Sunao Tawara was a prominent Japanese pathologist and anatomist best known for discovering in 1906 the atrioventricular node, also known as the AV node or bundle of Tawara. This small mass of specialized cardiac muscle fibers located between the atria and ventricles of the heart is a key component of the heart’s conduction system, responsible for regulating the heartbeat.

Born in 1873 in Oita Prefecture, Japan, Tawara studied medicine at Tokyo University and later worked as a pathologist. During his time working in the laboratory of Ludwig Aschoff in Germany in the early 1900s, he conducted extensive research on the anatomy and pathology of the heart’s conduction system.

Tawara’s rigorous studies utilizing serial microscopic sections of the heart allowed him to map the entire cardiac conduction system and led to his groundbreaking discovery of the AV node. He published his findings in a German publication in 1906 in a paper titled “Das Reizleitungssystem des Säugetierherzens” (“The Conduction System of the Mammalian Heart”).

Tawara’s discovery greatly advanced the understanding of cardiac physiology and had important clinical implications. Knowledge of the AV node’s role in regulating the heartbeat has been invaluable for the diagnosis and treatment of arrhythmias and other cardiac conduction disorders. His work laid the foundation for the development of cardiac electrophysiology.

After returning to Japan, Tawara became a professor at Kyushu University. He continued to make significant contributions to the field of pathology throughout his career. The Tawara-Aschoff bodies (granulomatous lesions seen in sarcoidosis) are named after him and Ludwig Aschoff.

Sunao Tawara’s discovery of the AV node was a milestone in cardiology. His dedication to meticulous research and his groundbreaking findings have had a lasting impact on the understanding and treatment of heart disease. He is remembered as one of the great pioneers in the field of cardiac pathology.