ACMT Toxicology Visual Pearl: The Heart Won’t Go On and On

1. Lily of the Valley

What type of plant is lily of the valley?

Lily of the valley (Convallaria majalis) is a woodland perennial with a sweet scented, white bell-shaped flower. It blooms from April to June in North America and bears orange-red berries in July [1]. It resembles wild leek or garlic (Allium tricoccum) and misidentification has led to case reports of toxicity [2]. It contains saponins that cause gastrointestinal symptoms and approximately 30 glycosides, notably convallatoxin.

Lily of the valley poisoning is important to recognize because it presents as digitalis toxicity [3]. The entire plant is toxic. The toxins can also leach into water from flowers during storage.

What other plants contain cardiac glycosides? [4]

More than 200 cardiac glycosides are known to occur naturally. Examples of other plants containing cardiac glycosides include:

• Digitalis purpurea (foxglove)
• Nerium oleander (common oleander)
• Thevetia peruviana (yellow oleander)
• Urginea maritima (squill or sea onion)
• Cerbera odollam (pong pong)
• Helleborus niger (henbane)
• Strophanthus spp. (ouabain, poison rope)
• Asclepias spp. (balloon cotton, red-headed cotton-bush, and common milkweeds)
• Calotropis procera (king’s crown)
• Carissa spectabilis (wintersweet)
• Carissa acokanthera (bushman’s poison)

What are the symptoms of lily of the valley poisoning? [2, 5]

• Poisoning from plant cardiac glycosides causes reversible inhibition of sodium-potassium ATPase, which increases cardiac inotropy and automaticity. This is indistinguishable from digoxin poisoning,
• Symptoms:
  • Nausea and vomiting
  • Headaches
  • Visual changes (classically seeing haloes around lights)
  • Cardiac toxicity (such as bradycardia, heart block, and dysrhythmias)

How do you diagnose lily of the valley poisoning? [4, 6]

• A confirmed history of exposure is helpful.
• Convallatoxin is known to cross-react with the assay used to measure digoxin. Thus, a serum digoxin level may be positive but due to unpredictable cross-reactivity, the level may not be reflective of the severity of exposure.
• An ECG may show signs similar to digoxin exposure
  • Classic “scooping” of ST segments
  • Heart blocks
  • Dysrhythmias
• Hyperkalemia may be seen with severe cardiac glycoside poisoning.

How do you treat lily of the valley toxicity? [2, 7]

• Gastrointestinal decontamination with activated charcoal may be considered in patients who present early after ingestion (up to 2-4 hours).
• Serial ECGs and monitoring of serum potassium should be done in cases of severe poisoning.
• Digoxin specific Fab fragments are recommended if significant toxicity is present.
• Patients with signs and symptoms of cardiac glycoside poisoning should be admitted for close monitoring.

Bedside Pearls

• Toxicity from cardiac glycoside containing plants can be indistinguishable from digoxin toxicity and can result in vomiting, visual changes, hyperkalemia, and cardiac rhythm disturbances.
• A digoxin assay may be positive, but may not correlate with severity of toxicity.
• Digoxin-specific Fab is the antidote.