ToF, AV canal defect

(See Normal Heart Image for comparison)

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• Tetralogy of Fallot (ToF) [tetra=four] – a combination of these four heart defects:

1. Large Ventricular Septal Defect (VSD) [septum=wall between the chambers of the heart, ventricles=lower chambers of the heart] – holes in the inner walls of the heart allowing extra blood flow between the two lower chambers of the heart (ventricles). This causes the oxygen-rich and oxygen-poor blood to mix before leaving the heart.
2. Enlarged Aorta (AO) that sits directly above the ventricular septal defect (VSD).  In a normal heart, the aorta carries oxygen-rich blood from the left ventricle to the body.
3. Pulmonary  Stenosis [pulmonary=having to do with the lungs, stenosis=narrowing of a passage, ] – a narrowing of the pulmonary artery (which carries blood from the heart to the lungs) at or near the pulmonary valve.
4. Right-Ventricular Hypertrophy [ventricles=lower chambers of the heart,hyper=excessive, trophy=condition of growth] thickening of the right-ventricular walls because the heart is working too hard.

• Atrialventricular Canal Defect (AVCD) [atrial=the top chambers of the heart, ventricles=lower chambers of the heart, canal=septum or wall] The tricuspid and mitral valves attach to each other instead of the septal wall.  Then you essentially have one combined valve (that doesn’t close all the way) instead of two valves that function properly.  This creates a hole between the 4 chambers of the heart. Blood from all 4 chambers mix together.  Blood leaving the heart (heading to the body AND heading to the lungs) contain an unhealthy mix of both oxygen-rich and oxygen-poor blood.

Click HERE for an alternate view of AV canal defect (viewed from the top) that will help to visualize it better.