In severe tetrodotoxin poisoning, which of the following can occur?

• A. Dysrhythmias
• B. Hypertension
• C. Seizures
• D. Rash

Answer: (A)

Tetrodotoxin blocks fast voltage-gated sodium channels, so nerve and muscle cells, including heart muscle, can’t depolarize properly. In severe poisoning, this directly impairs cardiac conduction, leading to dysrhythmias such as bradycardia or blocks and, in extreme cases, cardiac arrest. While other symptoms like neurological effects or hypotension can occur, the disruption of cardiac electrical activity is a hallmark and explains why dysrhythmias are the most characteristic and concerning finding. Hypertension and rash aren’t typical features, and seizures are less central to the presentation.