Arterial Switch Procedure
Click here to watch Arterial Switch Procedure video.
What is TGA (Transposition of the Great Arteries)?
Transposition of the Great Arteries or (TGA) is diagnosed when the two main blood vessels that carry blood away from the heart are formed in a position opposite from where they should be. The Aorta and the Pulmonary Artery are “transposed”. The Pulmonary Artery normally arises from the Right Ventricle pumping the “blue” or unoxygenated blood to the lungs. The Aorta normally arises from the Left Ventricle and pumps the “red” blood out to the head, limbs, and body. In Transposition of the Great Arteries the opposite holds true. The Pulmonary Artery arises from the Left Ventricle pumping the “red” blood to the lungs. The Aorta arises from the Right Ventricle pumping the “blue” blood to the body, head, and limbs. The heart wall or septum may be intact, or there may be a VSD (Ventricular Septal Defect), a hole between the lower two chambers of the heart, an ASD (Atrial Septal Defect), a hole between the upper two chambers of the heart. There may also be a PDA (Patent Ductus Ateriosus), a blood vessel connecting the Aorta to the Pulmonary Artery.
Transposition of the Great Arteries
with Intact Septum
What happens when Transposition of the Great Arteries occurs?
When the “Great Arteries”, the Aorta and the Pulmonary Artery, are transposed it creates a situation in which the body receives “blue” or unoxygenated blood instead of the “red” or oxygenated blood that it needs. In this defect the “blue” blood returns to the Right Atrium, flows through the Tricuspid Valve to the Right Ventricle and back out the Aorta to the body. The “red” blood returning to the heart from the lungs enters the Left Atrium, flows through the Mitral Valve to the Left Ventricle and back to the Lungs through the Pulmonary Artery. Since the “red” blood is already fully saturated with oxygen its trip back to the lungs is useless. This situation is not compatible with life unless there is a place for the “red” and “blue” blood to mix (ASD, VSD, and/or PDA).
A second concern that arises with Transpostions is the deconditioning of the Left Ventricle. In a normal heart the Right Ventricle is made up of tissue that is much less muscular that the Left Ventricle. The Right Ventricle is made to pump against the low-pressured lungs, and the Left Ventricle is made to pump against the high-pressured circulation of the body. With infants diagnosed with Transposition of the Great Arteries the opposite is true. The Right Ventricle must pump out the Aorta to the high-pressured circulation of the body, and the Left Ventricle pumps blood through the Pulmonary Artery to the low-pressured lungs. If the heart anatomy remains like this for any length of time complications can occur. The Left Ventricle (the more muscular ventricle) can become de-conditioned over time. This ventricle at the time of the operation to “switch” the Great Vessels must take over its intended job of pumping blood against the high-pressured circulation of the body. If the ventricle is de-conditioned it may fail. The Arterial Switch operation should be done within the first weeks of life to prevent the deconditioning of the Left Ventricular muscle.
For these infants to survive through the first few days, hours, or sometimes minutes, some mixing of the “red” and “blue” blood must occur. Mother Nature seems to step in at some critical point during the infant’s development in the womb creating one or more additional defects allowing for the mixing of “red” and “blue” blood. With the mixing of the “red” and “blue” blood occurring, the baby may be kept alive long enough to completely repair the defect, giving the baby a chance to live a normal healthy life.
At birth infants with TGA must have one or more of the “mixing” defects that are mentioned below in order to survive.
A “Ductus Arteriosus” is a blood vessel connecting the Aorta to the Pulmonary Artery. Through this vessel the “blue” blood from the Aorta can mix with the “red” blood coming from the Pulmonary Artery. A second defect that is commonly related to Transposition of the Great Arteries is an ASD or Atrial Septal Defect. This is a hole that occurs between the upper two chambers of the heart. Mixing of the “red” and the “blue” blood occurs through this lesion. The third defect that can be associated with TGA is a VSD or Ventricular Septal Defect. This is a hole between the lower two chambers of the heart. Mixing of the “red” and “blue” blood occurs through this lesion. The amount of mixing of the blood through an ASD or a VSD is directly related to the size of the defect.
Transposition of the Great
Arteries with Ventricular Septal Defect,
Atrial Septal Defect, Patent Ductus
Ateriosus
What occurs if Transposition of the Great Arteries is left untreated?
We have already learned that if there is no “mixing” between the “red” and “blue” blood shortly after birth the infant with Transposed Great Arteries will not survive. With few exceptions many of the children will not live to see their first birthday. There are a few circumstances in which children with Transposition of the Great Arteries can survive with little or no symptoms. One is a child with TGA, and a Ventricular Septal Defect. If the VSD is large enough it can allow for adequate mixing of the “red” and “blue” blood to occur, supplying the body, head, and limbs with enough oxygenated blood to function. We must remember that although the heart does receive oxygen in amounts that are adequate for activities of daily living, mixing of the “red” and “blue" blood through a VSD cannot supply the body with enough oxygen for prolonged work or play. These patients may present with symptoms later in childhood. Some of these symptoms include exercise intolerance, frequent chest colds, and fainting spells. Another fortunate combination of defects that may occur is Transposition of the Great Vessels with Ventricular Septal Defect and Pulmonary Stenosis, or narrowing of the Pulmonic Valve. In this combination the mixing of the “red” and “blue’ blood occurs through the VSD, but excessive Pulmonary Blood flow does not occur because of the Pulmonary Valve narrowing. You might say that the lungs are “protected” by Mother Nature. These patients may live into their 20’s or 30’s, before they start developing symptoms of Congestive Heart Failure. Since the Pulmonic Valve in these patients is abnormal these patients are not candidates for the Arterial Switch Operation and often times require a shunt to increase pulmonary blood flow early on in life. The complete repair is then done at 2-4 years of age with a cadaver valve (homograft) using the Rastelli procedure.
When should Transposition of the Great Arteries be treated?
The answer to this question is very simple in most cases. When the diagnosis is Transposition of the Great Arteries, correction should be planned as soon as possible. The development and the use of the drug Prostaglandin has given practitioners the ability to stabilize the infants, and plan the correction when the child is as healthy as he/she can be. In general the repair should be done within the first two weeks of life.
How is Transposition of the Great Arteries treated?
When an infant has been diagnosed with TGA time is a major factor. All
infants are born with a Patent Ductus Arteriosus. Although all infants are
born with this vessel open and mixing blood, the PDA normally closes itself
shortly after birth. In infants with Transposition of the Great Vessels,
if the PDA begins to close shortly after birth it can be kept open with
the help of an intravenous drug known as Prostaglandin. Prostaglandin is
usually started as soon as the diagnosis of TGA is made, and is continued
until the corrective surgery has been completed. Prostaglandin is a good
drug, but is not without its own risks. It must be administered intravenously,
and under close supervision of an experience physician.
If adequate mixing does not occur it may be necessary to create a “hole”
in the wall of the Atrium or enlarge the Atrial Septal Defect, if one exists,
through which the “red” and the “blue” blood mix. In this situation the
infant would be taken to the catheterization lab where a procedure known
as a Balloon Septostomy would be performed. During this procedure a “hole”
would be created in the wall between the Right and the Left Atria if one
did not already exist at birth. If the infant already had an Atrial Septal
Defect, but it was not large enough to allow for adequate mixing of the
“red” and “blue” blood, the “hole” could be enlarged by pulling a catheter
across it with a balloon on the tip. The “hole” in the septum would be “ripped”
larger, improving the oxygenation of the blood oxygen levels. This Atrial
Defect is then closed when the surgical procedure is done. If adequate mixing
through the Patent Ductus Arteriosus occurs, a Balloon Septostomy may not
be necessary.
Once the child has been stabilized a surgical option can be discussed. The “definitive treatment” for this defect is the ASO or “Arterial Switch Operation”.
What is the ASO or “Arterial Switch Operation”?
The Arterial Switch Operation is a simple concept. The Aorta and the Pulmonary Artery are transected above the valves, moved to the correct position, and sewn in place. The difficulty with this operation is the Coronary Arteries. They must also be moved during this operation. The Coronary Arteries are very small, and are critical to the perfusion and blood supply to the heart muscle itself. The Coronary Arteries normally arise from the Aorta, branching immediately off the ascending Aorta just beyond the aortic valve. In an infant with Transposition of the Great Vessels the Aorta arises from the Right side of the heart. When the Vessels are switched the Coronary Arteries must be freed from the Right side and moved to the Left side of the heart so that they are receiving oxygen-rich blood. The Coronaries are very thin, measuring only about 1-2 mm in an infant. Any kinking of the arteries would compromise the heart muscle perfusion, causing damage to the heart muscle. Abnormalities in the Coronary Artery anatomy increase the difficulty of the ASO and decrease the success rate of the operation.
Repaired Transposition of the
Great Arteries
Although the Arterial Switch Operation is technically demanding and difficult, it is the treatment of choice for most patients with Transposition of the Great Vessels. Once the switch is complete the heart is as good as new. The anatomy is that of a normal heart. The Left Ventricle, or the muscular ventricle, is pumping against the high-pressured circulation of the body. The Right Ventricle is pumping against the low-pressured lungs, and will not have to run the risk of failing due to increased demands on it by the body. Children who have Pulmonary Valve abnormalities and who present with TGA at an older age are not considered good candidates for the Arterial Switch Operation.
How is the Arterial Switch Operation done?
The Arterial Switch Operation is an “open heart operation”. The Aorta and
the Pulmonary Artery are disconnected above the valves. The Coronary Arteries
are “freed” from the right side by taking a “button” of tissue around each
coronary. The coronaries are then mobilized and moved into position just
above the valve on the left side of the heart. With the aid of the extra
“buttons” of tissue, each coronary is sutured into position with hair-like
sutures. Once the coronary buttons have been implanted the ascending Aorta
is anastomosed to the left side, just above the coronaries. The areas just
above the right-sided valve where the “coronary buttons” were excised, are
patched with small pieces of the pericardium (the sack that encloses the
heart). The Pulmonary Artery is then anastomosed to the right side just
above the valve. The ASD (Atrial Septal Defect) is closed. The VSD (Ventricular
Septal Defect) is closed if one exists, and the PDA (Patent Ductus Arteriosus)
is ligated if it is still open.
Transected Pulmonary Artery with pericardial patches on removed Coronary Artery button sites. |
Transected Aorta with anastimosed CoronaryArtery buttons |
Coronary Artery Re-implantation with repaired Transposition of the Great Arteries |
What are some of the complications with the Arterial Switch Operation?
Some of the complications that may occur with the Arterial Switch Operation include bleeding, and myocardial infarction (heart muscle damage from the lack of sufficient blood flow to the heart muscle), among others. The amounts of time from birth to diagnosis of TGA, as well as the anatomy of the coronary arteries, are big factors in how the patient will do after an Arterial Switch Operation.
What is Driscoll Children's Hospital success rate for the Arterial Switch Operation?
Driscoll Children’s Hospital performed the first successful Neonatal Arterial Switch in the State of Texas in the early 1980’s. The success rate is 96% for the last 4 years.
Contact Information:
John Mark Morales MD, FACS, FAAP
Chief of Cardiothoracic, Director of Perfusion Services
Certified by the American Board of Surgery, American Board of Thoracic SurgeryMark Bielefeld, MD
Driscoll Children's Hospital Chief of Staff
Certified by the American Board of Surgery, American Board of Thoracic SurgeryThoracic surgeons are available for questions and consultations: (361) 854-0201. For appointments, assistance, and physician references in Corpus Christi call: (361) 854-0201 or 800-DCH-LOVE
Fax : 361-855-7572
E-MAIL : jmarkmorales@aol.com
For further information on any surgical procedures you can contact Carol Kaplan, RN, Surgical Nurse Liaison at (361) 694-5150. Consultation and surgery for inpatients is provided in concert with neonatology and pediatric cardiology departments. Complete evaluation and management for infants, children, adolescents and adults with congenital or acquired cardiac, vascular or thoracic anomalies.
Cardiothoracic Associates
3533 S. Alameda, Suite 202
Corpus Christi, Texas 78411
Phone: (361) 694-5150
Fax: (361) 855-7572
Hours: 9am to 6pm
Fri 9am to 5pm
Statement of Compliance
Voted Best Place to Work in 2006 and 2007 | Ways to Give | Contact Us
Copyright © Driscoll Children's Hospital 2008
Corpus Christi, Texas
Live website tracking by Visistat
You
must have Windows Media Player 10 installed on your computer to view the
videos. Click here to download Windows Media Player 10
Click
here to learn about International Services
More
information about
