Quantitative evaluation of tricuspid regurgitation by digital simulation of cardiac time-activity curves

To estimate tricuspid regurgitation (TR) quantitatively, a curve fitting method by computer has been employed. Transport in the right cardiac chambers after intravenous bolus injection of macro-aggregated albumin labeled with technetium 99m (99mTc-MAA) was recorded in anterior view by a gammacamera system. Disturbance of the dilution curves from the left heart can be avoided by using 99mTc-MAA injection. To know the radioisotope activity during the transport, time-activity curves are recorded for the superior vena cava, right atrium, and right ventricle. Parametric differential equations, obtained from compartmental analysis, interpret these curves mathematically. The rate of regurgitation is determined by comparison, using an iterative process, between the original and simulated curves. The whole process is performed automatically by computer. The calculated regurgitation value correlated well with the value from the analog simulation. The method clearly separated those with TR from those without TR. This digital simulation for estimating parameters using a compartmental model is a feasible tool in detecting and quantifying TR.