Right Pulmonary Artery-to-Left Atrial Fistula: A Differential Diagnosis of Cyanosis without Structural Heart Disease

Direct communication between the right pulmonary artery and the left atrium is an unusual variation of a pulmonary arteriovenous fistula. In fact, there are only about 50 cases reported in the literature.¹ This is one condition in which clinical examination may reveal only cyanosis. Contrast echocardiography may show only right-to-left shunt, and only angiography is truly diagnostic.¹

Case study. A 19-year-old male presented to us with a history of recently detected cyanosis. His systemic saturation was 81%, with conjunctival congestion, pan-digital carpopedal cyanosis and clubbing, with no murmur. Chest X-ray and electrocardiography were not contributory. Transthoracic echocardiography showed no structural heart disease except for a dilated right upper pulmonary vein. Injection of contrast through the left arm showed contrast entering the left atrium through the right upper pulmonary vein 4 to 5 cardiac cycles after filling of contrast in the right atrium. Right pulmonary artery angiography showed a branch of the right pulmonary artery directly entering the left atrium via a track superolateral to the left atrium (Figure 1A). Selective injection into the track showed reflux of contrast into the pulmonary veins (Figure 1B). No devices were planned because of fear of pulmonary vein obstruction. Surgical division and suturing of the fistula were performed.

Discussion. Cyanosis without obvious cyanotic heart disease on transthoracic echocardiography often poses a diagnostic dilemma. Contrast injection often offers diagnostic clues, as was the case in our patient, and ideally should be done through the left upper limb to pick up a left superior vena cava-to-left atrial communication. If imaging techniques turn out to be negative, pigment hemoglobinopathies like methemogobinemia and sulfhemoglobinemia should be considered.

A pulmonary artery fistula to the left atrium may present either in the neonatal period with intense cyanosis,² or as large shunts causing severe heart failure requiring early intervention.³ A rarer presentation is as delayed cyanosis in childhood, adolescence or even adult life,² as in our patient.

Generally, early intervention is indicated to prevent complications, particularly emboli, cerebral abscess and rupture.² However, surgery can probably be postponed in children who only have mild cyanosis and no apparent heart failure.⁴ Though one older surgical series has reported a 22% mortality rate,⁵ newer surgical techniques and transcatheter procedures using coils and devices can provide a cure at acceptable risks.²

Acknowledgement. We wish to thank the referring cardiologist Dr. Anil N. Kumar for sending us the patient for evaluation of late-onset cyanosis.

References

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2. Duke C, Alwi M. Transcatheter closure of direct communication between right pulmonary artery and left atrium using Amplatzer device. Heart 2003;89:1210.

3. Saatvedt K, Stake G, Lindberg H. Fistula between the right pulmonary artery and the left atrium — An unusual cause of cyanotic heart disease. Cardiol Young 1995;5:85.

4. Cheatham JP, Barnhart DA, Gutgesell HP. Right pulmonary artery to left atrium communication. An unusual cause of cyanosis in the newborn. Pediatr Cardiol 1982;2:149–152.

5. Zeebregts CJ, Nijveld A, Lam J, et al. Surgical treatment of a fistula between the right pulmonary artery and the left atrium: Presentation of two cases and review of literature. Eur J Cardiothorac Surg 1997;11:1056–1061.