Management of VSD with Moderate Pulmonary Hypertension (mPAP 42 mmHg, PVR 0.2 WU)
Direct Answer
Yes, proceed immediately with vasodilator challenge testing via right heart catheterization, as this patient has a net left-to-right shunt (indicated by the low PVR of 0.2 Wood units) with moderate pulmonary hypertension, making them a potential surgical candidate if vasodilator testing demonstrates reversibility. 1
Critical Hemodynamic Analysis
Your patient's hemodynamics reveal an important pattern:
- mPAP of 42 mmHg indicates moderate pulmonary hypertension (>25 mmHg diagnostic threshold) 2, 3
- PVR of 0.2 Wood units is remarkably low—well below the normal range of 2-3 Wood units 4
- This discordance (elevated pressure with very low resistance) indicates high pulmonary blood flow from a significant left-to-right shunt 1
The extremely low PVR suggests this is primarily a high-flow state rather than fixed pulmonary vascular disease, which is prognostically favorable 1
Why Vasodilator Challenge is Essential
Guideline-Based Indications
The 2010 ESC Guidelines specifically state: 1
- Patients with VSD and PAH should be considered for surgery when there is still net L-R shunt (Qp:Qs >1.5) present and PAP or PVR are <2/3 of systemic values (baseline or when challenged with vasodilators, preferably nitric oxide, or after targeted PAH therapy) (Class IIa recommendation)
Your patient clearly has a net left-to-right shunt (evidenced by PVR 0.2 WU), making vasodilator challenge the critical next step 1
What the Challenge Will Determine
Vasodilator testing will establish:
- Whether the elevated PAP is reversible (suggesting reactive rather than fixed pulmonary vascular disease) 1
- The true operability status by measuring hemodynamics under optimal vasodilation 1
- Whether PVR remains <2/3 of systemic vascular resistance during vasodilation 1
Specific Testing Protocol
Preferred Vasodilator Agent
Use inhaled nitric oxide (NO) as the preferred agent for acute vasodilator testing, as specifically recommended by ESC guidelines for VSD with pulmonary hypertension 1
Alternative agents include intravenous prostacyclin or adenosine, but NO is preferred due to pulmonary selectivity 1
Critical Measurements During Challenge
Document the following hemodynamics at baseline and during maximal vasodilation: 1, 4
- Mean pulmonary artery pressure (mPAP)
- Pulmonary vascular resistance (PVR)
- Systemic vascular resistance (SVR)
- Calculate PVR/SVR ratio
- Cardiac output and Qp:Qs ratio
- Pulmonary capillary wedge pressure (to exclude left heart contribution)
Surgical Decision Algorithm Based on Challenge Results
Scenario 1: Positive Vasodilator Response
If vasodilator challenge demonstrates: 1
- PVR drops to <2/3 of SVR (PVR/SVR <0.67), AND
- Qp:Qs remains >1.5, AND
- No evidence of right-to-left shunting
→ Proceed with VSD closure (Class IIa indication per ESC guidelines) 1
Scenario 2: Inadequate Response but Borderline
If PVR remains elevated but patient has: 1
- PVRI <6 WU·m² after vasodilator challenge, AND
- PVR/SVR <0.3
→ Consider trial of targeted PAH therapy (bosentan or prostacyclin) for 4-6 months, then repeat catheterization with vasodilator testing 1, 5
This "treat and repair" strategy has shown favorable midterm outcomes in adults with VSD and severe PH 5
Scenario 3: Poor Response with Fixed Disease
If vasodilator challenge shows: 1
- PVR remains ≥2/3 of systemic values, OR
- Evidence of right-to-left shunting develops, OR
- Exercise-induced desaturation is present
→ Surgery is contraindicated (Class III recommendation) 1
These patients have developed Eisenmenger physiology and VSD closure would be fatal 1
Critical Caveats and Pitfalls
The PVR Value Requires Verification
Your reported PVR of 0.2 WU is unusually low—verify this measurement carefully: 4
- Ensure cardiac output measurement was accurate (thermodilution can be erroneous with significant TR) 4
- Confirm PCWP was properly measured at end-expiration 4
- Recalculate: PVR = (mPAP - PCWP) / cardiac output 4
If mPAP is 42 mmHg and PVR is truly 0.2 WU, this implies a cardiac output of approximately 210 L/min (if PCWP is normal), which is physiologically impossible. There may be a calculation or measurement error 4
Alternative Explanation
The more likely scenario is that PVR was reported in different units or there was a transcription error. If the actual PVR is 2.0 WU (not 0.2), this changes the clinical picture significantly—the patient would have borderline elevated PVR requiring more cautious evaluation 2, 3
Timing Considerations
Perform vasodilator challenge testing urgently but under controlled conditions: 1
- Must be done in a specialized ACHD center with expertise in congenital heart disease 1
- Requires experienced operators familiar with interpretation in shunt lesions 1
- Have resuscitation equipment and pulmonary vasodilators immediately available 1
Post-Challenge Management
If Surgery is Indicated
Perioperative pulmonary hypertension management is critical: 1, 6
- Consider leaving a small atrial communication (5mm ASD or patent foramen ovale) as a "pop-off" to reduce RV afterload acutely 6, 7
- Use flap-valved VSD closure technique in high-risk cases 7
- Plan for elective mechanical ventilation for 36 hours postoperatively 6
- Have pulmonary vasodilators ready (inhaled prostacyclin, IV nitrates, sildenafil) 6
If Surgery is Deferred
Initiate targeted PAH therapy and close follow-up: 5
- Start bosentan or other endothelin receptor antagonist 5
- Repeat right heart catheterization with vasodilator testing in 4-6 months 1, 5
- Monitor for development of Eisenmenger physiology (cyanosis, exercise desaturation) 1
Summary of Immediate Next Steps
- Verify the PVR measurement of 0.2 WU (likely calculation error) 4
- Refer urgently to ACHD center for right heart catheterization with vasodilator challenge 1
- Use inhaled nitric oxide as the vasodilator agent 1
- Measure complete hemodynamics including PVR/SVR ratio and Qp:Qs 1, 4
- Make surgical decision based on vasodilator response per algorithm above 1