Abbott Specimen 49
Specimen Card Nomenclature
Pulmonary stenosis with large defect of interventricular septum, deviation to right of aorta and patent foramen ovale.
International Classification of Diseases
Tetralogy of Fallot
Atlas Illustration
None
Donor
Dr. P.P. Smyth
Date
1921
Age
Ten years
Description
Front view shows an enlarged right ventricle (R) with a red rod extending through the tricuspid valve orifice. The pulmonary artery (long arrow) is markedly stenotic. The aortic valve (A) partly over-rides a large ventricular-septal defect (short arrows). The back view shows a normal left ventricle. A blue rod is present in an atrial septal defect.
Comment
The primitive heart consists of a straight tube whose proximal and distal ends are fixed within the pericardial cavity. Because the tube's growth is more rapid than that of the cavity, it is forced to bend, forming sulci and 鈥渟egments鈥� corresponding to future cardiac structures. The ascending limb of this bent structure (the bulbis cordis) differentiates into three components:
- Proximal - the trabeculated portion of the right ventricle
- middle (the conus cordis) - the outflow tracts of the ventricles
- distal (the truncus arteriosus) - the proximal aorta and pulmonary arteries
Four tissue ridges鈭抰wo each related to the truncus and the conus鈭抎evelop on the inner aspect of the bulbis cordis. The truncus swellings enlarge and fuse to form the truncus septum, which grows in a spiral course to divide the truncus into distinct pulmonary and aortic channels. The conus swellings also grow and fuse with each other and with the endocardial cushions inferiorly, eventually contributing to the development of the superior portions of both ventricles (including the membranous portion of the interventricular septum). An abnormality of this complex process is believed to underly the structural components of Tetralogy of Fallot.
Tetralogy is the most frequent congenital anomaly of the conotruncal region, occurring in about 1 per 1000 births. The structural abnormalities which define it are:
- stenosis of the pulmonary outflow tract
- a ventricular septal defect
- a partially displaced aorta that overrides the septal defect
The latter two abnormalities allow blood to flow from the venous to the systemic circulation. The fourth component of the anomaly鈭抮ight ventricular hypertrophy鈭抩ccurs as a consequence of elevated right ventricular pressure. The obligatory right to left shunt typically results in decreased systemic PO2 and cyanosis. Other clinical findings include dyspnea, digital clubbing, syncope (鈥渢et spells鈥�) and embolic stroke (as was likely the case in the boy whose heart is shown here).
Etienne-Louis Arthur Fallot was a French cardiologist who described the condition in detail in 1888. Despite the recognition given to him for this, the anomaly had been documented much earlier by the Danish anatomist Niels Stensen (Nicolas Steno) in 1672, as well as a variety of other physicians in the following years.