[The concise history of atrial fibrillation]

The author reviews the history of atrial fibrillation, the most common sustained cardiac arrhythmia. The chaotic irregularity of arterial pulse was clearly acknowledged by most of physicians of the ancient China, Egypt and Greece. William Harvey (1578-1657), who first described the circulatory system appropriately, was probably the first to describe fibrillation of the auricles in animals in 1628. The French "clinical pathologist", Jean Baptist de Sénac (1693-1770) was the first who assumed a correlation between "rebellious palpitation" and stenosis of the mitral valve. Robert Adams (1791-1875) also reported in 1827 the association of irregular pulses and mitral stenosis. The discovery of digitalis leaf in 1785 by William Withering (1741-1799) brought relief to patients with atrial fibrillation and congestive heart failure by reducing the ventricular rate. From an analysis of simultaneously recorded arterial and venous pressure curves, the Scottish Sir James Mackenzie (1853-11925) demonstrated that a presystolic wave cannot be seen during "pulsus irregularis perpetuus", a term very first used by Heinrich Ewald Hering (1866-1948). Arthur Cushny (1866-1926) noted the similarity between pulse curves in clinical "delirium cordis" and those in dogs with atrial fibrillation. The first human ECG depicting atrial fibrillation was published by Willem Einthoven (1860-1927) in 1906. The proof of a direct connection between absolute arrhythmia and atrial fibrillation was established by two Viennese physicians, Carl Julius Rothberger and Heinrich Winterberg in 1909. Sir Thomas Lewis (1881-1945), the father of modem electrocardiography, studied electrophysiological characteristics of atrial fibrillation and has shown that its basic perpetuating mechanism is circus movement of electrical impulse (re-entry). After him, the major discoveries relating to the pathophysiology and clinical features of atrial fibrillation in the 20th century stemmed from Karel Frederick Wenckebach (1864-1940), Gordon Moe (1915-1989), Bernhard Lown (*1921) and Maurits Allessie. Over the past ten years, awareness has increased of transcatheter radiofrequency and cryoablation of non-valvular atrial fibrillation and the battle against formation of intraatrial thrombi for preventing cerebral thromboembolism.

[One-hundred years of atrial fibrillation in the Dutch Journal of Medicine]

In the December 1, 1906 issue ofthis journal (Dutch journal of Medicine), the Dutch Nobel laureate Willem Einthoven presented the first ECG of atrial fibrillation in a patient with an irregular pulse. This clearly showed for the first time the importance of electrocardiography in the diagnosis of cardiac diseases. Even today, electrocardiography is still the primary diagnostic tool in cardiology. Einthoven did not realise at the time that in the elderly, atrial fibrillation would develop into an epidemic, with symptoms and complications that can be better dealt with now than in 1906.

[The 100(th) anniversary of "The Conduction System of the Mammalian Heart" by Sunao Tawara]

In 1906, Sunao Tawara published "Das Reizleitungssystem des Säugetierherzens" ("The Conduction System of the Mammalian Heart"). We remind of the centennial of this publication, really a morphological study, as it is a milestone of cardiac electrophysiology, too. Tawara not only described for the first time all compartments of the atrioventricular conduction as a continuous system but also derived its function from the morphological pecularities. Later, this was confirmed by physiological experiments. The significance of Tawara's discovery can be seen from reactions to his monograph documented in the contemporary literature.

The order of ventricular excitation in human bundle-branch block. 1932

IN previous articles from this laboratory^1,2 it has been pointed out that, in accordance with the laws which govern the flow of electric currents in volume conductors, the potential variations produced by the cardiac muscle are very much greater in magnitude in the immediate neighborhood of the heart than at a distance from it. It has been shown that when one electrode of the string galvanometer is placed upon the pre‐cordium, the position of the second electrode, so long as it is distant from the heart, has comparatively little influence upon the form of the ventricular electrocardiogram. Attention has been called to certain resemblances between leads of this type and direct leads of the kind employed by Lewis and Rothschild³ in which one electrode is placed in actual contact with the ventricular muscle and the other upon the chest wall. In both cases the form of the ventricular complex is determined in a very large measure, although not to quite the same extent in the former as in the latter, by the potential variations of the exploring electrode; in both cases the muscle units which lie nearest this electrode exert individually a much greater effect upon its potential than those which are more distant from it.

Curves obtained by leading from points on or near the heart to one of the extremities utilized in taking the three standard indirect leads may be freed from the influence exerted by potential variations of the indifferent electrode by a method which we have recently described.⁴ When this electrode is placed upon the left leg the correction is made by subtracting from each ordinate of the recorded curve one‐third of the sum of the deflections, measured in. millivolts, inscribed in Leads II and III at the corresponding instant in the cardiac cycle. It is possible in this way to determine, at least approximately, the time course of the potential of the exploring electrode, and thus to eliminate any difference beween direct and semidirect leads for which potential variations of the indifferent electrode are responsible.

Elucidation of the spatial ventricular gradient and its link with dispersion of repolarization

The ventricular gradient, a notion conceived by Wilson et al during the 1930s, has contributed considerably to a better understanding of the ECG manifestations of the cardiac repolarization process. The power of the ventricular gradient is its ability to assess the primary factors that contribute to the T wave (i.e., heterogeneity of action potential morphology throughout the ventricles) in the presence of secondary factors contributing to the T wave (i.e., heterogeneity in ventricular depolarization instants). Where T-wave morphology is an ECG expression of heterogeneity of the repolarization, the ventricular gradient discriminates between primary or secondary causes of such heterogeneity. Besides the spatial ventricular gradient (Burger's three-dimensional elaboration of Wilson's two-dimensional concept), body surface mapping of local components of the ventricular gradient has emerged as a technique for assessing local ventricular action potential duration heterogeneity. The latter is believed to contribute to localization of arrhythmogenic areas in the heart. The spatial ventricular gradient, which can be computed on the basis of a regular routine ECG and does not require body surface mapping, aims to assess the overall heterogeneity of ventricular action potential morphology. This review addresses the nature and diagnostic potential of the spatial ventricular gradient. The main focus is the role of the spatial ventricular gradient in ECG assessment of dispersion of repolarization, a key factor in arrhythmogeneity.

Early Detectors of the Heart's Electrical Activity

It was in Matteucci's rheoscopic frog in Pisa that evidence was first found for the electrical activity of the heart in 1844, and his results were confirmed and expanded 12 years later at Würzburg. The capillary electrometer gave a continuous record that could be photographed, and was used initially by Einthoven who, to obviate the onerous mathematical conversion of the electrometer record, developed the string galvanometer by the close of the century, and showed its clinical value in 1906.

Centenary of tele-electrocardiography and telephonocardiography

In the history of electrocardiography the names of two physiologists stand out: Augustus Waller (1865-1922) and Willem Einthoven (1860-1927). Waller was the first to show that the beating heart produces a weak electric potential, which can be registered by a measuring device connected to electrodes attached to the skin. Einthoven developed a 'string' galvanometer, which was much faster and more sensitive than the system used by Waller. Einthoven's electrocardiograph was ready for use in 1903. To facilitate investigations of patients Einthoven connected his instrument to the Academic Hospital in Leyden, by a telephone line, as suggested by his engineering colleague Johannes Bosscha in Delft. The first successful tele-electrocardiogram was transmitted on Sunday 22 March 1905. The heart tones were registered by wiring a specially developed microphone placed on the subject's chest to another string galvanometer. The event was therefore a first both for tele-electrocardiography and for telephonocardiography. We are still awaiting the full-scale implementation of these achievements, 100 years later.

[WPW cases in the literature prior to the publication of Wolff, Parkinson and White in 1930]

In 1930, Wolff, Parkinson and White described the clinical entity of what is today known as the preexcitation or WPW syndrome. In the preceding literature, the authors found four comparable cases. Later on, seven further cases published prior to 1930 were discovered. An analysis of the altogether eleven cases displays that, in addition to the anomalous ECG in sinus rhythm, nearly all typical electrocardiographic findings during the tachyarrhythmias are found in this early literature. As tachycardia ECGs especially help to understand the mechanism of the WPW syndrome, the question is discussed whether already Wolff, Parkinson and White would have been able to give the correct interpretation of the mechanism if they had taken into consideration their own tachycardia ECGs as well as those known to them from the literature.

Electricity and the heart

Understanding of cardiac rhythm requires application of physical principles governing electricity. Over a period of more than 100 years, application of the knowledge of electric current led to the gradual evolution of electrocardiogram, pacemaker, defibrillator, and ultimately electrophysiology. The discovery of electrocardiogram (ECG) by Einthoven in 1902 and that of pacing by Zoll in 1952 were two landmarks in this field.

A troubled beginning: evolving concepts of an old arrhythmia

The development of the sphygmograph in the nineteenth century marked the beginning of graphic registration of the arterial and venous pulse. Mackenzie, among other investigators, used this technique to study cardiac rhythm. In the early 20th century, Einthoven developed the electrocardiogram, which replaced the less sophisticated arterial and venous registrations of cardiac events and allowed for more detailed arrhythmia analysis. Interestingly, the early study of cardiac arrhythmias was obscured by misinterpretation. Specifically, atrial fibrillation stands out as a rhythm that was extensively studied though misconstrued in its early history. What follows is an in-depth consideration of the original investigations and evolving theories of this important arrhythmia.