Anatomophysiologic basis of tetralogy of Fallot and its clinical implications

Abstract

Tetralogy of Fallot is the most frequent cyanotic congenital cardiopathy. Its physiopathology has been progressively described which has made better treatment possible. The four characteristic morphologic abnormalities are: interventricular communication, subpulmonary stenosis, biventricular origin of the aortic valve and right ventricular hypertrophy, which are the direct result of the antero-cephalad deviation of the ventricular septal outlet and hypertrophy of the septoparietal trabeculations. These anatomic abnormalities result in decreased pulmonary blood flow, leading to hypoxia and cyanosis. The main determinants of pulmonary blood flow are the source of the blood flow to the lungs, the severity and functional behaviour of the subpulmonary obstruction, the right ventricular and arterial systemic pressures and the ductus arteriosus. The mechanism of cyanotic spells is not clear. Increases in infundibular contractility, peripheral vasodilatation and right ventricular mechanoreceptor stimulation are some of the proposed mechanisms. There are two surgical strategies in newborns/children: a staged approach (with a palliative procedure followed by the complete repair) or early complete repair. There are arguments for and against each of these strategies, and the debate about the ideal treatment continues. In conclusion, the correct understanding of this cardiopathy's physiopathology is essential to improving the child's treatment. This review is particularly contemporary and relevant issue because one must always bear in mind the physiopathology of the original disease in order to correctly follow-up a new patient population: adults with surgically corrected Tetralogy of Fallot.