Thomas Lewis was an English physician who played a major role in the development of electrophysiology and clinical electrocardiography. Following the invention of String Galvanometer in 1902, a more compact model became available in 1908. In Europe, Thomas Lewis' laboratory was one of the first to be equipped with this new instrument. In the United States, Mount Sinai Hospital was one of the first institutions to acquire the electrocardiograph.
Lewis started his investigational studies in cardiac arrhythmias after visiting Einthoven's laboratory in 1909. He was among the first to recognize atrial fibrillation in patients with "continuous and extremely irregular pulse" and reported his observations in an article published in 1909. In a short period of time, he performed extensive electrocardiographic studies and published his classic monograph entitled "The mechanism of the heart beat with especial reference to its clinical pathology" in 1911. In this masterpiece, he described for the first time the electrocardiographic features of many arrhythmias. The book is divided into 23 chapters and chapters 17 and 18 focus on "auricular fibrillation" (atrial fibrillation). He defined the characteristics of atrial fibrillation on electrocardiogram: the absence of P wave, the complete irregularity of the ventricular beat, and the supraventricular origin of the cardiac impulses. He also wrote "The oscillations are variable in their amplitude, but are quite distinct in all the curves." Several patients with atrial fibrillation presented also with mitral valve stenosis (see below). The entire text of chapter 17 is displayed.
Lewis also mentioned that the normal presystolic auricular contraction was abolished in the setting of atrial fibrillation. He, however, disagreed with the hypothesis of atrial paralysis suggested earlier by Mackenzie and in his conclusion he remarked:
"The auricle is the seat of an electric disturbance of a peculiar yet distinctive nature. The constancy of the oscillations, their unique appearance and their presence throughout the whole of the cardiac cycle, is responsible for the conviction that they are an essential feature of complete irregularity and that the activity of the auricle is continual."
He confirmed this hypothesis after an elegant comparative clinical and experimental study using an animal model which was described in chapter 18 of his textbook.
In 1913, Lewis published the first textbook of electrocardiography. In the preface, Lewis wrote:
"In offering to members of the medical profession an account of clinical electrocardiography, I do so with the conviction that this new method of examination has become essential to the modern diagnosis and treatment of cardiac patients."
The chapter 10 of this book is on electrocardiographic findings in patients with valve diseases including mitral stenosis and regurgitation.
Following this pioneering work of Thomas Lewis, electrocardiographic study became an essential tool in the diagnosis of mitral valve disease and the rhythm disturbances that accompany it.