If heat stroke is left untreated, it can cause damage to your brain, heart, kidneys, or muscles. Moreover, the potential damage to your organs and soft tissues worsens the longer that heatstroke is left untreated. With that in mind, you should seek immediate medical attention if you or someone you know is experiencing heatstroke. Heatstroke often develops from milder heat-related conditions, such as heat cramps, heat exhaustion, or heat fainting, but it can also strike without warning.