Assiut University Heart Hospital, Department of Cardiovascular Medicine, Assiut, Egypt
Clinical History
A 47-year-old woman presented with recurrent palpitations. She had a history of a secundum atrial septal defect (ASD) that was surgically repaired at 12 years of age. She now reported exertion-related palpitations. Physical examination revealed no cyanosis or clubbing. The jugular venous pressure was elevated to 6 cm above the sternal angle, with prominent systolic V waves. The pulse was regular at 80 beats/min, with normal volume. Blood pressure was 130/80 mmHg. Respiratory rate was normal, and arterial oxygen saturation was 99% on room air. Examination of the chest showed a well-healed median sternotomy scar. The apex beat was located in the left fifth intercostal space at the midclavicular line and was diffuse. A left parasternal heave was present. The first and second heart sounds were normal in intensity. A harsh grade 3/6 ejection systolic murmur was audible in the pulmonary area, radiating to the left infraclavicular region and the back, and increased in intensity with inspiration. A faint decrescendo diastolic murmur was also heard in the pulmonary area. In addition, a high-pitched pansystolic murmur was heard at the tricuspid area and became louder with inspiration.
A 12 lead electrocardiogram (ECG) demonstrated sinus rhythm with first-degree atrioventricular block, incomplete right bundle branch block, and an isolated premature ventricular complex visible in the limb leads (axis approximately −30°) (Figure 1). Transthoracic echocardiography (TTE) demonstrated situs solitus, levocardia, concordant atrioventricular and ventriculoarterial connections, and normally related great arteries. A well-seated ASD patch was visualized without a residual interatrial shunt. The right atrium (RA) and right ventricle (RV) were dilated, and the RV was hypertrophied with preserved systolic function. The left ventricle (LV) had normal size and systolic function. The pulmonary valve was thickened with systolic doming and demonstrated significant stenosis (peak velocity 3.5 m/s; peak systolic gradient 48 mmHg) and moderate pulmonary regurgitation (Movie 1.). The main and branch pulmonary arteries were dilated. Severe tricuspid regurgitation was present, with an RV–RA systolic pressure gradient of 53 mmHg. Cardiac magnetic resonance (CMR) imaging was subsequently performed for comprehensive assessment of RV volumes and function and to guide consideration of pulmonary valve intervention.
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| Figure 1. Twelve-lead electrocardiogram demonstrating sinus rhythm, first-degree atrioventricular block (prolonged PR interval), incomplete right bundle branch block, and a single premature ventricular complex.. |
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| Movie 1. Parasternal short-axis TTE view of the pulmonary valve with and without color Doppler. The valve leaflets are thickened, and color Doppler demonstrates turbulent flow across the valve, consistent with significant pulmonary stenosis and increased transvalvular flow. |
CMR Findings
CMR was performed on a 1.5-T Ingenia scanner (Philips Healthcare, Best, The Netherlands). Cine imaging demonstrated normal cardiac segmental anatomy with severe RA and RV dilatation (RV end-diastolic volume index (RVEDVi), 206 mL/m²; RV end-systolic volume index [RVESVI], 93 mL/m²), marked RV hypertrophy (RV mass index 67 g/m²), and moderate LV hypertrophy (LV mass index (LVMI), 75 g/m²) (Movie 2). The coronary sinus, inferior vena cava (IVC), hepatic veins, and the main and branch pulmonary arteries were also dilated. Both ventricles demonstrated preserved contractility, with paradoxical interventricular septal motion consistent with RV volume and pressure overload. Global systolic function was preserved (LV ejection fraction (LVEF) 58%; RV ejection fraction (RVEF) 55%).
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| Movie 2. Cine balanced steady state free precession (bSSFP) short axis stack. There is severe RA and RV chamber dilation with flattening of the ventricular septum during diastole and systole consistent with RV volume and pressure overload. |
To further investigate the etiology of the RV overload, dedicated RV outflow tract (RVOT) and pulmonary valve imaging was performed. The pulmonary valve was trileaflet, thickened, and demonstrated combined stenosis and regurgitation, although the pulmonary regurgitant fraction was only 12% (Movie 3). No residual ASD or other intracardiac shunt was identified. However, phase-contrast flow imaging demonstrated that net forward flow in the main pulmonary artery was nearly twice that in the ascending aorta (9.6 L/min vs. 5.0 L/min), yielding a pulmonary-to-systemic flow ratio (Qp:Qs) of 1.9 (Figure 2).
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| Movie 3. RVOT cine bSSFP shows thickened pulmonary valve with stenosis and regurgitation. |
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| Figure 2. Phase-contrast velocity-mapping–derived flow curves obtained from cross-sectional imaging of the main pulmonary artery (A) and ascending aorta (B). The area under each curve represents flow volume. Insets display the corresponding heart rate, net forward flow, and net forward output. Note the substantially greater net forward output in the main pulmonary artery compared with the ascending aorta, resulting in a calculated Qp:Qs ratio of 1.9. Abbreviations: MPA, main pulmonary artery; Ao, aorta. |
This discrepancy prompted a search for an additional left-to-right shunt. The left upper and lower pulmonary veins drained normally into the left atrium (LA). In contrast, the right upper and lower pulmonary veins formed a common confluence that coursed posterior to the LA and drained into the azygos vein. The azygos vein was markedly dilated and ascended cephalad, arching over the right pulmonary artery before draining into a right-sided superior vena cava (SVC) (Movie 4). This partial anomalous pulmonary venous return (PAPVR) was confirmed by contrast-enhanced magnetic resonance angiography (Figure 3, Movie 5). Furthermore, phase-contrast flow measurements obtained at the confluence of the right pulmonary veins immediately proximal to their connection with the azygos vein closely matched the difference between the net forward flows in the main pulmonary artery and ascending aorta, confirming the anomalous pulmonary venous drainage as the source of the left-to-right shunt.
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| Movie 4. Axial cine bSSFP stack showing the normal left pulmonary venous connection to the LA and the anomalous drainage of the right pulmonary veins into the azygous vein. |
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| Figure 3. Contrast-enhanced magnetic resonance angiography timed to the pulmonary veins and the LA. 3D volume rendered image (A) viewed from a left posterior oblique angle showing the normal drainage of upper and lower left pulmonary veins into the LA, and the anomalous drainage of the right upper and lower pulmonary veins via a confluence into the azygous vein which in turn drains into SVC. Thick-slab maximal-intensity projection images in the axial (B) and coronal (C) planes, respectively, showing the connection of the right anomalous vein confluence to the azygous vein (white arrow). The azygous vein increases in size at and cephalad to the anomalous venous connection (crosshair in C). LUPV: left upper pulmonary vein; SVC: superior vena cava; RUPV: right upper pulmonary vein; RLPV: right lower pulmonary vein; LLPV: left lower pulmonary vein. |
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| Movie 5. Contrast-enhanced angiography over-contiguous axial images delineating the anomalous right pulmonary venous drainage into the azygous vein that arches superiorly to drain into a right-sided SVC. PV: right pulmonary veins with anomalous drainage; C: confluence of the right pulmonary veins before they enter the azygous vein; A: azygous vein; S: superior vena cava. |
Conclusion
In conclusion, this patient has concomitant residual pulmonary valve disease and a previously unrecognized PAPVR involving both the right upper and lower pulmonary veins draining into the azygos vein, resulting in a net left-to-right shunt of 1.9:1. Both lesions contribute to significant RV volume and pressure overload, exceeding accepted thresholds for intervention, although RV systolic function remains preserved. At present, the patient remains reluctant to undergo either surgical or transcatheter intervention.
Perspective
PAPVR is a relatively common congenital anomaly, with an estimated prevalence of 0.4%–0.7%, and numerous anatomical variants have been described. However, anomalous pulmonary venous drainage into the azygos vein is exceedingly rare, reported in only 0.02% of autopsy examinations.[1] To date, only 29 cases have been reported in the literature.[2]
Although advances in cross-sectional imaging have improved detection rates, PAPVR may still remain unrecognized until after ASD closure.[3] Unlike in children, TTE is less reliable in adolescents and adults for defining pulmonary venous connections.[4] Furthermore, isolated PAPVR in the absence of an ASD should not be considered hemodynamically insignificant. Several reported patients with isolated PAPVR involving a single pulmonary vein have demonstrated a Qp:Qs ratio ≥ 1.5, and the hemodynamic consequences are expected to be even greater when the entire venous drainage of one lung is anomalous. The physiological impact depends on multiple factors, including the number of anomalous pulmonary veins and the pressure and compliance characteristics of the receiving chambers. This condition should be distinguished from Scimitar syndrome, in which part or all of the right lung drains anomalously into the IVC.[5] In the present case, neither right lung hypoplasia nor hypoplasia of the right pulmonary artery was present, and there was no dextroposition of the heart.
In retrospect, the PAPVR was overlooked at the time of ASD repair. It is also unclear why the pulmonary valve lesion was not addressed during the original operation. Failure to recognize the PAPVR initially complicates subsequent surgical correction, as reconstruction would require creation of an interatrial communication to baffle anomalous pulmonary venous return to the LA. To avoid diversion of systemic venous blood into the LA, the azygos vein may be ligated or occluded proximal to the anomalous pulmonary venous connection. The anomalous pulmonary venous return can then be redirected to the LA using a modified Warden-type repair.[6]
Another important aspect of this case is the coexistence of pulmonary valvular stenosis. Based on the peak instantaneous Doppler gradient, the stenosis would be classified as moderate. However, Doppler-derived gradients are highly dependent on transvalvular flow and may be overestimated in the setting of substantial left-to-right shunting. Nevertheless, the presence of significant RV hypertrophy, rather than isolated RV dilatation, together with an elevated RV–RA systolic pressure gradient of 53 mmHg, suggests that the pulmonary valve stenosis is truly hemodynamically significant. In contrast, the pulmonary regurgitant fraction of 12% is consistent with mild pulmonary regurgitation and is unlikely to be a major contributor to the observed RV remodeling.
The key learning points from this case are threefold. First, calculation of the Qp:Qs ratio revealed a clinically significant left-to-right shunt that might otherwise have remained undetected. CMR subsequently identified the precise anatomical source of the shunt through comprehensive structural and flow assessment. Second, in the presence of increased transvalvular flow, it is important to determine whether pulmonary valve stenosis is truly significant or whether the measured gradient is exaggerated by shunt-related flow augmentation, as this distinction may influence therapeutic planning. Third, failure to identify PAPVR before ASD closure may complicate future surgical repair by necessitating recreation of an atrial septal communication to redirect anomalous pulmonary venous return. This case highlights the critical role of comprehensive cross-sectional imaging in establishing a complete diagnosis before intervention and in guiding optimal management strategies.
References
- Thorsen MK, Erickson SJ, Mewissen MW, Youker JE. CT and MR imaging of partial anomalous pulmonary venous return to the azygos vein. J Comput Assist Tomogr. 1990 Nov-Dec;14(6):1007-9.<
- Toyoshima M, Sato A, Fukumoto Y, Taniguchi M, Imokawa S, Takayama S, Nishiyama T, Motegi Y, Nakazawa K, Hayakawa H, et al. Partial anomalous pulmonary venous return showing anomalous venous return to the azygos vein. Intern Med. 1992 Sep;31(9):1112-6.
- Hatipoglu S, Almogheer B, Mahon C, Houshmand G, Uygur B, Giblin GT, Krupickova S, Baksi AJ, Alpendurada F, Prasad SK, Babu-Narayan SV, Gatzoulis MA, Mohiaddin RH, Pennell DJ, Izgi C. Clinical Significance of Partial Anomalous Pulmonary Venous Connections (Isolated and Atrial Septal Defect Associated) Determined by Cardiovascular Magnetic Resonance. Circ Cardiovasc Imaging. 2021 Aug;14(8):e012371.
- Lapierre C, Siles A, Bigras JL. Partial anomalous pulmonary venous return to the azygos vein: an unusual case. Pediatr Cardiol. 2010 Jul;31(5):749-50.
- Ciçek S, Arslan AH, Ugurlucan M, Yildiz Y, Ay S. Scimitar syndrome: the curved Turkish sabre. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2014;17(1):56-61.
- Careddu L, Angeli E, Mariucci E, Quarti AG, Loforte A, Petridis FD, Mangerini VF, Donti A, Gargiulo GD. Staged approach for correction of anomalous venous return to the azygos vein. J Card Surg. 2022 Feb;37(2):440-442.
Case prepared by:
Jason N. Johnson, MD MHS
Editor-in-Chief, Cases of SCMR
Le Bonheur Children’s Hospital, The University of Tennessee Health Science Center, St. Jude Children’s Research Hospital