|Year : 2016 | Volume
| Issue : 2 | Page : 72-75
An unusual case of right-to-left shunt: Pulmonary artery to left atrium fistula
Kiran Ashok Kale, Tapan Chandrakant Patel, Swapnil Chandrakant Patil, Anagha Rajeev Joshi
Department of Radiology, Lokmanya Tilak Municipal General Hospital (LTMGH), Lokmanya Tilak Municipal Medical College (LTMMC), Mumbai, Maharashtra, India
|Date of Web Publication||6-Jun-2016|
Kiran Ashok Kale
Room No. 110, New RMO Hostel, Lokmanya Tilak Municipal General Hospital (LTMGH), Lokmanya Tilak Municipal Medical College (LTMMC), Sion (West), Mumbai - 400 022, Maharashtra
Source of Support: None, Conflict of Interest: None
We present a rare variant of pulmonary arteriovenous (AV) fistula (malformation), right pulmonary artery (RPA) to left atrium (LA) fistula, with its clinical and imaging findings with multidetector computed tomography (MDCT) pulmonary angiography and dynamic 3.0 T magnetic resonance imaging (MRI) pulmonary angiography in a 2-year-old female child who presented with central cyanosis at the age of 18 months.
Keywords: Cyanosis, pulmonary angiography, pulmonary arteriovenous (AV) fistula, right pulmonary artery (RPA) to left atrium (LA) fistula
|How to cite this article:|
Kale KA, Patel TC, Patil SC, Joshi AR. An unusual case of right-to-left shunt: Pulmonary artery to left atrium fistula. Heart India 2016;4:72-5
|How to cite this URL:|
Kale KA, Patel TC, Patil SC, Joshi AR. An unusual case of right-to-left shunt: Pulmonary artery to left atrium fistula. Heart India [serial online] 2016 [cited 2021 Dec 4];4:72-5. Available from: https://www.heartindia.net/text.asp?2016/4/2/72/183528
| Introduction|| |
In pulmonary arteriovenous (AV) fistula, a direct communication exists between a large pulmonary artery (PA), and a pulmonary vein. Pulmonary AV fistulas range in size from very small, without clinical findings, to very large communications with prominent clinical manifestations.
Direct communication between the right pulmonary artery (RPA) and the left atrium (LA) is a rare and unusual congenital malformation , and is considered as a form of pulmonary AV fistula or malformation.
The first case of RPA to LA communication was reported by Friedlich et al.  in 1950 and the first description of pulmonary arteriovenous malformation (PAVM) was reported by Churton in 1897. 
In a PA to LA fistula, pulmonary arterial blood that is low in oxygen content is delivered directly to the LA via the fistula bypassing the lungs. The result of this right-to-left shunt may be cyanosis, decreased oxygen saturation, tachypnea, and respiratory distress in neonates. Older patients have milder symptoms.  And there is the opportunity for paradoxical embolization to the systemic circuit.
This article presents a case of a child with an unusual form of pulmonary AV fistula, namely, direct communication of the right descending PA with the LA. This anomaly presents with large right-to-left shunt, as cyanosis, and is a prominent clinical sign in this patient.
| Case report|| |
A 2-year-old female child presented with complaints of bluish discoloration of lips, tongue, nail beds of both extremities, and breathlessness since 4 months when the child was of 18 months. Parents did not notice these symptoms before the age of 18 months.
On admission, the arterial oxygen saturation (SpO 2 ) was 67% and subsequent two-dimensional (2D) echocardiogram (echo) raised a suspicion of pulmonary AV fistula.
With the suspicion of pulmonary AV fistula, the patient was referred to our department.
Computed tomography (CT) pulmonary angiography was performed on a 64-detector row CT scanner (Brilliance CT; Philips, Best, the Netherlands) with 20 mL of intravenous nonionic iodinated contrast material (300 mg I/mL, Omnipaque: GE healthcare, Shanghai, China) at a rate of 2 mL/s via an automated pressure injector with retrospective electrocardiogram (ECG) gating.
The CT revealed dilated RPA that measured 17 mm in diameter with its dilated descending branch seen directly communicating with the LA [Figure 1]. The right inferior pulmonary vein was seen opening where the dilated inferior branch RPA opened into the LA.
|Figure 1: (a and b) MDCT pulmonary angiographic images in plane of the RPA to LA fistula (arrow) showing a wide direct communication between the descending branch of the RPA (star) and the left atrium (block arrow)|
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Moderate dilatation of the LA and mild dilatation of the left ventricle was seen in [Figure 2]a.
|Figure 2: CT pulmonary angiographic images in four-chamber view showing drainage of all four pulmonary veins into the dilated left atrium (star)-(a) right inferior (arrow), (b) right superior (arrow), and left superior (block arrow) and (c) left inferior (arrow) pulmonary veins|
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All pulmonary veins were seen draining into the LA [Figure 2]a-c.
Lung parenchyma was normal.
Followed by CT angiography, cardiac magnetic resonance imaging (MRI) with dynamic pulmonary angiography was done on 3 T MRI (Philips Achieva 3.0 T, Philips Medical Systems, Netherlands) using a 32-channel cardiac coil for acquisition.
MRI-compatible sensors were used for vectorcardiogram gating (VCG) and respiratory gating of the scans. The protocol took approximately 45 min. Intravenous injection of Gadopentetate Dimeglumine, Magnilek (Panoli, Bharuch, India) as a bolus of 0.2 mmoL/kg body weight at 1.2 mL/s, followed by a saline flush of 10 mL at 1.5 mL/s through a superficial upper limb vein was performed using an automated injector, Optistar LE (Mallinckrodt, Cincinnati, USA) during the Dynamic MIP s3_4D Trak SENSE.
The MRI revealed a short fistula of a size of 1 cm in diameter between RPA and LA with dilated LA [Figure 3] and [Figure 4] on cine bright blood sequences [steady state free precession (SSFP)] in-plane of fistula and high resolution white blood survey images in coronal plane.
|Figure 3: Balanced SSFP sequence in the plane of the fistula (arrow) wide direct communication between the descending branch of the RPA (star) and the left atrium (block arrow)|
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|Figure 4: (a-d) High resolution white blood surview images in coronal plane showing communication (arrow) between the descending branch of the RPA (star) and the dilated LA (block arrow)|
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Moderate dilatation of the LA and the left ventricle, and mild dilatation of the right atrium and RPA were noted.
On dynamic magnetic resonance (MR) angiography, early preferential flow through the fistula into the LA with mildly delayed flow of contrast into the pulmonary circulation was seen [Figure 5].
|Figure 5: MIP images of dynamic contrast-enhanced pulmonary angiographic sequence at 13 s, 14.3 s, and 19.4 s, showing; (a) fistulous tract between RPA and LA (arrow), (b) preferential filling of the left heart (arrow) and (c) delayed opacification of the pulmonary vasculature (arrows)|
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Phase contrast angiographic assessment of the main pulmonary artery (MPA), RPA, LPA, and fistula revealed the flow from the MPA into the RPA and via the fistula into the LA.
| Discussion|| |
Direct communication between the PA and the LA is a rare anomaly and is considered as a variant of pulmonary AV fistula. 
Pulmonary AV fistula is an abnormal communication between a PA and a pulmonary vein with absence of the capillary network that links the two.  Embryologically, pulmonary AV fistula develops due to incomplete degeneration of the septum between the arterial and venous plexus of the pulmonary vascular bed. It may be due to the formation of thin-walled sacs because of a defect in the capillary loops as well. A pulmonary vein connected to such a fistula is absorbed into the LA during development, forming a PA-LA fistula. 
Clinical diagnosis is difficult.
The age at diagnosis ranged from 1 month to 60 years  with most cases present in the third decade of life. 
Among common symptoms and signs are dyspnea (50%), neurological symptoms (20%),  telangiectasia (33%),  and cyanosis (60%). Among the reported cases, only one patient had murmur (continuous murmur).  ECG can be normal. 
The clinical findings in these cases differ only slightly from more common types of pulmonary AV fistula. The large diameter and short length of the fistulous channel in this type of fistula results in a low resistance in the fistulous channel and facilitates a large right-to-left shunt.
Complications are rupture, hemoptysis, polycythemia, and paradoxical emboli causing brain abscess. 
Associated atrial septal defects are common. Other associated cardiac malformations are rare, but anomalies of the right lung, such as the absence of the lower or middle lobe, right lung sequestration, and diverticulum of the right main bronchus, have been reported. ,
Friedlich and et al.  observed resistance in the fistula was equal to that seen in the normal pulmonary vascular bed, whereas the vascular resistance in the non-fistulous part of the pulmonary vascular system was about twice as normal. Because the normal and anomalous pulmonary circuits are in parallel, this difference of resistance favors flow through the low resistance (anomalous) channel. The common phenomenon of delay in appearance of cyanosis until adolescence or adult life is perhaps based on acquired increasing resistance in the non-fistulous part of the pulmonary vascular bed.
According to de Souza e Silva et al.,  communication between the RPA and the LA can be classified into three types, based upon the anatomy of pulmonary venous drainage pattern. An additional fourth type was later described by Ohara et al. 
Type I: Normal pulmonary venous drainage pattern.
Type II: Absent right inferior pulmonary vein with fistulous connection at the normal site of its origin. Associated are right lung abnormalities such as absent one or more lobes.
Type III: All pulmonary veins connected to the aneurysmal pouch.
Type IV: Right inferior pulmonary vein replaced by three small veins connected to the aneurysmal pouch.
Hence, our case is type I communication between the RPA and the LA.
| Summary|| |
PA to LA fistula is an unusual anomaly among a rare category of pulmonary AV malformations. Our case is unique in the form of age of presentation (2 years) and the type of fistula; between descending branch of the RPA and the LA with all pulmonary veins draining into dilated LA (type I). In addition, CT pulmonary angiography and cardiac MRI with dynamic pulmonary angiography obviated the need of cardiac catheterization for the diagnosis.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]