Forssmann's aim was to find a safe way to inject drugs for cardiac resuscitation. He was determined, and determined to prove, that catheterisation was the key, but at that time it was believed that any entry into the heart would be fatal. Forssmann was a man with enough personal courage to jeopardise his own life to prove his theory.
He was immediately fired when his self-experimentation became known in spite (or maybe because) of the scientific importance of his discovery. The popular press lauded his work, but the medical establishment denounced him as a madman and ignoring his work for over a decade.
He continued to experiment with catheterisation in dogs. It is said that he stopped self-experimentation only when he had used up all of his own veins.
Discouraged by this lack of acceptance, he turned to urology and eventually became a country surgeon. He never returned to cardiological research.
In 1956 he was rehabilitated and awarded the Nobel Prize for his outstanding pioneering efforts in medicine.
With his drive for knowledge and innovation and specifically his personal physical courage and disregard of any physical harm to himself, Werner Forssmann stands out even among Nobel Laureates.