Can nitrates (nitroglycerin) be given to a patient with mitral stenosis?

Nitrates in Mitral Stenosis: Clinical Guidance

Nitrates can be given to patients with mitral stenosis, but only when severe stenosis is excluded and systolic blood pressure exceeds 110 mmHg. 1

Critical Contraindication to Understand

Severe mitral stenosis is an absolute contraindication to nitrate administration. The European Society of Cardiology explicitly states that intravenous nitrate infusions should only be considered in patients with pulmonary congestion/edema who "do not have severe mitral or aortic stenosis." 1 This is a Class IIa recommendation with Level B evidence, meaning nitrates should be considered in appropriate patients but avoided when severe stenosis is present.

When Nitrates Can Be Used in Mitral Stenosis

Hemodynamic Requirements

• Systolic blood pressure must be >110 mmHg before administering nitrates 1
• Patient must have pulmonary congestion or edema as the indication 1
• The stenosis must be mild to moderate, not severe 1

Physiological Rationale

• Nitrates reduce pulmonary capillary wedge pressure through venodilation and preload reduction 2
• In non-severe mitral stenosis, sublingual nitroglycerin (0.4 mg) reduces mean pulmonary wedge pressure from 27 to 21 mmHg without compromising cardiac output 2
• Exercise duration improved by approximately 13% (5.02 to 5.66 minutes) with nitroglycerin in patients with pure or predominant mitral stenosis 2

Clinical Decision Algorithm

Step 1: Assess stenosis severity

• Severe mitral stenosis = absolute contraindication 1
• Mild-to-moderate stenosis = may proceed to Step 2 2

Step 2: Check blood pressure

• SBP >110 mmHg = may proceed 1
• SBP ≤110 mmHg = do not give nitrates 1

Step 3: Confirm indication

• Pulmonary congestion/edema present = appropriate indication 1
• No pulmonary congestion = reconsider need 1

Step 4: Monitor closely

• Check blood pressure frequently during administration 1
• Monitor for symptoms of hypoperfusion 1

Hemodynamic Effects in Mitral Stenosis

Beneficial Effects

• Reduces left ventricular end-diastolic pressure from 11 to 8 mmHg at rest 2
• Lowers pulmonary wedge pressure by approximately 6 mmHg at rest and 7 mmHg during exercise 2
• Decreases left ventricular systolic pressure by 10-11 mmHg 2

Neutral Effects

• Cardiac index remains unchanged (2.98 vs 2.68 L/min/m²) 2
• Heart rate unchanged (82 vs 87 bpm at rest) 2
• Stroke index unchanged 2

Critical Pitfalls to Avoid

Do not confuse mitral stenosis with mitral valve prolapse. Nitrates are safe in mitral valve prolapse and may even suppress ventricular arrhythmias in these patients, but the hemodynamic considerations are entirely different. 3, 4

Do not assume all vasodilators behave similarly. Nitroprusside has been studied in mitral stenosis and can improve cardiac index when severe pulmonary hypertension coexists, but this is a different agent with different properties. 5

Avoid nitrates in right ventricular infarction. Even in the absence of mitral stenosis, nitrates are contraindicated when right ventricular infarction is present due to preload-dependent hemodynamics. 1

Special Considerations

Postoperative Setting

• After mitral valve replacement for stenosis, low-dose intravenous nitroglycerin reduces pulmonary arterial pressure by 30% and pulmonary vascular resistance by 48% 6
• This demonstrates that once the mechanical obstruction is removed, nitrates become highly effective 6

Diagnostic Considerations

• Nitroglycerin administration during catheterization can eliminate pulmonary venoconstriction, which artificially elevates pulmonary capillary wedge pressure above true left atrial pressure 7
• This may lead to overestimation of stenosis severity if nitrates are not used during hemodynamic assessment 7