What is the most likely outcome in the next few weeks for a neonate with double-inlet left ventricle, normally related great arteries, and a 30-mm Hg peak gradient across the pulmonary valve?

Increasing Left Ventricular Outflow Tract Gradient in a Neonate with Double-Inlet Left Ventricle

In a 1-week-old neonate with double-inlet left ventricle, normally related great arteries, unrestricted bulboventricular foramen, and 30-mm Hg peak gradient across the pulmonary valve, the most likely clinical development in the next few weeks will be an increasing left ventricular outflow tract gradient.

Pathophysiology of Double-Inlet Left Ventricle

• Double-inlet left ventricle (DILV) is a rare congenital heart defect where both atrioventricular valves connect to a morphological left ventricle, with a rudimentary outlet chamber (right ventricle) connected through the bulboventricular foramen 1
• In DILV with normally related great arteries, the pulmonary artery arises from the outlet chamber (morphologic right ventricle), making the pulmonary outflow dependent on flow through the bulboventricular foramen 1
• The unrestricted bulboventricular foramen initially allows adequate flow to the pulmonary circulation, but this is likely to change over time 1

Expected Progression in the Coming Weeks

• The current 30-mm Hg gradient across the pulmonary valve indicates some degree of obstruction that is likely to worsen 2

• Left ventricular outflow tract gradients in congenital heart disease tend to increase over time due to several factors:

  • Progressive myocardial hypertrophy in response to pressure load 2
  • Changes in left ventricular wall remodeling that impair relaxation and decrease compliance 2
  • Growth of cardiac structures that may be disproportionate, leading to relative narrowing of outflow tracts 2

• In DILV specifically, the LV outflow tract obstruction typically worsens as:

  • The ventricle hypertrophies in response to volume and pressure load 2
  • The bulboventricular foramen becomes relatively smaller compared to the growing heart 1

Why Other Options Are Less Likely

• Decreasing oxygen saturations: The current oxygen saturation of 93% following ductal closure suggests adequate pulmonary blood flow. With an unrestricted bulboventricular foramen, significant desaturation is unlikely in the immediate weeks 1

• Progressive restriction of bulboventricular foramen: While this may occur eventually, it typically develops over months to years rather than weeks, especially when described as currently "unrestricted" 1

• Symptoms of congestive heart failure: With the current 30-mm Hg gradient across the pulmonary valve and unrestricted bulboventricular foramen, the pulmonary blood flow is likely balanced, making acute heart failure less likely in the immediate term 1, 3

Clinical Implications

• The increasing LVOT gradient will require close monitoring as it may eventually necessitate intervention 2
• Serial echocardiography should be performed to track the progression of the gradient 2
• As the gradient increases, it may lead to:
  • Increased left ventricular end-diastolic pressure 2
  • Potential development of diastolic dysfunction 2
  • Eventually, symptoms of heart failure may develop if the obstruction becomes severe 2

Management Considerations

• Early recognition of increasing LVOT gradient is essential for timely intervention 2
• These patients typically require staged surgical palliation toward a Fontan circulation 1
• Pulmonary artery banding may be considered if pulmonary overcirculation develops 1, 4
• Careful monitoring of ventricular function is crucial as diastolic abnormalities may develop 2

The natural history of DILV with normally related great arteries includes progressive obstruction to pulmonary blood flow, with the LVOT gradient being the most likely parameter to increase in the short term following ductal closure 1, 2.