What are the contraindications to using nitric oxide (NO) during cardiac catheterization for pulmonary hypertension (PH) evaluation?

Contraindications to Nitric Oxide for Pulmonary Hypertension Evaluation During Cardiac Catheterization

There are no absolute contraindications to using inhaled nitric oxide (NO) during cardiac catheterization for pulmonary hypertension evaluation, but caution is warranted in patients with left ventricular dysfunction due to risk of pulmonary edema. 1, 2

Primary Considerations for Nitric Oxide Use

Inhaled nitric oxide is the recommended standard agent for vasoreactivity testing during right heart catheterization, with several important considerations:

• Patient Selection: Vasoreactivity testing with NO is primarily indicated for patients with:

  • Idiopathic pulmonary arterial hypertension (IPAH)
  • Heritable pulmonary arterial hypertension (HPAH)
  • Drug-induced pulmonary arterial hypertension 1

• Not Recommended: Vasoreactivity testing is not recommended in:

  • PAH other than IPAH, HPAH, and drug-induced PAH
  • PH groups 2 (left heart disease), 3 (lung disease), 4 (CTEPH), and 5 (unclear mechanisms) 1

Relative Contraindications and Cautions

While not absolute contraindications, special caution should be exercised in:

1. Left Ventricular Dysfunction: Patients with pre-existing left ventricular dysfunction may experience increased pulmonary capillary wedge pressure leading to pulmonary edema 2

2. Right-to-Left Shunting: Neonatal data indicates NO is contraindicated in patients dependent on right-to-left shunting of blood, which may be relevant for adult congenital heart disease patients 2

3. Right Ventricular End-Diastolic Pressure Elevation: Patients with elevated right ventricular end-diastolic pressure may have poor vasodilatory response to inhaled NO 3

Technical Considerations

• Expert Centers Only: Vasoreactivity testing should only be performed in expert centers due to technical demands and potential complications 1

• Dosing: The recommended dose is 10-20 parts per million (ppm) for vasoreactivity testing 1

• Administration Duration: Typically administered for 5 minutes during the testing phase 1

• Monitoring Requirements:

  • Methemoglobin levels should be monitored as they increase with the dose of nitric oxide 2
  • Nitrogen dioxide (NO₂) levels should be monitored 2

Potential Adverse Effects

• Rebound Pulmonary Hypertension: Abrupt discontinuation can lead to worsening oxygenation and increasing pulmonary artery pressure 1, 2

• Methemoglobinemia: Risk increases with higher doses of nitric oxide 2

• Elevated NO₂ Levels: Can occur with prolonged administration 2

• Paradoxical Response: In rare cases (approximately 7.6% in one study), pulmonary vascular resistance may paradoxically increase 4

Clinical Pearls

• A positive response to vasoreactivity testing is defined as a reduction of mean PAP ≥10 mmHg to reach an absolute value of mean PAP ≤40 mmHg with an increased or unchanged cardiac output 1

• Alternative agents for vasoreactivity testing include intravenous epoprostenol (first alternative choice) and intravenous adenosine (second alternative) 1

• The use of oral or intravenous calcium channel blockers for acute vasoreactivity testing is not recommended 1

• Combining NO with oxygen may provide additional pulmonary vasodilation in patients with reactive pulmonary vascular beds 5

By following these guidelines, clinicians can safely and effectively use nitric oxide during cardiac catheterization for pulmonary hypertension evaluation while minimizing risks.