British Journal of Radiology 75 (2002),532-535 © 2002 The British Institute of Radiology
Idiopathic dilatation of the pulmonary artery
N J Ring, FRCR
1 and
A J Marshall, MD, FRCP
2
Departments of 1 Diagnostic Radiology and 2 Cardiology, Derriford Hospital, Derriford Road, Plymouth, Devon PL6 8DH, UK
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Abstract
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Idiopathic dilatation of the pulmonary artery is an uncommon cause of a large main pulmonary artery whose diagnosis is dependent on the exclusion of other causes of central pulmonary artery dilatation. We present four new cases who have been known to have large central pulmonary arteries for many years, and suggest that a long period of observation should be considered to be a further criterion for diagnosis as, in some patients who appear to have this condition, an underlying pathology will become apparent.
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Introduction
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Idiopathic dilatation of the pulmonary artery (idiopathic dilatation of the pulmonary trunk) has been recognized for many years as an uncommon condition in which there is enlargement of the main pulmonary artery, with or without dilatation of the right and left pulmonary arteries. To establish the diagnosis, other causes of central pulmonary artery enlargement must be excluded and it is sometimes difficult to be entirely certain that there is not significant underlying pathology. We have recently been involved in the management of four patients in whom the length of history lends considerable support to the presumed diagnosis.
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Case 1
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A 63-year-old male attended for chest radiography, requested as part of an application to emigrate to Australia. At the age of 17 years the patient was diagnosed as having a congenital cardiac abnormality, perhaps a ventricular septal defect, and had been refused entry into the Royal Navy. When the patient was 35 years old he had been seen by a cardiologist who thought him not to have a congenital heart defect, although the pulmonary artery was noted to be prominent on chest radiography. There was no other relevant past history, but the patient had been a heavy smoker for many years.
Physical examination was unremarkable, but chest radiography (Figure 1
) showed gross dilatation of the main, right and left pulmonary arteries but normal peripheral vessels and a normal sized heart. The right descending pulmonary artery measured 24 mm on the chest radiograph; the upper limit of normal is 16 mm [1]. Spirometry was normal and thoracic CT confirmed the large central pulmonary arteries but showed no evidence of parenchymal or interstitial lung disease. Transthoracic and transoesophageal echocardiography showed a normal right ventricle and no evidence of a shunt, but the main pulmonary artery was dilated with a diameter of 3.25 cm. The upper limit of normal is 2.1 cm for the main pulmonary artery on echocardiography, and 1.4 cm for the right and left pulmonary arteries [2]. At right heart catheter, the patient's mean main pulmonary artery pressure was minimally elevated at 22 mmHg and there was no step up in oxygen saturation.
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Case 2
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A 57-year-old asymptomatic male presented to his GP for a check-up. The patient was said to have had something wrong with his heart since childhood, however he was seen by a cardiologist whilst at university and was reassured that he was healthy. 30 years prior to the current presentation, the patient had been recalled for review following an abnormal chest radiograph. Cardiac auscultation revealed a murmur thought to be owing to pulmonary regurgitation, but no other abnormality. Lung function, including transfer factor, was normal. ECG was normal and echocardiography showed a normal right ventricle, and no evidence of pulmonary stenosis or significant pulmonary regurgitation. The pulmonary artery, however, was noted to be dilated. Chest radiography showed marked dilatation of the main pulmonary artery, but no other abnormality. MRI (Figures 2 and 3) demonstrates marked dilatation of the main pulmonary artery, which has a diameter of 5 cm, and this dilatation extends into the left pulmonary artery and into the artery to the left lower lobe, which was 2 cm in diameter. On MRI, the upper limit of normal for the main pulmonary artery is 2.8 cm and 1.8 cm for the left lower lobe artery [3].
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Figure 2. Axial T1 weighted MR image demonstrating marked dilatation of the main pulmonary artery (arrow).
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Figure 3. Image from cine MRI through the right ventricular outflow tract. There is aneurysmal dilatation of the pulmonary artery (arrows).
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Case 3
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A 73-year-old man presented with heart failure secondary to atrial fibrillation. Chest radiography (Figure 4) showed cardiomegaly and large pulmonary arteries. A ventilation/perfusion scan showed no evidence of pulmonary emboli, and MRI (Figure 5) demonstrated marked dilatation of the main pulmonary artery and left lower lobe artery. There was no clinical evidence of pulmonary stenosis, and a recent transoesophageal echocardiogram had shown a normal right ventricle.
Review of a chest radiograph taken 7 years earlier showed a large pulmonary artery at that time, and a report was available of a chest radiograph 13 years prior to that, which described dilatation of the right ventricular outflow tract. Subsequent follow-up over a period of a further 4 years showed slight enlargement of the pulmonary artery. It is therefore concluded that this patient had a large pulmonary artery over a period of at least 24 years.
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Case 4
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A 63-year-old man was referred for coronary artery bypass grafts. He had been seen 7 years earlier by a chest physician who noted a "prominent left hilum", but this was unchanged from a radiograph taken 5 years prior to that. Chest radiography on admission showed the large pulmonary artery but no other abnormality (Figure 6).
On opening the chest to perform coronary artery surgery, the pulmonary artery was noted to be large. This was confirmed by an intra-operative transoesophageal echocardiogram (TOE). Following completion of the grafts, the pulmonary artery was opened. This was confirmed to be aneurysmal with extension into the left and right pulmonary arteries. The pulmonary valve leaflets were thickened but not stenotic. The TOE showed no evidence of pulmonary regurgitation or right ventricular dilatation, so the valve was left alone and the main pulmonary artery was plicated.
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Discussion
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Idiopathic dilatation of the pulmonary trunk is an uncommon but well recognized cause of a large pulmonary artery. In 1949, Greene et al [4] identified eight cases with autopsy confirmation from the literature of the previous 30 years that satisfied the following criteria:- simple dilatation of the pulmonary trunk, with or without involvement of the rest of the arterial tree;
- absence of abnormal intracardiac or extracardiac shunts;
- absence of chronic cardiac pulmonary disease, either clinically or at autopsy;
- absence of arterial disease, such as syphilis, or more than minimal atheromatosis or arteriolar sclerosis.
Of our four patients, the first undoubtedly fulfils all the above criteria as he has been known to have a large pulmonary artery for 46 years, and the second case has a very long history and an abnormal chest radiograph for 30 years. In case 3 it was not possible to adequately assess the pulmonary artery pressures at echo, and it was thought inappropriate to undertake invasive studies. Nevertheless, demonstration of a large pulmonary artery over a 34-year period with a right ventricle that has remained normal presumably indicates that idiopathic dilatation of the pulmonary trunk is indeed the diagnosis. In case 4 the operative findings, including those of the intraoperative TOE, would indicate that idiopathic dilatation of the pulmonary trunk is the diagnosis. The large pulmonary artery had been known to be present for at least 12 years in this case.
Sporadic case reports of this condition have occurred in the literature [5–7], as have details of the echocardiographic findings [8]. Ugolini et al [9] report four cases in which MRI played a major role in the diagnosis. Idiopathic dilatation of the pulmonary artery is normally regarded as benign, so post-mortem results are very rarely available and operative specimens are seldom obtained. Andrews et al [10] report a case of pulmonary artery dissection in a patient who apparently had idiopathic dilatation of the pulmonary artery. The patient died but, on post-mortem, histological examination showed deposition of acid mucopolysaccharide in the media, similar to that seen in cystic medial necrosis, but less severe. It would therefore seem likely that this patient did not, in fact, have true idiopathic dilatation of the pulmonary trunk, but a connective tissue disorder that was unrecognized in life. Nair and Cobanoglu [11] describe a patient on whom they performed plication on an apparently idiopathic pulmonary artery aneurysm, but did not obtain histology on the resected specimen. Regrettably, histological examination was also not performed on the resected segment of pulmonary artery in our case 4.
There is only one previous case report of long-term follow-up of idiopathic dilatation of the pulmonary artery [12] and this patient was observed to have a large left pulmonary artery over a period of 39 years.
The four patients described here had follow-up periods of 46 years, at least 30 years, 34 years and 12 years, respectively, so clearly have a benign and non-progressive condition. It appears that some patients previously labelled as having this disorder will, in the long-term, turn out to have some underlying pathology such as an arteritis or connective tissue disorder. We would therefore propose that a prolonged period of observation without significant change in the size of the central pulmonary vessels should be added to the original diagnostic criteria for the diagnosis of this condition.
Received for publication October 17, 2001.
Revision received February 7, 2002.
Accepted for publication February 14, 2002.
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References
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- Chang CH. The normal roentgenographic measurement of the right descending pulmonary artery in 1085 cases. AJR 1962;87:929–35.
- Weyman AE. Principles and practice of echocardiography (2nd edn). Philadelphia, PA: Lea and Febiger, 1994:1294.
- Kruger S, Haage P, Hoffmann R, Breuer C, Bucker A, Hanrath P, et al. Diagnosis of pulmonary arterial hypertension and pulmonary embolism with magnetic resonance angiography. Chest 2001;120:1556–61.[Abstract/Free Full Text]
- Greene DG, Baldwin EF, Baldwin JS, et al. Pure congenital pulmonary stenosis and idiopathic congenital dilatation of the pulmonary artery. Am J Med 1949;6:24–40.[Medline]
- Chang RY, Tsai CH, Chou YS, Wu TC. Idiopathic dilatation of the pulmonary artery. A case presentation. Angiology 1996;47:87–92.
- Fang CC, Tsai CC. Idiopathic pulmonary artery aneurysm. J Formos Med Assoc 1996;95:873–6.[Medline]
- Corbi P, Jayle C, Christiaens L, Tailboux L, Rahmati M, Allal J. Idiopathic aneurysm of the pulmonary artery trunk. Report of a case. Ann Med Interne (Paris) 1999;150:67–9.[Medline]
- Asayama J, Matsuura T, Endo N, Watanabe T, Matsukubo H, Furukawa K, et al. Echocardiographic findings of idiopathic dilatation of the pulmonary artery. Chest 1977;71:671–3.[Free Full Text]
- Ugolini P, Mousseaux E, Sadon Y, Sidi D, Mercier LA, Paquet E, Caux JC. Idiopathic dilatation of the pulmonary artery: report of four cases. Magn Reson Imaging 1999;17:933–7.[Medline]
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- van Rens MT, Westermann CJ, Postmus PE, Schramel FM. Untreated idiopathic aneurysm of the pulmonary artery; long-term follow-up. Respir Med 2000;94:404–5.[Medline]
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Abstract
Introduction
