EVALUATION OF REGIONAL DIFFERENCES IN RIGHT-VENTRICULAR SYSTOLIC FUNCTION BY ACOUSTIC QUANTIFICATION ECHOCARDIOGRAPHY AND CINE MAGNETIC-RESONANCE-IMAGING

Background--Accurate quantitative evaluation of right ventricular (RV) function has been limited by its complex structural geometry. Althoug h embryological and anatomic observations suggest that the RV is compo sed of 2 distinct components, the RV sinus and infundibulum, most stud ies on RV dimensions and function viewed it as a single chamber. This study was designed to determine th volumes, relative contribution to g lobal systolic function, and temporal course of contraction and relaxa tion of the RV sinus and infundibulum. Methods and Results-Thirty-one individuals without heart disease (aged 1 month to 17 years, 16 boys a nd 15 girls) participated in this study. Instantaneous area over time, ics derivatives, and the temporal course of contraction and relaxatio n were studied by acoustic quantification echocardiography and phonoca rdiography in 20 individuals. Global and regional RV volumes and eject ion fraction were determined by cine MRI in 11 individuals. The KV sin us made up 81+/-6% of the combined RV end-diastolic volume and 87+/-4% of the combined stroke volume. The infundibulum accounted for the rem aining 19+/-6% and 13+/-4% respectively (P<0.0001). Compared with the infundibulum, the extent of RV sinus fiber shortening was significantl y greater: for ejection fraction (56+/-11% versus 38+/-13%, P<0.001), fractional area change (42+/-14% versus 28+/-9%, P<0.0001), and dA/dt (27+/-17% versus 13+/-6%, P<0.0001). Analysis of temporal course of co ntraction and relaxation (expressed as percentage of the cardiac cycle to adjust for differences in heart rate) showed that the infundibulum follows the RV sinus: onset of contraction 53%+/-14 versus 19+/-11% o f systole, time to peak systole 115+/-16% versus 97+/-19% (P less than or equal to 0.01), indicating a peristalsis-like pattern of contracti on and relaxation. Conclusions-The results of this study demonstrate s ignificant regional differences between the sinus and infundibulum com ponents of the RV with regard to contribution to stroke volume, extent of fiber shortening, and sequence of mechanical activation. These dat a from normal individuals can be used in future research on RV functio n in pathological conditions.