kardia + logos

Greek kardia meant heart — and also stomach, because the ancient Greeks located emotion and sensation in the upper abdomen rather than the chest. Cardiology (kardia + logos) is the medical discipline devoted to the heart and cardiovascular system. The formal establishment of cardiology as a specialty followed directly from William Harvey's 1628 publication De Motu Cordis et Sanguinis (On the Motion of the Heart and Blood).

Galen's model of blood movement — accepted for 1,400 years — held that blood was produced in the liver, consumed in the tissues, and replenished in an ebb-and-flow pattern, with blood seeping through invisible pores in the heart's septum between chambers. Harvey's calculations showed this was impossible: the heart pumps three ounces of blood per beat, at 72 beats per minute — far more blood than the body contains. Blood had to circulate.

The stethoscope, invented by René Laennec in Paris in 1816, gave cardiology its first diagnostic instrument. Laennec, embarrassed to press his ear against a patient's chest (the existing method), rolled paper into a tube — and found it amplified the heart sounds better. The modern stethoscope is directly descended from this paper tube.

Willem Einthoven's 1903 invention of the electrocardiograph (ECG) — measuring the heart's electrical activity — transformed cardiology from auscultation (listening) to electrical measurement. Coronary artery bypass surgery (1967), the implantable defibrillator (1980), and statins (1980s) have collectively transformed heart disease from a near-universal cause of death to a manageable chronic condition in the developed world.