Fallot's Tetralogy: The Pathological Aspect

THE general pathologist has, until very recently, shown little interest in congenital malformations of the heart. Apart from a few anomalies thought to be significant in the prodluction and localisation of bacterial endocarditis, most of these anomalies have been encountered by him in new-born infants, or in infants dying within the first six, or, at most, twelve months of life. The lesions have usually been complex and highly variable from case to case, and it has often been difficult to appreciate how the child lived at all. To make a detailed anatomical study of the abnormalities found in early infancy would deter anyone from ever expecting to make an accurate clinical diagnosis. Until Dr. Taussig's work, it may be said that only a few workers appreciated that, among those children surviving beyond the first vear of liPe and showing cyanosis, the great majority suffered from a fundamentally similar defect and showed the four features described by Fallot in 1888 and usually known as the "tetralogy of Fallot." No sound knowledge of any disease can be obtained without some understanding of its structural basis. Biochemical equations and biophysical concepts may be enough for some, but most of us will feel, as Robert Louis Stevenson said in another context, that these concepts lie in regions where there is no habitable city for the mind of man. Some such apology is necessary for this brief account of the morbid anatomy of the condition. The condition as described by Fallot consists of four features, hence the name "tetralogy." These are pulmonary stenosis or atresia, dextroposition of the aorta, an interventricular septal defect, and hypertrophy of the right ventric'e. These must be discussed separately.