Congenital Heart Disease: Causes, Types, and Management

Factors Leading to Congenital Heart Disease

Genetic Predisposition

• Children with trisomy 21 (Down syndrome) are more prone to congenital heart disease.

Environmental Risk Factors

• Viral infections, drug toxins: Taken by mothers, especially diabetic mothers, increase risk.
• Higher incidence in heterozygous mothers in Finland.

Classifications of Congenital Heart Disease

Increased Pulmonary Blood Flow

• Any communication from left side to right side: ASD (Atrial Septal Defect), VSD (Ventricular Septal Defect), PDA (Patent Ductus Arteriosus).
• Transpositions of main vessels.

Decreased Pulmonary Blood Flow

• Blood doesn’t reach pulmonary circulation, e.g., right-to-left shunt:
  • Tetralogy of Fallot (ToF).
  • Pulmonary atresia.
  • Tricuspid atresia.

Obstructive Lesions

• Aorta: Coarctation of the aorta.
• Pulmonary artery: Pulmonary stenosis.
• Cardiomyopathy.

Fundamentals of Venous and Arterial Circulation

Normal Circulation

• Venous Return: IVC/SVC to Right Atrium (RA), then pulmonary artery.
• Effective Pulmonary Blood Flow (QP): Blood flow from venous system to arterial pulmonary system.
• Effective Systemic Blood Flow (QS): Blood flow from pulmonary vein to systemic artery (aorta).
• In normal circulation, QP = QS (1:1 ratio).

Shunting

• Left-to-Right Shunt: E.g., ASD, VSD, PDA.
  • Increased pulmonary blood flow (QP > QS).
  • Symptoms: Volume overload, heart failure, increased pulmonary circulation.
• Right-to-Left Shunt: E.g., Tetralogy of Fallot (ToF).
  • Decreased pulmonary blood flow (QP < QS).
  • Symptoms: Cyanosis (poorly oxygenated blood in systemic circulation).

Tetralogy of Fallot (ToF)

Definition

• Four components:
  • Large, non-restrictive VSD.
  • Right ventricular outflow obstruction (Infundibular stenosis).
  • Overriding aorta.
  • Right ventricular hypertrophy.

Classification

• Pink ToF: Minimal right ventricular obstruction.
• Blue ToF: Severe obstruction.
• Profound Cyanosis: Extreme obstruction or atresia of pulmonary valve.

Symptoms and Signs

• Signs: Central cyanosis, clubbing, single S2 sound, ejection systolic murmur.
• Symptoms: Dyspnea, poor feeding, sweating, tachycardia, cyanotic episodes (Tet spells).

Complications

• Polycythemia: Increased red blood cell count leading to sludging and thromboembolism.
• Cerebral abscess: Common non-cardiac surgical emergency.
• Heart Failure: Due to increased right ventricular pressure.

Management

Preoperative Care

• Avoid Hypovolemia: Maintain hydration.
• Pre-medication: Reduce anxiety and prevent catecholamine release.
• Antibiotic Prophylaxis: Prevent bacterial endocarditis.

Intraoperative Management

• Anesthetic Choice: Ketamine preferred for maintaining systemic vascular resistance (SVR); avoid reducing SVR.
• Avoid Hypoxia, Hypercarbia, Acidosis: Use oxygen and correct acidosis.
• Right Ventricular Outflow Tract Function: Monitor with echocardiography.
• Avoid Air Bubbles: Prevent paradoxical embolism.

Treating Tet Spells

• Calm the child.
• Squatting or knee-chest position.
• Oxygen administration.
• Fluid bolus: Increase RV stroke volume.
• Phenylephrine: Increase SVR.
• Beta-blockers: Reduce infundibular spasm.
• Sedation as needed: Morphine or ketamine.

Postoperative Management

• Pain Management: Avoid regional blocks that decrease SVR.
• Hydration: Maintain adequate fluid balance.
• Monitor for Arrhythmias: Common post-surgical complication.

Conclusion

• Key management strategies for congenital heart diseases, focusing on Tetralogy of Fallot.
• Always aim to balance systemic and pulmonary vascular resistances, particularly note the differences between left-to-right and right-to-left shunts.
• Important to control right ventricular pressure and ensure proper blood flow to the lungs.