Treatment of Enlarged Pulmonary Artery
The treatment of an enlarged pulmonary artery must address the underlying cause, which is most commonly pulmonary arterial hypertension (PAH), and should be managed at a specialized center with expertise in PAH diagnosis and treatment. 1
Diagnostic Evaluation
Before initiating treatment, it's essential to determine:
- The underlying cause of pulmonary artery enlargement
- The severity of pulmonary hypertension (if present)
- The presence of right ventricular dysfunction
- Any associated complications
Key diagnostic tests include:
- Right heart catheterization (gold standard for PAH diagnosis)
- Echocardiography
- CT or MRI of the chest
- Vasoreactivity testing (in specialized centers)
Treatment Algorithm
1. Treatment of Underlying Pulmonary Arterial Hypertension
PAH is defined by:
- Mean pulmonary artery pressure >20 mmHg
- Pulmonary artery wedge pressure ≤15 mmHg
- Pulmonary vascular resistance ≥3 Wood units 2
Treatment options include:
a) Vasoreactivity Testing and Calcium Channel Blockers
- Perform vasoreactivity testing only in expert centers 1
- A positive response is defined as reduction of mean PAP ≥10 mmHg to reach an absolute value of mean PAP ≤40 mmHg with unchanged or increased cardiac output 1
- High-dose calcium channel blockers only for patients with idiopathic, heritable, or drug-induced PAH who show positive vasoreactivity 1
b) PAH-Specific Medications
- First-line therapy should include combination therapy targeting multiple biological pathways 2
- Options include:
- Endothelin receptor antagonists (bosentan, ambrisentan)
- Phosphodiesterase-5 inhibitors (sildenafil, tadalafil)
- Soluble guanylate cyclase stimulators (riociguat)
- Prostacyclin pathway agonists (epoprostenol, treprostinil)
For severe PAH:
- Intravenous epoprostenol is indicated to improve exercise capacity and has shown survival benefits in NYHA Class III-IV patients 3
- Epoprostenol produces dose-related increases in cardiac index and stroke volume while decreasing pulmonary vascular resistance 3
2. Interventional Procedures for Structural Issues
For pulmonary artery stenosis contributing to enlargement:
- Pulmonary angioplasty is indicated for significant peripheral branch pulmonary artery stenosis 1
- Primary intravascular stent implantation is indicated for significant proximal or distal branch pulmonary artery stenosis when the vessel/patient is large enough 1
- For main pulmonary artery stenosis that elevates RV pressure, stent implantation is reasonable provided it won't compromise pulmonary valve function 1
3. Management of Complications
Left Main Coronary Artery Compression
- Consider this complication in patients with severe pulmonary hypertension who experience angina 4
- Coronary angiography with intravascular ultrasound is the gold standard for diagnosis
- Percutaneous coronary intervention is recommended as the preferred revascularization strategy 4
Right Ventricular Failure
- Diuretics for volume overload
- Supplemental oxygen for hypoxemia
- Consider inotropic support in acute decompensation
Special Considerations
Segmental Pulmonary Artery Hypertension
- Often seen in complex congenital heart disease, particularly pulmonary atresia
- Endothelin receptor antagonists (e.g., bosentan) have shown improvement in functional class and exercise capacity in these patients 5
Congenital Heart Disease
- For patients with major aortopulmonary collateral arteries:
- A coordinated approach between surgery and cardiology intervention is required
- May need reconstruction of collaterals to a valved right ventricular pulmonary artery conduit 6
Monitoring and Follow-up
- Regular assessment of functional capacity (6-minute walk test)
- Echocardiographic evaluation of right ventricular function
- Laboratory monitoring for medication side effects
- Adjustment of therapy based on clinical response
Prognosis
With modern PAH-specific therapies, 5-year survival has improved from 34% in 1991 to more than 60% in 2015 2. Early diagnosis and prompt initiation of appropriate therapy are crucial for improving outcomes.