Effects of Injection Site on the Accuracy of Thermal Washout
For better understanding of right ventricular (RV) physiology, the indicator washout method for measurement of right ventricular ejection fraction (RVEF) has been developed because of RV anatomic characteristics. Fundamental investigations into the indicator washout method have been made in humans, animals, and artificial models using dye, electrical conductivity, and thermal washout methods, and the newly developed pulmonary arterial catheter equipped with a rapid response thermistor makes RVEF available for clinical investigation. A new algorithm for calculation of RVEF has been developed, based on the theory that the downslope of a thermal washout curve obtained after injecting cold water just above the tricuspid valve to attain good mixing in the right ventricle can be fitted to a single first-order exponential curve, and this method has been used clinically. buy birth control online
However, several important questions remain to be answered; whether the downslope of a thermal washout curve can be fitted to a single exponential curve and at what part (that is, the whole downslope or part of the downslope), whether successive ejection fractions (EFs) in a thermal washout curve are always the same, and whether the right atrial (RA) injection of cold water makes measurement of RVEF more accurate than does RV injection. The purpose of this study is to answer these questions. Serially measured EFs between RA or RV injections in the same patient were compared and the same procedure was repeated in a model heart. We determined that the serially measured EFs were different from each other (namely they did not fit a single exponential curve), the EFs obtained from RA injection were lower than those from RV injection, and that the recommended injection site was RV. Moreover, it was concluded that the first and/ or second calculated EFs in a thermal washout curve obtained from RV injection might be closest to the actual values, and that catheter cooling affected the results considerably.