Damage to the heartwhether from an infection, an inherited condition, or a heart attackcan interfere with the electrical signal and throw the heart off its rhythm. This is arrythmia.
A racing heartbeatventricular tachycardia, it turns outsent Shannon Schroeder, 37, of Poulsbo, Wash., to the emergency room. It's a good thing she went.
An echocardiogram showed that the walls of her left ventricle were thicker than they should be, and the muscle showed telltale damage of an earlier silent heart attack. The damage had weakened her heart and harmed the electric circuitry that maintains a normal rhythm.
Stimulantsincluding caffeine, nicotine, and drugscan also cause brief arrhythmias. They're usually harmless, but there are case reports of people dying from ventricular fibrillation after overdosing on controlled substances.