Pulmonary microthrombi. Caveat for successful modified Fontan operation

Area of Science:

• Cardiovascular Research
• Pediatric Cardiology
• Pulmonary Hypertension

Background:

• Functional single ventricle physiology presents unique challenges.
• Pulmonary hypertension is a significant complication in these patients.
• Microthrombosis has been observed in lung biopsies of affected individuals.

Purpose of the Study:

• To investigate the role of pulmonary microthrombosis in patients with functional single ventricle.
• To correlate microthrombosis findings with hemodynamic parameters and clinical outcomes.
• To assess the impact of microthrombosis on the suitability and success of the Fontan operation.

Main Methods:

• Retrospective review of medical records from eight patients (4-29 years) with functional single ventricle.
• Analysis of open lung biopsy specimens for pulmonary microthrombosis.
• Hemodynamic assessment including pulmonary artery pressure, arteriolar resistance, and blood flow.
• Evaluation of hemoglobin levels and pulmonary/systemic blood flow ratios.

Main Results:

• Pulmonary microthrombosis was identified in lung biopsies, with thrombotic lesions in 56% of muscular pulmonary arteries.
• Pulmonary hypertension and increased pulmonary arteriolar resistance were common findings.
• Elevated hemoglobin levels (polycythemia) were observed in most patients.
• Microthrombosis was linked to unexpected pulmonary hypertension, precluding or complicating the Fontan operation in several cases.

Conclusions:

• Microscopic pulmonary thrombi can cause significant pulmonary hypertension in functional single ventricle patients.
• Clinically significant thrombi should be suspected in patients with severe polycythemia and difficult hemodynamic assessments.
• Consideration of pulmonary microthrombosis is vital for patient management and surgical planning, particularly regarding the Fontan procedure.