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Branch Pulmonary Artery Stenosis on Echocardiography


 

Branch Pulmonary Artery Stenosis: Causes, Diagnosis & Management


Branch Pulmonary Artery Stenosis (BPAS) refers to narrowing of the right or left pulmonary artery—or one of their segmental branches—after they bifurcate from the main pulmonary artery. This narrowing obstructs blood flow to one lung or lung segment, leading to unequal perfusion, increased right ventricular (RV) workload, and potential pulmonary hypertension if significant.

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Why Branch PA Stenosis Matters


Branch PA stenosis may be mild and asymptomatic for years, but significant obstruction can cause:


Increased RV systolic pressure


Reduced blood flow to the affected lung


Compensatory overcirculation of the opposite lung


Risk of RV hypertrophy and failure in advanced cases



Early recognition is critical, especially in infants with congenital heart disease.

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Causes of Branch Pulmonary Artery Stenosis


1. Congenital Causes


Isolated BPAS (sporadic)


Post-ductal coarctation effect on the left PA in newborns


Williams syndrome (elastin gene defect)


Alagille syndrome


Tetralogy of Fallot (especially after surgical repair)


Truncus arteriosus and other conotruncal anomalies



2. Acquired Causes


Post-surgical scarring, especially after:


Blalock-Taussig shunt


Pulmonary artery patches / reconstructions



External compression by enlarged lymph nodes or vascular rings


Thrombus or intimal hyperplasia after stent placement or catheterization


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Symptoms


Many patients remain asymptomatic, especially if unilateral. Significant stenosis may cause:


Exertional dyspnea


Fatigue


Reduced exercise tolerance


Recurrent chest infections (due to unequal lung perfusion)


Cyanosis in infants with associated congenital heart disease




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Clinical Examination


Key findings may include:


Ejection systolic murmur at upper left sternal border radiating to the back


Differential breath sounds if severe stenosis reduces regional lung perfusion


Signs of RV pressure overload in advanced cases




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Diagnostic Evaluation


1. Echocardiography


First-line investigation


Assesses:


Peak gradients across branch PA


Size discrepancy between right and left PA


RV systolic pressure


Flow turbulence on color Doppler



Limitations: distal branches may not be well visualized



2. CT Pulmonary Angiography


Provides excellent anatomical detail:


Exact location and length of stenosis


Distal vessel size


Lung perfusion asymmetry



3. Cardiac MRI


Best for quantifying differential lung perfusion


Useful in serial follow-up of repaired congenital heart disease



4. Cardiac Catheterization


Both diagnostic and therapeutic:


Direct pressure gradients


Balloon angioplasty or stenting when indicated




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Management of Branch PA Stenosis


Observation


Mild stenosis


Minimal RV pressure elevation


Symmetric perfusion maintained

Regular follow-up with echo and CT/MRI is recommended.




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Intervention Indications


Consider treatment if:


Peak gradient > 20–30 mmHg


RV systolic pressure > 50% of systemic


> 20–25% perfusion difference between lungs


Symptoms or progressive RV dilation




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Catheter-Based Therapy (First-line)


1. Balloon Angioplasty


Useful for discrete stenosis


Initial therapy in infants and children



2. Stent Placement


Preferred in adolescents and adults


Maintains long-term patency


Can be dilated as the child grows




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Surgical Repair


Reserved for complex cases:


Long-segment narrowing


Ostial stenosis


Failed catheter-based interventions


Associated congenital heart defects requiring surgery



Techniques include patch augmentation and PA reconstruction.



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Prognosis


With timely intervention, prognosis is excellent. Untreated severe stenosis may lead to:


Chronic RV pressure overload


Pulmonary hypertension


Impaired lung development (in children)


Exercise limitation in adulthood




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Key Takeaways


Branch pulmonary artery stenosis is a significant cause of unequal lung perfusion and RV pressure overload.


Echocardiography is useful, but CT/MRI provide better anatomical detail.


Catheter-based therapy—especially stenting—is the cornerstone of treatment.


Early diagnosis ensures excellent long-term outcomes.

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