Which β-agonist primarily affects the heart and increases heart rate and contractility?

Dobutamine is a β-agonist that is primarily used in clinical settings to treat heart failure and certain cases of shock. It is distinguished by its selectivity for the β1-adrenergic receptors found primarily in the heart. When activated, these receptors lead to an increase in heart rate (positive chronotropic effect) and an increase in the force of heart muscle contractions (positive inotropic effect). This makes dobutamine particularly effective in improving cardiac output during periods of decreased heart function.

In contrast, while epinephrine does also stimulate both β1 and β2 receptors, it has a broader range of effects including vasodilation and bronchodilation, which may not be exclusively heart-focused. Albuterol mainly targets β2 receptors, primarily causing bronchodilation, and is typically used in asthma management rather than directly impacting heart contractility. Clonidine is primarily an α2-adrenergic agonist that is used as an antihypertensive agent, diminishing sympathetic outflow, and does not have a primary role in increasing heart rate or contractility.

Thus, dobutamine's specific action on β1 receptors in the heart is what makes it the correct choice in this context.