Transposition of the great arteries

D-TGA is when aorta arises from RV and RA arises from LV. Most common form of transposition.

Important associated defects for surgical planning are malalignment septal defects.

Anterior (rightward) defects are associated w/ varying degrees of overriding of pulmonary annulus onto RV.

Posterior (leftward) malalignment defects are associated w/ varying degrees of subpulmonary stenosis, annular hypoplasia, or pulmonary valvar atresia.

Important pre-op physiology

Dominant problems are poor oxygen delivery and excessive R and L ventricular workload.

MUST HAVE AN INTRACARDIAC (PFO, ASD, VSD) or EXTRACARDIAC (PDA) shunt to survive – may need emergent balloon atrial septectomy if pt not responding to prostaglandins!

Poor mixing  is often seen by low pO2, elevated pCO2 (despite good chest movement/ ventilation) and a metabolic acidosis!  Important because pt has severely decreased effective pulmonary and systemic flows. Need to ensure mixing and maximize oxygen delivery!

Surgical repairs

Arterial Switch – Great vessels are transected, coronaries inspected and translocated to new aorta, septal defects are repaired.

Rastelli – Used mostly for TGA w/ large VSD and extensive LVOTO.

LV output directed to aorta by intra-ventricular patch tunnel technique and RV is connected to PA by extracardiac valved conduit.

Post-operative issues

1) Arrhythmias – especially b/c of transfer of coronary arteries

2) LV dysfunction – may be due to coronary insufficiency or “unprepared” LV. LV may be poorly compliant following Switch. Need to give volume slowly as acute change in preload may increase LA pressure, cause pulm edema, and decrease cardiac output.

3) Rule-out any residual stenosis or ASD/VSDs (if initially present). Rule out conduit obstruction or branch PA distortion if Rastelli was performed.