Is nitroglycerin (NTG) safe to use in patients with severe aortic stenosis (AS)?

Nitroglycerin Use in Severe Aortic Stenosis

Nitroglycerin should be used with extreme caution in patients with severe aortic stenosis due to the risk of precipitating profound hypotension, though recent evidence suggests it may be safer than traditionally thought in specific clinical scenarios. 1

Hemodynamic Effects and Risks

• Nitroglycerin (NTG) acts as an endothelium-independent vasodilator with both peripheral and coronary vascular effects, primarily dilating capacitance vessels (venous bed), which decreases myocardial preload and reduces ventricular wall tension 2
• In severe aortic stenosis, the sudden reduction in preload from NTG can lead to dangerous drops in cardiac output due to the fixed obstruction at the aortic valve level 1
• The vasodilating effects of NTG can be exacerbated when combined with anesthetic agents, potentially leading to significant hypotension and myocardial ischemia 2

Clinical Contraindications

• NTG should not be administered to patients with systolic blood pressure less than 90 mmHg or ≥30 mmHg below baseline 2
• Other contraindications include severe bradycardia (<50 beats per minute), tachycardia (>100 beats per minute) in the absence of symptomatic heart failure, and right ventricular infarction 2
• NTG is also contraindicated after the use of phosphodiesterase inhibitors for erectile dysfunction (sildenafil within 24h, tadalafil within 48h) due to risk of profound hypotension 2

Emerging Evidence on Safety

• A retrospective study by Claveau et al. (2015) found that neither moderate nor severe aortic stenosis was associated with a greater risk of clinically relevant hypotension requiring intervention when nitroglycerin was used for acute pulmonary edema 1
• In this study, the incidence of clinically relevant hypotension was 26.2% for patients with moderate and severe aortic stenosis compared to 23.1% in patients without aortic stenosis 1
• However, sustained hypotension (systolic BP <90 mmHg lasting ≥30 minutes) occurred in 29.2% of patients with severe aortic stenosis versus 13.8% in those without aortic stenosis 1

Special Circumstances

• In critically ill patients with severe aortic stenosis AND left ventricular systolic dysfunction, nitroprusside (another nitrate) has been shown to rapidly improve cardiac function, providing a bridge to aortic valve replacement 3
• This suggests that in specific scenarios where peripheral vasoconstriction is contributing to afterload, carefully monitored vasodilator therapy may be beneficial 3

Recommendations for Clinical Practice

• If NTG must be used in a patient with severe aortic stenosis (such as for acute pulmonary edema or unstable angina):

  • Ensure continuous hemodynamic monitoring 1
  • Start with lower doses and titrate very slowly 2
  • Be prepared to intervene rapidly with fluid boluses or vasopressors if hypotension occurs 1
  • Consider intravenous administration rather than topical for more predictable absorption 2

• For perioperative use in patients with severe aortic stenosis:

  • The prophylactic use of intraoperative nitroglycerin in high-risk patients may have no benefit or may actually lead to cardiovascular decompensation through decreases in preload 2
  • NTG should be used only when the hemodynamic effects of other agents being used and intravascular volume status have been carefully considered 2

Conclusion

While traditionally considered an absolute contraindication, emerging evidence suggests NTG may be used with extreme caution in severe aortic stenosis when clinically indicated, particularly in acute pulmonary edema. However, careful hemodynamic monitoring and readiness to treat hypotension are essential. The risk-benefit ratio should be carefully evaluated in each individual case.