Table 2.
Characteristic findings in different causes or illnesses associated with dilated pulmonary artery
| Cause | Mechanism | Clinical Signs | Characteristic Imaging |
|---|---|---|---|
| Pulmonary hypertension | |||
| PAH | Increased pulmonary vascular resistance by endothelial and smooth muscle cell proliferation (78) | Loud P2, sternal heave, hepatomegaly, jugular venous distension, edema | Dilated central PA with rapid tapering to peripheral vessels, vascular pruning (39). Mosaic pattern of lung attenuation. |
| Thromboembolic disease (acute or chronic) | Increased pulmonary artery pressure from thrombus load (acute) or fibrous stenosis (chronic) (79) | Hypoxia, increased A–a gradient, hemoptysis | PA filling defects, irregularities, bands and webs. |
| Eisenmenger syndrome | Vascular remodeling from longstanding increased flow (80) | Cyanosis, clubbing, loud P2 | Peripheral PA pruning and neovascularity. |
| High altitude | Sustained alveolar hypoxia (81) | Nonspecific (exertional dyspnea), polycythemia, hypoxemia | Dilation of central PA and smaller arterial vessels. |
| Schistosomiasis | Chronic inflammation/immunological reaction with vascular remodeling (82) | Nonspecific (exertional dyspnea and PAH signs) | Dilation of the pulmonary trunk. |
| Increased or turbulent blood flow | |||
| Left-to-right shunt (PDA, ASD, VSD) | Increased blood flow and hemodynamic stress | Continuous machine-like murmur (PDA), fixed split of S2 (ASD), pansystolic murmur (VSD) | PA may approach aneurysmal size. Increased pulmonary vascularity that extends to the periphery of the lung fields. |
| Pulmonic valve stenosis | Post-stenotic flow pattern leads to increase wall shear stress (32, 83) | Delayed S2, systolic ejection murmur increased on inspiration | Post-stenotic PA dilation. |
| Arteriovenous malformations | High pulmonary flow | Asymptomatic or dyspnea, hypoxemia, hemoptysis, or cerebrovascular accidents | Well demarcated lung nodule(s) with taillike extension (supplying artery and draining vein). |
| Vasculitis | |||
| Behçet disease | Chronic vasculitis | Recurrent oral and genital ulcers, uveitis, hemoptysis | PA aneurysms in large proximal branches, pulmonary infarction, pneumonia, organizing pneumonia (39). |
| Hughes-Stovin syndrome | Chronic vasculitis | No oral or genital ulcers, no uveitis or skin lesions (39, 42) | PA aneurysm-thrombosis combination. Like Behçet, prone to rupture (22, 39). |
| Takayasu arteritis | Large vessel granulomatous vasculitis | Arm or leg claudication (“pulseless disease”), renal artery stenosis, Raynaud phenomenon | Narrowing of the aorta and/or main branches with thickening of the vascular wall. |
| Connective tissue disease | |||
| Marfan syndrome | Abnormal microfibrils from mutated fibrillin-1 gene | Various musculoskeletal manifestations, murmur of aortic regurgitation | Aortic dilation and/or dissection. May have pulmonary root involvement (38, 40). |
| Loeys-Dietz syndrome | Missense mutation of TGFBR1, TGFBR2, or SMAD3 genes (37) | Hypertelorism, cleft palate, club foot, craniosynostosis, vascular dilation and tortuosity (37) | Aortic aneurysm (39). May affect vessels other than the aorta. |
| Ehlers-Danlos syndrome | Disarray of collagen biosynthesis | Hyperextensible skin, hypermobile joints with frequent dislocations, tissue fragility (84) | Aneurysm of the iliac, splenic, or renal arteries (22). |
| Cystic medial necrosis | Disruption of smooth muscle, elastin, and collagen in vascular media (85) | Often present in Marfan and Ehlers- Danlos syndromes (85) | Dilation of large arteries, particularly the aorta. |
| Infectious | |||
| Pyogenic bacteria, syphilis, tuberculosis, fungi | Bacteremia with septic emboli or spread from adjacent pneumonia or lymphatics (39) | Various presentations of infectious diseases, endocarditis | Indolent infections often with true aneurysms, virulent organisms often with pseudoaneurysms (39). |
| Others | |||
| Trauma | Trauma from chest tube or pulmonary artery catheter | Asymptomatic to hemoptysis | Pseudoaneurysm from blood contained within adventitia (22). |
| Idiopathic | Unknown | Asymptomatic | May approach aneurysmal size (86, 87). |
Definition of abbreviations: ASD = atrial septal defect; P2 = pulmonic component of the second heart sound; PA = pulmonary artery; PAH = pulmonary arterial hypertension; PDA = patent ductus arteriosus; S2 = second heart sound; VSD = ventricular septal defect.
Patients with pulmonary hypertension may have dilated right ventricle and right atrium when compared to left side chambers. In addition, these patients may also have a smaller angle between the interventricular septum and the horizontal line or deviation of the interventricular septum toward the left (11). A vascular cause of the mosaic pattern is suggested when large-caliber vessels are surrounded by high attenuation areas and small-caliber vessels by low attenuation zones (88).