Which scenario most strongly contraindicates nitroglycerin in suspected MI?

• A. Recent use of phosphodiesterase inhibitors within 24 hours
• B. Inferior MI with RV infarction
• C. SBP < 90 mmHg
• D. Severe bradycardia

Answer: (B)

The key idea is that nitroglycerin lowers preload by dilating veins. In a right‑sided infarction accompanying an inferior MI, the right ventricle relies on adequate preload to maintain cardiac output. Reducing preload with nitroglycerin can cause a dangerous drop in both blood pressure and overall cardiac output, making this scenario the one that most strongly contraindicates its use.

Other factors are important precautions but not as decisive. Recent use of phosphodiesterase inhibitors within 24 hours markedly increases the risk of severe hypotension with nitrates. An systolic blood pressure below 90 mmHg is an absolute reason to withhold nitrates due to the danger of life‑threatening hypotension. Severe bradycardia is a concern and warrants careful assessment, but it is not the strongest contraindication in this context.