Latrodectus mactans, or black widow spider. The poison can have effects remarkably similar to the classic heart attack symptoms, with severe chest pains radiating to the left arm and a terrible feeling of dread. The homeopathic remedy made from that poison has been used effectively in acute myocardial infarction.
Quoting from the proving:
"Appearance anxious, with extreme fear of dying. Violent, constrictive precordial pain, spreading towards the axilla, shoulder and along the left arm. Coldness of the body, with rapid pulse which is feeble, thready.... Sensitive to noise. Intense anguish making him scream, with the sensation of severe thoracic constriction. Extreme state of nervous irritation, with fear of going mad." [Julian, A Materia Medica of New Homeopathic Remedies, Paris (1971).]