| Feature | Details |
|---|---|
Affected structure | Tetralogy of Fallot results from abnormal development of the bulbar septum. |
Normal relationship | The bulbar septum separates the ascending aorta from the pulmonary artery and normally aligns and fuses with the outflow part of the interventricular septum. |
| Feature | Details |
|---|---|
Usual location | Obstruction is most often subvalvular and muscular. |
Other locations | Obstruction may be valvular, supravalvular or a combination of these forms. |
Dynamic component | Subvalvular obstruction may suddenly increase with sympathetic stimulation. |
| Feature | Details |
|---|---|
Defect size | The ventricular septal defect is usually large, with an aperture similar to the aortic orifice. |
Pressure and shunting | The combination elevates right ventricular pressure and causes right-to-left shunting of cyanotic blood across the ventricular septal defect into the aorta. |