So where does the energy for blood flow to the lungs come from ?

First, you must understand that any fluid flowing in a tube will continue to move, becoming slower and slower, until the resistance offered by the tube makes it stop. In a Fontan type circulation, the left ventricle pumps blood into the aorta and arteries. This blood flows at first rapidly into the different organs. The very same force pushes the blood across capillaries, and through the veins, but with lesser force. Slowly, blood enters the right atrium, and then passes across the surgical connection into the lungs - all the while unaided by a right ventricle.
But by its very nature, this flow depends on many factors. For instance, if the blood vessels in the lung are thick walled and narrow before surgery, they will offer very high resistance to passive blood flow. In such a state, the Fontan operation cannot be performed, or will have a high risk of failure, since the extra energy needed to maintain lung blood flow is not available.
Even normally a small amount of resistance will exist across the lung blood vessels. After a Fontan operation, the pressure in the veins will therfore be higher than normal, in order to overcome this resistance and maintain lung blood flow. The elevated pressure in the veins has a few ill effects.

• First, there may be swelling of the entire body due to fluid from the blood leaking out of the vein walls.
• There may be facial puffiness, fluid accumulation in the abdomen (ascites) or chest (pleural effusion).
• Sometimes even absorption of nutrients from the intestines is affected.

What are the criteria for selecting a patient for Fontan operation ?

Ten characteristics were identified which would permit a good outcome after the Fontan operation, called the TEN COMMANDMENTS.
The ten commandments included data which could be obtained before surgery by examining the patient, and carrying out tests like echocardiography and cardiac catheterization. When more of the ten commandments are "obeyed", the better are the chances of a happy - "heavenly" - result from surgery.
In effect, all these criteria were to ensure that the resistance of blood vessels in the lung was not too high. A high resistance would interfere with passive lung blood flow. This could be produced by very small pulmonary arteries, blood vessel wall thickening and hardening, mitral valve leak or reduced function of the left ventricle. In all of these conditions, a Fontan operation would not be performed, or modified to reduce the risks.

What are the kinds of Fontan-type operations ?

 

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