Which of the following is a β1-selective antagonist?

Atenolol is a β1-selective antagonist, known for its action primarily on the β1 adrenergic receptors found in the heart. By selectively inhibiting these receptors, atenolol effectively reduces heart rate and cardiac contractility, making it useful for conditions such as hypertension and angina. This selectivity is significant because it minimizes the potential adverse effects associated with non-selective beta-blockers, such as bronchoconstriction that can occur when β2 receptors are blocked.

In comparison, propranolol is a non-selective beta-blocker that affects both β1 and β2 receptors, which can lead to broader systemic effects and is not limited just to cardiac applications. Carvedilol, on the other hand, is a mixed-action agent that antagonizes both β1 and β2 receptors as well as having α1-blocking properties. Metoprolol, while also a β1-selective antagonist, is distinct from atenolol since their pharmacokinetics differ; atenolol has a longer half-life and is more water-soluble. Nevertheless, the question specifically asks for a β1-selective antagonist, making atenolol the precise answer due to its clear and definitive selectivity.