Which plant causes cardiotoxicity in the digitalis glycoside toxicosis category?

• A. laurel (kalmia)
• B. redroot pigweed (amaranthus)
• C. bracken fern (pteridium)
• D. foxglove (digitalis)

Answer: (D)

Cardiac glycosides from certain plants produce a distinctive cardiotoxic effect by inhibiting the Na+/K+-ATPase in heart cells. This inhibition raises intracellular calcium, leading to stronger but more dysregulated heart contractions and a tendency toward rhythm disturbances and blocks. Foxglove, or Digitalis, is the classic source of these cardiac glycosides (digoxin/digitoxin). When ingested, foxglove causes the characteristic digitalis glycoside toxicosis with arrhythmias and conduction abnormalities, reflecting the drug-like effects on the heart. The other plants listed contain different toxins (for example, grayanotoxins in laurel causing hypotension and bradycardia, or other plant toxins in bracken fern and amaranth) and do not produce the same cardiac glycoside toxicosis.