Electrocardiogram # 6
Four year old boy with Tetralogy of Fallot
Right Ventricular Hypertrophy – Right axis deviation (QRS negative in lead 1 and positive in AVF), Deep S wave in V6 and upright T in V1
Tetralogy of Fallot as per renowned Professor of paediatric cardiac morphology Robert Anderson should really be named “Monology of Fallot”. The single significant abnormality present is antereo and cephalad deviation of the infundibular septum leading to right ventricular out flow obstruction. The overriding aorta, ventricular septal defect (VSD) occur as a result of this deviation and of course right ventricular hypertrophy the consequence of the right ventricular outflow obstruction. Commonly there is associated pulmonary valve and artery stenosis.
The electrocardiogram finding associated with this condition reflects this principle and tells the story. Right ventricular outflow obstruction causing pressure load on the right ventricle.
Although there is a large VSD, both ventricles are at the same pressure so there is no left ventricular overload (LVH) from VSD flow. The Right ventricular pressure is never super high as the VSD acts as a pop off valve for the right ventricle. So clinically heart failure is not a feature of this condition.