Which of the following is a contraindication to initiating beta-blocker therapy after myocardial infarction?

• A. Signs of heart block
• B. Asthma with bronchospasm (non-selective)
• C. Severe bradycardia
• D. All of the above

Answer: (D)

Starting beta-blockers after a myocardial infarction is usually beneficial, but certain conditions make initiating them unsafe because they can worsen heart conduction, heart rate, or airway status. Signs of heart block mean the heart’s electrical conduction is already impaired; beta-blockers slow AV nodal conduction further and can lead to higher-degree block or failure of the heart to pace adequately. Severe bradycardia shows the heart is already beating too slowly, so further slowing with a beta-blocker can reduce cardiac output and cause syncope or shock. Asthma with bronchospasm, particularly with non-selective beta-blockers, risks constricting the airways by blocking beta-2 receptors in the bronchi, precipitating severe bronchospasm. For these reasons, each of these situations is a contraindication to starting beta-blocker therapy after a myocardial infarction, so all of the above applies.