A new method for measurement of right ventricular residual ratio using 121I-MAA.

A new technique of precordial counting with 131I-MAA for measurement of right ventricular residual ratio (RVRR) was described. 131I-MAA was rapidly injected injected into the right ventricle at the time of right heart catheterization. The fraction of isotope discharged from this chamber per beat was determined with a crystal detector with tapered collimator which was pointed to the center of right ventricle. The radioisotope dilution curve was corrected by using the lung built up curve recorded by the other detector pointed to the lung field. Then, the right ventricular end-systolic volume (ESV) and the right ventricular end-diastolic volume (EDV) were calculated from the RVRR and stroke volume. In 6 patients with normal hemodynamics, the RVRR averaged 57.8 plus or minus 4.9%, the ESV 52.2 plus or minus 13.6 ml/M(2) and the EDV 89.4 plus or minus 15.1 ml/M(2). In 16 patients with heart diseases, the RVRR averaged 60.6 plus or minus 7.1%, the ESV 80.6 plus or minus 34.0 ml/M(2) and the EDV 127.2 plus or minus 43.6 ml/M(2). In 11 patients with chronic pulmonary diseases, the RVRR averaged 70.7 plus or minus 9.9%, the ESV 94.7 plus or minus 42.4 ml/M(2) and the EDV 133.0 plus or minus 46.5 ml/M(2). The RVRR in the last group increased significantly.