The purpose of this clinical investigation is to analyse the growth of the ventricular volumes and the changes of indices of cardiac performance during infancy and childhood. The materials were composed of 129 healthy infants and children (4 months to 13 years of age), who had a history of Kawasaki disease and without any evidence of coronary artery lesion. All the cases underwent cardiac catheterization and cineangiography under sedation. Volumes of the left and right ventricles were calculated by integration methods in tow frames for end-diastole and end-systole from biplane cineangiograms. Left ventricular mass was calculated in 120 infants and children by Rackley's method.
All the volumes and masses were deviled by body surface area in order to normalize the crude values for infants and children of different size. The mean values of left ventricular end-diastolic volume index (LVEDVI), right ventricular end-diastolic volume index (RVEDVI) and stroke index (SI) for each age were less in the younger children than those in the older children, and abrupt stepwise increase was observed at 1 year, 6 years and 10-11 years of age in the values of LVEDVI, RVEDVI and SI.
The infants and chidren were divided into four groups according to age (under 1 year, 1 to 5 years, 6 to 10 years and more than 11 years) . The values of LVEDVI, RVEDVI, SI and LVmass index were less in the younger age groups than those in the older age groups, and the difference of each age groups was statistically significant. The value of left ventricular ejection fraction (LVEF) was less in the youngest group (under 1 year) than those in the another groups (p<0.01) . The value for right ventricular ejection fraction (RVEF) was not significantly different in the age groups. End-systolic pressure-volume ratio was normalized with left ventricular mass (LVESP/ (LVESV/LVmass) ) . This normalized ratio was the lowest in the youngest group (under 1 year) and the highest in the oldest group (more than 11 years) .
As mentioned before, abrupt stepwise increase was observed in the“normal”values of LVEDVI, RVEDVI and SI in infancts and children. The explanation of this fact may be difficult at present. By the evidence of the normalized end-systolic pressure-volume ratio, it can be said that the contractility of the left ventricle in“healthy”infants and children was increased according to age. The reason why the value of LVEF was less in the youngest group than those in the another groups can be attributed to the lower contrac-tility in the youngest group. A possible factor that the value of RVEF was not significantly different between the youngest group and the another groups is; because the right ventricle works under higher pressure during fetal and neonatal period, then the right ventricular performance developed already in infancy.