Cardiotoxins

Cardiotoxins are substances that harm heart function or disrupt cardiac electrical activity. The term encompasses a broad range of natural toxins from plants, animals, and microorganisms, as well as synthetic compounds, all capable of affecting the heart or its rhythm.

One major group comprises cardiac glycosides produced by certain plants, such as digitalis species. These compounds inhibit the Na+/K+ ATPase pump in cardiac myocytes, increasing intracellular calcium and enhancing contractility. At higher exposures, they can cause dangerous arrhythmias or conduction blocks. In medical practice, this mechanism underlies the therapeutic use of these agents in controlled doses, but overdose or interactions can be life-threatening.

Other cardiotoxins act by modulating cardiac ion channels. Toxins from some venoms and marine organisms bind to voltage-gated sodium or calcium channels in cardiac cells, altering action potential duration and rhythm. These agents are studied to understand cardiac electrophysiology, and severe envenomations can produce cardiotoxic effects such as arrhythmias or cardiac arrest.

Additional sources include certain chemotherapeutic drugs and environmental toxins that cause cardiotoxicity through mechanisms like oxidative stress or mitochondrial injury, contributing to cardiomyopathy or heart failure with chronic exposure.

Clinical effects vary with the toxin and exposure, ranging from palpitations and lightheadedness to life-threatening arrhythmias. Management emphasizes removal of exposure when possible, supportive cardiac care, electrolyte management, and specific antidotes where available, such as digoxin-specific antibody fragments for digitoxin or digoxin overdose. In research, cardiotoxins are used as tools to study heart function under controlled conditions, with appropriate safety measures.