural challenges and the higher risks of complications associated with fibrotic and narrowed collaterals. In these patients, surgical intervention involving pneumonectomy of the affected lung may be considered a safer choice; however, surgical intervention is highly invasive and warrants careful consideration of its indications. 7
Patients with UPAA with pulmonary hypertension may show improvement by revascularization of the affected side. If revascularization is not considered feasible or does not improve pulmonary hypertension, long-term vasodilator therapy, such as orally administered calcium channel blockers or continuous intravenous infusions of prostacyclin, may enhance survival. 8
Although many patients with UPAA can be asymptomatic for a considerable time, The development of pulmonary hemorrhage or pulmonary hypertension can impact their long-term survival. The overall mortality rate observed was 7%. 8
Abbreviations
blood urea nitrogen computed tomography digital subtraction angiography electrocardiogram high-density lipoprotein intensive care unit low-density lipoprotein pulmonary arterial hypertension systolic pulmonary arterial pressure transcatheter arterial embolization tricuspid regurgitation unilateral pulmonary artery agenesis
Footnotes
Acknowledgements
We thank Dr Ahmad G. Hammouri, Radiologist at Al-Ahli Hospital.
Author contributions
Rola: Conceptualization, Writing—Original Draft.
Daleen: Conceptualization, Writing—Original Draft.
Raneen: Conceptualization, Writing—Original Draft.
Mahmoud: Conceptualization, Review and Editing.
Baha: Conceptualization, Review and Editing.
Bajis: Conceptualization, Review and Editing.
Consent to participate
Our patient provided his consent for this study with a written informed consent, approved by our institution.
Data availability
The data that support the findings of this study are available on request from the corresponding author.
Declaration of conflicting interest
The authors declare that there is no conflict of interest regarding the publication of this article.
Ethical considerations
This case report has been reviewed and approved by all authors for submission to Therapeutic Advances in Cardiovascular Disease journal.
Funding
The authors declare that writing and publishing this manuscript was not funded by any organization.
Implications for clinical care
The case of isolated right pulmonary artery agenesis (PAA) demonstrates the need for the following:
Early Diagnosis: Chest radiographs and computed tomography (CT) scans should be indicated in patients with high suspicion for unilateral PAA with unexplained respiratory symptoms for obtaining an accurate diagnosis. Detailed Imaging: Advanced imaging, such as CT angiography, is crucial for assessing the extent of collateral vessels and planning management. Management of Collaterals: Understanding and performing potential interventions for systemic collaterals is important for managing symptoms and complications. Ongoing Monitoring: Regular assessment for complications such as pulmonary hypertension and treatment plan compliance as needed. Multidisciplinary Approach: Coordination among cardiologists, pulmonologists, and radiologists ensures comprehensive care. Patient Education: Informing patients about their condition, symptoms to watch out for, and the importance of follow-up care.
