Active agents in foxglove that improve heart contractility belong to which class?

• A. Beta Blockers
• B. Foxglove (Purple Foxglove)
• C. ACE Inhibitors
• D. Calcium Channel Blockers

Answer: (B)

The active agents that improve heart contractility from foxglove are digitalis glycosides, a cardiac glycoside class derived directly from the foxglove plant. They work by inhibiting the Na+/K+ ATPase pump in cardiac muscle cells, which raises intracellular calcium through the Na+/Ca2+ exchanger. The resulting higher calcium availability strengthens myocardial contraction (positive inotropy). They also increase vagal tone, which can slow AV nodal conduction and help control rapid heart rates in atrial fibrillation. Clinically, they're used for certain cases of heart failure and atrial arrhythmias, but they have a narrow therapeutic window and potential toxicity.

From the options, the best fit is the plant itself because the active agents come from foxglove. The other choices refer to drug classes that do not increase myocardial contractility.