Nakata Index & McGoon Ratio Calculator

Nakata Index and McGoon Ratio: Explanation and Clinical Context Nakata Index and McGoon Ratio are quantitative assessments of pulmonary artery size often used when evaluating patients with congenital heart diseases that involve reduced pulmonary blood flow. Both indices help clinicians determine surgical suitability, especially for procedures such as systemic to pulmonary artery shunts, complete repair of Tetralogy of Fallot, and evaluation for cavopulmonary anastomosis. Nakata Index represents the cross sectional area of the branch pulmonary arteries normalized to body surface area.

A higher value indicates more adequate pulmonary arterial development. Values of two hundred mm² per m² or greater are generally considered adequate for definitive surgical repair, while values below one hundred and fifty mm² per m² suggest significant hypoplasia. McGoon Ratio is a simpler linear measurement comparing the sum of right and left pulmonary artery diameters to the diameter of the descending aorta.

A ratio of one point eight or above is widely used as a threshold indicating adequate pulmonary artery size for complete repair, while values below one point two represent hypoplastic pulmonary arteries with higher operative risk. Both indices provide complementary insights in pre operative planning. They assist in predicting postoperative outcomes, guiding the need for staged intervention, and identifying patients who may require augmentation of pulmonary arteries prior to definitive repair.