Tetralogy of Fallot (ToF)
In 1888, French physician Etienne-Louis Fallot published the first in a series of articles on the cardiac malformation know today as tetralogy of Fallot (TOF). The works describe the clinical demise and post mortem cardiac structure of 3 cyanotic adult males whom Fallot cared for at the Hospital of the Conception in Marseille, France. Dr Fallot described the cardiac specimens as having:
- a ventricular septal defect (VSD) in exactly the same place,
- valvar and subvalvar pulmonary stenosis,
- ventricular hypertrophy worse in the right ventricle and
- an aorta which deviated to the right.
Fallot stated, “The more we thought about it, the more we thought that the Blue Disease was caused by these lesions, multiple but constant, so that together they constituted a type, perfectly definedߪ we ourselves with our 3 subjects found not one simple anomaly, but a veritable series of lesions, a true anatamo-pathologic tetralogy”. This clinicopathologic correlation is the reason the cardiac malformation bears his name. It has been proposed that Fallot believed the cardiac lesions were the result of an in utero process involving the maldevelopment of the subpulmonary infundibulum and pulmonary valve.
Fallot was not the first to describe the cardiac pathology. Nils Stenson, the Dutch scientist and anatomist, described the cardiac malformation in 1671, 10 years before his detailed description of the parotid duct. One hundred years later, Eduardus Sandifort, a Danish physician, described the pathologic examination of the heart of a 12-year-old child who died of progressive cyanosis. The heart had all four features which would be later described by Fallot. Maude Abbott, the founder of modern day pediatric cardiology and pediatric cardiac pathology popularized the term tetralogy of Fallot in many of her works in the 1920’s.
Tetralogy of Fallot is one of the most researched subjects in the study of congenital heart disease.
As the name tetralogy implies, Tetralogy of Fallot includes the following four related cardiac malformations:
- ventricular septal defect (VSD)
- right ventricular outflow tract obstruction (RVOTO), which can include valvar pulmonary stenosis, subvalvar pulmonary stenosis, and supravalvar pulmonary stenosis
- aortic override of the ventricular septum
- right ventricular hypertrophy
As discussed in detail below, many believe that tetralogy of Fallot is actually a "monology" (i.e., "monology of Fallot") that can be defined by either:
- anterior deviation of the infundibular septum (i.e., conal septum) (Anderson), or, in other words,
- underdevelopment of the subpulmonary conus (Van Praagh)
In this chapter, we will focus on the following form of tetralogy of Fallot:
- tetralogy of Fallot with pulmonary stenosis
This chapter will not discuss the following forms of tetralogy of Fallot, which will be discussed in other chapters of this STS e-Book:
- tetralogy of Fallot with pulmonary atresia
- tetralogy of Fallot with atrioventricular septal defect (i.e., tetralogy of Fallot with atrioventricular canal defect)
- tetralogy of Fallot with absent pulmonary valve
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