You need a good basic education in the sciences as well as the liberal arts in order to become the best physician you can become.
Specific requirements for medical school include:
8 hours of biology, chemistry, organic chemistry, and physics
3-6 hours of English
3 hours of Calculus (some medical schools)
You also need to complete a bachelor's degree in some field (of your choosing), take the MCAT, and be accepted to medical school. You will then need to complete a surgical residency and be accepted to a cardiothoracic surgery fellowship.