The history of cardiology begins in the Renaissance period, with the first accurate analysis of the heart's role of oxygenating and distributing blood throughout the body. For three centuries after that doctors slowly developed the means to accurately monitor this vital organ and understand the ailments that could befall it. It was not until the middle of the 20th century though that technology had advanced to the point at which surgical procedures became a viable approach to mending a damaged heart.
Many point to British doctor William Harvey for the first true milestone in the history of cardiology in 1628, when he articulated the heart's role of pumping blood through a complex system of veins and arteries. Until then, it was thought that each blood vessel had a natural pulsing rhythm and was not recycled. It took another 80 years for the first accurate description of the heart's construction was delivered by French biologist Raymond de Vieussens; for the first time, the organs anatomical mechanics were able to be understood.
Throughout the ensuing two centuries, much of the history of cardiology entailed acquiring a firmer grasp on heart health and the conditions that could befall it. In the 18th century, doctors started monitoring blood pressure to gauge the organ's vitality. By the beginning of the 19th century, doctors could monitor a heartbeat with a stethoscope. The electrocardiograph (ECG or EKG) was invented just after the turn of the 20th century, which allowed doctors to more closely analyze the heart's overall performance via electrical impulses. Arterial clogging called arteriosclerosis was first observed about a decade later.
Before the 20th century, scattered surgical firsts occurred in the history of cardiology. Most were attempts to mend critically injured patients. In 1896, a German doctor named Ludwig Rehn performed the first successful open-heart surgery to mend a wound that tore through the heart of a soldier. This type of surgery was not commonly attempted, however, until 1953. American John Gibbons invented a so-called heart-lung machine that allowed a surgeon to keep blood oxygenated and circulating through a patient during repair or transplantation surgeries.
These repairs were mostly reactionary until the dawn of heart repair surgery in 1950, when a successful implantation of an artificial aortal valve was performed by American surgeon Charles Hufnagel. Two years later, another pair of American surgeons used hypothermia to slow the heart of a patient who successfully underwent the repair of a hole in her heart. The innovations intensified with the pacemaker came in 1958. In 1967, the first coronary artery bypass surgery was performed — a procedure that is performed several million times every year in the 21st century. That same year, the first successful heart transplantation was performed by South African doctor Christiaan Barnard.
Scattered among these many pivotal firsts in the history of cardiology are many others of note. De-fibrillation was first performed on dogs in 1899. Humans did not benefit until 1947, when the machine was used to restore heart function to a young teen with a heart defect. One of the more recent milestones happened in 1982, when William DeVries, an American cardiologist, implanted the first heart made completely of artificial tissue.