Congenital Heart Disease: Causes, Types, and Management

Jul 17, 2024

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.