Heart pearls!

Definition

• Discordant ventriculoarterial connection.

Incidence

• Four times more in males
• Predisposing factors-
  • Maternal diabetes
  • Maternal exposure to sex hormones
  • Multiparity

Embryology

• Theory of conal inversion
  • Subaortic conus persists while subpulmonic conus is absorbed.
  • So aorta comes anterior and is connected to the anterior ventricle which is the RV.

Classification

• Simple TGA-
  • No associated anomaly
  • Some authorities include VSD, PDA and LVOTO also under simple TGA.
• Complex TGA-
  • Associated anomalies

Pathology

• D of D-TGA refers to D loop of ventricle.
• Aortic position-
  • Usually anterior and right (two-thirds)
  • Less commonly anterior or anterior and left
  • Rarely posterior
• Coronary anomalies-
  • LCx from RCA- 16%
  • Single RCA- 4%
  • Single LCA- 2%
• Associated anomalies-
  • VSD alone- 30%
  • VSD + LVOTO- 10%
  • LVOTO alone- 5%
  • PDA
  • Mitral anomalies
  • Juxtaposition of atrial appendages
• VSD- subaortic or muscular.
• LVOTO-
  • 15% at birth, 30% later
  • Usually associated with VSD
  • Dynamic or fixed    
• PDA-
  • Half of infants have PDA which closes by one month.
  • Persists less commonly
• Mitral anomalies-
  • Cleft, straddling etc
  • Usually functionally insignificant
• Juxtaposition of atrial appendages
  • Left sided
  • Male preponderance is lost

Hemodynamics

• Basics-
  • Systemic and pulmonary circulations are in parallel.
  • Effective systemic blood flow is equal to effective pulmonary blood flow.
  • Inter-circulatory mixing
    • By ASD, VSD or PDA- usually by VSD
    • Poor, good or balanced
• Poor mixing
  • Cyanosis from birth
  • Metabolic acidosis
  • No heart failure
• Good mixing
  • Heart failure from birth
  • No cyanosis
• Balanced mixing
  • No heart failure or cyanosis at birth
  • May change to poor mixing if VSD/ASD/PDA becomes smaller
• Good mixing becoming cyanotic-
  • PDA closing at one month
  • VSD or ASD becoming smaller
  • PVOD (pulmonary vascular obstructive disease)
  • LVOTO

Clinical features

• Cyanosis or heart failure from birth.
• Heart failure decreasing and cyanosis increasing-
  • PDA closing at one month
  • ASD or VSD decreasing in size
  • PVOD- PDA with PVOD can cause reverse differential cyanosis and necrotizing enterocolitis
  • LVOTO- Dynamic obstruction can cause cyanotic spells
• Hypoglycemia, hypocalcemia
• Single loud S2-
  • A2 is loud as aorta is anterior
  • P2 is not heard even in high pulmonary blood flow situations
• PES may be heard in high pulmonary blood flow situations
• VSD, LVOTO and PDA may cause murmurs. If these are not present, there are no murmurs (simple TGA with intense cyanosis at birth is characteristically murmurless).

ECG

• Cyanotic cases- RVH, right axis deviation
• HF cases- BVH, normal axis or just right axis
• Left axis- AVCD with TGA

Chest X-ray

• Egg on side-
  • Narrow superior mediastinum-
    • Absent thymus
    • Anteroposterior great vessels
  • Cardiomegaly
• Cardiomegaly and increased pulmonary vasculature
  • Absent in poor mixing cases
  • Prominent in good mixing cases
  • Right sided vascularity may be more as MPA may be directed to right
• Right aortic arch
  • TGA in general- 8%
  • TGA + VSD + PS- 15%

Echocardiography

• Double circle in PSAX. Aorta is right and anterior.
• Aorta and MPA are parallel.
• Fetal echo can diagnose.

Cath study

• If PA pressure cannot be measured, find pulmonary vein wedge pressure.
• Laid back balloon occlusion aortic root angiogram to find coronary anomalies.

Natural history

• 1 year survival-
  • Poor mixing- 4% (1 month- 20%)
  • VSD- 30%
  • VSD with LVOTO- 70%
• Surviving child with TGA-
  • VSD with PVOD- more common
  • VSD with LVOTO- less common
• Large VSD-
  • Grade 3 to 4 Heath-Edwards
    • 20% at 2 months
    • 80% at 1 year

Management

• Medical
  • PG E1
  • Balloon atrial septostomy- success means 10% increase in saturation
• Arterial switch in first month of life itself along with closure of ASD, VSD or PDA.
• For TGA + VSD + PS- Rastelli procedure.