Radioisotopic diagnosis and quantitation of left to right shunts in childhood and adolescence.

In 187 patients (141 adults and 46 children) left to right shunts were assessed using quantitative radionuclide angiography. After injection of 99mTc into the femoral vein time activity curves were registered over both lungs and the heart (Ohio Nuclear Camera, ON SIGMA 400, 110, HP 5407 computer). Using a modified gamma function area ratio technique the shunt sizes were calculated. The radioisotopic method allows a precise quantitation of left to right shunts ranging from 15--80%. There was a good agreement between the shunt sizes calculated by the radioisotopic method and oximetry or dye-dilution at cardiac catheterization (adults r = 0,87, children r = 0,85). The shunts sizes assessed with this nontraumatic method appear sufficiently reliable to be a real alternative to conventional techniques in screening for shunts.