Would untreated Tetralogy of Fallot (TOF) lead to cardiomegaly in an 18-year-old?

Untreated Tetralogy of Fallot and Cardiomegaly in an 18-Year-Old

Yes, untreated tetralogy of Fallot (TOF) commonly leads to cardiomegaly, particularly right ventricular hypertrophy and dilation, in an 18-year-old patient. 1 This cardiomegaly is a direct consequence of the pathophysiological changes associated with the uncorrected congenital defect.

Pathophysiological Basis for Cardiomegaly

Untreated TOF leads to cardiomegaly through several mechanisms:

1. Right Ventricular Hypertrophy (RVH)

   • The right ventricle hypertrophies in response to right ventricular outflow tract obstruction (RVOTO) 1
   • RVH is one of the four cardinal features of TOF and develops as a compensatory mechanism to overcome the RVOTO

2. Right Ventricular Dilation

   • Chronic volume and pressure overload of the right ventricle leads to progressive dilation 1
   • The non-restrictive ventricular septal defect (VSD) contributes to this volume overload

3. Chronic Cyanosis Effects

   • Long-standing cyanosis leads to compensatory mechanisms including increased red blood cell production
   • Mean hematocrit in untreated adult TOF patients can reach 53.6±10% 2

Evidence from Adult Patients with Uncorrected TOF

The 1979 study of 147 adult patients with TOF demonstrated that cardiac enlargement was present in 25.8% of untreated adult patients 3. By age 18, this percentage would likely be higher due to:

• Progressive nature of the disease
• Increasing severity of pulmonary stenosis with age
• Worsening right-to-left shunting through the VSD

Imaging Findings in Untreated TOF

Cardiomegaly in untreated TOF typically manifests as:

• Boot-shaped cardiac silhouette on chest X-ray due to right ventricular hypertrophy 1
• Echocardiography showing dilated, severely hypertrophic right ventricle 4
• Increased right ventricular end-diastolic volume and pressure 3

Natural History Without Surgical Correction

Without surgical correction, TOF has a poor prognosis:

• More than 95% of patients die before age 40 without intervention 1
• Only 3% of patients reach age 40 without surgery 4, 5
• By age 18, significant cardiac remodeling has already occurred

Clinical Implications

The presence of cardiomegaly in an 18-year-old with untreated TOF indicates:

• Disease progression requiring urgent evaluation
• Need for comprehensive assessment of right ventricular function
• Evaluation for potential surgical correction, which remains the preferred treatment even in adults 4

Conclusion

Cardiomegaly is an expected finding in an 18-year-old with untreated tetralogy of Fallot, primarily manifesting as right ventricular hypertrophy and dilation. This represents a compensatory response to the underlying anatomical defects and hemodynamic abnormalities, particularly right ventricular outflow tract obstruction and the ventricular septal defect.