Anatomical Components of the Defect
The pathological anatomy of Tetralogy of Fallot represents a complex of interrelated intracardiac anomalies. The morphological picture of this severe congenital defect consists of four strictly defined pathological features, each of which contributes to hemodynamic impairment.
The first core component is a large ventricular septal defect (VSD). The second mandatory feature is an overriding aorta (dextroposition of the aorta). In this spatial anomaly, the aortic root is shifted and located directly over the septal defect. This specific anatomical position causes the aorta to receive blood simultaneously from both ventricles, mixing the blood streams.
The third crucial component is pulmonary stenosis, which creates a mechanical obstruction to normal blood flow. The fourth feature, completing the tetrad, is right ventricular hypertrophy. This thickening of the muscular wall develops as a direct consequence of altered intracardiac hemodynamics.
Clinical Features and Compensation
The clinical presentation of Tetralogy of Fallot has several specific features that directly stem from the anatomical defects described above. One of the main visual manifestations of the defect is cyanosis. Notably, the presence of skin cyanosis is neither static nor identical in all patients: the severity of cyanosis directly depends on the degree of pulmonary outflow obstruction.
An interesting clinical feature is that this defect is very frequently combined with other vascular anomalies that may paradoxically alleviate the patient's general condition. In particular, Tetralogy of Fallot is often accompanied by a patent ductus arteriosus (PDA). The presence of this patent duct is vital in severe pulmonary stenosis, as it allows the patient to survive under conditions of restricted pulmonary blood flow. Furthermore, the clinical course of the defect is significantly facilitated by a well-developed bronchial collateral arterial system, which forms as an additional compensatory mechanism.
Prognosis and Causes of Death
In the natural history of the disease, without timely surgical intervention, the prognosis is considered extremely poor. The vast majority of patients with diagnosed Tetralogy of Fallot die in childhood. Statistical data show that the average life expectancy of such patients without adequate treatment is only twelve years.
Death in this congenital defect results from severe, life-threatening complications. One of the main causes of death is progressive right ventricular hypertrophy and failure, developing against the background of pronounced hypertrophy of the right heart chambers. Patients are also extremely vulnerable to infectious complications, among which infective endocarditis and severe recurrent pulmonary infections play a leading role in thanatogenesis. A specific and extremely dangerous cause of death in this defect is central nervous system involvement, specifically the formation of embolic brain abscesses.