In a patient with an ejection fraction (EF) of 20% who experiences bronchospasm, what medication is likely responsible?

In patients with heart failure, a low ejection fraction (EF) indicates impaired heart contractility, and the management of cardiovascular issues often involves the use of various medication classes. Beta blockers, while they are critical in managing heart failure and reducing mortality, can also contribute to bronchospasm due to their mechanism of action.

Beta blockers can block beta-2 adrenergic receptors in the lungs, which are responsible for bronchodilation. In susceptible individuals or those with underlying reactive airway disease, this can lead to bronchospasm. In this scenario, given the patient's significantly reduced ejection fraction, the use of a non-selective beta blocker (as opposed to a cardioselective agent) could exacerbate any pre-existing bronchoconstriction, leading to bronchospasm.

While calcium channel blockers and ACE inhibitors primarily affect the cardiovascular system and diuretics target fluid balance, they do not have the same potential for bronchodilation interference as beta blockers. Therefore, the association of bronchospasm in this patient with a low ejection fraction points towards beta blockers as the likely culprit.