What is partial anomalous pulmonary venous return (PAPVR)?

Partial Anomalous Pulmonary Venous Return (PAPVR)

Partial anomalous pulmonary venous return (PAPVR) is a congenital cardiovascular malformation in which one or more, but not all, pulmonary veins connect abnormally to the right atrium or to its venous tributaries, while the remaining pulmonary veins connect normally to the left atrium. 1

Definition and Prevalence

PAPVR is a relatively common congenital anomaly with a prevalence of approximately 1% 1. It occurs when some pulmonary veins drain erroneously into the systemic venous circulation instead of the left atrium, creating a left-to-right shunt. This is in contrast to total anomalous pulmonary venous connection (TAPVC), where all pulmonary veins connect abnormally to the right atrium or systemic veins.

Anatomical Variants

PAPVR has several common variants:

• Right-sided PAPVR: Most common form

  • Right upper pulmonary vein(s) connecting directly to the superior vena cava (SVC)
  • Often associated with sinus venosus atrial septal defect
  • May cause significant right heart volume overload

• Left-sided PAPVR:

  • Left upper pulmonary vein connecting to the left brachiocephalic vein via a vertical vein
  • Less common than right-sided variants 2, 3

• Scimitar syndrome:

  • Part or all of the right pulmonary veins connect to the inferior vena cava
  • Often associated with hypoplastic right lung and anomalous bronchial/arterial anatomy 1

Clinical Presentation

The clinical manifestations of PAPVR depend on:

1. The number of anomalous veins (extent of shunt)
2. Presence of associated cardiac anomalies
3. Degree of pulmonary hypertension

Patients may present with:

• Asymptomatic (incidental finding)
• Dyspnea on exertion
• Right heart failure symptoms
• Recurrent pulmonary infections
• Pulmonary hypertension
• Atrial arrhythmias (in longstanding cases) 2, 4

Diagnosis

Diagnosis of PAPVR typically involves:

1. Transthoracic Echocardiography (TTE):

   • Initial imaging modality
   • May show right-sided cardiac chamber dilation
   • Often limited in fully delineating pulmonary venous anatomy

2. Advanced Imaging (when TTE is inadequate):

   • Cardiac CT Angiography (CTA): Excellent for defining anatomical details of anomalous connections 1, 2
   • Cardiac MRI: Provides anatomical definition and quantifies shunt fraction
   • Cardiac Catheterization: Less commonly used now, but can quantify shunt via oximetry 1

Management

Management decisions are based on:

1. Shunt fraction: Significant left-to-right shunts (typically Qp:Qs > 1.5:1)
2. Symptoms: Presence and severity of symptoms
3. Right ventricular function: Evidence of right ventricular dilation or dysfunction
4. Pulmonary hypertension: Presence and severity
5. Associated anomalies: Particularly atrial septal defects

Treatment options include:

• Surgical correction: Indicated for symptomatic patients or those with significant shunts

  • Various techniques depending on anatomy and associated defects
  • May involve creation of intra-atrial baffles or direct reimplantation of anomalous veins

• Medical management: For patients with mild symptoms or those who are poor surgical candidates

  • Pulmonary vasodilators (e.g., riociguat, ambrisentan) for pulmonary hypertension 4
  • Management of right heart failure symptoms
  • Treatment of arrhythmias

• Observation: For asymptomatic patients with small shunts

Long-term Complications

Without treatment, significant PAPVR may lead to:

• Progressive right ventricular dilation and dysfunction
• Pulmonary hypertension
• Atrial arrhythmias
• Right heart failure

Key Pitfalls and Caveats

1. Missed diagnosis: PAPVR may be overlooked on routine imaging, particularly left-sided variants
2. Underestimation of shunt: Clinical assessment may underestimate the hemodynamic significance
3. Post-surgical complications: Pulmonary vein stenosis, baffle obstruction, or arrhythmias may occur after repair
4. Misdiagnosis: Left-sided PAPVR can be mistaken for other vascular anomalies on imaging 3
5. Associated anomalies: Always evaluate for concurrent atrial septal defects, which are present in up to 90% of cases 5

PAPVR requires careful evaluation with appropriate imaging to determine the exact anatomy and hemodynamic significance before making management decisions.