What is an "Outflow Patch" ? When is it needed ?

The passage or tunnel leading from the right ventricle into the pulmonary artery is called the "outflow tract" of the right ventricle. Through this blood flows OUT of the right ventricle. When this tract is narrowed, due to a small pulmonary valve annulus (or ring) - pulmonary annular hypoplasia - a special operation is required to relieve the obstruction. A vertical (length-wise) cut is made in the wall of the right ventricle and extended into the pulmonary artery ACROSS the narrow pulmonary annulus. This adequately "opens up" the narrow outflow tract.
But the problem now is the opening in the wall of the outflow tract. This defect is closed using a "patch" of Dacron or PTFE, so that it does not become narrow again. The natural covering of the heart - called the PERICARDIUM - may be used for the outflow patch too. Because this patch goes across the outflow tract of the right ventricle, it is called an "Outflow Patch".
When there is obstruction even above the pulmonary valve - in the main pulmonary artery trunk, or in one of its branches or divisions - further modification of the outflow patch repair is needed. The outflow patch is tailored to be longer. The vertical incision in the right ventricle is extended even further, right across the pulmonary artery and its branches, until it has crossed the area of narrowing. When the obstruction has thus been relieved, the defect in the wall of the pulmonary artery is now repaired using the tailored patch. However, in the very severe case where pulmonary arteries are not formed at all - pulmonary atresia - this repair is not possible. I will explain this in another section.

Though it relieves the obstruction of blood flow into the pulmonary artery very effectively, there are some problems with an outflow patch. First, the pulmonary valve becomes "leaky" and blood flowing into the lungs can easily return back into the right ventricle. This is called Pulmonary Regurgitation. As a consequence of this, the right ventricle has to pump a larger amount of blood. Over the years the right ventricle may become weak and "fail".
In an attempt to avoid this, some surgeons place an artificial valve in the outflow patch. A "monocusp valve" may be created by simply sewing on a flap of fabric or pericardium to the inside of the outflow patch. Another choice is to use a "homograft" patch with a valve cusp. This monocusp valve, though not perfect, may reduce the amount of blood leaking back into the right ventricle. In theory, this should reduce the chance of right ventricle failure.
Another problem with the outflow patch is that calcium may get deposited on it, making it rigid and hard. It may also be weakened by the forceful contraction of the right ventricle, and balloon out - a condition called "aneurysmal dilatation". After many years, a second operation to repair or replace the outflow patch may be required sometimes.

Palliative Operations - What are they ? Read on .....

 

---

home	|	disease	|	webcast	|	latest	|	links
news	|	archive	|	contact	|	books	|	disclaimer

 

Member of the Internet Link Exchange

Conceived, created and designed by Dr.S.Sivasubramanian. Copyright 1998, All rights reserved.