Ueber die form des menschlichen electrocardiogramms. Pflugers Arch gets Physiol, 1895, 60, 101-123
Beitrag zur theorie des capillar-elektrometers. Pflugers Arch gets Physiol, 1900, 79, 1-25
Un nouveau galvanometre. Arch. neerl. Sci. exactes nat., 1901, 2 ser., 6, 625-33
The string galvanometer and the human electro-cardiogram. K. Akad Wet. Amst., Proc. Sect. Sci., 1903-04, 6, 107-15
Le telecardiogram. Arch Internat Physiol, 1906, 4, 132-164
Einthoven W, Fahr G, De Waart A. Uber die richtung und die manifeste grosse der potentialschwankungen im menschlichen herzen und uber den einfluss der herzlage auf die form des elektrokardiogramms. Pflugers Arch gets Physiol, 1913, 150, 275-315
Gabriel Lipmann, a French physicist, invented the capillary electrometer in 1875. Burdon-Sanderson and Page applied this instrument to obtain a graphic recording of the heart beat. Their tracing showed the first ventricular depolarization and repolarization. Augustus Waller, a British physiologist, used this device to study the electrical activity of the heart and recorded the first human electrocardiogram. Waller attached electrodes to the front and back of a man's chest and connected them to a capillary electrometer. He observed that each heartbeat caused an electrical variation and utilized the letters A,B,C,D to designate the deflections that he recorded with the capillary electrometer. Waller, as a scientist, continued to investigate the theoretical aspects of electrophysiology and showed little interest in its potential clinical applications. In 1890's, Willem Einthoven, from Netherlands, started his research on the electrical activity of the heart. He recognized the limitations of the capillary electrometer and used complex mathematic calculations and physical approaches to improve the quality of his recordings. In his first major paper, which was published in 1895, he was able to show five deflections corresponding to the heart's electrical activity which he labeled P,Q,R,S,T. It is important to note that prior to these modifications, his tracings were recording 4 deflections labeled A,B,C,D.
Because of the limitations inherent to the concept of capillary electrometer, Einthoven turned his attention to the galvanometer invented by Arsene D'Arsonval and Clement Ader. In a historical publication in 1901, he reported his modifications of string galvanometer and recorded the first electrocardiogram with this new device. Einthoven's string galvanometer consisted of a thin silver-coated quartz filament (string) placed in a strong magnetic field generated by a massive electromagnet. The electric activity of the heart would produce movements of the string in the magnetic field and the photographic recordings of these minuscule displacements would generate the electrocardiogram. In 1903, he described his early experience with electrocardiography in a landmark paper entitled, "The String galvanometer and the human electro-cardiogram." In 1906, Einthoven published his work, "Le telecardiogram," in which he presented several tracings in normal and pathological conditions. It included extrasystole, ventricular bigeminy, and heart block. Einthoven also showed tracings of atrial flutter and atrial fibrillation ("pulsus inaequalis et irregularis"), although their significance was not understood yet. Finally, he presented electrocardiographic tracings of patients with valvular heart disease such as mitral stenosis, mitral regurgitation and aortic regurgitation.
In 1913, Einthoven with two of his pupils, De Waart and Fahr, made another seminal contribution with their study on the direction and size of the variations of potential in the human heart. Einthoven and his colleagues believed that there was a mathematic relation between the direction and size of the deflections obtained in the three limb leads. Their hypothesis was that the electromotive forces of the heart can be presented by a vector in the center of an equilateral triangle in the frontal plane. They postulated that the calculation of the electrical axis of the heart would allow physicians to distinguish between pathologic conditions (e.g. left ventricular hypertrophy) and simple changes in the position of the heart. The introduction of the concept equilateral triangle inaugurated the field of vectocardiography.
Willem Einthoven was awarded the Nobel prize in medicine in 1924.
A few years after the invention of string galvanometer, the clinical application of electrocardiogram began.
Burdon-Sanderson J. Experimental results relating to the rhythmical and excitatory motions of the ventricle of the heart of the frog. Proc R Soc Lond 1878;27:410-414
Burdon-Sanderson J, Page FJM. On the time-relations of the excitatory process in the ventricle of the heart of the frog. J Physiol (Lond) 1880;2:384-435
Burdon-Sanderson J, Page FJM. On the electrical phenomena of the excitatory process in the heart of the frog and of the tortoise, as investigated photographically. J Physiol (Lond) 1884;4:327-338
Waller AD. A demonstration in man of electromotive changes accompanying the heart's beat. J Physiol (Lond) 1887;8:229-234
Fye WB. Disorders of the heartbeat: a historical overview from antiquity to the mid-20th century. Am J Cardiol 1993;72:1055-1070
Fye WB. A history of the origin, evolution, and impact of electrocardiography. Am J Cardiol 1994;73:937-949