Operability Assessment for Shunt Lesions with Pulmonary Hypertension
Patients with left-to-right shunt lesions and pulmonary hypertension are operable when pulmonary artery pressure is less than two-thirds of systemic pressure AND pulmonary vascular resistance (PVR) is less than two-thirds of systemic vascular resistance, with documented net left-to-right shunting. 1
Critical Hemodynamic Thresholds
The operability decision hinges on specific hemodynamic parameters obtained via cardiac catheterization at an adult congenital heart disease (ACHD) regional center 1:
For VSD with Pulmonary Hypertension:
- Operable (Class IIa): Qp/Qs >1.5 with PAP <2/3 systemic pressure AND PVR <2/3 systemic vascular resistance 1
- Definitely operable (Class I): Qp/Qs ≥2.0 with clinical LV volume overload 1
- Inoperable (Class III): Severe irreversible PAH with no net left-to-right shunt 1
For ASD with Pulmonary Hypertension:
The 2022 Canadian guidelines provide more granular thresholds 2:
- Operable: PAP <50% systemic pressure AND/OR PVR <1/3 systemic vascular resistance (SVR) with net left-to-right shunt
- Borderline operable: PAP <2/3 systemic AND PVR <2/3 SVR with net left-to-right shunt (requires multidisciplinary PAH expertise)
- Inoperable: PAP >2/3 systemic OR PVR >2/3 systemic OR net right-to-left shunt
Mandatory Assessment Components
All patients with shunt lesions and PAH must undergo cardiac catheterization for operability assessment 1. This is non-negotiable and should be performed at an ACHD regional center with PAH expertise.
Key Catheterization Data Required:
- Baseline pulmonary artery pressures (mean PAP)
- Pulmonary vascular resistance (indexed and absolute)
- Systemic vascular resistance
- Qp/Qs ratio (pulmonary-to-systemic flow)
- Direction of shunting (critical—any right-to-left component contraindicates closure)
- Pulmonary artery wedge pressure (to exclude left heart disease)
Acute Vasodilator Testing:
While guidelines don't mandate this, recent research suggests oxygen challenge during catheterization can help predict reversibility 3, 4. A post-oxygen Qp/Qs <0.9 predicts poor surgical outcomes 3.
Clinical Red Flags for Inoperability
Beyond hemodynamics, certain clinical features strongly suggest inoperability 3, 4:
- Age >2 years with severe PAH (suggests established pulmonary vascular disease)
- Bidirectional or predominantly right-to-left shunting on echocardiography
- Absence of RV or LV volume overload (indicates balanced or reversed shunt)
- Single or narrowly split S2 (suggests severe PAH)
- Cyanosis at rest
- Developmental lung disease (particularly in infants) 4
The "Treat-and-Repair" Strategy
For patients with borderline operability (PVR 3-6 Wood units, Qp/Qs ≥1.5), targeted PAH therapy followed by reassessment may enable closure 5, 6. This approach requires:
- Initiation of pulmonary vasodilator therapy (endothelin receptor antagonists, phosphodiesterase-5 inhibitors, or prostacyclins)
- Treatment duration of 3-6 months
- Repeat catheterization to document:
- PVR reduction to <3 Wood units (ideally)
- Increase in Qp/Qs to >1.5
- Maintained left-to-right shunt direction
Recent data shows this strategy can convert 22% of initially inoperable patients to operable status 5.
Common Pitfalls to Avoid
Do not rely solely on echocardiographic estimates of pulmonary pressure—catheterization is mandatory for operability decisions 1. Echocardiography frequently misidentifies VSD jets as tricuspid regurgitation jets, leading to false PAH diagnoses 1.
Do not use fixed PVR cutoffs in isolation—the ratio of pulmonary to systemic pressures (PAm/SAm ratio <0.70) and resistance ratio (RR <0.25) are better predictors of reversibility than absolute PVR values 7.
Do not close defects in patients with Eisenmenger physiology (net right-to-left shunt with cyanosis)—this is absolutely contraindicated and carries excessive mortality 1.
Surgical Considerations
When operability criteria are met:
- Surgery must be performed by a congenital heart surgeon with specific CHD expertise 1, 2
- Consider fenestrated closure in borderline cases with persistently elevated PVR despite medical therapy—this allows a "pop-off" mechanism if RV fails postoperatively 8
- Expect potential transient RV dysfunction postoperatively even in operable patients 8
Post-Closure Monitoring
Patients who undergo closure with elevated (but acceptable) preoperative PVR require:
- Annual follow-up at ACHD centers 1
- Continued PAH-targeted therapy in many cases
- Vigilance for persistent or recurrent PAH (occurs in 5-10% despite meeting operability criteria) 5
The key distinction is that operability is determined by hemodynamics showing reversible pulmonary vascular disease with preserved left-to-right shunting, not by the presence of PAH alone. Patients with severe irreversible PAH should receive PAH-specific medical therapy but defect closure is contraindicated as it worsens outcomes and mortality 1.