Cyanotic Disorder with mixed circulation
Complete D- transposition of great arteries (TGA)
TGA is a cyanotic defect in which aorta arise from right ventricle and pulmonary artery arises from the left ventricle. Resulting in two separate and parallel circulation.
Pathophysiology
Pulmonary artery arising from left ventricle carries blood to lungs for oxygenation.
Oxygenated blood returns to left atrium then to left ventricle.
From left ventricle through pulmonary artery the blood is recycled to the pulmonary circulation.
Aorta arising from right side of heart deliver unoxygenated blood to systemic circulation.
This blood the returns to right atrium and right ventricle without oxygenated, circulated back to systemic circulation via aorta.
Cause progressive hypoxemia
Mixing of oxygenated and unoxygenated blood occurs in presence of patent foramen ovale, ASD, VSD, PDA.
If not present (death may occur).
Clinical feature
TGA is diagnosed in infancy.
1. Cyanosis always present.
Incase of mild- if mixing occurs through a large VSD or PDA.
Incase of severe - if ventricular septum is intact or PDA is closing.
2. Hypoxic spell; during crying
3. Clubbing; seen in older children.
Diagnostic Evaluation
1. Cardiac examination
Murmurs- cardiac defect (PDA,VSD).
Increase intensity of heart sound because aorta arising from right ventricle.
2. Electrocardiogram
ECG may normal for neonate or demonstrate right ventricular hypertrophy.
Rarely left ventricular hypertrophy and combined ventricular hypertrophy.
3. Chest radiograph
Heart size may normal or moderately enlarged.
Cardiac silhouette - assume shape of egg lying.
Pulmonary vascularity may normal, increased or decreased depending on the extent of defect.
.
4. Echocardiogram
Color flow 2D to visualized cardiac defect.
Therapeutic Management
1. Medical management
a. Prostaglandin Infusion- given IV - to keep ductus arteriosus open - untill palliative procedure or corrective surgery performed.
2. Surgical management
1. Palliative surgery
a. Rashkind procedure
Enlargement of interatrial communication by atrial balloon septostomy done during cardiac catheterization.
Helps in establishing adequate mixing of oxygenated and unoxygenated blood.
Balloon catheter is passed through the foramen ovale, it inflated and pulled back to tear and stretch open foramen ovale, creating enlarged opening between two atria.
b. Blalock Hanlon procedure
Creation of ASD or enlargement of foramen ovale surgically.
2. Corrective surgery
1. Arterial switch procedure
Pulmonary artery and aorta transected above respective valve.
2. Mustard procedure
New atrial septum created by using pericardium to make baffle ( use to redirect flow of blood).
This baffle alters blood flow by redirecting unoxygenated blood from right atrium to left ventricle and out to lungs via pulmonary artery.
Oxygenated blood from left atrium is redirected to right ventricles and then to systemic circulation via aorta.
3. Senning procedure
Senning procedure creates same redirection of blood flow using atrial flaps but without use of pericardial patch.
Atrial septum and a portion of atrial wall are used to reroute the blood flow.
Above three procedure recommend in First year of life.
These procedures performed through median sternotomy and open heart procedure requiring cardiopulmonary bypass or deep hypothermia.
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