Electrocardiographs before 1910: Manufacturers and surviving instruments

Abstract

Background: Early electrocardiograph predates electronic amplification and therefore required innovative and highly sensitive instrumentation. Willem Einthoven's introduction of the string galvanometer in 1903 enabled recording of clinically useful electrocardiograms and established electrocardiography as a diagnostic method.

Objectives: To describe the provenance and technical features of a uniquely complete string-galvanometer system preserved in Lund, Sweden, and to review early commercial production and surviving string galvanometers manufactured before 1910.

Methods: The Lund electrocardiograph was examined and compared with historical photographs, documentation from Einthoven's laboratory, archival sources, and contemporary literature. Museum and institutional collections as well as manufacturers' records were surveyed for surviving old instruments.

Results: The Lund string galvanometer electrocardiograph, constructed in 1909 from Einthoven's original drawings, retains its optical, magnetic coil system, cooling, and recording components and closely matches documented laboratory models. Only two companies produced string galvanometers commercially by then: Professor Max Th. Edelmann's Physikalisch-mechanisches Institut (Munich, Germany) and the Cambridge Scientific Instrument Company (Cambridge, England). Cambridge sold only 14 devices before 1910, and no complete instrument is known to have survived; Edelmann's production is poorly documented, with only few examples preserved.

Conclusions: Intact electrocardiographs from the earliest period of electrocardiography are extremely rare. The Lund instrument represents one of the best-preserved surviving complete devices and underscores the importance of documenting and conserving early biomedical technology.