Cardiac's origin in his own words:
(Talking to Spider-Man) "Perhaps I can make you understand! Listen while I tell a tale of two brothers, who shared a love as deep as the soul. The younger one idolized his sibling--and was shattered when that older boy fell into a coma, victim of a rare disease. A rare, incurable disease. As a result, the boy vowed to become a healer, the best ever. He would save lives, to honor the one who would never live again. And so the boy became a man; the world of science and scalpels his life. He was good, for his motivation was strong. During this period, he learned that a chemical company had produced a new miracle drug. One that would have cured his brother's disease! He altered focus. And put his labor, knowledge and business acumen into building a power structure, with which to help not only individuals , but humankind as a whole. As part of it, he acquired the chemical company. But in studying old records, he found their miracle drug had been developed years earlier, in time to save his brother...but had been kept off the market until the 'economic climate' was more favorable. In other words--his brother had DIED for GREED! And so the boy who had become a man--became more than a man. He became Cardiac!" ASM #360