Cardiovascular Pathophysiology Produced by Natural Toxins and Their Possible Therapeutic Implications

Venoms are complex concentrates of biologically highly active molecules known as toxins, and they exist mainly as peptides and proteins. Several natural toxins are produced by plants, bacteria, phytoplanktonic dinoflagellates, sea anemones, insects, fungi and animals. In nature, toxins have two main functions: to capture their preferred prey (e.g. spiders, snakes, scorpions, etc.) or to serve as defence (e.g. bee sting, frog poison, etc.). Toxins produced by micro-organisms are important virulence factors. On the other hand they are also tools to combat diseases. Some of them are used in low quantities as drugs, to prepare vaccines and as important tools in biomedical research. Toxins affecting heart physiology are very effective in the sense of defence and especially in capturing prey. They can disturb electrical (producing arrhythmias) and mechanical activity of the heart affecting pumping or leading even to cardiac arrest. The aim of this chapter is to describe most of the toxins affecting heart function, their targets in the heart tissue, mode of action and the most important clinical effects of envenomation.