Transposition of the Great Arteries
What is the TGA defect development similar to?
TOF, Truncus arteriosus
What causes truncus arteriosus in embryology?
The anomaly is thought to result from failed septation of the embryonic truncus arteriosus. -abnormality of conotruncal septation
What are the types of truncus arteriosus?
Type I: truncus leads to one PA and two lateral PAs (usually branches from left lateral aspect of common trunk initially) Type II: truncus leads to two posterior/posteriolateral PAs Type III: truncus leads to two lateral PAs (the main differences between the types is where the PA branches off from the trunk) (Slide 45!)
What are often required following the repair of truncus arteriosus?
delayed sternal closing
Transposition has to have the following features:
transposed arteries not connected to what they should be...
What TGA type is the Le Compte Maneuver ASO done for?
when TGA is associated with LVOT obstruction
When should the Jatene arterial switch operation (ASO) be performed?
when the infant is younger than 4 weeks
When does TGA form/arise in embryonic development?
{Weeks 5-6} Conotruncal ridges grow towards each other, spiralling and forming the PA and aorta. "Conotruncal septation"
Know slide 34!
Case notes for TGA.
When might an arterial switch operation may not be feasible?
In TGA w/ VSD and LVOT due to pulmonary (LVOT) stenosis or atresia. -if ventricular septal defect is nonrestrictive and not too remote from aorta, a Rastelli intracardiac repair is possible (This is a palliative treatment!) -the VSD is also closed for this technique
What are the CPB considerations for Truncus Arteriosus?
Incision: median sternotomy Arterial: aortic Venous: bicaval Temp: mild to moderate (about 28 degrees C), may involve DHCA CPG: antegrade and possible retrograde
What site of entry for a PA band provide excellent exposure for isolated pulmonary artery banding?
Left anterior thoracotomy approach through the second or third intercostal space. -extracardiac procedure, no CPB needed
Is TGA more common in girls or boys?
More common in males, with a ratio of about 3:1.
What is the palliative procedure for Truncus Arteriosus?
PA band the pulmonary arteries coming off the truncus to reduce pulmonary BF.
Which type of atrial switch procedure had better results?
Senning had better results than Mustard.
What is the L-TGA defect?
-"congenitally corrected" transposition -the aortopulmonary septum fails to rotate 180 degrees and you get ventriculoarterial discordance -the blood flows in normal direction, but it passes through wrong chambers because the ventricles fail to rotate
What is causing TGA in embryology?
-A bulbus cordis defect -Improper spiraling of the aorticopulmonary septum -septation still happens but it just fails to rotate
What are the complications that may occur (later in life) in patients who have had TGA correction surgery?
-Narrowing of the coronary arteries -Heart rhythm abnormalities (arrhythmias) -Heart failure -Leaky heart valves
What is the atrial switch procedure?
-a patch/baffle is created from the body (vena cavas) through the ASD so blood gets shunted to the left side of the heart -so all the venous return gets shunted through the baffle to the left side of heart to the lungs -the oxygenated blood is returned to the right side of the heart and goes out the aorta (The blood is switched between the atria, hence the name!) (Slide 20!)
What is happening in Truncus Arteriosus?
-since truncal valve is above VSD, blood is pumped from both the RV and LV to the lungs and body (so the body and lungs gets mixed blood) -PVR is lower than SVR so you usually get increased PBF and can lead to CHF -you will eventually get irreversible pulmonary hypertension due to exposure of high pressure and extra blood to the lungs
What are the two anatomical classifications of TGA?
1) D-Transposition {dextro (right)} -60% of TGA patients -Aorta is anterior and to the right of the PA --The great vessels fail to rotate =parallel 2) L-Transposition {levo (left)} -Aorta is anterior and to the left of the PA -"congenitally corrected TGA" (The ventricles failed to rotate but the great vessels still face the correct side of the heart.)
What are the two types of arterial switches?
1) Jatene 2) LeCompte
What are the two types of atrial switch corrective procedures?
1) Mustard -uses pericardium for the baffle 2) Senning -uses atrial tissue for the baffle (They are exactly the same except for the material they use for the baffle.)
What are the two types of double switch operations?
1) Mustard/Senning + Arterial Switch 2) Mustard/Senning + Rastelli
What maternal risk factors are associated with TGA?
1) Rubella/viral illness during pregnancy 2) Alcoholism 3) Geriatric pregnancy :) maternal age >40 4) Poorly controlled Diabetes 5) Poor nutrition during pregnancy 5) Down syndrome in the baby
What are the common presentations of TGA?
1) TGA w/ IVS (intact ventricular septum) 2) TGA w/ VSD 3) TGA w/ VSD & LVOT obstruction 4) TGA w/ VSD & pulmonary vascular obstructive disease
What were the common complications of the atrial switch procedure?
1) baffle stenosis/narrowing 2) pulmonary hypertension -the LV is built to pump against systemic pressure, not the pulmonary pressure 3) arrhythmias 4) obstruction of SVC (SVC syndrome) 5) systemic AV valve regurgitation is common 6) 1/3 to 1/2 of patients demonstrated decreased RV (systemic) function 15-18 years after repair (By the 1980s, late complications of these repairs had become well recognized which led to the adoption of the neonatal arterial switch procedure which is now standard therapy for transposition!)
What are the symptoms of truncus arteriosus?
1) cyanosis 2) delayed growth or growth failure 3) fatigue 4) lethargy 5) poor feeding 6) rapid breathy (tachypnea) 7) SOB (dyspnea) 8) clubbing
What two problems occur if truncus arteriosus is left untreated?
1) too much pulmonary blood flow 2) the blood vessels to the lungs become permanently damaged and pulmonary HTN develops (The major problem in truncus arteriosus is that the lungs are flooded with blood and heart muscle is overloaded!)
What percentage of congential heart defects are TGA?
5%
What happens to TGA patients if left untreated?
>>>Lack of oxygen to tissues (hypoxia). >>>Heart failure: the heart can't pump enough blood to meet the body's needs & RV is pumping under higher pressure than usual. >>>Lung damage: The oxygen-rich blood causes damage to the lungs, making breathing difficult. (Fact: Too much O2 damages the tiny vessels in the lungs & also the eyes).
What is the complete surgical repair for Truncus Arteriosus?
A modified Rastelli procedure. -PA's are excised and the truncus defect is closed with direct suture -a R. ventriculotomy is made -VSD is closed -placement of a valved conduit into pulmonary arteries -proximal end of conduit is anastomosed to RV (Slide 61!)
What is Truncus Arteriosus?
A rare type of congenital heart disease in which a single blood vessel comes out of the right and left ventricles instead of the normal two (PA and aorta). (Slide 39 for visual!)
What defects do patients with TGA frequently have?
ASDs, VSDs, PDA *Incompatible with life unless some communication exists between the 2 separate (pulmonary & systemic) circulatory systems.
What is transposition of the great arteries/vessels TGA/TGV ?
Abnormal antero/posterior relationship of the two arterial trunks. The aorta is in front of the pulmonary artery and either primarily to the right (in D-TGA) or to the left (in L-TGA). The aorta arises from the right ventricle. The pulmonary artery arises from the left ventricle. *Communication must exist between the 2 separate (pulmonary & systemic) circulatory systems.
What are the CPB considerations for ASO?
Arterial: aortic Venous: single atrial OR bicaval Temp: 24-28 degrees C CPG: antegrade, retrograde, and ostial (usually give multiple doses)
What are patients with L-TGA often, asymptomatic or symptomatic?
Asymptomatic unless associated with other CHD. -common to see VSD, PS, TI -CHF may develop later as the systemic RV fails to pump against high SVR
Why is a PDA not required in truncus arteriosus?
Because the common trunk originates from both the LV and RV, and PAs arise directly from the common trunk.
What are the symptoms of TGA?
Blue color of the skin (cyanosis). Shortness of breath/Problems breathing Lack of appetite/Poor weight gain. Pounding heart/Weak pulse
Follow the path of the 2 parallel circulations in TGA?
Body →RA →RV →Ao →Body Lungs →LA →LV →PA →Lungs
Which type of TGA is the Jatene ASO used for?
D-TGA
What is the Le Compte Maneuver ASO?
The great vessels are transected and switched similar to Jatene ASO, but the infundibular septum is resected and the pulmonary outflow tract is widened.
What is the Jatene arterial switch procedure?
The great vessels are transected. The coronary buttons are taken off and the PA is pulled in front of the aorta. The great vessels are reanastomosed. So the aorta is sewn to the previous pulmonary trunk and the PA is sewn to the previous aortic trunk. The coronary buttons are reimplanted. (It represents an anatomic repair! and establishes ventriculoarterial concordance.)
What is the treatment for L-TGA?
double switch operation
What is the survival rate of TGA in today's society?
greater than 90%
What is the initial treatment for TGA patients?
maintain ductal patency with continuous IV prostaglandin E1 infustion (PGE1) -this increases pulmonary blood flow and increases left atrial pressure -it promotes L > R shunting at atrial level to decrease cyanosis (Very important in patients with severe LVOT obstruction!)
