Étienne-Louis Arthur Fallot was a physician working in France during the late nineteenth century who studied and described the four cardiac anatomical defects that cause the congenital anomaly known as the Tetralogy of Fallot. Those four heart defects result in deoxygenated blood recirculating through the body, giving the skin a blue-like color, a process called cyanosis. Numerous physicians and researchers before Fallot had identified and described the anatomical cardiac defects that would eventually be included in the Tetralogy. However, Fallot was among the first to note that the four anatomical heart defects tended to occur together. Through autopsy investigations, Fallot established the Tetralogy as one unified pathology rather than four unrelated anatomical abnormalities, providing a basis for the eventual surgical treatment of the condition, which affects approximately four out of every one thousand births worldwide.